Healthy Eating: To cook, or not to cook

Is it better to eat vegetables raw? Or cooked? This debate has been raging on for years, but now there may be a few new helpful answers.

By KATHRYN RUBIN
tomatoes311 (photo credit: MCT)
tomatoes311
(photo credit: MCT)
Should you steam your greens tonight? Or is it healthier to leave them raw? Are there more cancer-fighting antioxidants in stewed or raw tomatoes? And what about carrots?
The debate over whether it is healthier to cook your vegetables or leave them raw has been argued for years. One camp claims that cooking (i.e steaming, roasting or grilling) diminishes and even destroys all the vegetable’s nutritional content, while others disagree, maintaining that cooking does little to the nutritional value and may even increase it. So who wins? Find out now as four vegetables go under the “cook, or not too cook” knife.
Tomatoes
It is lycopene that gives tomatoes their bright fire engine hue. However, apart from turning tomatoes the color of a stop sign, this carotenoid also acts a potent anti-oxidant that has long been linked with reducing the risk of cancer and heart disease. But what happens to lycopene when you heat tomatoes? Contrary to what you may think, the lycopene content actually increases, exponentially in fact.
Research has found that the heating processing increases the lycopene in tomatoes, as well as helps the body absorb more of this powerful antioxidant. In fact, one study (conducted at the University of Cornell) found that after heating tomatoes to 88°C, the lycopene content rose by over 50 percent in just two minutes and more than doubled in just over a quarter of an hour.
Unfortunately though, cooking tomatoes does reduce the vitamin C content. Most people consume enough of this important vitamin, but if you are worried about not getting enough Vitamin C, mix and match cooked and fresh tomatoes. Also don’t forget to drizzle on some olive oil, as this monounsaturated fat helps the body absorb up to seven times more lycopene than it normally would.
Broccoli
Broccoli typically earns top spots on many “superfood” lists. And why shouldn’t it?  Not only does it provide a healthy dose of essential vitamins and minerals, but it is also rich in many other disease fighting compounds. Unlike the tomato, where cooking increases its anti- cancer “superpowers”, studies have found that cooking broccoli may reduce its cancer-fighting abilities. 
Studies have found that heating this green vegetable reduces its sulforaphane, a compound that is thought to help prevent the formation of precancerous cells, as well as stomach ulcers. In fact, according to a study published in the Journal of Agricultural and Food Chemistry, cooking broccoli can decrease the sulforaphane by nearly 90%. Heating this green also decreases Vitamin C levels, as well as calcium and iron.
Carrots
As most of us have heard, carrots are good for our eyes because they are loaded with Vitamin A, well beta-carotene to be exact. The carotenoid responsible for this vegetable’s vivacious tone, beta-carotene is converted (inside the body) into Vitamin A - a vitamin not only needed for proper vision, but also reproduction, bone growth, and a healthy immune system.
It also acts as a powerful antioxidant, fighting off harmful free radicals that can cause cellular damage. While heating carrots breaks down the vitamin C – a vitamin that easily degrades when exposed to water and heat – cooked carrots offer significantly more beta-carotene than raw ones.
Spinach
A dark leafy green vegetable, spinach is rich in many essential nutrients, such as calcium, iron and magnesium.
It contains high levels of calcium, and at a rate of 122mg per 1/2 cup it is considered an excellent non-dairy source of this bone healthy mineral. However, spinach also contains oxalic acid, a substance that binds with the calcium and as a result prevents the body from properly absorbing it. This compound also prevents the body from properly absorbing the iron found in this leafy green. Cooking spinach does reduce the oxalic acid and therefore allows the body to fully absorb the calcium and iron.
While there are some definite differences between cooked and raw spinach, be careful when comparing their nutritional contents side by side, as cooking spinach significantly reduces its size, so one cup raw is not comparable to one cup cooked. However, whatever your preference, make sure to squeeze some lemon (or another citrus fruit) on top, as the Vitamin C in these fruits helps make plant based iron more absorbable by the body.
The verdict
There is no clear-cut answer as to the “to cook or not to cook” question, as it varies depending on the vegetable and even the specific nutrient. Cooking can increase certain health beneficial nutrients, in particular antioxidants, while decreasing and even destroying specific vitamins. At the same time it is also important to pay attention to the cooking method. Studies have found that steaming helps to retain more Vitamin B and C, and other water-soluble nutrients than boiling; while microwaving and baking also results in lower “nutrition” losses. Above all it is important to remember that long cooking times and high temperatures will be more likely to destroy heat-sensitive nutrients, particularly those water-soluble vitamins.