Month: March 2023

Many health-conscious consumers have already cut back on hamburgers, steaks, and deli meats, often by swapping in poultry or seafood. Those protein sources are better than beef, and not just because they’re linked to a lower risk of heart disease, diabetes, and cancer. Chicken and fish are also better for the environment, as their production uses less land and other resources and generates fewer greenhouse gas emissions.

And choosing seafood that’s lower on the food chain — namely, small fish such as herring and sardines and bivalves such as clams and oysters — can amp up those benefits. “It’s much better for your health and the environment when you replace terrestrial food sources — especially red meat — with aquatic food sources,” says Christopher Golden, assistant professor of nutrition and planetary health at the Harvard T.H. Chan School of Public Health. But instead of popular seafood choices such as farmed salmon or canned tuna, consider mackerel or sardines, he suggests.

Why eat small fish?

Anchovies, herring, mackerel, and sardines are all excellent sources of protein, micronutrients like iron, zinc, and vitamin B12, and heart-healthy omega-3 fatty acids, which may help ease inflammation within the body and promote a better balance of blood lipids. And because you often eat the entire fish (including the tiny bones), small fish are also rich in calcium and vitamin D, says Golden. (Mackerel is an exception: cooked mackerel bones are too sharp or tough to eat, although canned mackerel bones are fine to eat).

Small fish are also less likely to contain contaminants such as mercury and polychlorinated biphenyls (PCBs) compared with large species like tuna and swordfish. Those and other large fish feed on smaller fish, which concentrates the toxins.

It's also more environmentally friendly to eat small fish directly instead of using them to make fish meal, which is often fed to farmed salmon, pork, and poultry. Feed for those animals also includes grains that require land, water, pesticides, and energy to produce, just as grain fed to cattle does, Golden points out. The good news is that increasingly, salmon farming has begun using less fish meal, and some companies have created highly nutritious feeds that don’t require fish meal at all.

Small fish in the Mediterranean diet

The traditional Mediterranean diet, widely considered the best diet for heart health, highlights small fish such as fresh sardines and anchovies, says Golden. Canned versions of these species, which are widely available and less expensive than fresh, are a good option. However, most canned anchovies are salt-cured and therefore high in sodium, which can raise blood pressure.

Sardines packed in water or olive oil can be

• served on crackers or crusty, toasted bread with a squeeze of lemon
• prepared like tuna salad for a sandwich filling
• added to a Greek salad
• tossed with pasta, either added to tomato sauce or with lemon, capers, and red pepper flakes.

Golden is particularly fond of pickled herring, which you can often find in jars in supermarkets, or even make yourself; here’s his favorite recipe.

Bivalve benefits

Bivalves are two-shelled aquatic creatures that include clams, oysters, mussels, and scallops. Also known as mollusks, they’re good sources of protein but are quite low in fat, so they aren’t as rich in omega-3’s as small, fatty fish. However, bivalves contain several micronutrients, especially zinc and vitamin B12. Zinc contributes to a healthy immune system, and vitamin B12 helps form red blood cells that carry oxygen and keep nerves throughout the body healthy. While most Americans get enough B12, some may not.

And from a planetary health perspective, bivalves are among the best sources of animal-based protein. “Bivalves can be ‘nature positive’ because they don’t require feed and they filter and clean up water,” says Golden.

Be aware, however, that bivalves can become contaminated from runoff, bacteria, viruses, or chemicals in the water. So be sure to follow FDA advice about buying and preparing seafood safely.

Although we tend to think of coastal cities as the best places to find seafood, it’s available throughout the United States. For less-common varieties, try larger Asian markets, which often carry a wide variety of fish and bivalves, Golden suggests.

Aquatic plant foods

You can even go one step further down the aquatic food chain by eating aquatic plant foods such as seaweed and kelp. If you like sushi, you’ve probably had nori, the flat sheets of seaweed used to make sushi rolls. You can also find seaweed snacks in Asian and many mainstream grocery stores. The truly adventurous may want to try kelp jerky or a kelp burger, both sold online.

Nutrients in seaweed vary quite a bit, depending on species (kelp is one type of brown seaweed; there are also numerous green and red species). But seaweed is low in calories, is a good source of fiber, and also contains iodine, a mineral required to make thyroid hormones. Similar to terrestrial vegetables, seaweeds contain a range of other minerals and vitamins. For now, aquatic plant foods remain fringe products here in the United States, but they may become more mainstream in the future, according to Golden.

About the Author

Julie Corliss, Executive Editor, Harvard Heart Letter

Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio View all posts by Julie Corliss

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Howard LeWine, M.D., 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

When I took up running in college, a friend of mine scoffed at the idea. He hated running and was convinced runners were “wearing out” their joints. He liked to say he was saving his knees for his old age.

So, was he onto something? Does running really ruin your joints, as many people believe?

Runners can get arthritis, but is running the cause?

You may think the answer is obvious. Surely, years of running (pounding pavements, or even softer surfaces) could wear out your joints, much like tires wear out after you put enough miles on them. And osteoarthritis, the most common type of arthritis, usually affects older adults. In fact, it’s often described as age-related and degenerative. That sounds like a wear-and-tear sort of situation, right?

Maybe not. Sure, it’s easy to blame running when a person who runs regularly develops arthritis. But that blame may be misguided. The questions to ask are:

• Does running damage the joints and lead to arthritis?
• Does arthritis develop first and become more noticeable while running?
• Is the connection more complicated? Perhaps there’s no connection between running and arthritis for most people. But maybe those destined to develop arthritis (due to their genes, for example) get it sooner if they take up running.

Extensive research over the last several decades has investigated these questions. While the answers are still not entirely clear, we’re moving closer.

What is the relationship between running and arthritis?

Mounting evidence suggests that that running does not cause osteoarthritis, or any other joint disease.

• A study published in 2017 found that recreational runners had lower rates of hip and knee osteoarthritis (3.5%) compared with competitive runners (13.3%) and nonrunners (10.2%).
• According to a 2018 study, the rate of hip or knee arthritis among 675 marathon runners was half the rate expected within the US population.
• A 2022 analysis of 24 studies found no evidence of significant harm to the cartilage lining the knee joints on MRIs taken just after running.

These are just a few of the published medical studies on the subject. Overall, research suggests that running is an unlikely cause of arthritis — and might even be protective.

Why is it hard to study running and arthritis?

• Osteoarthritis takes many years to develop. Convincing research would require a long time, perhaps a decade or more.
• It’s impossible to perform an ideal study. The most powerful type of research study is a double-blind, randomized, controlled trial. Participants in these studies are assigned to a treatment group (perhaps taking a new drug) or a control group (often taking a placebo). Double-blind means neither researchers nor participants know which people are in the treatment group and which people are getting a placebo. When the treatment being studied is running, there’s no way to conduct this kind of trial.
• Beware the confounders. A confounder is a factor or variable you can’t account for in a study. There may be important differences between people who run and those who don’t that have nothing to do with running. For example, runners may follow a healthier diet, maintain a healthier weight, or smoke less than nonrunners. They may differ with respect to how their joints are aligned, the strength of their ligaments, or genes that direct development of the musculoskeletal system. These factors could affect the risk of arthritis and make study results hard to interpret clearly. In fact, they may explain why some studies find that running is protective.
• The effect of running may vary between people. For example, it’s possible, though not proven, that people with obesity who run regularly are at increased risk of arthritis due to the stress of excess weight on the joints.

The bottom line

Trends in recent research suggest that running does not wear out your joints. That should be reassuring for those of us who enjoy running. And if you don’t like to run, that’s fine: try to find forms of exercise that you enjoy more. Just don’t base your decision — or excuse — for not running on the idea that it will ruin your joints.

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

The transgender population is steadily increasing. Last year, investigators reported that 1.3% of people between the ages of 18 and 24 in the United States identify as transgender, compared to 0.55% of the country’s older adults. This trend has implications for public health, and one issue in particular concerns the risk of prostate cancer in transgender women.

Because removing the prostate can lead to urinary incontinence and other complications, doctors leave the gland in place when initiating hormonal treatments to induce female sex characteristics in transitioning people. This process, which is called feminizing or gender-affirming hormonal therapy (GAHT), relies on medications and surgery to block testosterone, a male sex hormone. Prostate cancer is fueled by testosterone, and therefore GAHT lowers overall risks for the disease. But transgender women can still develop prostate cancer in ways that remain poorly understood, according to the authors of a new paper.

“More individuals are openly identifying as transgender, particularly as advances are made in reducing the discrimination and marginalization that this group has faced,” says Dr. Farnoosh Nik-Ahd, a urologist at the University of California, San Francisco, and the paper’s first author. “Thus, it’s important to understand their health outcomes and how best to care for this population.”

Dr. Nik-Ahd and her colleagues wanted better insights into prostate cancer incidence and screening rates among transgender women, so they performed a comprehensive review of the literature that generated some notable findings. One is that that the prevalence of GAHT in the transgender population is still unknown. Some studies put the figure at roughly one in every 12,000 to 13,000 people who identify as transgender. But this is likely an underestimate, the authors claim, and it’s not broken out by sex.

Questions over GAHT

Similarly, little is known about the impact of GAHT on the likelihood of developing prostate cancer, the team reported. Prostate cancer rates do appear to be lower among transgender women than they are among cisgender men (men whose gender identify matches their sex at birth). For instance, one study found just a single case of prostate cancer among 2,306 transgender women receiving routine health care at a clinic in Amsterdam, Holland, between 1975 and 2006. Another study, also from Holland, detected six cases of prostate cancer among 2,281 transgender women over 17 years, which again is less than the comparable rate among cisgender men.

But the interpretation of these rates is limited by the fact that transgender women often experience barriers to care. Nearly a third of them live in poverty, and many avoid the health system for fear of mistreatment. Some scientists suspect that estrogen given during GAHT may somehow contribute to prostate cancer development when given over long durations. However, more confirmatory evidence is needed. Worryingly, one study found that survival among transgender women with prostate cancer is worse than it is in cisgender men with the disease, yet that research lacked data on GAHT use.

Interpreting PSA values for specific populations

Dr. Nik-Ahd’s team was especially concerned about the lack of guideline recommendations for prostate-specific antigen (PSA) screening in the transgender population. None of the available guidelines worldwide mention transgender women, and the PSA cutoff of 4 nanograms per milliliter (ng/mL) of blood — which raises suspicions for prostate cancer — is specific to cisgender men. PSA levels ordinarily plummet in people taking GAHT, so the limit for what’s considered normal in transgender women should be capped at 1.0 ng/mL, the researchers propose. In the absence of more specific guidance, they also recommend that people meeting age criteria for PSA screening get tested before starting on GAHT, in order to obtain a baseline value.

Many doctors are already familiar with other common drugs that alter PSA values — in this case with screening implications for cisgender men, points out Dr. Heidi Rayala, a urologist affiliated with Beth Israel Deaconess Medical Center in Boston, and a member of the Harvard Medical School Annual Report on Prostate Diseases editorial board. For instance, PSA values drop by half in men taking finasteride or dutasteride for hair loss (or to shrink an enlarged prostate). “Doctors take extra care when interpreting PSA in cisgender men who take these drugs,” she says. “The same care needs to be taken in interpreting PSA values in transgender women. And there needs to be broader education on this topic for both primary care doctors as well as the transgender community.

Dr. Nik-Ahd agrees. “Future research should aim to understand baseline PSA values for those on gender-affirming hormones, and to understand how to navigate some of the psychosocial barriers around PSA screening so as to not stigmatize transgender patients,” she says.

About the Author

Charlie Schmidt, Editor, Harvard Medical School Annual Report on Prostate Diseases

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

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