Osteoporosis is a very serious disease in which bones become brittle and can break easily. It has been recognized as an important public health problem and has become a major cause of disability in the elderly, with older women being the fastest growing segment. Osteoporosis currently affects the lives of more than 25 million people in the United States. It is the principal underlying cause of an estimated 1.5 million bone fractures of the hip, spine, wrist, and other sites that occur yearly at an annual cost of $10 to 20 billion. It is estimated that more than half of all women and about one third of men will have fractures caused by osteoporosis during their lives.
Bone is connective tissue that becomes hard when minerals (primarily calcium), are deposited on it. Although bone doesn’t look very active, it is constantly being built up and broken down. Bones become weak when the amount being broken down exceeds the amount being rebuilt. Some factors that influence bone strength are calcium intake, exercise, and the presence of the hormone estrogen, which protects bone from losing too much calcium.
The most common form of osteoporosis occurs in women after menopause. Bone quickly begins to lose calcium and break down in response to the drastic reduction in estrogen. Estrogen replacement therapy can reduce the risk of osteoporosis; however, it may not be appropriate for some women, and many choose not to take hormones. Women give various reasons for not wanting estrogen replacement therapy, including trust that ” nature knows best” and that you should just “tough it out.”
They also have doubt about estrogen’s effectiveness, anxiety about estrogen’s immediate side effects (such as water retention and reappearance of menstrual bleeding), and concern about the possible long-term effects of estrogen, primarily a fear of cancer.5 One large study of postmenopausal women showed that only about 17 percent were taking estrogen, 27 percent had taken estrogen in the past and stopped, and 55 percent had never taken estrogen therapy.6 Observations that Asian women have lower rates of osteoporosis while using much less hormone replacement therapy7 and consuming less calcium,8 have led researchers to take a closer look at the role of soy foods in the Asian diet.
One issue in bone health appears to be the type and amount of protein consumed. Research shows that as protein intake increases, the amount of calcium excreted in urine increases. However, not all proteins have the same effect on calcium. Compared with animal protein, vegetable protein, such as soy, causes a much smaller amount of calcium excretion, leaving more available to strengthen bone. Americans eat a lot of protein, which may be one reason why we have a higher recommended calcium intake than in other countries. Not only do we traditionally eat a lot of protein, but much of it comes from animal sources.
The ongoing Nurses Health Study has shown a greater number of forearm fractures as animal protein intake increases. No such association has been found with vegetable protein intake. A second issue is that studies of soy isoflavones, especially genistein, show that they act like a weak form of estrogen. As such, isoflavones may be able to preserve and improve bone health.
A study of postmenopausal women compared the effects of consuming either soy protein or dairy protein on bone weight and on the amount of mineral present to strengthen bone. The results showed that women who consumed soy protein with naturally occurring isoflavones had significant increases in bone weight and in the amount of mineral in their bones, especially their spines, compared to women consuming dairy protein. Research also indicates that isoflavones may decrease the breakdown of bone.
A more recent study in postmenopausal women compared soy protein with isoflavones against dairy protein, measuring changes in bone density and bone mineral content over a six-month period. Between three groups, 66 participants were randomly assigned and received 40 grams of protein per day. One group received isolated soy protein with 1.39 mg of isoflavones per gram of protein (ISP-Group), a second group received isolated soy protein with 2.25 mg of isoflavones per gram of protein (ISP+Group), and the control group received milk protein. The soy protein diets were fortified with calcium to equal that of the control diet. Results showed that the milk protein group lost more bone mineral and bone density than the first soy group, but both mineral and density actually increased significantly in the group with increased isoflavones (see table).
The results indicate a potential role for soy protein with isoflavones in maintaining bone health in postmenopausal women. There is also much interest in ipriflavone, a synthetic isoflavone similar in structure to the soy isoflavones. This compound is used to treat osteoporosis in Japan and is currently being evaluated in European and American studies. One of the active compounds formed when ipriflavone is metabolized in the body is daidzein, an isoflavone found in soy.
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Although menopause is much less serious than heart disease, cancer, and osteoporosis, women experiencing it can be very miserable. In many women, menopause discomforts can continue for years. These include hot flashes, insomnia, heavy sweating (especially at night, which further contributes to insomnia), headaches, mood swings, nervousness and irritability, depression, and vaginal dryness and soreness, which make intercourse painful. Although women can reduce postmenopausal discomforts by taking estrogen, the vast majority choose not to have this hormone replacement therapy because of the negative side effects, such as water retention, reappearance of menstrual bleeding, increased blood triglycerides, and tissue changes in the breast and endometrium. Private chefs often can make amazing recipes with soy.
There are noticeable differences in menopausal discomforts between women from the East and West. For example, it is estimated that while up to 85 percent of women in Western cultures have hot flashes and night sweats, less than 10 percent of Japanese women have hot flashes and less than four percent have night sweats. One Japanese-born women commented that she had never heard of hot flashes until she came to the United States and wasn’t aware of a Japanese word for this condition. Although there may be several explanations for these differences between women in the East and West, researchers have focused on the possible effects of phytoestrogens found in the soy foods so abundant in the Japanese diet.
In 1998, Albertazzi and her colleagues studied the effect of isolated soy protein on hot flashes in postmenopausal women. The 104 women in the study received either 60 grams of isolated soy protein or 60 grams of milk protein per day for three months. Women in the soy-protein group had a 26% reduction in the mean number of hot flashes by week 3, a 33% reduction by week 4, and a 45% reduction by the end of week 12. As shown in the table below, the soy-protein group had significantly fewer hot flashes than the milk-protein group.
It seems reasonable for women suffering from menopausal symptoms to take advantage of the possible benefits of adding soy foods that contain phytoestrogens into their daily diets. The research is on their side and soy foods have a long track record of safety, having been consumed in Eastern countries without negative effects for thousands of years. Because research on the health benefits of soy foods and their naturally occurring phytoestrogens is increasing, there should be a steady stream of information about the connection between soy phytoestrogens and menopausal symptoms in the future.
Cancer is the second largest killer in the United States and the most dreaded disease. Certain types of cancer are more common in Western nations than in many Eastern countries (see table), and researchers have looked at dietary factors that might possibly affect cancer. Many research studies support the idea that soy protein and its naturally occurring isoflavones (mainly genistein and daidzein) have anticancer activity. Studies have shown that the isoflavones in soy may help interfere with the growth and multiplication of cancer cells. Some research even suggests that genistein’s antioxidant activities may explain its anticancer effect. Stress proteins are another area of interest. When your body is under stress, such as in the beginning of cancer, it produces stress proteins. Most of the cells in your private chef in NYC’s body have a certain life span built into their genetic code, but stress proteins protect cells against their normal cell death. In this same way, stress proteins can also protect cancer cells, allowing them to live longer. Laboratory research has shown that genistein can inhibit this stress response in cancerous and pre-cancerous cells.
Since soy isoflavones are phytoestrogens, compounds with a structure that mimics the hormone estrogen, researchers logically have looked at hormone-dependent tumors. Consequently, isoflavones can bind to estrogen receptors, preventing the binding of more potent estrogens. Isoflavones also increase the production of sex hormone-binding globulin, a special protein that binds to estrogen and testosterone and lowers the amount of free hormones circulating in the body. One of the newest areas of cancer research is angiogenesis, the process where tiny blood vessels are developed to provide oxygen and nutrients to new tissues in the body. Substances that prevent the development of these blood vessels can limit the growth of tumors by denying them the oxygen and nutrients they need. Some studies have shown genistein to be very effective in blocking angiogenesis. It has been suggested that this fact may help explain why Chinese men may have about half the number of prostrate tumors as Western men and 20 times less diagnosed prostate cancer and cancer deaths than in the West.…Read More →