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By now, most people know they should be eating more vegetables. But are there ways to get more from the vegetables you already eat?

When it comes to vegetables, it’s not only how much we eat, but how we prepare them, that influences the amount of phytochemicals, vitamins and other nutrients that enter our body.

The benefits are significant. People who consume lots of vegetables have lower rates of heart disease, hypertension, diabetes, eye problems and even cancer. 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% 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-pigmented vegetables that is one of the most potent antioxidants.

“There is a misperception that raw foods are always going to be better,” says Steven K. Clinton, a nutrition researcher and professor of internal medicine at Ohio State University. “For fruits and 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 nutrients called polyphenolics are often lost in processing.

Studies show that after six months, frozen cherries have lost as much as 50% of anthocyanins, the healthful compounds found in the pigment of red and blue fruits and vegetables. Fresh spinach loses 64% of its vitamin C after cooking. Canned peas and carrots lose 85 - 95% of their vitamin C, according to 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 over all, 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 significantly increased measurable 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 - 34% loss of vitamin C. Microwaved and pressure-cooked vegetables retained 90% 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 4 times more lycopene, 7 times more lutein and 18 times the beta carotene than those who had their vegetables plain or with low-fat dressing.

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.

Source

Labels: healthy cooking, healthy diet, NY Times, vegetables, Vitamins