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8 tips for your health and the planet’s

Suggestions for how to be healthy and “green.”

Aside from pesticide usage and a few other issues, most of us haven’t worried much about the connections between health issues and the environment. For our health, we work on our waistlines and fret over our cholesterol levels. For the environment, we recycle and maybe drive a fuel-efficient car.

But because of accelerating climate change and the havoc it could wreak, it’s not so easy to send environmentalism off into its own separate compartment these days. In February, the Intergovernmental Panel on Climate Change said the evidence for global warming is “unequivocal.” Everything we do now can be measured for its effect on the environment — and greenhouse gas emissions in particular.

There’s always danger in doling out “what you can do” advice. Bite-size solutions sometimes trivialize larger problems. We end up doing easy things because they make us feel good, not because they do much good. Policies set in Washington and elsewhere are far more important.

Still, there’s a place for individual responsibility — and certainly for voting with our dollars. “The real answers are not going to come from individual action, but I do think that individual actions can have ripple effects,” says Dr. Paul Epstein, associate director of the Harvard Medical School’s Center for Health and the Global Environment. “We can educate our friends and colleagues and work to change the practices of employers, schools, even places of worship. As individuals, I think we can set in motion new patterns of sustainable consumption and help create markets for clean, efficient technologies.”

We thought we’d bring personal and environmental health together and provide eight “green” health tips.

1. Walk or bike to work. At a bare minimum we’re supposed to get 20–30 minutes of exercise most days of the week. The Institute of Medicine says that isn’t really enough and recommends a full hour of moderately intense activity a day (biking and walking at a 4-mile-per-hour clip meet the moderately intense standard). But we’re a nation of drivers, not walkers or bikers, and almost every driving statistic you can think of is headed in the direction of a hotter planet. The average fuel economy of new cars has declined since 1988 because of the popularity of minivans and SUVs. Vehicle miles traveled per person have grown twice as fast as the American population in recent years. Households with four or more cars now outnumber those with no car. And the proportion of commuters who carpool or walk or bike to work has slid since 1980, while the percentage of those driving alone has crept up from 64% to 76%. Could there be a better good-for-you, good-for-the-planet twofer than the walking or biking commute? Combining exercise and a commute builds exercise into your day, which means you don’t have to summon extra willpower, to say nothing of time, to go to the gym. If you live too far away, consider walking or biking to public transportation or driving only part of the way.

2. Go to bed early. Americans weigh more and are sleeping less. Average daily sleep time has decreased from about nine hours a century ago to about seven now. Epidemiologic studies have identified a correlation between short sleep and being overweight or obese. Hormones may be why: Lack of sleep depresses the levels of leptin, the hormone that tells the brain we’re full, and increases ghrelin, the hormone that makes us hungry. Meanwhile, all the lights, televisions, computers, microwave ovens, and music players that help keep us up at night use electricity, most of it generated by burning coal and natural gas. Household use of electricity has increased by over 50% since the early 1980s. By turning in earlier, we’ll dial down our appetite for kilowatts and maybe food.

3. Turn down the heat and the air conditioning. Humans, like other mammals and birds, control their body temperature by continually adjusting their metabolisms. When the air is cool, metabolism revs up to produce more heat. When it’s hot, sweating and other responses also burn up extra energy. But when air temperatures are in the thermoneutral zone (TNZ) — which for humans with their clothes on tends to be in the mid-70s — our metabolisms don’t have to work so hard to maintain body temperature, and we burn fewer calories. We’re spending more time in our TNZs these days because of heating and — particularly — air conditioning. Some experts believe all that time in the comfort zone is contributing to the obesity epidemic. The amount of energy used to heat American homes has actually declined a little bit since 1978, the result of better insulation, more efficient furnaces, and, yes, warmer winter temperatures because of global warming. But the amount of electricity used to cool homes has almost doubled in that span. So by adjusting your thermostat, you may keep your metabolism from getting lazy and also use less of another kind of energy.

4. Eat fish, but the right kind. Fish needs no introduction as a healthful food, especially in these pages. As the main food source of long-chain omega-3s, it’s good for your heart and probably your brain. But the sterling health credentials have some environmental tarnish. Some species are contaminated with pollutants — mercury and PCBs are the main concern. Stocks of others have been dangerously depleted by too much fishing. Some groups are working to steer consumers to species that are in good supply. The Marine Stewardship Council, a British group, certifies fisheries as sustainable. Environmental Defense, a New York-based environmental group, has posted a helpful list of best and worst fish choices at www.oceansalive.org. The Blue Ocean Institute has a useful guide at www.blueocean.org/seafood. But making the right “eco-choice” does involve some homework — maybe a bit too much for many of us. Take swordfish. It’s on every list of mercury-contaminated fish but it’s also a good source of omega-3s. Once scarce, populations are almost fully recovered in the North Atlantic, according to the Oceans Alive Web site, and the United States has strict rules for swordfish fishing in the Pacific, where fishing practices threaten endangered sea turtles. But foreign fleets don’t have to follow those rules, so not only would you need to know which ocean your swordfish came from to make an environmentally sensitive choice, you’d also need to know the origin of the fleet that caught it.

5. Switch to energy-saving light bulbs, but don’t throw them in the regular trash. Those curlicue compact fluorescent light bulbs that Home Depot wants you to buy are the real deal. They use two-thirds less energy than a regular incandescent bulb and last up to 10 times longer. The Natural Resources Defense Council, a mainstream environmental group, estimates that each compact bulb keeps half a ton of carbon dioxide out of the air over its lifetime. But all fluorescent bulbs need mercury to work, and the compact versions contain about five milligrams of the metal. That’s not much — an old-fashioned home thermometer contains a hundred times that amount — but if you throw them out in the regular trash, that mercury may end up in the air or water, and, by climbing the food chain, in the fish on your plate. The environmentally good deed you performed by buying the light bulbs would be completely undone by the way you got rid of them. Call your town or city’s public works department to find out where you can dispose of fluorescent light bulbs safely. A corporate-sponsored Web site, www.earth911.org, lists businesses and local governments that handle household hazardous waste.

6. Learn a lesson from palm oil and good intentions gone awry. As the tide turns against trans fat, food manufacturers are scrambling for substitutes. Palm oil has emerged as a candidate. Some varieties of trans fat-free Oreos are made with palm oil and another trans fat replacement, high-oleic canola oil. In Europe, palm oil has also been touted as an environmentally friendly renewable “biofuel” alternative to fossil fuels like coal and gas. But to satisfy the growing demand for the tropical oil, huge tracts of Southeast Asian rainforest are being cut down and planted with palm trees. Farmers are also draining and burning huge swathes of peatlands, which help offset greenhouse emissions by soaking up carbon. The New York Times described palm oil as a green fairy tale that is beginning to look more like an environmental nightmare. Palm oil is an improvement over trans fat as far as personal health is concerned, but that’s not saying much. About half of the fat molecules in palm oil are saturated, and saturated fat increases cholesterol levels. The moral of the story is not to be dazzled by alternatives in either the environmental or personal health realms. They, too, may have dark sides. As best we can, we need to look before we leap.

7. Eat local fruits and vegetables. By all means, eat fruits and vegetables. Good health depends on it. But Michael Pollan’s book The Omnivore’s Dilemma raises some questions about the means by which we get them. Flying kiwis in from New Zealand and grapes up from Chile is an energy-intensive way to fulfill the fruit-and-vegetable imperative. It’s possible only if energy is cheap, and cheap energy in this fossil fuel-era of ours means tons of greenhouse gas emissions and global warming. The Pollan book has inspired the buzzword “food miles” — how far food has been transported to reach our plates. “Local and sustainable” is flaunted as a virtue on restaurant menus. Some economists take issue with putting “local” on a pedestal. Their point: Global trade may entail high transportation costs, but it also organizes food production to occur where it’s most efficient. Besides, isn’t it wonderful to have fresh produce out of season? The reasonable middle ground is to give some preference to locally grown food. Is that shiny Granny Smith apple from New Zealand worth the greenhouse emissions when a Macintosh from a nearby orchard might do? And shopping at farmers’ markets is a good way to reduce your food mileage. You’ll be even “greener” if you walk or bike there.

8. Get behind the greening of hospitals and medical buildings. American hospitals are on a building spree that rivals the post-World War II boom. Hospitals aren’t getting bigger — the number of beds is declining. But they’re getting more deluxe, with additional private rooms and more sophisticated technology. Health economists worry that these gold-plated facilities will put further pressure on health care costs. In some cases, though, hospitals are seizing the opportunity to build “greener” buildings, which have attributes that may also improve the health and well-being of patients. Building a hospital or nursing home with more natural light not only saves energy but may also enhance the mood of patients (and staff!) and keep them more oriented. Some hospitals are taking steps to improve indoor air quality with proper ventilation and use of materials that don’t emit volatile organic compounds. As individuals we can’t go build a green hospital the way we can buy an energy-efficient car. But we can encourage their construction by writing a letter (hospitals are very public relations conscious) and supporting policies and programs that encourage energy-efficient construction.

All rights reserved.
Harvard Health Letter
www.health.harvard.edu/health
Volume 32 - Number 6 - April 2007

Selenium and prostate cancer

Selenium is a mineral with a long and interesting history. Discovered in 1817 and named after the moon goddess, it was considered a poison during much of the 19th century. In the 20th century, selenium found a use in many industries, from ceramics to rubber to agriculture; imagine life without selenium and you’ll conjure up a world without photocopiers. No longer considered toxic, selenium is the active ingredient in many therapeutic shampoos. But the greatest potential for selenium is as a supplement to reduce the risk of prostate cancer.

Only time will tell if that potential will be fulfilled, but it makes selenium a timely topic for health-conscious men.

Meet the mineral

Selenium is found in the earth’s crust, but its concentration is lower than gold’s. Selenium finds its way into plants, then works its way up the food chain. But since the selenium content of soil varies widely from place to place, the selenium content of food varies and is hard to predict. In general, the best sources are whole grains, tomatoes and other vegetables, seafood, nuts (particularly Brazil nuts), garlic, and onions; meat and poultry also provide significant amounts.

Selenium is essential for human health, but since only tiny amounts are required, it is classified as a trace mineral. The Recommended Dietary Allowance for adult men is 55 micrograms. Daily amounts as high as 400 micrograms appear entirely safe; beyond that, supplements can cause hair loss, nausea, or diarrhea.

Selenium and the heart

Scientists don’t fully understand how selenium functions in the body, but one important role is its antioxidant activity. As a result, doctors have wondered if it might help fight atherosclerosis. Indeed, in 1982, a Finnish study reported that people with low blood selenium levels had an increased risk for developing coronary artery disease, and a 1991 study of Finnish men linked low selenium levels to atherosclerosis of the carotid artery. But in 1995, the Harvard Physicians’ Health Study cast considerable doubt on the hypothesis that selenium protects the heart. In fact, in American men, high selenium levels were associated with a very slight increase in heart attack risk. And a 2006 study reported that taking selenium supplements had no effect on cardiovascular disease.

Researchers are now concentrating on selenium and cancer. The first glimmers came from the observation that cancer is less common in parts of the world that have high levels of selenium in the soil. Experiments in test tubes and laboratory animals followed, and many found potential anticancer activities for selenium. But a 1996 publication really put selenium on the map.

The Nutritional Prevention of Cancer Trial

To learn if selenium supplements might reduce the risk of recurrent skin cancer, a team of scientists working at seven American health centers gave either 200 micrograms of selenium or a placebo to 1,312 volunteers with an average age of 63; the participants took their tablets daily for an average of four and a half years. When the results were analyzed in 1996, the researchers were disappointed to learn that there was no difference in the occurrence of skin cancer in the two groups, but they were startled to find that there were 50% fewer cancer deaths in the selenium group. Selenium was linked to a significant reduction in deaths from lung, colon, esophageal, and prostate cancer; protection appeared strongest for prostate cancer, with 63% fewer deaths in the men who took selenium. There were no cases of selenium toxicity. These results were greeted with great interest but also with caution; some doctors felt they were too good to be true, and most stressed the need for further research.

The Nutritional Prevention of Cancer Trial has issued two subsequent reports, which extend the observation period by 25 months, to the end of the trial. The initial hopes that selenium might reduce the incidence of lung and colorectal cancer did not hold up. But the men who received selenium continued to enjoy a 49% lower risk of prostate cancer through a follow-up period that averaged 7.6 years. The apparent protection was strongest in the men with the lowest blood selenium levels before starting the supplements and in men with PSA levels below 4.0 ng/ml.

The Harvard studies

The Nutritional Prevention of Cancer Trial is the only randomized clinical trial — the gold standard of evaluation — of selenium supplements that has been completed. Still, that trial did not settle the selenium question. For one thing, it designated skin cancer as its primary end point; prostate cancer was just a secondary end point. For another, every study, however well done, requires confirmation, particularly when the results are surprising. Indeed, a large trial of selenium for prostate cancer prevention is already under way. But until the results are available, scientists have tried to shed light on the issue by performing observational studies to compare the risk of prostate cancer in men with low and high selenium levels.

Just two years after the 1996 report, Harvard’s Health Professionals Follow-up Study weighed in with a study of 33,737 men between the ages of 40 and 75. The researchers did not administer selenium supplements, nor did they measure blood levels of the mineral. Instead, they asked the volunteers to submit toenail clippings at the start of the study. The clippings were analyzed for selenium concentration, which reflects the selenium intake over the many months during which nails are formed.

When the scientists tracked the men for six years, they found that the men with the highest selenium levels at the start of the study had a 65% lower incidence of advanced prostate cancer than the men with the lowest levels, even after taking other prostate cancer risk factors into account. The Harvard team calculated that a daily consumption of 159 micrograms of selenium would prove protective.

A second Harvard study followed in 2004. The Physicians’ Health Study collected blood samples in 1982 from 14,916 American doctors who were in good health. Over the next 13 years, the men with the highest initial blood selenium levels had a 48% lower incidence of advanced prostate cancer than those with the lowest levels. Men with high selenium levels who also had elevated PSA levels at the start of the study experienced the additional benefit of a lower risk of early prostate cancer.

Other opinions

The Harvard scientists are not the only ones who can measure selenium levels. Researchers worldwide have used nail clippings, blood samples, and dietary questionnaires to evaluate selenium consumption and the risk of prostate cancer. The populations have included men living in regions with low, moderate, and high soil selenium levels. Some studies were short-term; others followed their subjects for more than six years. One report evaluated more than 58,000 men, another just 150. Some studies took other prostate cancer risk factors into account, others did not. And while some studies included early prostate cancers, others focused on advanced cases or prostate cancer deaths.

With so many variables, it’s not surprising that the results varied widely, with some studies reporting substantial protection from selenium while others found no benefit. But when researchers from Canada performed a meta-analysis of 16 individual trials, they found that a moderate intake of selenium was linked to a 26% reduction in the risk of developing prostate cancer. The protection appeared greater with higher selenium levels and was most pronounced for advanced cancers.

Tomorrow and today

It’s a familiar refrain: The only way to sort out an unsettled area of research is to perform additional studies. In the case of selenium, a definitive randomized clinical trial is already in progress. Sponsored by the National Cancer Institute, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) will evaluate the effects of selenium and vitamin E, singly or in combination, in 32,400 men.

SELECT will provide much-needed answers about selenium and another controversial supplement, vitamin E. But the results won’t be announced for years. In the meantime, what’s a man to do?

The choice is yours. It’s far too early to recommend a supplement for all men, but it’s certainly important to recommend a healthful diet that will provide good amounts of the mineral. And if you are attracted to supplements, selenium is a reasonable choice. The best dose and form of the mineral are not known, but since the 1996 trial used 200 micrograms a day, that dose seems appropriate. Similarly, it’s wise to use an organic form of the mineral, such as the selenomethionine that the NPC administered in selenized yeast.

Historians tell us that selenium was named for a goddess, and geologists say that it’s rarer than gold. Soon, doctors will tell us if it’s worth its weight in health or if it’s a false idol.

All rights reserved.
Harvard Men’s Health Watch
www.health.harvard.edu/men
Volume 11 - Number 8 - March 2007

Heart disease in women: A better way to predict cardiovascular risk

We know how important cholesterol levels are, but what about inflammation?

Since the 1980s, we’ve made enormous progress in understanding cardiovascular disease (CVD) in women. Recent findings help explain why CVD (heart disease and stroke) has been more difficult to diagnose and treat in women than in men: Our heart attack symptoms are often different; standard diagnostic tests don’t predict our heart problems as reliably; and we may not get as much benefit from such treatments as angioplasty and bypass surgery.

We’ve also learned much more about the biology of cardiovascular disease. It’s not just a matter of cholesterol clogging the arterial plumbing. Low-level inflammation also contributes to the atherosclerotic plaques that can block blood flow to the heart and brain. In 1997, researchers at Boston’s Brigham and Women’s Hospital found an association between high-sensitivity C-reactive protein (hsCRP) — a marker for inflammation — and the risk of having a heart attack or stroke in healthy men. A test was developed to detect subtle changes in hsCRP, and later research showed that elevated hsCRP also predicted coronary events in women — even when their cholesterol levels and blood pressure were normal.

Despite these advances, the usual models for predicting CVD in women don’t take into account markers of inflammation. A study published in February 2007 proposes a model that incorporates hsCRP and promises greater precision in identifying women at risk.

What’s wrong with the current model?

To determine the risk for cardiovascular disease, clinicians look at factors such as age, cholesterol levels, high blood pressure, smoking status, and diabetes. These factors are incorporated into the Framingham Risk Score, a risk-assessment tool based on the long-term Framingham Heart Study. This tool is used to evaluate the 10-year risk of having a heart attack in both women and men. According to this model, a woman’s risk is regarded as “low” if her score is less than 5%; “low to moderate” if her score is 5% to less than 10%; “moderate to high” if it’s 10% to less than 20%; and “high” if it’s 20% or greater. All high-risk women and some in the moderate-risk groups are advised to modify their diet and other lifestyle factors and possibly take medications that lower LDL “bad” cholesterol.

The trouble is that up to 20% of heart attacks occur in women without any of the major risk factors covered by the Framingham model, partly because that model doesn’t include markers of inflammation or genetic predisposition, both of which are important in CVD.

The moderate-risk groups are the most puzzling. Many doctors suspect that some of these women are actually at high risk and need more intensive treatment, so they have turned to hsCRP testing (which can be performed at the time of cholesterol evaluation) to identify those at higher risk than the Framingham model would suggest. A woman who is at moderate risk by Framingham criteria but has an hsCRP level greater than 3.0 mg/L could actually be at high risk even if her cholesterol levels are normal. (See “Cardiovascular risk by hsCRP level” below.)

Finding a new predictive model

The Brigham and Women’s researchers — led by Dr. Paul Ridker, director of the Center for Cardiovascular Disease Prevention — set out to develop a risk model for women that combined newer risk markers, including hsCRP, with traditional risk factors and family history. They assessed 35 risk factors among 24,558 initially healthy women ages 45 and over who were participating in the Women’s Health Study. The women were followed for 10 years to see who had heart attacks or strokes, needed bypass surgery, or died from CVD.

The researchers used data from two-thirds of the women selected at random to develop a risk model that takes better account of both inflammatory biomarkers and heredity. The new model contains eight risk factors, five of which are familiar from the Framingham Risk Score — age, smoking status, systolic blood pressure, HDL (“good”) cholesterol, and total cholesterol — plus hsCRP, parental history of a heart attack before age 60, and for women who have diabetes, hemoglobin A1c (a measure of blood sugar control).

To test the model, the researchers applied it to the remaining one-third of study participants and found that it was more accurate than the Framingham model. Of the women whose Framingham risk scores placed them at moderate risk, 40% to 50% were reclassified into higher- or lower-risk groups that better matched their actual rate of cardiovascular events. These findings were published in the Feb. 14, 2007, Journal of the American Medical Association.

This model, called the Reynolds Risk Score, could help clinicians target women who could benefit from more aggressive preventive treatment, including diet and exercise, a statin or other cholesterol-lowering medication, and possibly aspirin (which has been shown to reduce the risk of heart attack in women ages 65 and over).

What now?

You can calculate your Reynolds Risk Score at www.reynoldsriskscore.org. The model still needs more testing, as the authors point out. For example, most of the study participants were white professional women; the results might not apply fully to other groups.

The evergreen recommendations for reducing cardiovascular risk haven’t changed: Don’t smoke, actively or passively; control your weight and cholesterol with diet and exercise; and if you have high blood pressure or diabetes, do what’s necessary to get it under control — including appropriate medications. If your cholesterol is normal but you have another major risk factor for cardiovascular disease, it’s worth asking your doctor whether hsCRP testing could help clarify your overall risk.

All rights reserved.
Harvard Women’s Health Watch
www.health.harvard.edu/women
Volume 14 - Number 8 - April 2007

New Start! for exercise

Instead of playing solitaire on your home computer, turn it into a fitness center. The American Heart Association’s Start! program aims to help Americans walk more and eat better. According to the association, every hour of regular exercise buys you two extra hours of life expectancy, even if you don’t become more active until middle age.

The centerpiece of the program is called MyStart! Online (www.americanheart.org/start), a free Web site. You enter what you eat each day and how much you exercise, and the personalized program gives you a summary of your day’s calories in and out. It also offers daily tips for getting more exercise and choosing a more healthful diet, and sends you weekly summaries of your progress, reminders, and encouragement.

Start! is an excellent program if you need some help becoming more active or improving your diet. The program sponsors, two food companies and one large drug maker, don’t influence the program, but you sure see their logos.

All rights reserved.
Harvard Heart Letter
www.health.harvard.edu/heart
Volume 17 - Number 8 - April 2007

Harvard Health Publications e-Newsletter is published monthly by the Harvard Health Publications division of the Harvard Medical School. Copyright © 2007 by the President and Fellows of Harvard College. All rights reserved.

This information is for educational purposes only. For personal medical advice, please contact your physician.

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Medical Disclaimer

Harvard Health Publications
Editor in Chief: Anthony L. Komaroff, M.D.
Publishing Director: Edward H. Coburn

Editors
Harvard Health Letter: Anthony L. Komaroff, M.D., Peter Wehrwein
Harvard Heart Letter: Thomas H. Lee, M.D., P.J. Skerrett
Harvard Men’s Health Watch: Harvey B. Simon, M.D.
Harvard Mental Health Letter: Michael C. Miller, M.D., James Bakalar, J.D.
Harvard Women’s Health Watch: Celeste Robb-Nicholson, M.D., Carolyn Schatz

All editorial board members of Harvard Health Publications are faculty members of Harvard Medical School and doctors at its affiliated hospitals.

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