Walkersizzling

Driving along the freeway recently, a billboard caught my eye. In bold letters it proclaimed:

Milk hydrates better than water.

Wait, could this be true? And if so, should I be rehydrating with milk after a workout? And should we all have milk, rather than water, in our water bottles?

What’s behind the claim?

Unsurprisingly, the ad is sponsored by the milk industry. And while I’d never heard this claim before, the studies behind the idea aren’t particularly new or compelling. The website supporting this ad cites three small studies dating back more than a decade:

• A 2007 study enrolled 11 volunteers (five men, six women) who exercised until they were markedly dehydrated on several occasions. Each time they rehydrated with a different drink, and their urine output was measured over the following five hours. After drinking milk, the study volunteers produced less urine (and therefore retained more fluid) than with water or a sports drink (Powerade). Therefore, milk was considered to provide better hydration.
• A study published in 2016 described seven men with marked dehydration following exercise who drank fat-free milk, water, or Powerade. The results were similar.
• A 2016 study enrolled 72 healthy, well-hydrated men who drank various fluids and then had their urine production measured over the next four hours. The drinks used in this study were water, whole milk, skim milk, beer, Dioralyte (an oral rehydration solution used after fluid loss from diarrhea), tea, coffee, diet cola, regular cola, orange juice, and Powerade. The researchers found that fluid retention was best after drinking either type of milk or the oral rehydration solution; results for the other drinks were similar to water.

Sounds like milk is a winner, right? Maybe. But there are other things to consider.

The study details matter

The findings of these studies aren’t definitive. As with all research, there are important limitations. For example:

• The small number of participants in these studies means that just a few people could have an outsized impact on the results.
• Two of the three studies involved significant dehydration by intensely exercising in a warm environment, leading to several pounds of fluid loss. Therefore, the results may not apply to people engaged in more typical daily activities or workouts. In addition, the studies equated better hydration with less urine production in the hours after drinking various fluids. This is only one way to define hydration, and not clearly the best one.
• The advantage of milk reported in these studies may be too small or too temporary to matter much. For example, in the study of 72 people, milk drinkers produced about 37 ounces of urine over four hours while water drinkers produced 47 ounces. Does the 10-ounce difference have a meaningful health impact? If the study participants had been monitored for a longer period, would this difference disappear?
• The amount of milk consumed in the study of seven men would contain more than 1,000 calories. That may be acceptable for an elite athlete after hours of intensive exercise in the heat, but counterproductive and costly for someone working out for 30 minutes to help maintain or lose weight. Tap water is free and has no calories!

Hyping hydration: Many claims, little evidence

The billboard promoting milk reflects our relatively recent focus on hydration for health. This is promoted — or perhaps created — by advertisers selling sports drinks, energy drinks and, yes, water bottles. But does drinking “plenty of water” translate to weight loss, athletic performance, and glowing appearance? Does monitoring urine color (darker could indicate dehydration) and downing the oft-recommended eight glasses of water daily make a difference in our health? On the strength of evidence offered so far, I’m not convinced.

But wait, there’s more! Emotional support water bottles, a trend popularized recently in Australia, offer one part public expression of your commitment to health and one part security blanket. (Yes, it’s a thing: #emotionalsupportwaterbottle has more than 80 million views on TikTok.) And then there’s intravenous hydration on demand for healthy (and often wealthy) people convinced that intravenous fluids will improve their looks, relieve their hangovers, help with jet lag, or remedy and prevent an assortment of other ailments.

Is this focus on hydration actually helpful?

Before water bottles were everywhere and monitoring fluid intake became commonplace, medically important dehydration wasn’t a problem for most healthy people who were not rapidly losing fluids due to heat, intense exercise, diarrhea, or the like.

The fact is, drinking when thirsty is a sound strategy for most of us. And while there are important exceptions noted below, you probably don’t need fluids at hand at all times or to closely monitor daily fluid intake to be healthy. There are far more important health concerns than whether you drink eight glasses of water each day.

When is dehydration a serious problem?

Weather, exercise, or illness can make dehydration a major problem. Particularly susceptible are people who work or exercise outside in hot and humid environments, those at the extremes of age, people experiencing significant fluid loss (as with a diarrheal illness), and those without reliable access to fluids. If significant dehydration occurs, replacing lost fluids is critically important, and may even require a medical setting where intravenous fluids can be provided quickly.

The bottom line

Despite the claims of milk ads and the iffy studies justifying them, the idea of replacing water with milk for rehydration may not convince everyone: the taste, consistency, and extra calories of milk may be hard to get past.

As for me, until there’s more convincing evidence of an actual health advantage of milk over water for routine hydration, I’ll stick with water. But I’ll forego the water bottle.

Follow me on Twitter @RobShmerling

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

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 fires 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

Turns out that when your mother told you to stop sitting near the TV or you might need glasses, she was onto something.

Myopia, or nearsightedness, is a growing problem worldwide. While a nearsighted child can see close objects clearly, more distant objects look blurry. Part of this growing problem, according to experts, is that children are spending too much time indoors looking at things close to them rather than going outside and looking at things that are far away.

What is nearsightedness?

Nearsightedness is very common, affecting about 5% of preschoolers, 9% of school-age children, and 30% of teens. But what worries experts is that over the last few decades its global prevalence has doubled — and during the pandemic, eye doctors have noticed an increase in myopia.

Nearsightedness happens when the eyeball is too large from front to back. Genes play a big role, but growing research shows that there are developmental factors. The stereotype of the nerd wearing glasses actually bears out; research shows that the more years one spends in school, the higher the risk of myopia. Studies also show, even more reliably, that spending time outdoors can decrease a child’s risk of developing myopia.

Why would outdoor time make a difference in nearsightedness?

While surprising, this actually makes some sense. As children grow and change, their lifestyles affect their bodies. A child who is undernourished, for example, may not grow as tall as they might have if they had better nourishment. A child who develops obesity during childhood is far more likely to have lifelong obesity. And the eyes of a child who is always looking at things close to him or her might adjust to this — and lose some ability to see far away.

Nearsightedness has real consequences. Not only can it cause problems with everyday tasks that require you to see more than a few feet away, such as school or driving, but people with myopia are at higher risk of blindness and retinal detachment. The problems can’t always be fixed with a pair of glasses.

What can parents do?

• Make sure your child spends time outdoors regularly — every day, if possible. That’s the best way to be sure that they look at things far away. It’s also a great way to get them to be more active, get enough Vitamin D, and learn some important life skills.
• Try to limit the amount of time your child spends close to a screen. These days, a lot of schoolwork is on screens, but children are also spending far too much of their playtime on devices rather than playing with toys, drawing, or other activities. Have some ground rules. The American Academy of Pediatrics recommends no more than two hours of entertainment media a day, and has a great Family Media Plan to help families make this happen.
• Have your child’s vision checked regularly. Most pediatricians do regular vision screening, but it is important to remember that basic screening can miss vision problems. It’s a good idea for your child to have a full vision examination from an ophthalmologist or an optometrist by kindergarten.
• Call your pediatrician or child’s eye doctor if you notice signs of a possible vision problem, such as
  • sitting close to the television or holding devices close to the face
  • squinting or complaining of any difficulty seeing
  • not being able to identify objects far away (when you go for walks, play I Spy and point to some far-away things!)
  • avoiding or disliking activities that involve looking close, like doing puzzles or looking at books, which can be a sign of hyperopia (farsightedness)
  • tilting their head to look at things
  • covering or rubbing an eye
  • one eye that turns inward or outward.

If you have any questions or concerns about your child’s vision, talk to your pediatrician.

Follow me on Twitter @drClaire

About the Author

Claire McCarthy, MD, Senior Faculty Editor, Harvard Health Publishing

Claire McCarthy, MD, is a primary care pediatrician at Boston Children’s Hospital, and an assistant professor of pediatrics at Harvard Medical School. In addition to being a senior faculty editor for Harvard Health Publishing, Dr. McCarthy … See Full Bio View all posts by Claire McCarthy, MD

In today’s fast-paced world, our waking hours are filled with decisions — often surrounding what to eat. After a long day, dinner could well be fast food or takeout. While you may worry about the toll food choices take on your waistline or blood pressure, as a liver specialist, I also want to put fatty liver disease on your radar.

One variant, officially called nonalcoholic fatty liver disease (NAFLD), now affects one in four adults globally. Sometimes it progresses to extensive scarring known as cirrhosis, liver failure, and higher risk for liver cancer. The good news? Fatty liver disease can be prevented or reversed.

What is fatty liver disease?

Fatty liver disease is a condition caused by irritation to the liver. Liver tissue accumulates abnormal amounts of fat in response to that injury. Viral hepatitis, certain medicines (like tamoxifen or steroids, for example), or ingesting too much alcohol can all cause fatty liver disease.

However, NAFLD has a different trigger for fat deposits in the liver: a group of metabolic risk factors. NAFLD is most common in people who have high blood pressure, high cholesterol, insulin resistance (prediabetes), or type 2 diabetes. It is also common among people who are overweight or obese, though it is possible to develop NAFLD even if your body mass index (BMI) is normal.

What helps prevent or reverse NAFLD?

Diet can play a huge role. Because NAFLD is so closely tied to metabolic health, eating more healthfully can help prevent or possibly even reverse it. A good example of a healthful eating pattern is the Mediterranean diet.

Overweight or obesity is a common cause of NAFLD. A weight loss program that includes activity and healthy eating can help control blood pressure, cholesterol, and blood sugar. Among the many healthful diet plans that help are the DASH diet and the Mediterranean diet. Talk to your doctor or a nutritionist if you need help choosing a plan.

To vigorously study any diet as a treatment for fatty liver disease, researchers must control many factors. Currently, no strong evidence supports one particular diet over another. However, the research below highlights choices to promote a healthy liver.

Avoid fast food

A recent study in Clinical Gastroenterology and Hepatology linked regular fast-food consumption (20% or more of total daily calories) with fatty liver disease — especially in people who had type 2 diabetes or obesity. Fast foods tend to be high in saturated fats, added sugar, and other ingredients that affect metabolic health.

Steer clear of soft drinks and added sugars

Soft drinks with high-fructose corn syrup, or other sugar-sweetened beverages, lead directly to large increases in liver fat deposits, independent of the total calories consumed. Read labels closely for added sugars, including corn syrup, dextrose, honey, and agave.

Instead of sugary drinks, sip plain water. Black coffee or with a splash of cream is also a good pick; research suggests coffee has the potential to decrease liver scarring.

Avoid alcohol

Alcohol directly damages the liver, lacks nutritional value, and may affect a healthy microbiome. If you have NAFLD, it’s best to avoid any extra cause for liver injury. We simply do not know what amount of alcohol is safe for those with fatty liver disease — even social drinking may be too much.

Eat mostly whole foods

Vegetables, berries, eggs, poultry, grass-fed meats, nuts, and whole grains all qualify, but cutting out red meat may be wise. An 18-month trial enrolled 294 people with abdominal obesity and lipid imbalances such as high triglycerides. Regular activity was encouraged, and participants were randomly assigned to one of three diets: standard healthy dietary guidelines, a traditional Mediterranean diet, or a green-Mediterranean diet. (The green-Med diet nixed red and processed meats and added green tea and a dinner replacement shake rich in antioxidants called polyphenols.)

All three groups lost some weight, although the Mediterranean diet groups lost more weight and kept it off for a longer period. Both Mediterranean diet groups also showed reduced liver fat at the end of 18 months, but liver fat decreased twice as much in the green-Med group as in the traditional Mediterranean diet group.

Healthy fats are part of a healthy diet

We all need fat. Dietary fats help your body absorb vitamins and are vital in the protection of nerves and cells. Fats also help you feel satisfied and full, so you’re less likely to overeat. Low-fat foods often substitute sugars and starches, which affect blood sugar regulation in our bodies. But all fat is not created equal.

It’s clear that Mediterranean-style diets can help decrease liver fat, thus helping to prevent or possibly reverse NAFLD. These diets are high in healthful fats, such as monounsaturated fats found in olive oil and avocados and omega-3 fats found in walnuts and oily fish like salmon and sardines.

With so many choices, it’s hard to know where to start in the healthy eating journey. Let’s strive to eat whole foods in their natural state. Our livers will thank us for it.

About the Author

Kathleen Viveiros, MD, Contributor

Dr. Kathleen Viveiros is a clinical hepatologist at Brigham and Women’s Hospital who sees patients in Boston and in Foxborough and Westwood, MA. She is an instructor in medicine at Harvard Medical School. Her professional interests … See Full Bio View all posts by Kathleen Viveiros, MD