Eat, Drink, and Be Healthy

by Walter Willett

  Extra calories. Three glasses of whole milk a day add 450 calories to your diet—nearly one-quarter of the average person’s recommended daily intake. Low-fat milk, at 330 calories, adds a bit fewer, but that is still a lot of calories if the main goal is just to get more calcium.

  Extra hormones. Cows make most of the same hormones that humans make. Before farming turned into agribusiness, the hormone levels in milk weren’t an issue. Today, though, they may well be a cause for concern.

  Over the years, dairy cattle have been bred to produce more milk. Since 1960, American Holstein cows’ genetic potential for milk production has increased nearly 7,000 pounds after each birth. Cows today are routinely milked while they are pregnant, which also keeps milk production high. This is great for cattle farmers and milk producers, and it helps keep the price of milk relatively low. But it also means that today’s milk contains a more concentrated mix of hormones than it did years ago. Naturally occurring hormones in milk include estrogens and progestins (so-called female hormones), testosterone and other androgens (so-called male hormones), and insulin-like growth factor, to name just a few. Estrogens and progestins can stimulate breast cancer, testosterone and androgens can promote prostate cancer, and elevated levels of insulin-like growth factor have been linked with breast, prostate, and colon cancer.

  Twenty years ago, my colleagues and I started the Growing Up Today Study. It enrolled more than 25,000 volunteers, all children of women in the Nurses’ Health Study. The participants complete questionnaires on diet, exercise, lifestyle factors, and health, much as their mothers do. In this group, teenage acne, a largely hormone-driven condition, is more common among milk drinkers.12 This is important, because it suggests that the hormones in milk are strong enough or abundant enough to stimulate glandular tissue such as the sebaceous glands in the skin—and possibly mammary glands in the breast. Low-fat and skim milk were more strongly associated with acne than whole milk. That’s probably because removing fat from milk also removes fat-soluble female hormones (estrogens), which tend to counter the acne-driving effects of water-soluble male hormones (androgens), which are left behind.

  Cardiovascular disease. There’s no clear overall connection between consuming milk or other dairy foods and cardiovascular disease. That’s largely because what individuals choose to drink in place of milk influences their overall health. Swapping milk for soda would tip you toward worse health. Swapping it for water, coffee, tea, or water with a splash of fruit juice would benefit your heart and blood vessels by helping cut calories. Eating a peanut butter sandwich instead of a cheese sandwich, or sprinkling nuts on a salad instead of cheese, would reduce your risk of heart disease.

  Prostate cancer. A diet high in milk or dairy foods has been implicated as a risk factor for prostate cancer. In a meta-analysis of thirty-two cohort studies, total dairy foods, milk, low-fat milk, and cheese were all significantly associated with a higher risk of prostate cancer.13 In the most detailed of these studies, the Health Professionals Follow-Up Study, men who drank two or more glasses of milk a day were almost twice as likely to develop advanced or metastatic (spreading) prostate cancer as those who didn’t drink milk at all.

  What’s the connection? Drinking milk increases blood levels of insulin-like growth factor 1, which has been linked to higher risk of prostate cancer. This growth factor is what’s partly responsible for helping children and teens grow taller. It continues to rev up cell multiplication throughout life. But it also stimulates the growth of cancer cells. It’s possible that calcium contributes to the excess risk of prostate cancer too. In the Health Professionals Follow-Up Study, men who took in more than 2,000 milligrams of calcium a day from food and supplements combined were almost three times as likely to develop advanced prostate cancer and more than four times as likely to develop metastatic prostate cancer as men who got less than 500 milligrams a day. Inside the prostate (and elsewhere), the active form of vitamin D may act like a brake on the growth and division of cancer cells. Too much calcium slows or even stops the conversion of inactive vitamin D to its biologically active form and so may rob the body of a natural anticancer mechanism.

  Uterine cancer. Endometrial cancer, the glandular form of cancer affecting the uterus, is strongly promoted by higher estrogen levels, whether they are naturally produced or result from medication. Because of concerns about the naturally occurring hormone levels in milk, we examined milk consumption and risk of this cancer in the Nurses’ Health Study. Overall, there was a modest increase in risk with greater milk consumption. But among postmenopausal women not taking hormone medications, there was a 60 percent higher risk when the women consumed three or more servings of dairy foods per day.14 This finding adds to evidence that the hormone levels in milk are high enough to be biologically important.

  Other cancers. Overall, there is little connection between drinking milk during midlife or later and breast cancer.15 Milk consumption during this period is related to lower risk of colorectal cancer, almost certainly due to its calcium content, but it’s probably better to get calcium from other sources without the extra calories or saturated fat. Drinking milk during childhood and adolescence, however, may be a different story. Children and adolescents who drink a lot of milk tend to be taller than those who don’t drink much milk, and greater height has been linked to an increased risk of cancers of the breast, colon, and other sites.16 Today we have limited data directly relating consumption of milk during childhood and adolescence to risk of cancers during adulthood, but the potential for increases in risk suggest caution over high dairy consumption during these formative years.

  Fractures. As noted in chapter ten, the observation that rates of hip fractures are highest in countries with the greatest milk consumption has been a long-standing paradox. Because of the provocative finding that being tall is associated with increased risks of many cancers, we explored our data on diet during adolescence in the Growing Up Today Study to identify the aspects of diet that were most strongly predictive of gain in height and ultimately attained height. The answer was simple and clear: milk.17 Even the same amount of protein from red meat wasn’t related to gain in height. This shouldn’t be surprising, because milk is beautifully designed to promote the growth of young mammals, including humans. But we are the only mammal to continue to drink milk after we are weaned from our mothers’ milk.

  Twenty years ago my research team published a paper showing that greater height is a strong risk factor for hip fracture, probably because of simple physics: a long stick is easier to break than a shorter stick.18 I hypothesized that high milk consumption during adolescence might actually increase fracture risks later in life by promoting greater height. Fortunately, we had the data to test this idea, because we had asked participants in our adult cohort studies about their milk consumption during high school. As expected, their reported milk consumption during high school correlated with their adult height and in men also predicted higher risk of hip fracture later in life. The risk increased by 9 percent for each additional glass of milk per day.19 Among women, we didn’t see an increase or a decrease in hip fractures with milk consumption, possibly because height is determined earlier in girls than in boys. While these relationships need further examination, the international correlation between milk consumption and fracture risk is a bit less paradoxical than it seems.

  • Environmental issues. As practiced in the United States, it takes a lot of water and energy to make milk. Dairy farming and milk production make significant contributions to the greenhouse gases we generate each year.20 The average American currently consumes about one and a half glasses of milk or equivalent amounts of other dairy foods a day. Getting us up to three a day would appreciably increase the already substantial environmental impact of dairy farming and milk production—from water use and water pollution to the release of greenhouse gases.

  COFFEE

  Here’s something you may not have been expecting to read in a book about food and health: coffee is a remark
ably safe and healthy beverage. Its dubious reputation, which stretches back hundreds of years, is more image than substance.

  Over the years, hundreds of studies have been done on the health effects of coffee. Some early ones linked the bitter brew with breast cancer, pancreatic cancer, and heart disease. Many of these studies had a major flaw: they didn’t take into account a key habit—cigarette smoking—that once went hand in hand with coffee drinking. More carefully controlled studies eventually showed that it was the smoking, not the coffee drinking, that accounted for health problems.

  In fact, a growing body of research shows that coffee may actually be good for a few things that ail us.

  I don’t mean to imply that coffee is as innocuous as water. It isn’t. The caffeine in coffee—and tea, many sodas, and chocolate—has definite drug-like activity. The pep and mild euphoria that caffeine offers is probably why most people drink coffee and other caffeine-containing beverages. As with any drug, there are downsides to caffeine. Too much of it can give you the shakes, make you irritable, and keep you from sleeping. Many people don’t connect their caffeine consumption with trouble sleeping; for some people, consuming any caffeine after lunch can do this. It’s also mildly addictive. Regular caffeine consumers tend to get nasty headaches if they miss their morning dose. Drinking espresso, French press, or other coffee that doesn’t drip through a paper filter can increase your cholesterol a few points. However, when drunk in moderation, coffee is low on the totem pole of health risks and even has a number of benefits. In addition to the gentle pick-me-up, these include the following:

  Lower chance of developing kidney stones. Few afflictions are as painful as kidney stones. These nuggets of calcium, oxalate, and phosphate plague hundreds of thousands of adults each year in the United States alone. Stones form for a variety of reasons: not drinking enough water, chronic urinary tract infections, diseases such as gout, and as a side effect of some medications. Among the men and women of the Health Professionals Follow-Up Study and the Nurses’ Health Study, coffee drinkers were less likely to develop these stones than non–coffee drinkers.21 While we aren’t certain why this is so, caffeine’s activity as a diuretic—a substance that stimulates the body to excrete more water—may help flush out the plumbing and make urine that is too dilute to form kidney stones.

  Lower chance of developing gallstones. Each year, about 1 million Americans are diagnosed with gallstones. These solidified chunks of cholesterol or bile salts can be as small as a grain of sand or as large as a golf ball. People who drink coffee aren’t as prone to gallstones as those who don’t partake of the bean. Exactly how coffee does this isn’t exactly clear. It stimulates the gallbladder to contract regularly, and this churning may stir things up enough to prevent stone formation. Caffeine also interferes with cholesterol crystallization, a key step in stone formation. Some of this reduction in risk may come from the same metabolic benefits of coffee consumption that are related to lower risk of diabetes; gallstone formation has long been known to be part of the metabolic disorder that includes type 2 diabetes.

  Lower risk of type 2 diabetes. Coffee drinking has been associated with lower risk of type 2 diabetes with remarkable consistency. A meta-analysis of twenty-eight studies that included more than 1 million men and women who were followed for an average of eleven years showed a clear connection between coffee drinking and diabetes—and the more coffee, the better.22 Compared with non–coffee drinkers, those who drank a cup a day had an 8 percent lower risk of developing type 2 diabetes, while those drinking six cups a day had a 33 percent lower risk. Similar benefits were seen for both caffeinated and decaffeinated coffee. It is possible that the many potent antioxidants in coffee beans may be responsible.

  Fewer suicides. Coffee and other caffeinated beverages act like mild antidepressants. Findings from the Nurses’ Health Study, the Health Professionals Follow-Up Study, and other cohorts have shown that suicide rates are as much as 50 percent lower among coffee drinkers than they are among non–coffee drinkers.23

  Less Parkinson’s disease. Connections between coffee consumption and protection against Parkinson’s disease, a debilitating neurodegenerative disorder, were first suggested at least fifty years ago. In one of the latest analyses, coffee drinkers were about 25 percent less likely to have developed Parkinson’s disease.24 The benefit peaked at about three cups of coffee a day.

  Lower risk of liver cancer. Drinking more coffee has been consistently connected with lower risk of liver cancer. Substantially lower risks have been seen in Asia, Europe, and the U.S.25 Although this is a relatively rare type of cancer in the U.S., it is more common in other parts of the world.

  Hidden Calories in Coffee Drinks

  * * *

  All by itself, coffee is a very low calorie drink: an 8-ounce cup contains just 2 calories. Adding a spoonful of sugar and a tablespoon of cream turns that into a 50-calorie beverage. Drinking that three times a day is like drinking one sugar-sweetened soda. Without cutting back on calories elsewhere, that could translate into packing on 15 extra pounds over the course of a year.

  The real caloric danger comes from specialty mochas, lattes, and blended coffee drinks. These are often supersized and can contain 500 calories or more. If you like such sweet coffee-based beverages, enjoy them as a treat or dessert, and stick with plain, minimally sweetened coffee for your day-to-day drink.

  Lower overall mortality. Adding up all of these benefits, including a modestly lower risk of heart disease, the overall risk of dying prematurely seems to be slightly lower among those who drink three or more cups of coffee per day—caffeinated or decaffeinated—compared to those who drink little coffee.26

  Bottom line: Given the massive body of research on coffee, it’s safe to say that there aren’t any major health hazards lurking in the murky depths of your cup. In short, when drunk in moderation, coffee is no threat to your health and there are, in fact, some important benefits. Some of these are due to the caffeine, but decaffeinated coffee also appears to contribute to lower risks of type 2 diabetes.

  TEA

  According to Chinese mythology, Emperor Shen Nung discovered how to make tea in 2737 B.C. using the leaves of the plant known today as Camellia sinensis. Nearly 5,000 years later, tea is right up there with coffee as one of the most consumed beverages in the world behind water. The health-promoting properties long ascribed to tea are only now receiving the careful scientific scrutiny they deserve.

  Some of the benefits attributable to coffee also apply to tea, such as a gentle mental and physical pick-me-up and lower risk of kidney stones and gallstones. Some studies have suggested that drinking tea may protect against specific types of cancers, but a massive review found no clear evidence for reductions of common cancers.27 Substances in tea called flavonoids may reduce the risk of cardiovascular disease. In the laboratory, tea and/or flavonoids improve cholesterol levels and artery function, but in real life the evidence is mixed and often contradictory.

  Flavonoids aren’t limited to tea. Other good sources include berries, apples, tomatoes, broccoli, carrots, and onions. It may be necessary to look at all their contributions simultaneously to determine whether or not the current enthusiasm for flavonoids is warranted.

  Bottom line: For now, don’t count on tea to bring any special benefits besides a reduced risk of kidney stones and a pleasant way to begin, enjoy, or end the day.

  ALCOHOL

  Public health campaigns have traditionally urged people to cut back on their drinking or to avoid alcohol altogether. Concerns about alcohol are definitely justified. Alcohol is implicated in about one-third of all deadly traffic accidents. Heavy drinking is a major cause of preventable deaths in the United States. It contributes to liver disease, a variety of cancers, high blood pressure, so-called bleeding strokes, and a progressive weakening of the heart and other muscles. Too much alcohol can dissolve the best of intentions and the closest relationships.

  Alcohol in moderation, though, can have benefits. A drink
before a meal can improve digestion or offer a soothing respite at the end of a stressful day, and the occasional drink with friends can be a social tonic. These physical and psychic effects may improve health and well-being. Well-documented benefits exist for most adults who are middle-aged or older.

  Drinking alcohol helps raise levels of HDL, the protective form of cholesterol, and also reduces the formation of clots that can block arteries in the heart, neck, and brain and ultimately cause heart attacks and the most common kind of stroke. There is good evidence that these and other effects of moderate alcohol consumption translate into protection against heart disease and ischemic strokes, and much evidence that it protects against diabetes and gallstones. Keep in mind that these benefits are almost exclusively for (and mostly harm) younger individuals.

  What does moderate alcohol drinking actually mean? That’s a tricky question and a topic that is the focus of intense research. For men, study after study has shown that men who have one or two alcoholic drinks a day are 30 to 40 percent less likely to have heart attacks than men who don’t drink alcohol at all. That’s about the same reduction in risk seen with the powerful cholesterol-lowering drugs known as statins. For men with diabetes, who are at very high risk of developing heart disease, a drink or two a day has similar benefits. More than two drinks a day further increases heart and stroke protection but also increases the chances that the dark side of alcohol will emerge (see Figure 18).