Eat, Drink, and Be Healthy

by Walter Willett

  A meta-analysis of thirty randomized controlled trials that included 82,000 participants showed that getting extra folic acid from supplements decreased the risk of stroke by 10 percent and the risk of any kind of cardiovascular disease by 4 percent. The benefit was biggest among participants with low folate levels to start.9

  Folate’s key role in building DNA means that it plays a role in cell division and so may help prevent cancer as well. Getting enough folic acid seems to decrease the risk of developing colon cancer and possibly breast cancer. One of the interesting findings we have seen in the Nurses’ Health Study—and that other researchers have seen in other populations—is that folic acid may temper the increase in breast cancer seen in women who average more than one alcoholic drink a day.10 The same is true for colon cancer, another disease that is more common among alcohol drinkers than nondrinkers. People who drink alcohol and get 600 micrograms or more of folic acid each day aren’t at increased risk, however.11 This makes sense, because alcohol blocks the absorption of folic acid and also inactivates circulating folic acid.

  Recommended intake: Adult women and men should get at least 400 micrograms a day of folate/folic acid, ideally from food.

  Good food sources: There are many excellent sources of folate and folic acid (see the table on page 211). Most breakfast cereals are now fortified with folic acid and contain 100 micrograms per serving; some contain as much as 400 micrograms, a full day’s requirement. Green leafy vegetables are an excellent source of folate, with beans, lentils, chickpeas, and black beans delivering 20 to 50 micrograms per serving. Oranges and orange juice are other good sources of folate and folic acid. Whole grains are good sources of folate, but processed grains aren’t: folate is lost when grains are refined. As mentioned earlier, fortified refined flour adds about 100 micrograms per day to the average American’s diet, but this varies widely depending on how much refined flour an individual consumes.

  Homocysteine and the Heart

  * * *

  Homocysteine is a byproduct of protein digestion. High levels of it in the bloodstream have been linked to heart disease. Three B vitamins—B6, B12, and folate/folic acid—help recycle homocysteine into harmless, protein-building amino acids called methionine and cystathionine. A diet low in one or more of these vitamins leads to higher homocysteine levels and possibly an increased risk of heart disease and stroke. So getting enough folate/folic acid, vitamin B6, and vitamin B12 may be one more nutritional strategy for protecting yourself against heart disease, stroke, and other forms of cardiovascular disease.

  Even if homocysteine isn’t a direct cause of cardiovascular disease, there’s strong evidence to show that getting enough folic acid and possibly other B vitamins cuts the risk of developing this all-too-common condition.

  Figure 20. Homocysteine and the Three Bs. Three B vitamins—vitamin B6, vitamin B12, and folic acid—help the body turn the protein breakdown product homocysteine into less damaging substances. A buildup of homocysteine could be involved in the artery-clogging process known as atherosclerosis.

  Safety: In animal studies, too little folic acid increases the development of cancer. But so does too much. These animal studies have raised a red flag that a similar effect may occur in humans. This has delayed fortification of flour with folic acid in many countries. In the United States, when folic acid fortification became mandatory in 1998, a small increase in colon cancer followed. However, this coincided with a large increase in the use of colonoscopy, which created an artificial increase in colorectal cancer due to detection of lurking tumors. Reassuringly, there was no increase in deaths from colorectal cancer. Instead, that has steadily declined, probably due in part to both colonoscopy and increased intake of folic acid. The tolerable upper limit for folic acid is 1,000 micrograms a day from supplements.

  CAROTENOIDS: BETA-CAROTENE, LYCOPENE, AND MORE

  Plants make hundreds of different pigments. Some trap sunlight and transform it into chemical energy; others prevent the sun’s rays from damaging the plant. Some pigments advertise ripeness to the animals that will disperse the plant’s seeds; others warn hungry critters that the plant contains nasty or poisonous chemicals.

  One large group of plant pigments is the carotenoid family. You probably know a number of carotenoids by sight if not by name. Beta-carotene is the pigment that gives carrots and sweet potatoes their characteristic orange hues. Lycopene is responsible for the tempting red of a juicy tomato or the cool pink of watermelon flesh. Other well-studied carotenoids include lutein and zeaxanthin (the only carotenoids found in the eye’s retina), alpha-carotene, and beta-cryptoxanthin. These six are just a drop in the bucket of the five hundred or so known carotenoids. Beta-carotene and alpha-carotene are vitamins, both forms of vitamin A; most others are not considered vitamins.

  The human body uses carotenoids for two main functions: some of them are turned into vitamin A, and others act as powerful and adaptable antioxidants. Other important functions are waiting to be discovered.

  There’s a widely held notion that carotenoids in general, and several carotenoids in particular, prevent a variety of chronic ills. Dozens of observational studies show that people who choose to eat more fruits and vegetables high in carotenoids have less cardiovascular disease; cancers of the prostate, lung, stomach, colon, breast, cervix, and pancreas; memory loss; multiple sclerosis; and cataract formation and macular degeneration. Unfortunately, randomized trials in which volunteers have consumed specific antioxidants have not (so far) shown much reduction in risk of developing cancer or cardiovascular disease.

  This seeming contradiction could be the result of weak studies that set up false hopes. It could mean that you need the whole complex net of antioxidants delivered by fruits and vegetables, not just one or two specific ones. It could mean that we just haven’t tested the right carotenoid or carotenoid combination for long enough periods. It could also mean that many of those in the study are already consuming adequate amounts of carotenoids.

  After several decades of research, some true benefits for specific carotenoids are strongly supported. There is good evidence that lutein and zeaxanthin are important for preventing macular degeneration and cataract. And a strong report from the Harvard-based Physicians’ Health Study is reviving interest in beta-carotene as a supplement that can help preserve memory and thinking skills into old age (see “New Hope for Multivitamins” on page 236).

  VITAMIN C

  Do you reach for an orange, a glass of orange juice, or a vitamin C tablet at the first sign of a cold? If so, you aren’t alone. It’s an impulse nudged by Vitamin C and the Common Cold, written in 1970 by Linus Pauling, a double Nobel laureate and self-proclaimed champion of vitamin C. Pauling fervently believed that megadoses of vitamin C—between 1,000 and 2,000 milligrams a day (the amount in twelve to twenty-four oranges!) could prevent and abort colds . . . and could do the same for cancer.

  There’s no question that vitamin C plays a role in fighting infection. It helps make collagen, a substance you need for healthy bones, ligaments, teeth, gums, and blood vessels. It helps make several hormones and chemical messengers used in the brain and nerves. It is also a potent antioxidant that can neutralize the tissue-damaging free radicals that assail the body.

  We’ve known for almost two hundred years that citrus fruits prevent scurvy, a once feared disease that killed an estimated 2 million sailors between 1500 and 1800. It wasn’t until 1932, though, that vitamin C was discovered and found to be the active agent in citrus fruits responsible for fighting scurvy.

  Can high doses of vitamin C fight other diseases? Not the common cold: study after study has failed to prove Pauling’s proposition.13 There’s a smattering of evidence that a little extra vitamin C, about the amount found in a typical multivitamin, at the very beginning of a cold might relieve some symptoms, but there’s no support for megadoses. Prevent cancer and heart disease? The evidence is thin and most studies don’t support that. It’s possible that some extra vitamin C might h
elp prevent cataract formation, but here again more research is needed.

  Recommended intake: The current recommended dietary allowance for vitamin C is 75 milligrams a day for women and 90 milligrams a day for men, with an extra 35 milligrams a day for smokers. As the evidence continues to unfold, I suggest getting 200 to 300 milligrams of vitamin C a day. This is easy to do with a good diet and a standard multivitamin pill.

  Good food sources: Good food sources of vitamin C are citrus fruits and juices, berries, green and red peppers, tomatoes, broccoli, and spinach. Many breakfast cereals are also fortified with vitamin C.

  Safety: There seems to be no harm in getting more, although the latest dietary reference intake report on vitamin C cautions against taking megadoses above 2,000 milligrams a day. But there’s really no need to overdo vitamin C. Your body can’t store much of it (about 1,500 to 3,000 milligrams at a time) and flushes out the excess in bright yellow urine. What’s more, there’s no evidence that big daily doses help. At high concentrations, vitamin C can switch roles and act like a free radical instead of an antioxidant and theoretically could cause the things you may be trying to prevent.

  VITAMIN D

  We are only now beginning to understand the widespread importance of vitamin D. Once known solely for its ability to help the body absorb and hold on to calcium and phosphorous, vitamin D is turning out to be far more versatile and important.

  Vitamin D isn’t exactly a vitamin. Instead it is a hormone made by a rather unusual gland: your skin. Sunlight striking the skin turns a cousin of cholesterol into pre–vitamin D. This is first processed by the liver and then activated by the kidneys or by cells in the heart, immune system, breast, or prostate.

  Although calcium usually gets all the credit for building bones and preventing fractures, vitamin D should get equal billing. It helps on several levels. Vitamin D ensures that calcium and phosphorus (another integral part of bone) are absorbed as they pass through the digestive system. It signals the kidneys to hang on to these minerals so they aren’t lost in urine. It also inhibits the breakdown of bone and boosts bone-building activity.

  In chapter ten, I mentioned that many women who break a hip have an unsuspected vitamin D deficiency. A growing body of research suggests that many Americans could reduce bone loss by getting extra vitamin D. In fact, doing this more effectively reduces hip and wrist fractures in older women and men than does dramatically increasing calcium consumption.

  There are other reasons to get more vitamin D besides strong bones. Here are a few of them: fewer falls, probably less cancer, as well as the possibilities of better blood pressure, a stronger heart, fewer serious infections, reduced likelihood of asthma, and protection against multiple sclerosis.

  • Stronger muscles and fewer falls. Vitamin D signals muscle cells to make new protein. This may strengthen muscle and improve stability, especially in older people. A pooled analysis of ten randomized trials of vitamin D supplementation (200 to 1,000 IU) showed that it resulted in 14 percent fewer falls than calcium alone or a placebo.14 However, too much vitamin D may tip the balance in the other direction. A randomized clinical trial published in 2016 showed that 60,000 IU of vitamin D given in a single dose each month increased falls compared to 24,000 IU per month.15 Falls are the single largest cause of injuries among older people. They can lead to permanent disability, loss of independence, and even death. So determining the right dose of vitamin D is important.

  • Cancer. In test tubes, vitamin D strongly inhibits the growth and reproduction of a variety of cancer cells, including those from the breast, ovary, colon, prostate, and brain. This means vitamin D can stifle new cancer cells much like a blanket on a small fire, snuffing out their progression to life-threatening tumors. The evidence is particularly strong for colorectal cancer. With remarkable consistency, men and women with higher blood levels of vitamin D have lower future risks of this serious cancer.16

  • Heart disease. Several small studies suggest that getting more vitamin D, especially from sunlight, helps lower blood pressure. Several small and short-term trials suggest that vitamin D supplements may have some benefit for preventing heart failure—the inability of the heart to meet the body’s needs for blood and oxygen—but not for preventing heart attack or stroke.17

  • Multiple sclerosis. This disease, which occurs when the immune system mistakenly attacks the protective covering of nerves, is more common in countries farther from the equator, which have lower vitamin D levels. In mice, vitamin D prevents or slows the course of experimentally induced multiple sclerosis; it likely does the same thing in humans. In a study that used stored blood samples provided by 7 million men and women when they entered the U.S. armed forces, those with the highest levels of vitamin D in their blood had a 60 percent lower risk of later developing multiple sclerosis.18 In the Nurses’ Health Study, women who took vitamin D supplements were almost half as likely to develop multiple sclerosis as those who didn’t take vitamin D.19 Also, variations in DNA that result in lower levels of vitamin D strongly predict higher risk of this disease.20 The weight of evidence from these various lines of investigation makes a strong case that adequate vitamin D intake will reduce the risk of multiple sclerosis.

  People who can bask in strong sunlight for a few minutes on most days year-round make plenty of vitamin D. That rules out everyone living north of San Francisco, Denver, Indianapolis, and Philadelphia. During the winter months, the amount of ultraviolet light hitting those northern regions (above 40 degrees latitude) isn’t enough to generate vitamin D. It also rules out people who work inside all day and can’t, or don’t, get out for a fifteen-minute walk when the sun is high in the sky; those whose ability to get outside is limited by arthritis or other chronic diseases; and those who live in nursing homes. In other words, millions of people. Two in three Americans between the ages of fifty-one and seventy fall short of what appears to be the optimal level for vitamin D; older people fare even worse, with nine in ten not meeting this level.

  The darker your skin color, the less effectively your body converts sunlight to vitamin D. In a national survey of Americans, black men and women had about half the vitamin D in their blood as their white counterparts.

  The gradual loss of skin pigmentation as humans migrated northward from the so-called cradle of mankind in Africa was probably an evolutionary adaptation to capture more vitamin D from less sunlight. Yet even the near-complete loss of melanin in the skin in very fair Scandinavians isn’t enough to compensate for the lack of strong sunlight, and thus many have low levels of vitamin D. Northern populations have compensated for this by eating plenty of fatty fish, including the vitamin D–rich livers, or taking cod-liver oil. The loss of such traditions may have major impacts on health.

  Unless you live in the southern United States and get out in the sun most days of the week, or eat very large amounts of fish, the only way to reliably achieve the recommended intake of vitamin D is by taking a supplement. Many multiple vitamins contain only 400 IU. Don’t take two a day, because the extra preformed vitamin A may work against vitamin D. Some calcium supplements contain 220 IU of vitamin D along with 500 milligrams of calcium. So one option for women is to take a standard multiple vitamin and two of these calcium pills, but this is more calcium than most women need. I don’t recommend this for men because of the possible connection between high calcium intake and fatal prostate cancer. A standard multivitamin plus a specific vitamin D supplement is another option. Your best bet is to find a multivitamin that delivers 800 to 1,000 IU of vitamin D. Some of these are on the market, and I hope more will be coming soon.

  Recommended intake: The current recommended dietary allowance for vitamin D for men is 600 IU a day (15 micrograms) after age nineteen. It’s the same for women, except they should get 800 IU a day (20 micrograms) after age seventy. The optimal intake of vitamin D remains a topic of debate. I believe that the evidence shows that most people need to get at least 800 to 1,000 IU a day of vitamin D, and possibly 2,000 to
3,000 IU to get the full benefits of this vitamin. People who have darker skin or spend little time in the sun may need even more. In a 2014 study among African Americans living in Boston, increasing the daily intake to 4,000 IU offered metabolic benefits, although it did not examine actual disease risks.21 Ongoing research will, I trust, give more precise guidance about the best daily dose of vitamin D.

  You don’t need regular blood tests for vitamin D, because the level varies over time and we just don’t know the right target. Instead, it’s best to take a vitamin D supplement to make sure you have enough on board.

  Good food sources: Very few foods naturally contain vitamin D. Cold-water fish such as mackerel, salmon, sardines, and bluefish contain good doses of this fat-soluble vitamin; their livers contain very high levels. Most of what we get from food comes from dairy products (which by law must be fortified with vitamin D); vitamin-fortified breakfast cereals; and eggs from hens that are fed vitamin D.

  Safety: You can’t get too much vitamin D from the sun, but you can from supplements. The National Academy of Medicine says that intakes of vitamin D up to 4,000 IU a day are safe. As a fat-soluble vitamin, D can be stored and can reach very high levels in the body. Too much vitamin D can cause nonspecific symptoms such as anorexia and weight loss. It can also raise blood levels of calcium, which can, over the long term, damage the heart, blood vessels, and kidneys. In the Women’s Health Initiative, use of a calcium and vitamin D supplement boosted the risk of developing kidney stones by 17 percent. This was most likely due to the calcium, as the amount of vitamin D in the supplement was low.22

  VITAMIN E

  The vitamin E story is much like the one for beta-carotene: early curiosity, intriguing laboratory results, and promising observational studies that documented a relationship between vitamin E and decreased risk of heart disease followed by disappointing clinical trials in which large groups of volunteers—mostly people already diagnosed with heart disease—were randomized to take either vitamin E or placebo pills. There are some important differences between the two stories, though. Most people get between 5 and 15 IU of vitamin E a day. Yet it takes several hundred IU a day to significantly block the oxidation of LDL cholesterol, and the biggest inhibition happens at about 800 IU a day.