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by author Jane Thornthwaite, RDN
The brassica family of vegetables, which includes broccoli, cabbage, kale, cauliflower and brussels sprouts, is one of your most powerful weapons in warding off many common diseases such as cancer, heart disease, diabetes and hypertension.
All fruits and vegetables are valuable sources of nutrients that fight disease. They are naturally low in fat, cholesterol, calories and sodium; but rich in potassium, fibre, folic acid, beta-carotene and vitamins C and K. In fact, it is estimated that cancer rates would drop 20 per cent if Canadians ate five to 10 servings of vegetables and fruit each day. And it is the brassica family that contains the highest level of disease-fighting substances per serving.
Phytochemicals In Food
In addition to being loaded with vitamins and minerals, the brassicas contain high levels of phytochemicals, or non-nutritive substances in plants, that possess protective health benefits.
Some of these phytochemicals protect our arteries. Others act as powerful antioxidants to reduce the activity of cell-damaging free radicals and protect against cancer or diabetes. Brassica vegetable components, such as indoles, isothiocyanates and dithiolthiones block various hormone actions and metabolic pathways that are associated with the development of cancer. Other substances, such as indole-3-carbinol, also in the brassicas, are powerful inducers of enzymes known to prevent estrogen action and thereby reduce the risk of breast or uterine cancer.
The most powerful phytochemical is sulforaphane, found in broccoli. Broccoli contains different substances that break down into sulforaphane when it is cut, chopped and/or chewed. Bacteria in your intestines can also act on broccoli to produce sulforaphane. This phytochemical is so interesting that scientists are looking into it as a potential treatment for cancer.
According to a recent study of 48,000 male health-care professionals, men with the highest intake of broccoli, cabbage, kale, cauliflower, brussels sprouts and other brassica vegetables were found to have half the risk of bladder cancer of those who consumed one serving or less per week.
The flavonoids in vegetables extend the activity of vitamin C. They also act as antioxidants and protect the low density lipoprotein (LDL) cholesterol–or bad cholesterol–from oxidation. Flavonoids prevent platelet aggregation and have anti-inflammatory and anti-tumor action. All these help to prevent both heart disease and cancer. Kale and broccoli are rich sources of one of these flavonoids: quercetin.
Research at the US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University has quantified the antioxidant value of certain foods. Phytochemicals with a high antioxidant potential are said to boost the antioxidant power of human blood substantially. The carotenoids and flavonoids that give fruits and vegetables their colors are also protective against heart disease and cancer. The brassica vegetables are particularly high in such pigments.
Health With Brassicas
A recent study in the Journal of the American Medical Association found that people who ate at least five servings of fruits and vegetables a day had a 30 percent lower risk of ischemic stroke. Each daily serving reduced the risk by six per cent. The most protective choices included the brassica vegetables. The protective elements noted in these foods were folic acid, potassium, vitamin C and the flavonoid pigments mentioned above.
Given the large amount of calcium-containing plant foods on the market these days, milk is no longer the golden standard for calcium. Dark green leafy vegetables are high in calcium and iron. The bioavailability of calcium is actually higher in kale and other dark green leafy vegetables (like broccoli) than in milk. The trick is, you have to eat a large variety of calcium-containing plant foods to ensure you are getting enough, especially if you don’t consume dairy products.
The bioavailability of iron in brassica vegetables is improved by consuming vitamin C with them. This is not difficult considering almost all fruits and vegetables are good sources of vitamin C. A small dash of lemon juice over lightly steamed kale is a favorite with our family.
In addition to calcium, the vitamin K found in leafy greens can also improve your bones. In a recent study of 72,000 middle-aged nurses, those who consumed moderate or high amounts of vitamin K had a 30 percent lower risk of hip fractures than those who did not.
Only plant foods contain fibre and the brassica vegetables are excellent sources–with brussels sprouts leading the pack at over four grams per serving. North Americans rarely consume even half of the 25-35 grams of fibre recommended per day. Insoluble fibre helps to prevent constipation and reduce colorectal cancer risk. Soluble fibre helps to reduce blood cholesterol and blood sugar, thereby reducing the risk of heart disease and diabetes.
Most phytochemical compounds found in the brassicas are heat stable and not lost by cooking. In some instances, their bioavailability may even increase during cooking. Cooking or processing breaks down certain chemical bonds in the vegetables and releases some phyto- chemicals, such as the indoles in broccoli. However, water-soluble vitamins like vitamin C are significantly lost with extended cooking.
If you must cook your vegetables, I recommend lightly steaming them in a small amount of water. Since many of the brassicas can cause gas, steaming increases their tolerance in some people. Save the cooking water for use in a soup, sauce or other recipe. Certainly, eating cooked vegetables is better than not eating them at all. For children, cut-up broccoli stalks and florets with a herbed, quark flax oil dip are a great after-school snack.
Jane Thornthwaite is a registered dietitian nutritionist in private practice in Vancouver, BC.
Source: alive #215, September 2000
