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It’s fairly common for a medical treatment to cause side effects: think headache, upset stomach, sleepiness, and occasionally more severe side effects. Far more rarely, a side effect provides an unexpected benefit. This might be the case for the shingles vaccine.

Shingles is a painful, blistering skin rash caused by the varicella zoster virus responsible for chickenpox. The virus lies dormant in nerve tissue and can reactivate to cause shingles in anyone who has had chickenpox in the past. A vaccine to prevent shingles is recommended for adults ages 50 and older, and for people 19 and older who have an impaired immune system.

While we know the shingles vaccine is effective at preventing shingles, evidence is mounting that it might also reduce the risk of dementia. Yes, a vaccination to prevent shingles may lessen your risk of dementia.

Dementia is on the rise

Dementia is a devastating condition for those affected and their families. Currently, an estimated nine million people in the US have dementia. The number is expected to double by 2060, primarily because of the aging population. In most cases, no highly effective treatments are available. An effective preventive measure could have an enormous impact, especially if it’s safe, inexpensive, and already available.

Can shingles vaccination prevent dementia?

Some (though not all) studies have found that having shingles increases your risk of dementia in the future. And that’s led researchers to explore the possibility that preventing shingles through vaccination might reduce dementia risk.

Several studies suggest this is true. For example:

• A study of more than 300,000 adults found that among those 70 and older, dementia was less common among those who had received shingles vaccination than among those who did not.
• A study of more than 200,000 older adults compared rates of dementia between those receiving a newer (recombinant) shingles vaccine and those who had an older (live) vaccine that is no longer approved in the US. Researchers found that the risk of dementia was lower six years after receiving either vaccine. But the effect was larger for the newer vaccine: those given the recombinant vaccine spent more time living dementia-free (164 days longer) compared with those given the older vaccine.

What is a natural experiment?

Perhaps the best evidence suggesting that shingles vaccination prevents dementia comes from a natural experiment recently published in the journal Nature.

A natural experiment takes advantage of real-world circumstances by dividing people into an exposed group and an unexposed group and then comparing specific outcomes.

• Examples of exposures might be an illness (like the COVID pandemic), a policy (like a smoking ban in one state), or a vaccination (like the shingles vaccine).
• Outcomes might include virtual versus in-person learning during the pandemic, smoking-related illnesses in a state with a smoking ban compared to a state without that ban, or dementia rates among people who did or didn’t receive a vaccine.

Natural experiment studies bypass the challenges of having to recruit hundreds or thousands of study subjects who might differ from one another in important ways, or who might alter their behavior because they know they’re in a study. The results can be even more valuable than — and as credible as — standard randomized trials.

What did this natural experiment study look at?

In 2013, Wales made the shingles vaccination available to individuals based on their date of birth: anyone born after September 2, 1933, was eligible, while anyone born before that date was not. Researchers took this opportunity to analyze health records of nearly 300,000 people: half were two weeks older than the cutoff date and half were two weeks younger. The study looked at whether people developed dementia over a seven-year period.

Researchers found that compared to those who didn’t get the shingles vaccination, those who received it

• developed shingles less often
• were 3.5% less likely to develop dementia over seven years (a 20% reduction)
• were more likely to be protected from dementia if female.

A study of this type cannot prove that shingles vaccination prevents dementia. But along with the studies cited above, there’s a strong suggestion that it does. We’ll need additional studies to confirm the benefit. We also want to understand other details of the vaccine’s effect, such as whether protection applies more to some types of dementia (such as Alzheimer’s disease) than others, and whether the effect of vaccination changes over time.

Why might the shingles vaccine prevent dementia?

With any unexpected finding in science, it’s a good idea to ask whether there is a reasonable explanation behind it. Scientists call this biologic plausibility. In general, the more plausible a result is, the more likely it is to hold up in later research.

In this case, several lines of reasoning explain how a shingles vaccine might reduce the risk of dementia, including:

• Reduced inflammation: Preventing shingles may prevent harmful inflammation in the body, especially in the nervous system.
• Impact on immune function: Vaccination might alter immune function in a way that protects against dementia.
• Reducing stroke risk: Some evidence shows that shingles may increase the risk of stroke. A stroke can contribute to or cause dementia, so perhaps vaccination leads to less dementia by reducing shingles-related strokes.

The observation that women had more protection from dementia than men after shingles vaccination is unexplained. It’s possible that the immune response to vaccination is different in women, or that dementia develops differently in women compared with men.

The bottom line

All of us can take steps to lower dementia risk, mostly through healthy behaviors such as being active regularly and choosing a healthy diet. Evidence is mounting that shingles vaccination should be added to the list. It’s a story worth following. Future studies of the shingles vaccine could even provide insights into how dementia develops, and how to better prevent and treat it.

Until then, get your shingles vaccination if you’re eligible for it. It can prevent painful episodes of shingles — and may do much more.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD Share

If you've been cocooning due to winter’s cold, who can blame you? But a lack of activity isn't good for body or mind during any season. And whether you're deep in the grip of winter or fortunate to be basking in signs of spring, today is a good day to start exercising. If you’re not sure where to start — or why you should — we’ve shared tips and answers below.

Moving more: What’s in it for all of us?

We’re all supposed to strengthen our muscles at least twice a week and get a total at least 150 minutes of weekly aerobic activity (the kind that gets your heart and lungs working). But fewer than 18% of U.S. adults meet those weekly recommendations, according to the CDC.

How can choosing to become more active help? A brighter mood is one benefit: physical activity helps ease depression and anxiety, for example. And being sufficiently active — whether in short or longer chunks of time — also lowers your risk for health problems like

• heart disease
• stroke
• diabetes
• cancer
• brain shrinkage
• muscle loss
• weight gain
• poor posture
• poor balance
• back pain
• and even premature death.

What are your exercise obstacles?

Even when we understand these benefits, a range of obstacles may keep us on the couch.

Don’t like the cold? Have trouble standing, walking, or moving around easily? Just don’t like exercise? Don’t let obstacles like these stop you anymore. Try some workarounds.

• If it’s cold outside: It’s generally safe to exercise when the mercury is above 32° F and the ground is dry. The right gear for cold doesn’t need to be fancy. A warm jacket, a hat, gloves, heavy socks, and nonslip shoes are a great start. Layers of athletic clothing that wick away moisture while keeping you warm can help, too. Consider going for a brisk walk or hike, taking part in an orienteering event, or working out with battle ropes ($25 and up) that you attach to a tree.
• If you have mobility issues: Most workouts can be modified. For example, it might be easier to do an aerobics or weights workout in a pool, where buoyancy makes it easier to move and there’s little fear of falling. Or try a seated workout at home, such as chair yoga, tai chi, Pilates, or strength training. You’ll find an endless array of free seated workout videos on YouTube, but look for those created by a reliable source such as Silver Sneakers, or a physical therapist, certified personal trainer, or certified exercise instructor. Another option is an adaptive sports program in your community, such as adaptive basketball.
• If you can’t stand formal exercise: Skip a structured workout and just be more active throughout the day. Do some vigorous housework (like scrubbing a bathtub or vacuuming) or yard work, climb stairs, jog to the mailbox, jog from the parking lot to the grocery store, or do any activity that gets your heart and lungs working. Track your activity minutes with a smartphone (most devices come with built-in fitness apps) or wearable fitness tracker ($20 and up).
• If you’re stuck indoors: The pandemic showed us there are lots of indoor exercise options. If you’re looking for free options, do a body-weight workout, with exercises like planks and squats; follow a free exercise video online; practice yoga or tai chi; turn on music and dance; stretch; or do a resistance band workout. Or if it’s in the budget, get a treadmill, take an online exercise class, or work online with a personal trainer. The American Council on Exercise has a tool on its website to locate certified trainers in your area.

Is it hard to find time to exercise?

The good news is that any amount of physical activity is great for health. For example, a 2022 study found that racking up 15 to 20 minutes of weekly vigorous exercise (less than three minutes per day) was tied to lower risks of heart disease, cancer, and early death.

"We don't quite understand how it works, but we do know the body's metabolic machinery that imparts health benefits can be turned on by short bouts of movement spread across days or weeks," says Dr. Aaron Baggish, founder of Harvard-affiliated Massachusetts General Hospital's Cardiovascular Performance Program and an associate professor of medicine at Harvard Medical School.

And the more you exercise, Dr. Baggish says, the more benefits you accrue, such as better mood, better balance, and reduced risks of diabetes, high blood pressure, high cholesterol, and cognitive decline.

What’s the next step to take?

For most people, increasing activity is doable. If you have a heart condition, poor balance, muscle weakness, or you’re easily winded, talk to your doctor or get an evaluation from a physical therapist.

And no matter which activity you select, ease into it. When you’ve been inactive for a while, your muscles are vulnerable to injury if you do too much too soon.

“Your muscles may be sore initially if they are being asked to do more,” says Dr. Sarah Eby, a sports medicine specialist at Harvard-affiliated Spaulding Rehabilitation Hospital. “That’s normal. Just be sure to start low, and slowly increase your duration and intensity over time. Pick activities you enjoy and set small, measurable, and attainable goals, even if it’s as simple as walking five minutes every day this week.”

Remember: the aim is simply exercising more than you have been. And the more you move, the better.

About the Author

Heidi Godman, Executive Editor, Harvard Health Letter

Heidi Godman is the executive editor of the Harvard Health Letter. Before coming to the Health Letter, she was an award-winning television news anchor and medical reporter for 25 years. Heidi was named a journalism fellow … See Full Bio View all posts by Heidi Godman

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD Share

By the time boys are 8 or 10, they’re steeped in Marvel action heroes with bulging, oversized muscles and rock-hard abs. By adolescence, they’re deluged with social media streams of bulked-up male bodies.

The underlying messages about power and worth prompt many boys to worry and wonder about how to measure up. Sometimes, negative thoughts and concerns even interfere with daily life, a mental health issue known body dysmorphic disorder, or body dysmorphia. The most common form of this in boys is muscle dysmorphia.

What is muscle dysmorphia?

Muscle dysmorphia is marked by preoccupation with a muscular and lean physique. While the more extreme behaviors that define this disorder appear only in a small percentage of boys and young men, it may color the mindset of many more.

Nearly a quarter of boys and young men engage in some type of muscle-building behaviors. “About 60% of young boys in the United States mention changing their diet to become more muscular,” says Dr. Gabriela Vargas, director of the Young Men’s Health website at Boston Children’s Hospital. “While that may not meet the diagnostic criteria of muscle dysmorphia disorder, it’s impacting a lot of young men.”

“There’s a social norm that equates muscularity with masculinity,” Dr. Vargas adds. “Even Halloween costumes for 4- and 5-year-old boys now have padding for six-pack abs. There’s constant messaging that this is what their bodies should look like.”

Does body dysmorphic disorder differ in boys and girls?

Long believed to be the domain of girls, body dysmorphia can take the form of eating disorders such as anorexia or bulimia. Technically, muscle dysmorphia is not an eating disorder. But it is far more pervasive in males — and insidious.

“The common notion is that body dysmorphia just affects girls and isn’t a male issue,” Dr. Vargas says. “Because of that, these unhealthy behaviors in boys often go overlooked.”

What are the signs of body dysmorphia in boys?

Parents may have a tough time discerning whether their son is merely being a teen or veering into dangerous territory. Dr. Vargas advises parents to look for these red flags:

• Marked change in physical routines, such as going from working out once a day to spending hours working out every day.
• Following regimented workouts or meals, including limiting the foods they’re eating or concentrating heavily on high-protein options.
• Disrupting normal activities, such as spending time with friends, to work out instead.
• Obsessively taking photos of their muscles or abdomen to track “improvement.”
• Weighing himself multiple times a day.
• Dressing to highlight a more muscular physique, or wearing baggier clothes to hide their physique because they don’t think it’s good enough.

“Nearly everyone has been on a diet,” Dr. Vargas says. “The difference with this is persistence — they don’t just try it for a week and then decide it’s not for them. These boys are doing this for weeks to months, and they’re not flexible in changing their behaviors.”

What are the health dangers of muscle dysmorphia in boys?

Extreme behaviors can pose physical and mental health risks.

For example, unregulated protein powders and supplements boys turn to in hopes of quickly bulking up muscles may be adulterated with stimulants or even anabolic steroids. “With that comes an increased risk of stroke, heart palpitations, high blood pressure, and liver injury,” notes Dr. Vargas.

Some boys also attempt to gain muscle through a “bulk and cut” regimen, with periods of rapid weight gain followed by periods of extreme calorie limitation. This can affect long-term muscle and bone development and lead to irregular heartbeat and lower testosterone levels.

“Even in a best-case scenario, eating too much protein can lead to a lot of intestinal distress, such as diarrhea, or to kidney injury, since our kidneys are not meant to filter out excessive amounts of protein,” Dr. Vargas says.

The psychological fallout can also be dramatic. Depression and suicidal thoughts are more common in people who are malnourished, which may occur when boys drastically cut calories or neglect entire food groups. Additionally, as they try to achieve unrealistic ideals, they may constantly feel like they’re not good enough.

How can parents encourage a healthy body image in boys?

These tips can help:

• Gather for family meals. Schedules can be tricky. Yet considerable research shows physical and mental health benefits flow from sitting down together for meals, including a greater likelihood of children being an appropriate weight for their body type.
• Don’t comment on body shape or size. “It’s a lot easier said than done, but this means your own body, your child’s, or others in the community,” says Dr. Vargas.
• Frame nutrition and exercise as meaningful for health. When you talk with your son about what you eat or your exercise routine, don’t tie hoped-for results to body shape or size.
• Communicate openly. “If your son says he wants to exercise more or increase his protein intake, ask why — for his overall health, or a specific body ideal?”
• Don’t buy protein supplements. It’s harder for boys to obtain them when parents won’t allow them in the house. “One alternative is to talk with your son’s primary care doctor or a dietitian, who can be a great resource on how to get protein through regular foods,” Dr. Vargas says.

About the Author

Maureen Salamon, Executive Editor, Harvard Women's Health Watch

Maureen Salamon is executive editor of Harvard Women’s Health Watch. She began her career as a newspaper reporter and later covered health and medicine for a wide variety of websites, magazines, and hospitals. Her work has … See Full Bio View all posts by Maureen Salamon

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD Share

An F may mean failure in school, but the letter earns high marks in your diet. The two biggest dietary Fs — fiber and fermented foods — are top priorities to help maintain healthy digestion, and they potentially offer much more. How can you fit these nutrients into meals? Can this help your overall health as well as gut health?

Fiber, fermented foods, and the gut microbiome

The gut microbiome is a composed of bacteria, viruses, fungi, and other microorganisms living in the colon (large intestine). What you eat, the air you breathe, where you live, and many other factors affect the makeup of the gut microbiome. Some experts think of it as a hidden organ because it has a role in many important functions of the body — for example, helping the immune system function optimally, reducing chronic inflammation, keeping intestinal cells healthy, and providing some essential micronutrients that may not be included in a regular diet.

Your gut communicates with your brain through pathways in the gut-brain axis. Changes in the gut microbiome have been linked with mood and mental health disorders, such as depression and anxiety. However, it’s not yet clear that these changes directly cause these types of problems.

We do know that a healthy diet low in processed foods is key to a healthy gut microbiome. And increasing evidence suggests that fiber and fermented foods can play important parts here.

Fiber 101

Fiber’s main job is to make digestion smoother by softening and adding bulk to stool, making it pass quickly through the intestines.

But fiber has other benefits for your microbiome and overall health. A high-fiber diet helps keep body weight under control and lowers LDL (bad) cholesterol levels. Research has found that eating enough fiber reduces the risk of heart disease, type 2 diabetes, and some cancers.

What to know about fiber

There are two types of fiber: insoluble (which helps you feel full and encourages regular bowel movements) and soluble (which helps lower cholesterol and blood sugar). However, recent research suggests people should focus on the total amount of fiber in their diet, rather than type of fiber.

If you’re trying to add more foods with fiber to your diet, make sure you ease into new fiber-rich habits and drink plenty of water. Your digestive system must adapt slowly to avoid gas, bloating, diarrhea, and stomach cramps caused by eating too much too soon. Your body will gradually adjust to increasing fiber after a week or so.

How much fiber do you need?

The fiber formula is 14 grams for every 1,000 calories consumed. Your specific calorie intake can vary depending on your activity levels.

“But instead of tracking daily fiber, focus on adding more servings of fiber-rich foods to your diet,” says Eric Rimm, professor of epidemiology and nutrition at Harvard’s T.H. Chan School of Public Health.

Which foods are high in fiber?

Fruits, vegetables, legumes, nuts, seeds, and whole grains are all high in fiber. The Dietary Guidelines for Americans has a comprehensive list of fiber-rich foods and their calorie counts.

What about over-the-counter fiber supplements that come in capsules, powders that you mix with water, and chewable tablets? “If you have trouble eating enough fiber-rich foods, then these occasionally can be used, and there is no evidence they are harmful,” says Rimm. “But they should not serve as your primary source of dietary fiber.”

Fermented foods 101

Fermented foods contain both prebiotics — ingredients that create healthy changes in the microbiome — and beneficial live bacteria called probiotics. Both prebiotics and probiotics help maintain a healthy gut microbiome.

What to know about fermented foods

Besides helping with digestion and absorbing vital nutrients from food, a healthy gut supports your immune system to help fight infections and protect against inflammation. Some research suggests that certain probiotics help relieve symptoms of gut-related conditions like inflammatory bowel disease and irritable bowel syndrome, though not all experts agree with this.

Many foods that are fermented undergo lacto-fermentation, in which natural bacteria feed on the sugar and starch in the food, creating lactic acid. Not only does this process remove simple sugars, it creates various species of good bacteria, such as Lactobacillus or Bifidobacterium. (Keep in mind that some foods undergo steps that remove probiotics and other healthful microbes, as with beer or wine, or make them inactive, like baking and canning.)

The exact amounts and specific strains of bacteria in fermented foods vary depending on how they are made. In addition to probiotics, fermented foods may contain other valuable nutrients like enzymes, B vitamins, and omega-3 fatty acids.

How often should you eat fermented foods?

There is no recommended daily allowance for prebiotics or probiotics, so it is impossible to know precisely which fermented foods or quantities are best. The general guideline is to add more to your daily diet.

Which fermented foods should you choose?

Fermented foods have a range of tastes and textures because of the particular bacteria they produce during fermentation or that are added to foods. Yogurt is one of the most popular fermented foods (look for the words “live and active cultures” on the label). Still, many options are available if you are not a yogurt fan or want to expand your fermented choices. Kimchi, sauerkraut, kombucha, and pickles are a few examples.

As with fiber, probiotics are also marketed as over-the-counter supplements. However, like all dietary supplements, they do not require FDA approval, so there is no guarantee that the types of bacteria listed on a label can provide the promised benefits — or are even in the bottle. “Therefore, it is best to get your probiotics from fermented foods,” says Rimm.

To learn more about the value of fiber, fermented foods, and a healthy gut microbiome, listen to this episode of the Food, We Need to Talk podcast, “Understanding the Microbiome.”

About the Author

Matthew Solan, Executive Editor, Harvard Men's Health Watch

Matthew Solan is the executive editor of Harvard Men’s Health Watch. He previously served as executive editor for UCLA Health’s Healthy Years and as a contributor to Duke Medicine’s Health News and Weill Cornell Medical College’s … See Full Bio View all posts by Matthew Solan

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD Share

Heavy rains and sea level rise contribute to major flooding events that are one effect of climate change. Surging water rushing into buildings often causes immediate harms, such as drowning deaths, injuries sustained while seeking shelter or fleeing, and hypothermia after exposure to cold waters with no shelter or heat.

But long after news trucks leave and public attention moves on, flooding continues to affect communities in visible and less visible ways. Among the less visible threats is a higher risk of respiratory health problems like asthma and allergic reactions. Fortunately, you can take steps to minimize or avoid flooding, or to reduce respiratory health risks after flooding occurs.

How does flooding trigger respiratory health issues?

Flooding may bring water contaminated with toxic chemicals, heavy metals, pesticides, biotoxins, sewage, and water-borne pathogens into buildings. Afterward, some toxic contaminants remain in dried sediments left behind. When disturbed through everyday actions like walking and cleaning, this turns into microscopic airborne dust. Anything in that dried flood sediment — the toxic chemicals, the metals, the biotoxins — is now in the air you breathe into your lungs, potentially affecting your respiratory health.

Buildings needn’t be submerged during flooding to spur respiratory problems. Many homes we studied after Hurricane Ida suffered water intrusion through roofs, windows, and ventilation ducts — and some were more than 100 miles away from coastal regions that bore the brunt of the storm.

The growth of mold can also affect health

Another common hazard is mold, a fungal growth that forms and spreads on damp or decaying organic matter. Indoor mold generally grows due to extensive dampness, and signals a problem with water or moisture. Damp materials inside buildings following a flood create perfect conditions for rapid mold growth.

Mold can be found indoors and outdoors in all climates. It spreads by making tiny spores that float through the air to land in other locations. No indoor space is entirely free from mold spores, but exposure to high concentrations is linked with respiratory complications such as asthma, allergic rhinitis, and sinusitis. Thus, flooding affects respiratory health by increasing the risk of exposure to higher concentrations of mold spores outdoors and indoors.

For example, after Hurricane Katrina in New Orleans in 2005, the average outdoor concentration of mold spores in flooded areas was roughly double that of non-flooded areas, and the highest concentrations of mold spores were measured indoors. A study on the aftermath of Hurricane Katrina and the flooding in the UK in 2007 showed that water damage accelerated mold growth and respiratory allergies.

Children are especially vulnerable to health problems triggered by mold. All respiratory symptoms — including asthma, bronchitis, eye irritation, and cough — occurred more often in homes reporting mold or dampness, according to a study on the respiratory health of young children in 30 Canadian communities. Other research demonstrates that mold contributes to development of asthma in children.

What can you do to protect against the health harms of flooding?

Our research in New Orleans, LA after Hurricane Ida in 2021 identified common factors — both in housing and flooding events — with great impact on respiratory health. Preliminary results suggest two deciding factors in whether substantial indoor mold appeared were the age of a building’s roof and how many precautionary measures people took after flooding from the hurricane. The impact on respiratory health also varied with flood water height, days per week spent at home, and how many precautionary measures were taken after Ida swept through.

Informed by this and other research, we offer the following tips — some to tackle before flooding or heavy rains, and some to take afterward. While you may not be able to entirely prevent flooding from hurricanes or major storms, taking these and other steps can help.

Before seasonal storms, flooding, or heavy rains start: Protect against water intrusion

• Repair the roof, clean gutters, and seal around skylights, vent pipes, and chimneys to prevent leaks. These are some of the most vulnerable components of a building during storms and hurricanes.
• Declutter drains and empty septic tanks.
• Construct barriers and seal cracks in outer walls and around windows, to prevent heavy rain and floodwater from entering.
• Install a sump pump to drain water from the basement, and backflow valves on sewer lines to prevent water from backing up into the home.

After flooding or major rainstorms: Move quickly to reduce dampness and mold growth

The Environmental Protection Agency recommends limiting contact with flood water, which may have electrical hazards and hazardous substances, including raw sewage. Additionally:

• Minimize your stay in flooded regions (particularly after hurricanes) or buildings until they are dry and safe.
• Check building for traces of water intrusion, dampness, and mold growth immediately after flooding.
• Drain floodwater and dispose of remaining sediment.
• Remove affected porous materials. If possible, dry them outdoors under sunlight.
• Increase the ventilation rate by leaving all windows and doors open, or use a large exhaust fan to dry out the building as fast as possible.
• Use dehumidifiers in damp spaces such as basements.
• Upgrade the air filters in your HVAC system to at least MERV 13, or use portable air cleaners with HEPA filters to reduce your exposure to airborne mold spores.

What to do if you spot mold growth

• Wear a well-fitted N95 face mask, gloves, and rubber boots to clean.
• Clean and disinfect anything that has been in contact with water using soap, detergents, and/or antibacterial cleaning products.
• Dispose of moldy materials in sealed heavy-duty plastic bags.

Taking steps like these — before and after a major storm — goes a long way toward protecting your respiratory health.

Read Flooding Brings Deep Trouble in Harvard Medicine magazine to learn more about the health hazards related to floods.

About the Authors

Parham Azimi, PhD, Contributor

Dr. Parham Azimi is a research associate in the department of environmental health at the Harvard T.H. Chan School of Public Health, investigating the indoor environment’s impact on occupant health and wellness and strategies to improve … See Full Bio View all posts by Parham Azimi, PhD

Joseph Allen, DSc, MPH, CIH, Contributor

Dr. Joseph Allen is an associate professor in the department of environmental health at the Harvard T.H. Chan School of Public Health, and the director of Harvard’s Healthy Buildings Program. He is the coauthor of Healthy … See Full Bio View all posts by Joseph Allen, DSc, MPH, CIH Share

Has the recent news about measles outbreaks in the US surprised you? Didn’t it seem like we were done with measles?

In the US, widespread vaccination halted the ongoing spread of measles more than 20 years ago, a major public health achievement. Before an effective vaccine was developed in the 1960s, nearly every child in the US got measles. Complications like measles-related pneumonia or hearing loss were common, and 400 to 500 people died each year.

As I write this, there have been 1,227 confirmed cases in 36 states, mostly among children. The biggest outbreak is in west Texas, where 97 people have been hospitalized and two unvaccinated school-age children recently died, the first measles deaths in the US since 2015. Officials in New Mexico have also reported a measles-related death.

Can we prevent these tragedies?

Measles outbreaks are highly preventable. It’s estimated that when 95% of people in a community are vaccinated, both those individuals and others in their community are protected against measles.

But nationally, measles vaccination rates among school-age kids fell from 95% in 2019 to 92% in 2023. Within Texas, the kindergarten vaccination rates have dipped below 95% in about half of all state counties. In the community at the center of the west Texas outbreak, the reported rate is 82%. Declining vaccination rates are common in other parts of the US, too, and that leaves many people vulnerable to measles infections.

Only 3% of the recent cases in the US involved people known to be fully vaccinated. The rest were either unvaccinated or had unknown vaccine status (95%), or they had received only one of the two vaccine doses (2%).

What to know about measles

As measles outbreaks occur within more communities, it’s important to understand why this happens — and how to stop it. Here are seven things to know about measles.

The measles virus is highly contagious

Several communities have suffered outbreaks in recent years. The measles virus readily spreads from person to person through the air we breathe. It can linger in the air for hours after a sneeze or cough. Estimates suggest nine out of 10 nonimmune people exposed to measles will become infected. Measles is far more contagious than the flu, COVID-19, or even Ebola.

Early diagnosis is challenging

It usually takes seven to 14 days for symptoms to show up once a person gets infected. Common early symptoms — fever, cough, runny nose — are similar to other viral infections such as colds or flu. A few days into the illness, painless, tiny white spots in the mouth (called Koplik spots) appear. But they’re easy to miss, and are absent in many cases. A day or two later, a distinctive skin rash develops.

Unfortunately, a person with measles is highly contagious for days before the Koplik spots or skin rash appear. Very often, others have been exposed by the time measles is diagnosed and precautions are taken.

Measles can be serious and even fatal

Measles is not just another cold. A host of complications can develop, including

• brain inflammation (encephalitis), which can lead to seizures, hearing loss, or intellectual disability
• pneumonia
• eye inflammation (and occasionally, vision loss)
• poor pregnancy outcomes, such as miscarriage
• subacute sclerosing panencephalitis (SSPE), a rare and lethal disease of the brain that can develop years after the initial measles infection.

Complications are most common among children under age 5, adults over age 20, pregnant women, and people with an impaired immune system. Measles is fatal in up to three of every 1,000 cases.

During the latest outbreaks, 148 cases — about one in eight — have required hospitalization.

Getting measles may suppress your immune system

When you get sick from a viral or bacterial infection, antibodies created by your immune system will later recognize and help mount a defense against these intruders. In 2019, a study at Harvard Medical School (HMS) found that the measles virus may wipe out up to three-quarters of antibodies protecting against viruses or bacteria that a child was previously immune to — anything from strains of the flu to herpesvirus to bacteria that cause pneumonia and skin infections.

“If your child gets the measles and then gets pneumonia two years later, you wouldn’t necessarily tie the two together. The symptoms of measles itself may be only the tip of the iceberg,” said the study’s first author, Dr. Michael Mina, who was a postdoctoral researcher in the laboratory of geneticist Stephen Elledge at HMS and Brigham and Women’s Hospital at the time of the study.

In this video, Mina and Elledge discuss their findings.

Vaccination is highly effective

Two doses of the current vaccine provide 97% protection — much higher than most other vaccines.  Rarely, a person gets measles despite being fully vaccinated. When that happens, the disease tends to be milder and less likely to spread to others.

The measles vaccine is safe

 The safety profile of the measles vaccine is excellent. Common side effects include temporary soreness in the arm, low-grade fever, and muscle pain, as is true for most vaccinations. A suggestion that measles or other vaccines cause autism has been convincingly discredited. However, this often-repeated misinformation has contributed to significant vaccine hesitancy and falling rates of vaccination.

Ways to protect yourself from measles infection

• Vaccination. Usually, children are given the first dose around age 1 and the second between ages 4 and 6 as part of the Measles-Mumps-Rubella (MMR) vaccine. If a child — or adult — hasn’t been vaccinated, they can have these doses later.

  If you were born after 1957 and received a measles vaccination before 1968, consider getting revaccinated or tested for measles antibodies (see below). The vaccine given before 1968 was less effective than later versions. And before 1957, most people became immune after having measles, although this immunity can wane.

• Isolation. To limit spread, everyone diagnosed with measles and anyone who might be infected should avoid close contact with others until four days after the rash resolves.
• Mask-wearing by people with measles can help prevent spread to others. Household members or other close contacts should also wear a mask to avoid getting it.
• Frequent handwashing helps keep the virus from spreading.
• Testing. If you aren’t sure about your measles vaccination history or whether you may be vulnerable to infection, consider having a blood test to find out if you’re immune to measles. Memories about past vaccinations can be unreliable, especially if decades have gone by, and immunity can wane.
• Pre-travel planning. If you are headed to a place where measles is common, make sure you are up to date with vaccinations.

The bottom line

While news about measles in recent months may have been a surprise, it’s also alarming. Experts warn that the number of cases (and possibly deaths) are likely to increase. And due to falling vaccination rates, outbreaks are bound to keep occurring. One study estimates that between nine and 15 million children in the US could be susceptible to measles.

But there’s also good news: we know that measles outbreaks can be contained and the disease itself can be eliminated. Learn how to protect yourself and your family. Engage respectfully with people who are vaccine hesitant: share what you’ve learned from reliable sources about the disease, especially about the well-established safety of vaccination.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD Share

Marketed as a natural remedy for an enlarged prostate, saw palmetto is a top-selling dietary supplement. It’s extracted from berries that grow on saw palmetto palm trees, which are native to the southeastern United States.

By one estimate, more than a third of all US adults who take supplements use saw palmetto specifically. Some evidence suggests that saw palmetto has anti-inflammatory properties, and its use as folk medicine dates back over a century.

But experts at Harvard say men should view its supposed benefits for prostate health skeptically. “Saw palmetto is unlikely to harm you, but it probably won’t provide any major benefits either,” says Dr. Heidi Rayala, an assistant professor of urology at Harvard Medical School and Beth Israel Deaconess Medical Center.

BPH and the potential effect of saw palmetto

It’s common for men to develop an enlarged prostate, or benign prostatic hyperplasia (BPH), when they get older. BPH impedes urinary flow through the urethra, causing obstructive symptoms that can worsen with time.

Just how saw palmetto might act on the prostate to improve symptoms isn’t entirely clear, however. Some evidence suggest it mimics the effects of certain drugs used for treating BPH, including 5-alpha reductase inhibitors such as finasteride (Proscar), which shrink the prostate gland.

In the US, no herbal supplement is approved as BPH treatment. The American Urological Association cautions that studies backing saw palmetto for treating enlarged prostates have numerous flaws, including short durations and a lack of placebo controls. Most of the supporting evidence comes from small studies paid for by companies that sell dietary supplements.

What do randomized clinical trials show?

The best-conducted research shows no benefits from saw palmetto for BPH. During one study, 225 men with moderate to severe BPH were treated with either a placebo or 160 milligrams (mg) of saw palmetto, taken twice daily for a year. The investigators detected no difference in outcomes, but they also acknowledged that doses tested in the study may have been too low to produce measurable effects.

So, during a larger subsequent study, researchers tested higher doses of saw palmetto ranging up to 320 mg given three times a day. Nearly 370 men ages 45 and older were randomized to treatment or placebo groups. After year and a half, men in both groups reported feeling either no worse or a little better. Remarkably, 40% of the placebo-treated men said symptoms had improved, suggesting the simple act of taking a pill could have something to do with the supplement’s perceived benefits.

Dr. Michael Barry, a professor of medicine at Harvard Medical School, led the study. He urges men to consult with their doctors before trying saw palmetto, mainly to rule out other potential causes of urinary obstruction, which can include bladder or prostate cancer. And saw palmetto may interfere with the blood’s clotting ability, making it risky for men who take blood thinners.

Recent results and comments

The latest evidence on saw palmetto and BPH comes from a Cochrane Review of 27 placebo-controlled studies enrolling a combined 4,656 participants. Results published in 2024 showed no improvement in urinary symptoms or quality of life from taking saw palmetto (alone or with other herbal supplements) over durations ranging up to 17 months.

“If the ingredients in these herbal products worked well for urinary symptoms, drug companies would have already had them approved by the FDA as a medicine that insurance companies would have to cover,” Dr. Rayala said. “It’s okay to take them, but just be cautious about spending too much of your own money on these alternatives.”

“It is easy to understand why so many find taking a naturally occurring supplement for treating urinary difficulties in middle age appealing,” said Dr. Marc Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and editor in chief of the Harvard Medical School Guide to Prostate Diseases. “However, evidence of effectiveness with saw palmetto is lacking, and its use for BPH and other common urinary symptoms without a full evaluation of the potential cause should be discouraged.”

About the Author

C.W. Schmidt, Editor, Harvard Medical School Annual Report on Prostate Diseases

C.W. Schmidt is an award-winning freelance science writer based in Portland, Maine. In addition to writing for Harvard Health Publishing, he has written for Science magazine, the Journal of the National Cancer Institute, Environmental Health Perspectives, … See Full Bio View all posts by C.W. Schmidt

About the Reviewer

Marc B. Garnick, MD, Editor in Chief, Harvard Medical School Annual Report on Prostate Diseases; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Marc B. Garnick is an internationally renowned expert in medical oncology and urologic cancer. A clinical professor of medicine at Harvard Medical School, he also maintains an active clinical practice at Beth Israel Deaconess Medical … See Full Bio View all posts by Marc B. Garnick, MD Share

Everything is connected. You’ve probably heard that before, but it bears repeating. Below are five ways to boost both your individual health and the health of our planet — a combination that environmentalists call co-benefits.

How your health and planetary health intersect

Back in 1970, Earth Day was founded as a day of awareness about environmental issues. Never has awareness of our environment seemed more important than now. The impacts of climate change on Earth — fires, storms, floods, droughts, heat waves, rising sea levels, species extinction, and more — directly or indirectly threaten our well-being, especially for those most vulnerable. For example, air pollution from fossil fuels and wildfires contributes to lung problems and hospitalizations. Geographic and seasonal boundaries for ticks and mosquitoes, which are carriers of infectious diseases, expand as regions warm.

The concept of planetary health acknowledges that the ecosystem and our health are inextricably intertwined. Actions and events have complex downstream effects: some are expected, others are surprising, and many are likely unrecognized. While individual efforts may seem small, collectively they can move the needle — even ever so slightly — in the right direction.

Five ways to improve personal and planetary health

Adopt plant-forward eating.

This means increasing plant-based foods in your diet while minimizing meat. Making these types of choices lowers the risks of heart disease, stroke, obesity, high blood pressure, type 2 diabetes, and many cancers. Compared to meat-based meals, plant-based meals also have many beneficial effects for the planet. For example, for the same amount of protein, plant-based meals have a lower carbon footprint and use fewer natural resources like land and water.

Remember, not all plants are equal.

Plant foods also vary greatly, both in terms of their nutritional content and in their environmental impact. Learning to read labels can help you determine the nutritional value of foods. It’s a bit harder to learn about the environmental impact of specific foods, since there are regional factors. But to get a general sense, Our World in Data has a collection of eye-opening interactive graphs about various environmental impacts of different foods.

Favor active transportation.

Choose an alternative to driving such as walking, biking, or using public transportation when possible. Current health recommendations encourage adults to get 150 minutes each week of moderate-intensity physical activity, and two sessions of muscle strengthening activity. Regular physical activity improves mental health, bone health, and weight management. It also reduces risks of heart disease, some cancers, and falls in older adults. Fewer miles driven in gas-powered vehicles means cleaner air, decreased carbon emissions contributing to climate change, and less air pollution (known to cause asthma exacerbations and many other diseases).

Start where you are and work up to your level of discomfort.

Changes that work for one person may not work for another. Maybe you will pledge to eat one vegan meal each week, or maybe you will pledge to limit beef to once a week. Maybe you will try out taking the bus to work, or maybe you will bike to work when it’s not winter. Set goals for yourself that are achievable but are also a challenge.

Talk about it.

It might feel as though these actions are small, and it might feel daunting for any one individual trying to make a difference. Sharing your thoughts about what matters to you and about what you are doing might make you feel less isolated and help build community. Building community contributes to well-being and resilience.

Plus, if you share your pledges and aims with one person, and that person does the same, then your actions are amplified. Who knows, maybe one of those folks along the way might be the employee who decides what our children eat from school menus, or a city planner for pedestrian walkways and bike lanes!

About the Author

Wynne Armand, MD, Contributor

Dr. Wynne Armand is a physician at Massachusetts General Hospital (MGH), where she provides primary care; an assistant professor in medicine at Harvard Medical School; and associate director of the MGH Center for the Environment and … See Full Bio View all posts by Wynne Armand, MD Share