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How to eat veggies: both raw and cooked A growing body of research shows that when it comes to vegetables, it's not only how much we eat, but how we prepare them, that determines the amount of phytochemicals, vitamins and other nutrients that enter our bodies. The benefits of eating vegetables are gargantuan. Numerous studies show that people who consume lots of vegetables have lower rates of heart disease, hypertension, diabetes, eye problems and even cancer. The latest dietary guidelines call for five to 13 servings - that is 2 to 6 cups a day. For a person who maintains her weight on a 2,000- calorie-a-day diet, this translates into nine servings, or 4 1/2 cups a day, according to the Harvard School of Public Health. But how should they be served? Surprisingly, raw and plain vegetables are not always best. In The British Journal of Nutrition next month, researchers will report a study involving 198 Germans who strictly adhered to a raw food diet, meaning that 95 percent of their total food intake came from raw food. They had normal levels of vitamin A and relatively high levels of beta carotene. But they fell short when it came to lycopene, a carotenoid found in tomatoes and other red foods that is one of the most potent antioxidants. Nearly 80 percent of them had plasma lycopene levels below average. "There is a misperception that raw foods are always going to be better," says Steven Clinton, a nutrition researcher and professor of internal medicine in the medical oncology division at Ohio State University. "For vegetables, a lot of times a little bit of cooking and a little bit of processing actually can be helpful." The amount and type of nutrients that eventually end up in the vegetables are affected by a number of factors before they reach the plate, including where and how they were grown, processed and stored before being bought. Then, it's up to you. No single cooking or preparation method is best. Water-soluble nutrients like vitamins C and B and a group of nutrients called polyphenolics are often lost in processing. For instance, studies show that after six months, frozen cherries have lost as much as 50 percent of anthocyanins, the healthful compounds found in the pigment of red and blue fruits and vegetables. Fresh spinach loses 64 percent of its vitamin C after cooking. Canned peas and carrots lose 85 percent to 95 percent of their vitamin C, according to data compiled by the University of California, Davis. Fat-soluble compounds like vitamins A, D, E and K and the antioxidant compounds called carotenoids are less likely to leach out in water. Cooking also breaks down the thick cell walls of plants, releasing the contents for the body to use. That is why processed tomato products have higher lycopene content than fresh tomatoes. In January, a report in The Journal of Agriculture and Food Chemistry concluded that overall, boiling was better for carrots, zucchini and broccoli than steaming, frying or serving them raw. Frying was by far the worst. Still, there were tradeoffs. Boiling carrots, for example, significantly increased carotenoid levels but resulted in the complete loss of polyphenols compared with raw carrots. That report did not look at the effects of microwaving, but a March 2007 study in The Journal of Food Science looked at the effects of boiling, steaming, microwaving and pressure cooking on the nutrients in broccoli. Steaming and boiling caused a 22 percent to 34 percent loss of vitamin C. Microwaved and pressure-cooked vegetables retained 90 percent of their vitamin C. What accompanies the vegetables can also be important. Studies at Ohio State measured blood levels of subjects who ate servings of salsa and salads. When the salsa or salad was served with fat-rich avocados or full-fat salad dressing, the diners absorbed as much as four times more lycopene, seven times more lutein and 18 times the beta carotene than those who had their vegetables plain or with low- fat dressing. Fat can also improve the taste of vegetables, meaning that people will eat more of them. This month, The American Journal of Preventive Medicine reported on 1,500 teenagers interviewed in high school and about four years later on their eating habits. In the teenage years, many factors influenced the intake of fruits and vegetables. By the time the study subjects were 20, the sole factor that influenced fruit and vegetable consumption was taste. Young adults were not eating vegetables because they didn't like the taste. Because nutrient content and taste can vary so widely depending on the cooking method and how a vegetable is prepared, the main lesson is to eat a variety of vegetables prepared in a variety of ways. Dr. Cinque's comments: I agree that the way to maximize the benefits from vegetables is to eat some of them raw and some of them cooked. Start with a large raw vegetable salad, with plenty of leafy greens, and eat it every day. And if you want to have two salads a day, that would be fine too, unless you are underweight, in which case one is definitely enough. You can't be loading up on salad and expect to gain weight. Then have steamed vegetables, and make sure that at least one of them is from the cruciferous family, such as broccoli, brussel sprouts, or kale. In general, I am not in favor of cooking fruits at all because it does not improve their flavor nor their nutrition. The exception is the tomato, if you want to consider it a fruit, since it has been demonstrated repeatedly that more lycopene gets absorbed from cooked tomatoes than raw ones. Also, I think that eating nuts and oilseeds raw is very important, and that's why I go to the the trouble of ordering raw almonds. But it is only an assumption that eating every last article of food raw is nutritionally superior. Based on what? Where's the proof? In truth, it is just a naturalistic argument: animals do no cooking so neither should we. But I don't consider that argument valid. Humans have been cooking for a very long time- more than a million years- which means since before we technically became human; and it's unclear what would have happened to the human race if we hadn't started cooking. Let me give you a parallel argument: we humans are unique in that we enclose our feet within shoes to walk around. Whether or not it is natural to do so, the fact is that our feet are tender and delicate, compared to those of animals, and so we need the protection, not only on man-made surfaces, but on many natural ones as well. And it's not as though we don't suffer ill-effects from wearing shoes because we most certainly do. But, it's still the most practical alternative, and we just have to find ways to minimize the problems from shoe-wearing. And it's the same with cooking. Our digestive tracts are tender and delicate, relatively speaking, and therefore, the softening and tenderizing of vegetables (some of them) by cooking is a very practial alternative. We're not built like cows. And although we're related to gorillas, we can't eat like they do either. Remember, the bottom line in nutrition is how many nutrients you absorb- not just how many you ingest. It's one thing to emphasize raw foods- which I think is an excellent idea-but to say that we have to eat every last article of food, 100 percent of our diet, raw is extremely extreme. It's naturalistic philosophy run amuk. E-mail to a friend Previous Article Next Article |
