Vitamin E supplements have been tested against heart disease in randomized trials such as the Cambridge Heart Antioxidant Study (CHAOS), the Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardio (known as the GISSI Prevention Trial), and the Heart Outcomes Prevention Evaluation (HOPE). Early results suggested a cardiovascular benefit of taking vitamin E supplements, but most of the later larger studies did not. For example, in the Women’s Health Study, which enrolled relatively healthy middle-aged women, there was no reduction in heart attacks or cancer, among participants assigned to vitamin E, but a significantly lower risk of total cardiovascular mortality was seen23
Much of the research on vitamin E has focused on its activity as an antioxidant. But it also helps reduce the tendency for clots to form in the bloodstream; such clots can trigger a heart attack or stroke. In the Women’s Health Study trial, women taking vitamin E were less likely to have developed serious clots in the legs and lungs, especially those who unknowingly had a genetic predisposition to clot formation.30
It’s hard to say why the results from randomized trials and those from observational studies don’t square. There are multiple potential explanations and they will be grist for future research. With the information we have in hand right now, don’t rely on high doses of vitamin E to protect you against a heart attack, stroke, or cancer.
Another possible benefit of vitamin E is protection against age-related dementia. Some early studies suggested that people who took vitamin E supplements were less likely to develop this common and troubling condition, but those findings haven’t held up in further studies.31 Another possibly promising line of research involves vitamin E and amyotrophic lateral sclerosis (also known as Lou Gehrig’s disease). This rapidly progressive, invariably fatal disease attacks nerve cells responsible for controlling arm, leg, and other so-called voluntary muscles. In a combined analysis of large prospective studies, men and women who used vitamin E supplements for more than five years had about one-third lower risk of developing this disease compared to those who didn’t take vitamin E.32
Antioxidants: More Smoke than Fire?
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On a list of the biggest nutritional buzzwords from the last couple of decades, “antioxidant” would be near the top. Before 1990 this pack of electron-donating compounds was of interest mostly to chemists and food researchers. Today antioxidants are touted in books with titles like The Antioxidant Miracle and Antioxidant Smoothies. They are promoted in herbal pharmacies and mainstream magazines as wonder substances that can prevent cancer, heart disease, memory loss, and cataracts and even reverse the aging process.
The term “antioxidant” refers to these nutrients: vitamin C, vitamin E, beta-carotene and other related carotenoids, the minerals selenium and manganese, glutathione, coenzyme Q10, lipoic acid, flavonoids, phenols, polyphenols, phytoestrogens, and more. In reality, there are probably hundreds of antioxidants in the foods we eat.
These substances guard against the constant attack of free radicals, highly reactive substances constantly generated by oxygen-using reactions such as those needed to burn fats and carbohydrates. Free radicals are present in the air you breathe, the food you eat, and the water you drink. They are plentiful in cigarette smoke, yours or someone else’s. Sunlight hitting your skin or beaming into your eye also generates free radicals.
Free radicals are born missing one or more electrons, so they scavenge them from nearby DNA, important structural or functional proteins, LDL cholesterol particles, and even cell membranes. This can subtly alter the function of these substances or cell parts, or outright damage them. Over time, this damage adds up: free radicals are thought to play roles in cancer, heart disease, arthritis, cataract formation, memory loss, and aging, to name just a few health issues.
Bruce Ames, a noted molecular biologist at the University of California, Berkeley, has estimated that the genetic material in each cell of the human body gets about 10,000 “oxidative hits” a day.24 Multiply this by the several trillion cells in your body and factor in the other cellular components that can be damaged by free radicals and oxidizing agents, and you get an idea of the magnitude of the attack.
Like marines, antioxidants stand ever ready to neutralize free radicals. Deployed strategically throughout all cells and tissues, antioxidants generously, even aggressively, give up electrons to free radicals without turning into electron-scavenging substances themselves.
No single antioxidant can do the work of the whole crowd. Taking high-dose beta-carotene or vitamin E pills is like listening to a single violin play a Mozart symphony: you get a little something but not the full, glorious effect. It’s also possible that the imbalance that occurs by taking too much of any one antioxidant may be like listening to an orchestra in which one section is playing at eardrum-shattering volume.
While some initial studies were generally bullish on the benefits of antioxidants against heart disease and cancer, little or no benefit has been seen in most large, randomized controlled trials of high-dose antioxidant supplements, and harm was seen in some trials.
James Watson, who won a Nobel Prize for helping work out the structure of DNA, has even suggested that taking in loads of antioxidants from supplements may actually contribute to cancer. Free radicals help kill cancer cells. Taking an excess of antioxidants from supplements, he argues, destroys this natural anticancer activity and may prevent cancer drugs from destroying cancer cells.25
Two bright spots for antioxidant vitamin supplements are for eye health and brain health.
Cataracts form when damage from sunlight and free radicals clouds the clear proteins that make up the lens of the eye, much as heat clouds the clear protein in egg white. Cataracts are the leading cause of vision problems among older people. They affect more than 20 million Americans over age forty; more than half of those over age eighty have cataracts. At least 1 million cataract extraction operations are done in the United States each year, at a cost of more than $3 billion.
In the six-year Age-Related Eye Disease Study (AREDS), a combination of vitamin C, vitamin E, beta-carotene, and zinc offered some protection against the development of advanced age-related macular degeneration, but not cataracts, in people who were at high risk of the disease.26 Lutein, a naturally occurring carotenoid found in green, leafy vegetables such as spinach and kale, and other phytonutrients may also protect vision. A new trial of the AREDS supplement regimen added lutein and the closely related carotenoid zeaxanthin.27 Overall, lutein and zeaxanthin modestly reduced risk of advanced macular degeneration, but a large reduction in risk was seen among those who had low blood levels of lutein and zeaxanthin at the beginning of the study. Together with results from long-term cohort studies,28 there is strong reason to get adequate lutein in our diets, but this can be achieved by including green leafy vegetables on a daily basis without supplements.
Results from the Physicians’ Health Study II randomized trial showed that a beta-carotene supplement taken for more than ten years helped preserve memory and thinking skills.29
Bottom line: A diet naturally rich in antioxidants—meaning a diet rich in whole vegetables, fruits, grains, nuts, and other plant-based foods—will help protect you against heart disease, cancer, dementia, eye disease, and other chronic conditions. This is currently the most reliable way to get your antioxidants, along with the other beneficial components these foods contain. By relying on pills from a bottle, you run the risk of missing some important nutrients. That said, I think we should keep an open mind about other carotenoids. Supplements may be a more reliable way for many people—especially those not eating plenty of fruits and vegetables—to get healthy doses of carotenoids, Stay tuned.
Recommended intake: The current recommended dietary allowance for vitamin E is 15 milligrams a day of vitamin E from food, the equivalent of 22 IU from natural-source vitamin E or 33 IU of the synthetic form. The evidence is clear that taking more than this in supplements doesn’t help people with heart disease. Whether it h
elps otherwise healthy individuals is up in the air.
Good food sources: Some of the best sources of vitamin E are nuts, seeds, and vegetable oils such as soybean, canola, and corn oil. Green leafy vegetables and fortified cereals are also significant sources.
Safety: One meta-analysis of vitamin E trials showed that the use of high-dose vitamin E (more than 400 IU a day) might slightly increase death rates.33 Headlines screamed, “Vitamin E Death Risk,” but I don’t believe this is so. Most of the trials in the analysis included only volunteers with heart disease. An exhaustive review of vitamin E by the Institute of Medicine concluded that vitamin E is safe up to doses of 1,000 milligrams a day (1,500 IU of natural-source vitamin E).34 The only documented harmful effect of too much vitamin E is the worsening of a rare eye problem known as retinitis pigmentosa. One thing to be aware of: If you take a blood thinner, talk with your health care providers before starting to take a vitamin E supplement, since it can reduce the blood’s ability to clot.
VITAMIN K
This fat-soluble vitamin helps make six of the thirteen proteins needed for blood clotting. Recent research showing that some of these same proteins are involved in building bone suggests another possible function: maintaining bone health. Low levels of circulating vitamin K have been linked with low bone density. A report from the Nurses’ Health Study suggests that women who don’t get much vitamin K are twice as likely to break a hip as women who get plenty. We estimated that eating a serving of lettuce or other green leafy vegetables a day cut the risk of hip fracture in half when compared with eating one serving a week.
According to conventional wisdom, most adults get enough vitamin K because it is found in so many foods, especially green leafy vegetables and commonly used cooking oils. That wasn’t entirely backed up by a survey of vitamin K in the American diet, which showed average intakes hovering slightly under the recommended daily intake.35 It also revealed that a fair number of Americans, particularly young ones, aren’t getting the vitamin K that they need, mainly because they don’t eat enough green leafy vegetables.
Recommended intake: The recommended dietary allowance for vitamin K is 90 micrograms a day for adult women and 120 micrograms a day for adult men.
Good food sources: In the United States, the most common sources of vitamin K are green leafy vegetables such as spinach, broccoli, lettuce, kale, and collard and turnip greens, as well as vegetable oils. Natto, a traditional Japanese food made by fermenting soybeans, is also rich in vitamin K.
Safety: Vitamin K from foods is very safe. The Institute of Medicine has not set a tolerable upper limit because of its low potential for toxicity. That said, people who take warfarin (Coumadin) to prevent blood clots must be careful with their vitamin K intake, because this vitamin nullifies the activity of warfarin. That doesn’t mean striking green leafy vegetables from your diet. Instead, try to eat the same amount of them every day.
CALCIUM
The role of calcium, and how much of it you need, is covered in detail in chapter ten. In a nutshell, calcium is essential for health, but the high levels recommended by the Dietary Guidelines for Americans and the National Academy of Medicine aren’t necessary for good bone or overall health.
Recommended intake: The current recommended daily intakes for adults are 1,000 milligrams a day for women up to age fifty and 1,200 milligrams a day after that; and 1,000 milligrams a day for men up to age seventy and 1,200 milligrams a day after that. Given the inconsistent and sometimes misleading evidence on calcium and bone health, this is probably more than enough. You certainly need some calcium each day—it’s a good idea to get at least 500 milligrams—but 1,200 milligrams is probably more than you need, especially for men.
Good food sources: Contrary to the catchy milk-mustache campaign, dairy products aren’t the only, or the best, way to get plenty of calcium. Other good food sources of calcium include sardines, tofu, canned salmon, turnip greens and kale, and fortified soymilk or orange juice. If you feel that you aren’t getting enough calcium in your diet and want to get more, try a calcium supplement. They contain no calories and no saturated fat and are far cheaper than several daily servings of dairy products. Chewable calcium-based antacids such as Tums are a cheap and efficient way to get calcium. A calcium supplement that also includes vitamin D is even better.
Safety: A high level of calcium in the blood (hypercalcemia) can cause problems ranging from kidney stones to hardening of the arteries. Although this can happen as a result of very high calcium intake, it is usually caused by overactivity of the parathyroid glands or cancer. Consuming too much calcium can cause constipation and may interfere with the absorption of iron and zinc. As I describe in chapter ten, current evidence links higher intake of calcium from supplements with increased risk of kidney stones and prostate cancer. Calcium from foods, though, may reduce the risk of kidney stones by binding oxalate, a compound found in rhubarb, beets, spinach, nuts, tea, and a variety of chocolate and soy products, that has been linked to the formation of kidney stones.
IRON
You need iron mainly to help your red blood cells ferry oxygen from your lungs to your tissues. Iron-poor blood can leave a person pale, fatigued, and mentally sluggish. Lack of iron stunts the growth and development of children and can damage long-term thinking skills.
Iron deficiency isn’t a major problem in the United States. But it is elsewhere: half of the earth’s inhabitants don’t get enough iron.
Most Americans get plenty of iron from eating meat and iron-fortified grain and other products. However, infants and women in their childbearing years often don’t get enough iron. That’s why infant formulas contain extra iron, why pregnant women are encouraged to take a multivitamin supplement with extra iron, and why women are urged to get enough iron from their diets or from supplements while they are menstruating.
There are two types of iron in food. Heme iron, which travels around the bloodstream in the oxygen-carrying protein hemoglobin, comes from red meat, poultry, and fish. Non-heme iron comes from fruits, vegetables, grains, nuts, and other plants. The body absorbs heme iron more easily than it absorbs non-heme iron, even when we already have enough iron aboard.
People who need extra iron are often advised to eat lean red meat. Meat is certainly a great source of this mineral, but it is also high in calories, saturated fat, and cholesterol. Another drawback is that your body doesn’t regulate the absorption of iron from meat as carefully as it does from grains, fruits, vegetables, and supplements. If your iron storehouse is well stocked, the kind of iron in plants and supplements passes through your body. But the iron in meat slides under this mineral radar and adds to the stockpile even if your body already has plenty of iron.
That could be a problem if, as some research has shown, iron acts as a powerful generator of free radicals. A controversial “iron hypothesis” for heart disease was first floated in 1981. It suggested that the more iron you store, the higher your risk of heart disease. However, the evidence supporting this idea was weak to begin with and has gotten weaker with further studies. A similar hypothesis has been raised for cancer, and the jury is still out on that too.
Recommended intake: The current daily target for iron is 8 milligrams for men, 18 milligrams for women up until menopause, and then 8 milligrams after that. Healthy men and postmenopausal women rarely run low on iron. In fact, low iron levels in these groups are usually a tip-off of internal bleeding.
Good food sources: Good sources of heme iron include red meat, poultry, and seafood. Nuts, beans, vegetables, and fortified grain products such as breakfast cereal and bread provide non-heme iron.
Safety: If your intestinal function is normal, it’s hard to get too much iron from food. However, getting big doses from supplements can irritate the stomach and cause constipation, abdominal pain, nausea, and vomiting. A large overdose can cause organ failure, coma, and even death. I recommend that men and postmenopausal women choose a supplement that doesn’t contain any iron. Women in their ch
ildbearing years shouldn’t take a supplement with more than the recommended amount of iron without talking with a health care provider.
MAGNESIUM
This common element is essential for hundreds of biological processes, from building substances such as DNA and proteins from scratch to releasing the energy in food, contracting muscles, and sending signals along nerves. Your heart, muscle, nerve, bone, reproductive, and other cells all depend on having enough magnesium.
In the United States, relatively few people are truly magnesium deficient. That said, Americans get less magnesium today than they did a century ago. Fewer fruits and vegetables in the diet are one reason; fewer whole grains are another. White bread and white rice, for example, contain four times less magnesium than whole wheat bread and brown rice.
Few adults meet the recommended dietary allowance for magnesium, with average intakes hovering about 100 milligrams below these targets among whites and even lower among blacks and Hispanics. Less-than-healthy magnesium levels are common among older people, who may not be getting enough in their diets or who may have trouble absorbing what they get. Magnesium deficiency can also be a problem for people taking diuretics (a type of high-blood-pressure medication) and for heavy drinkers. Diabetes speeds the loss of magnesium. So does drinking alcohol or caffeinated beverages. Caffeinated soft drinks represent a double whammy, because the phosphates found in carbonated drinks also wash magnesium from the system.
Eat, Drink, and Be Healthy Page 29