The World's Healthiest Cooking

Q: The World's Healthiest Cooking

## Dried beans (especially red kidney beans) In raw form, beans can contain excessively high amounts of a potentially toxic substance called phytohemagglutinin. This substance is classified as a lectin glycoprotein, and in sufficiently high amounts it has been shown to disrupt cellular metabolism. The amount of this toxin in beans is usually measured in terms of hemagglutinating units, or hau. In their raw form, red kidney beans can contain 20,000 to 70,000 hau. This number drops down to 200 t

Dried beans (especially red kidney beans)

In raw form, beans can contain excessively high amounts of a potentially toxic substance called phytohemagglutinin. This substance is classified as a lectin glycoprotein, and in sufficiently high amounts it has been shown to disrupt cellular metabolism.

The amount of this toxin in beans is usually measured in terms of hemagglutinating units, or hau. In their raw form, red kidney beans can contain 20,000 to 70,000 hau. This number drops down to 200 to 400 hau with fully cooked red beans.

White kidney beans start off with about 1/3rd less hemagglutinin than reds. Other beans, like broad beans (also called fava beans) contain only 5 to 10% the amount that red kidney beans contain. Soybeans are also in this lower category of hemagglutinin content.

In some studies of soybean cooking, researchers have actually arrived at optimal cooking time and temperature recommendations based on decreases in hemagglutinin and other potentially toxic substances. In these studies, optimal time and temperature was found to be 120 minutes at 140°C (284°F), or 30 minutes at 160°C (320°F).

The most common cooking method, however, would be overnight soaking of the beans, discarding the water, then immersion in boiling water, followed by simmering for 2-3 hours or until tender.

Grains

Phytic acid is a naturally-occurring substance in grains that can partially block the availability of the grain minerals, including iron and zinc. The processing and cooking of grains lowers their phytic acid content, often by more than 50%. The sprouting of raw grains also lowers their phytic acid content. To minimize the mineral-blocking effects of phytic acid and maximize mineral availability, grains should be sprouted or cooked rather than eaten raw.

Eggs

Two substances in raw eggs have been shown to block nutrient availability. Conalbumin is a protein that can bind together with iron and block its availability. Avidin is a second egg protein that can bind together with biotin (a B-vitamin) and make it unavailable.

The cooking of eggs helps denature both of these proteins, and can increase the availability of both iron and biotin from eggs. Of course, another reason for cooking eggs involves health safety. The U.S. Centers for Disease Control and Prevention estimate that 1 of every 20,000 eggs may be contaminated with the bacterium Salmonella, which is actually passed from the infected hen to the egg before the shell is formed.

Are there any foods that I should always avoid heating?

This question is more difficult to answer with a simple “yes” or “no,” but there is increasing research evidence against the heating of fats and oils, particularly at high heats (used in stove-top frying) or prolonged medium heats (like stove-top sautéeing for 15 minutes).

The heating of fats and oils makes them lose their natural properties; they become oxidized and altered in structure. This change in structure involves formation of an increased percentage of trans fatty acids. Both of these events — oxidation and production of trans fatty acids — have been repeatedly linked to formation of plaque in the arteries and a variety of cardiovascular problems.

Aren’t most important nutrients, like protein and fiber, fairly stable in food and unaffected by cooking?

No, cooking affects most nutrients, including macronutrients like protein and fiber. While cooking seldom destroys protein or fiber, overcooking (either for too long, or at too high a temperature) can alter the structure of nutrients and decrease their health benefits. In some cases — like heating polyunsaturated oils — helpful macronutrients are actually converted into harmful ones.

Nutrition has traditionally focused on macronutrients like protein and fiber, and micronutrients like vitamins and minerals. But there are also a vast array of other nutrients in food. Plant foods contain thousands of compounds that are collectively known as phytonutrients (phyto=plant).

The major classes of phytonutrients include:

Organo-sulfurs: For example, the glucobrassins found in crucifers such as broccoli and cabbage and the allyl sulfur compounds in garlic.
Terpenoids: These include the basic terpenoids like limonene found in citrus foods and menthol, as well as the carotenoids (vitamin A precursors), coenzyme Q10, the phytosterols, and the tocopherols and tocotrienols.
Flavonoids: Flavonoids are the plant pigments that give plants their colors, like the deep blue of blueberries, the purple of grapes, the orange of pumpkins, or the red of tomatoes. Flavonoids include the anthocyanins in blueberries and quercetin found in onions.

Although research studies have yet to determine all the effects of cooking on phytonutrients, some evidence of unwanted effects is visible to the naked eye. Just look at the water in your saucepan after boiling a batch of beets. The water has turned red because anthocyanins (flavonoid phytonutrients) have been leeched from the beets into the boiling water.

Is it true that vegetables are particularly sensitive to cooking methods?

Yes! The nutritional and healing properties of vegetables are in special need of your help when it comes to proper cooking technique! Here are our six cardinal rules for preserving the power of vegetables:

Don’t pre-soak vegetables to make them tender. REASON: nutrients that dissolve in water can be lost by pre-soaking.
Cook vegetables in as little water as possible. REASON: nutrients that dissolve in water are less likely to be lost.
Leave vegetables in contact with water for as little time as possible. REASON: nutrients that dissolve in water are less likely to be lost.
Balance heat and water contact. If you use high heat, keep water contact at a minimum, either by steaming, or baking in a dry oven. If you use low heat, you can allow more water contact. For example, simmering is okay because you bring the water to a boil and then turn down the temperature. But never boil on high heat with direct water contact for more than a few minutes. REASON: nutrients that dissolve in water are less likely to be lost.
Use the Color Power test: when vegetables become more vivid in their colors, with brighter greens and yellows and reds, the power of the vegetables is being enhanced. When the colors begin to pale or become lost, the power is also being lost.
Think tender, not soft. Tender is what your digestive system needs with several types of vegetables, especially those with tough stems and stalks. But soft almost always means less healing power.

For specific vegetable cooking techniques, consult our power-preserving chart below.

Power-Preserving Vegetable Cooking Chart

Food Group

Food Examples

Cooking Method

Time

Special Instructions

Green Vegetables

spinach

steam

3 minutes