Wed, 13 Aug 2003

Are raw vegetables much healthier?

Melissa Southern-Garcia, Dietitian, Jakarta,

Dear Melissa,

Is it true that it's healthier to eat vegetables raw instead of cooking them? Thanks.

-- Ray

Dear Ray,

You have touched on a very interesting question that gives me the opportunity to dispel yet another myth about food and nutrition.

I have always been a proponent of eating plenty of fruits and vegetables as they are excellent sources of vitamins, minerals, fire?, and antioxidants, which have been linked to numerous health benefits. Therefore, it makes sense that when we eat our fruits and vegetables, we make sure we prepare them in a way that allows our bodies to take advantage of these substances to their fullest.

There is an entire movement devoted to eating only raw foods and in fact, in many large cities, restaurants that serve only raw foods have become trendy.

This love for raw food has extended well beyond just fruits and vegetables to include meats and starchy foods. The latter trend has developed due to studies that indicate that cooking grains and starchy foods such as potatoes at high temperatures -- particularly baking or frying in high fat -- can create possible carcinogens, or cancer-causing compounds called acrylamides.

However, the research on whether or not acrylamide is actually linked to disease in humans is still in its early stages. The wise approach would be to avoid foods that are high in fat or fried -- something I recommend for many other reasons as well including preventing heart disease and obesity.

A trend towards eating raw meat and fish, completely separate from cuisines such as sashimi, sushi, tartare or carpaccio; has developed due to studies indicating that grilling, frying, or broiling high-protein items such as meat or fish can cause other potentially dangerous substances called heterocyclic amines.

However, there are sensible ways to lessen or prevent the formation of these compounds. One of the main culprits of heterocyclic amine formation is fat dripping onto the hot surface of the grill or stove. Choosing lean cuts of meat and trimming off the visible fat are easy ways to avoid this problem.

Marinating meat and fish in an acidic substance such as lemon or any kind of fruit juice before cooking helps prevent up to 85 percent formation of heterocyclic amines. The key factor is the antioxidant action of vitamin C in the marinade.

It should also be pointed out that only skilled, trained chefs should prepare and serve raw meat and only high quality meat and fish that has been properly handled at all levels of distribution should be used. Persons who are at risk such as children, the elderly, pregnant women or anyone with weakened immune systems should avoid raw meat and fish.

In short, eating uncooked meat and seafood can increase your risk of food-borne illness, commonly known as food poisoning.

So what about fruits and vegetables?

Proponents of the raw food movement claim that cooking robs fruits and vegetables of their nutritional value. This is true up to a certain point. Some vitamins and minerals are sensitive to high temperatures and can be destroyed with cooking. These include several of the B vitamins like folate and also vitamin C.

Cooking in water further compounds the problem since even more of the vitamins and minerals as well as fiber are lost when they are leached out into the water.

Finally, proponents of raw food also claim cooking destroys many of the natural enzymes found in food which help with digestion and absorption of nutrients. However, even if we eat raw foods, most of those enzymes are killed as soon as they reach the stomach due to the highly acidic environment necessary for digestion to occur.

Losses from boiling can be addressed by using alternate cooking methods such as stir-frying or steaming and by avoiding over-cooking. Vegetables should only be stir-fried or steamed until they are still crisp and bright-colored.

Loss of nutrients due to heat can only be avoided up to a certain point, but when proper cooking methods are used, these losses usually only amount to about 15-30 percent.

Ironically, there are also some benefits to be derived from cooking your vegetables since cooking weakens cell walls and allows the body to extract more of the nutrients that remain after cooking. Cooking also makes for more dense servings since vegetables tend to be high in water content. Half a cup of cooked spinach weighs three times as much as a half cup of raw spinach.

Even accounting for losses during cooking, the half-cup of cooked spinach contains three times as much calcium, iron, and vitamin A. It is also significantly higher in fiber, folate, and vitamin C.

Properly cleaning raw produce to ensure it's safe to eat is a lengthy process which may be difficult to control outside of your home, so one other benefit of eating cooked vegetables is that food safety concerns can be alleviated.

Eating raw food does not necessarily ensure that nutrients won't be lost. In fact, any kind of preparation process, not just cooking, results in some loss of nutrients. Peeling exposes produce to oxygen and causes the break-down of vitamins C and E for example. Chopping and blending may lead to further losses however just as with cooking, these losses are compensated as nutrients become more available when cell walls break down.

Juices still contain some nutrients, but many of the nutrients as well as the fiber are lost when peels and pulp are discarded in the juicing process.

In short, make sure you eat plenty of fruits and vegetables and use a variety of methods to enjoy them: cooked, raw or juiced. Just remember to keep your fruits and vegetables healthy by using proper cooking methods, and accompanying them with healthy dressings, dips, and sauces!