Foods you should eat to prevent disease, plus expert advice on supplements and fad diets.
Cancer
Take this fruit and eat it! You'll be doing your heart and your midsection a favor.
Fruits? Veggies? Carbs? Leading nutrition researcher Walter Willett explains what you should fork up (and push aside) to cut your risk of cancer, heart disease, type 2 diabetes, and more.
Our expert, Walter Willett, MD, PhD, is the chairman of the Department of Nutrition at the Harvard School of Public Health. Since 1976, he's directed the Nurses' Health Study dietary investigation, tracking the food, lifestyle diaries, and health records of 121,000 nurses, plus another 116,000 younger nurses who joined the study in 1986. It's the biggest, longest-running national research program, and has yielded dozens of findings, from the link between trans fats and heart disease to the new respect for whole-grain foods. Author of Eat, Drink, and Be Healthy (Free Press, 2002), he's taken on the USDA to change the food pyramid and has successfully lobbied food companies to get the trans fats out of your food.
Q. In the nearly 30 years you've been involved with the Nurses' Health Study, what have you learned that we can use to improve our health?
A. What you eat matters. Even more than the number of calories you consume. That's become clear in our data in the Nurses' Health Study in ways I didn't even anticipate at the beginning.
With heart disease, for example, in the late '70s, we were really focused on cholesterol and saturated fat. But it's turned out that these are really a small part of the picture.
Instead, trans fat [the solid, partially hydrogenated fat found in fried foods, some margarines, and baked goods] is a far more important risk factor for heart disease. So is eating an excess of refined carbohydrates and sugar. And, in a twist, eating unsaturated fats, particularly the omega-6 and omega-3 polyunsaturated types, can substantially reduce the risk of heart disease as well as type 2 diabetes.
Q. Are there links between our diets and the kind of cancers we tend to get?
A. The most important nutrition-related factor with cancers is excess weight. That wasn't appreciated or understood 10 years ago. After quitting smoking, weight control is the next most important thing you can do to keep your cancer risk low.
Eating a diet high in fruits and vegetables won't protect you from cancer. But for heart disease, fruits and vegetables do turn out to be beneficial, so it's still good to eat them. There is quite good evidence that eating lots of red meat and, particularly, processed meat, may boost your risk of colon cancer. Inadequate folic acid is also related to colon cancer and probably breast cancer, particularly in those people who are moderate drinkers.
But the top line is weight: We see that the risk and death rates of breast cancer in the U.S. could be roughly cut in half if women didn't gain weight during midlife.
Obesity, Weight Loss, and Carbs
Q. Is obesity truly a health crisis among middle-aged women?
A. I prefer phrasing it as a healthy weight-control issue rather than an obesity issue. The word obesity tends to stigmatize the extremely overweight person. And it's not just the extremely overweight person who's at high risk; it's the average person in the United States, who tends to be just a few pounds overweight, who is fueling the increasing level of adverse health outcomes.
As a country, we need to find a healthier way to live than we have now, where weight gain starts in childhood and continues through our entire life. It's better to start early, but you can still benefit by losing a few pounds at age 50 or 60 or even 70.
Q. So it's absolutely not acceptable to gain weight as you age?
A. That's my point. What we consider to be the typical increase with age, that gradual pound-or-two-a-year creep, can add up to a substantial health risk in a relatively short period of time.
The period between 20 and 55 is when many people put on most of their weight. Being obese can shorten your life by up to eight years. You need to pay increasing attention to physical activity and your diet as you get older. Fitting into your college jeans is a good standard, but even if you can't get into them, staying as close to that size as you can is a good goal.
Q. Is dieting the answer? Which diets really work?
A. Every diet works in the short run. The real challenge is to find a way of eating that is satisfying and sustainable over the long term. Aiming for a weight loss you can maintain is much better than going on a plan that loses you lots of pounds quickly. For most people a diet in the middle of the road, one that's neither extremely low-fat nor extremely low-carbohydrate, is probably optimal. The South Beach Diet is moderate in the way I'm talking about, but the Atkins Diet has been moving in that direction, too. We've seen a lot of evolution in the Atkins Diet from its original "eat all the butter, sausage, and red meat you like." The latest book backed away from that and toward healthier sources of protein and fat, as well as allowing more vegetables.
But one thing the original Atkins did do quite successfully is make people aware of adverse consequences of overeating carbohydrates, what nutritionists technically call a high-glycemic load. By cutting back on the carbohydrates, particularly refined ones, many dieters have found it easier to control their weight, reducing their heart disease risk and type 2 diabetes risk, too.
Q. Should we all be counting our carbs?
A. It doesn't make sense for a woman to be adding up grams of carbohydrates or even grams of fat on a daily basis. The important thing is to look at the quality of the carbohydrates and fats you're eating, keep an eye on the scales, and adjust up or down accordingly.
If weight control is a problem, many people find that controlling their intake of carbohydrates allows them to control their caloric intake easily, so they can lose the extra weight.
Q. But carbohydrates make up the whole base of the USDA food pyramid. What's your feeling on the pyramid?
A. It's too simple a visual and doesn't promote a healthy diet. The current pyramid, suggesting eight to 11 servings a day of bread, cereal, pasta, and rice at the bottom, with "sparing" consumption of fats at the apex, just isn't healthy.
But rather than blaming the USDA for the pyramid, my No. 1 criticism is directed at the inertia in the mainstream nutrition community. There has been such strong, almost religious, belief in the idea that fat is bad and carbohydrates are good. That is just not correct.
Calcium and Other Supplements
Q. With all the talk about carbs, both good and bad, it's easy to forget that our diets supply vital minerals and vitamins. But what's the most reliable source -- foods or supplements?
A. It really depends on the nutrient. As you age, vitamin B12 from food is less well absorbed by the body, so supplementation makes sense. If you don't eat lots of fortified foods (like Total cereal), you should take a multivitamin to ensure that you get adequate folic acid. Vitamin D is also difficult to get from your diet alone. Newer studies suggest that the majority of Americans would benefit from vitamin D, and this will mainly need to come from supplements. The RDA for vitamin D of 400 IU is almost certainly too low; 800 or 1,000 IU would be better for those over 40, and it is possible that even more might be helpful. But for now, until further studies are done, I would not suggest taking more than 1,000 IU as a regular supplement.
Q. Of course, we need to take a daily calcium supplement, right?
A. Not necessarily. You do need some calcium, but the exact amount is not clear. The United Kingdom recently reviewed their RDAs for this mineral, and they came up with 700 mg per day for everybody over 19, which is very different from the US RDA, which goes up to 1,200 mg for women over 50.
As a rough estimate, an average healthy diet gives you about 300 mg of calcium. Add one serving of dairy, like a glass of milk, and you get about another 400 mg, for a daily total of 700 mg. That's probably most of the benefit there is to be gained from calcium.
Women should not feel obligated to drink milk if they don't like it. And if they're not taking in any dairy foods, it's reasonable for them to take a calcium supplement to add maybe 500 to 1,000 mg, which would have no downside.
Q. But doesn't calcium help to prevent bone fractures?
A. Reducing the rate of fractures is the main justification given for high dairy consumption or high calcium supplement intake. But the evidence to support this doesn't exist. And, in fact, all the large studies that have looked at this topic have shown no benefit in terms of fracture reduction. And there are possible adverse consequences of high dairy consumption that are not yet totally proven, but are worrisome. We have seen some evidence of elevated risks of ovarian cancer and prostate cancer in several studies now. This area is one of the most unsettled scientifically; we are actively engaged in researching this.
But for now, if you really want to lower your fracture risk, I recommend taking more vitamin D -- it's likely to do more than calcium, because it helps your body absorb and use calcium. A large percentage of the U.S. population is already short on it. In addition to supplements, regular exercise, both cardio and strength training, is also key to building and maintaining bone strength. We have really strong evidence there.
Q. The headlines on vitamin E have been both for and against supplements. Where do you stand?
A. Taking a vitamin E supplement is prudent, since it's very inexpensive and, from what we can see, safe. For most people in midlife, it is reasonable to take 400 IU a day. In terms of protection against heart disease and Alzheimer's, there is a very good possibility of benefit, but no clear evidence as yet. But there doesn't seem to be any harm to taking it, either.
Originally published in MORE magazine, October 2004.
