Bone-strengthening: The remarkable soya bean can help guard against osteoporosis, and that’s only the beginning.
What’s one of the best ways for female athletes to combat osteoporosis as they get older? Eat soya protein. Keeping a strong spine is now that much easier, thanks to research at the University of Illinois which reveals that soya beans can strengthen the lumbar vertebrae. Soya beans? Sure thing – women taking part in the study were able to expand their bone density by 2.2 per cent over a six-month period simply by eating a couple of ounces (about 56 grams) of soya protein each day. The bean protein was enriched with 92 milligrams of soya isoflavones. Isoflavones are ‘phytoestrogens’ – chemical compounds in plants which are similar to the key female sex hormone, oestrogen.
‘This is incredibly encouraging and surprising,’ said John Erdman, Jr., director of the Nutritional Sciences Department at the University of Illinois. ‘The most we were hoping for was slower bone loss.’
If a 2.2 per cent gain in bone sounds like a small hill of beans, remember that in the first few years after menopause women actually lose a comparable amount of bone mass. In addition, many hard-training female athletes have trouble maintaining the integrity of their skeletal systems. During periods of very heavy training, especially when it is combined with an inadequate caloric intake, menstrual functioning may halt and oestrogen levels may decline, in some cases weakening a female athlete’s skeletal system. It’s possible that soya isoflavones could help protect a woman’s bones during such periods of rigorous training and/or amenorrhoea.
Although the bone-building benefit would be enough to induce most women to reach for soya, the Illinois researchers also unearthed an extra bonus: subjects who ingested soya protein decreased their low-density lipoprotein cholesterol (aka ‘bad cholesterol’) by 8 per cent, an effect which should greatly reduce the risk of heart disease.
The beneficial impact of soya on the cardiovascular system was also demonstrated in recent research carried out by scientists at the Bowman Gray School of Medicine in Winston Salem, North Carolina – and presented at the 70th Annual Meeting of the American Heart Association (held November 9 – November 12, 1997 in Orlando, Florida). In this study, monkeys ingested either their regular diet, their normal diet plus oestrogen, their regular diet plus soya protein, or the normal fare plus both oestrogen and soya. As it turned out, the soya protein decreased total cholesterol and increased HDL-cholesterol (aka ‘good’ cholesterol). Monkeys receiving soya also enjoyed improved cardiac function: the coronary arteries leading into their hearts dilated to a significantly greater extent, providing heart muscle with greater amounts of oxygen and energy.
Breast cancer as well
The new information about soya protein should also be great news for women worried about breast cancer. Although at first glance soya appears to act like the key female sex hormone – oestrogen – by lowering heart-attack risk and building bone, soya isoflavones actually seem to block oestrogen’s potentially dangerous effect on breast tissue at the same time they are delivering their benefits to the spine and the heart. Researchers note that breast cancer is four times less common among Japanese women, compared to women in the UK and the US (Japanese women eat lots of soya products). Soya bean consumption has also been linked with reduced rates of colon cancer and a lower risk of prostate cancer in men.
In recent research, healthy women aged 22 to 29 ingested a 12-ounce glass of soya milk with each of their three daily meals for a one-month period. Daily soya isoflavone intakes amounted to about 100 mg of genistin and 100 mg of daidzein (more about these two key isoflavones in a moment). Blood oestrogen levels decreased by 31 to 81 per cent and stayed down for two to three menstrual cycles after soya-milk drinking ceased. As the researchers put it, ‘Such effects may account at least in part for the decreased risk of breast cancer that has been associated with legume consumption’ (‘Effects of Soya Consumption for One Month on Steroid Hormones in Premenopausal Women: Implications for Breast Cancer Risk Reduction,’ Cancer Epidemiol Biomarkers Prev, vol. 5(1), pp. 63-70, 1996).
How can soya beans to do such wonderful things? Research suggests that soya beans contain two key isoflavones – genistin and daidzin – which produce a variety of beneficial effects. In a recent investigation, it was determined that genistin inhibited the activity of osteoclasts, special cells which actively break down bone (although we think of bones as static structures, they are actually quite dynamic, with cells called osteoblasts constantly building bony tissue and osteoclasts doing the reverse; inhibition of osteoclast activity would tend to increase the density of bone). In the same study, researchers gave genistin to female rats whose ovaries had been removed (without ovaries, the rats would be unable to synthesize bone-building oestrogen). After 30 days, thigh-bone weight was 12-per cent greater in genistin-fed rats, compared to controls (‘Variable Effects of Tyrosine Kinase Inhibitors on Avian Osteoclastic Activity and Reduction of Bone Loss in Ovariectomized Rats,’ J Cell Biochem, vol. 61(4), pp. 629-637, 1996).
Genistin also appears to have a strong anti-carcinogenic activity. In research carried out in Japan, genistin strongly blocked the growth of human stomach cancer cells and moderately suppressed proliferation of oesophageal and colon-cancer cells (‘Antiproliferative Effects of Isoflavones on Human Cancer Cell Lines Established from the Gastrointestinal Tract,’ Cancer Research, vol. 53(23), pp. 5815-5821, 1993).
In addition, genistin is a potent inhibitor of the growth of three different cell lines of human breast cancer (‘Genistein Inhibition of the Growth of Human Breast Cancer Cells: Independence from Estrogen Receptors and the Multi-Drug Resistance Gene,’ Biochem Biophys Res Commun, vol. 179(1), pp. 661-667, 1991). Incredibly enough, genistin is also able to inhibit the replication of the herpes simplex virus (‘Inhibition of Herpes Simplex Virus Replication by Genistein, an Inhibitor of Protein-Tyrosine Kinase,’ Archives of Virology, vol. 132 (3-4), pp. 451-461, 1993).
And it helps keep you sober
Daidzin, another important isoflavone found in soya beans, is mildly anti-carcinogenic and produces other potentially beneficial effects. For one thing, Chinese researchers have been able to show that daidzin can lessen the intoxicating effects of alcohol. When laboratory rats recently imbibed a fixed quantity of 80-proof alcohol while lounging around in their cages, rats given daidzin along with their booze had 33-per cent lower blood-alcohol levels and took three times as long to reach peak blood-alcohol amounts, compared to daidzin-free drinkers. Amazingly enough, daidzin controlled drunkenness, even if it was ingested during the week leading up to – but not the day of – alcohol ingestion. Daidzin also decreased the amount of time rats required to ‘sleep off’ an over-consumption of booze (‘Daidzin, an Antioxidant Isoflavonoid, Decreases Blood Alcohol Levels and Shortens Sleep Time Induced by Ethanol Intoxication,’ Alcohol Clin Exp Res, vol. 18(6), pp. 1443-1447, 1994). Daidzin spontaneously decreases laboratory animals’ intakes of alcoholic beverages, suggesting to some scientists that this soya isoflavone might be useful in the treatment of alcohol abuse in humans (‘Therapeutic Lessons from Traditional Oriental Medicine to Contemporary Occidental Pharmacology,’ EXS, vol. 71, pp. 371-381, 1994).
There are just two cautions concerning soya: (1) The women in the intriguing University of Illinois study boosted bone mass only in their spines, not their hips (oestrogen can thicken hip bones). (2) A woman would have to eat a pound of tofu each day to ingest as many isoflavones as the Illinois subjects were getting.
However, neither concern is particularly troubling. It’s possible that future research will show that soya’s isoflavones bolster the hips, in addition to the vertebrae. In addition, several large food companies are seriously considering plans to sell soya-fortified drinks, muffins, and bagels, so tofu binges will probably be unnecessary. Finally, a couple of companies are already selling soya powder which is enriched with extra isoflavones. One of the best such products is something called ISO SOY, made available by the venerable Solgar Laboratories of Leonia, New Jersey in the United States and sold widely at health-food stores. An ounce of ISO SOY contains 12 grams of high-quality soya protein, 12.5 grams of carbohydrate, less than one gram of fat, and over 102 mg of isoflavones – slightly more than the bone-building women in the University of Illinois study were getting. ISO SOY dissolves easily in milk, juice or yoghurt and actually tastes great.
Two new drugs
Speaking of bone preservation, there are two new osteoporosis drugs available to older female athletes (and women at large). Both drugs may be preferred by women concerned about the possibly increased risks of uterine and breast cancer associated with oestrogen therapy (oestrogen was previously the most powerful treatment that physicians could offer).
First, alendronate, sold under the brand name Fosamax, boosts bone mass in the spine by as much as 3 per cent per year and also cuts the the risk of spinal-compression fractures in half (spinal-compression fractures are small cracks in vertebrae which can create the curved upper back called ‘dowager’s hump’). Like soya’s genistin, the drug seems to work by preventing the bone-eating cells called osteoclasts from breaking down skeletal tissue.
A recent study found that women with osteoporosis who took Fosamax were only half as likely to break a hip as women who didn’t take it. Thus, Fosamax can be a true life-saver. ‘Nearly all hip fractures require hospitalization, and up to 20 per cent of older women with hip fractures die within a year,’ says Dennis Black, an epidemiologist at the University of California at San Francisco.
The second new drug, calcitonin, is prescribed as a nasal spray called Miacalcin. It’s a synthetic hormone that also slows down bone-eating cells. Miacalcin only builds about half as much bone as Fosamax does, but it’s much easier to use. A patient can take one daily spritz anytime she wants, and there are few side effects (Fosamax sometimes produces digestive-system irritation and ‘wooziness’).
In combination with either of the new drugs, many experts are also recommending between 1,500 and 2,500 milligrams of calcium daily, plus 400 IU of vitamin D. Weight training is also particularly beneficial for constructing bone (no huge weights are necessary; small hand weights or even body weight can provide the needed resistance).