Why Isoflavones?
Health Benefits of Isoflavones
The importance of isoflavones is widely appreciated and is currently the subject of intense research and discussions. Isoflavones appear to protect against hormone-related disorders such as breast cancer and prostate cancers.The chemical structure of isoflavones is very similar to that of our own estrogen. Because of this similarity in structure, isoflavones can interfere with the action of our own estrogen. Sometimes isoflavones will reduce the effects of estrogen because they compete with the same receptor sites on our cells. Some of the risks of excess estrogen can be lowered in this way.
Isoflavones can also increase the estrogen activity. If during menopause the body's natural level of estrogen drops, isoflavones can compensate this by binding to same receptor sites, thereby easing menopause symptoms as a result. The best way to consume isoflavones is in the form soy or soyfoods, so you can benefit from other healthy components of soy. Soy contains many types of isoflavones, but the most beneficial are genistein (see picture) and daidzein. The highest amounts of isoflavones can be found in soy nuts and tempeh. Isoflavones are fairly stable. Under normal cooking conditions, isoflavones are not destroyed.
Health benefits of isoflavones
Research in several areas of healthcare has shown that consumption of isoflavones may play a role in lowering risk for disease. Isoflavones can fight disease on several fronts. The following potential health benefits are attributed to isoflavones:
Ease menopause symptoms - The benefits of soy go beyond reducing long-term cancer risk. Recent studies have found that soy isoflavones can reduce menopause symptoms such as hot flushes and increase bone density in women. Indeed, many menopausal and post-menopausal health problems may result from a lack of isoflavones in the typical Western diet. Although study results are not entirely consistent, isoflavones from soy or red clover may be helpful for symptoms of menopause.
>> Symptoms of menopause
Reduce heart disease risk - Soy isoflavones also appear to reduce cardiovascular disease risk via several distinct mechanisms. Isoflavones inhibit the growth of cells that form artery clogging plaque. These arteries usually form blood clots which can lead to a heart attack. A review of 38 controlled studies on soy and heart disease concluded that soy is definitely effective for improving cholesterol profile. There is some evidence that isoflavones are the active ingredients in soy responsible for improving cholesterol profile.
>> Isoflavones and Vascular Protection
Protect against prostate problems - Eating isoflavones rich products may protect against enlargement of the male prostate gland. Studies show isoflavones slowed prostate cancer growth and caused prostate cancer cells to die. Isoflavones act against cancer cells in a way similar to many common cancer-treating drugs.>> Isoflavones and Men's Health
Isoflavones improve bone health - Soy Isoflavones help in the preservation of the bone substance and fight osteoporosis. This is the reason why people in China and Japan very rarely have osteoporosis, despite their low consumption of dairy products, whereas in Europe and North America the contrary happens. Unlike estrogen, which helps prevent the destruction of bone, evidence suggests that isoflavones may also assist in creating new bone. Other studies are not entirely consistent, but evidence suggests that genistein and other soy isoflavones can help prevent osteoporosis.
>> Isoflavones and Osteoporosis
Reduce cancer risk - Isoflavones act against cancer cells in a way similar to many common cancer-treating drugs. Population-based studies show a strong association between consumption of isoflavones and a reduced risk of breast and endometrial cancer. Women who ate the most soy products and other foods rich in isoflavones reduced their risk of endometrial cancer by 54%.
>> Isoflavones and anti tumor
Isoflavones are natural plant hormones
Isoflavones can be found in many foods but the best known source of isoflavones is the soy bean (Glycine max). The soy isoflavones are responsible for most of the soy health benefits. The Soy bean is a plant cultivated as foodstuff whose health properties have recently been discovered. Thorough studies have revealed that the consumption of the soy beans or soy foods containing isoflavones have favorable effects on people's health. Another source of isoflavones is red clover. As opposed to soy beans, red clover is normally not eaten but the isoflavones are extracted in industrial processes and used to make isoflavones supplements.
Isoflavones are natural antioxidants
A recent study has demonstrated that isoflavones have potent antioxidant properties, comparable to that of the well known antioxidant vitamin E. The anti-oxidant powers of isoflavones can reduce the long-term risk of cancer by preventing free radical damage to DNA. Genistein is the most potent antioxidant among the soy isoflavones, followed by daidzein. More literature about isoflavones
Alekel DL et al. Isoflavones-rich soy protein isolate attenuates bone loss in the lumbar spine of perimenopausal women. Am J Clin Nutr 2000;72:844.852.
Anthony MS et al. Soybean isoflavones improve cardiovascular risk factors without affecting the reproductive system of peripubertal rhesus monkeys. J Nutr 1996;126:43.50.
Arjmandi BH et al. Bone-sparing effect of soy protein in ovarian hormone-deficient rats is related to its isoflavone content. Am J Clin Nutr 1998;68:1364S.1368S.
Cassidy A et al. Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausesal woman. JAMA 280:60-113.
Crouse JR et al. A randomized trial comparing the effect of casein with that of soy protein containing varying amounts of isoflavones on plasma concentrations of lipids and lipoproteins. Arch Intern Med 1999;159:2070-2076.
Jayo MJ. Dietary soy isoflavones and bone loss: a study in ovariectomized monkeys. J Bone Miner Res 1996;11:S228.
Setchell KD, Cassidy A. Dietary isoflavones: biological effects and relevance to human health. J Nutr. 1999 Mar;129(3):758S-767S.
Potter SM et al. Soy protein and isoflavones: their effects on blood lipids and bone density in postmenopausal women. Am J Clin Nutr. 1998 Dec;68(6 Suppl):1375S-1379S.
What are isoflavones?
Isoflavones are secondary vegetable substances, which can act as estrogens in the body and have protective functions. The estrogen effects of isoflavones are much less powerful than the estrogen hormones (it.s effectiveness represents around 1/1000 of the estrogen hormones). This is why isoflavones and phyto-estrogens exercise a balancing effect when the level of estrogens is low, such as during the menopause, and cause less menopause symptoms. Isoflavones can also reduce the effect of the estrogen on cells and skin layers when the hormone levels are high, and then essentially reduce the risk of estrogen linked cancers.
As nutrition related observations have shown, diseases and troubles mentioned above are uncommon in countries where a lot of soybeans are consumed, because soybeans bring to the organism isoflavones.
Scientific literature contains data about the synergy effects. Within the isoflavones we find daidzein and genistein.
Digestion of isoflavones
Isoflavones are transformed by bacteria in the intestinal flora during digestion. It is only once this transformation has been completed that the isoflavones exercise their beneficial effects in the body. Lower absorption in the intestine has been observed following a lengthy intake of antibiotics or in the case of diarrhea. This can result in a reduction of the protective functions of these substances for the body.
In order to obtain a regular absorption of isoflavones, the intake isoflavones rich foods or isoflavones supplements must be spread during the day.
How do isoflavones work?
In the eighties, scientists discovered the alpha- and beta-receptors for estrogens. Estrogens, like all hormones, act by using receptors located on the cell, which provokes some reaction. The alpha-receptors are linked with a risk of estrogen related cancers. On the other hand, the beta-receptors initiate only favorable effects. The repartition of these two types of receptors in the cells and organs is different. Different tissues appear to have different ratios of each receptor type. This discovery allowed us to understand why isoflavones can act differently than estrogens even though the structure of isoflavones is similar to estrogens.
The isoflavones mechanism
How can we explain that isoflavones have an estrogenic effect and an anti-estrogenic effect? When the natural levels of estrogens are low, isoflavones can help the estrogens by activating the beta-receptors.
When the natural levels of estrogen are high, for example during Adolescence, the isoflavones bind with the alpha-receptors and prevent the natural estrogens from binding with these receptors.
How do isoflavones influence health?
Isoflavones activate the beta-receptor and reinforce the favorable estrogenic properties. On the other hand, isoflavones protect the estrogen alpha-receptors. Consequently the proneness to estrogen-related cancers is lower.
The beta-receptors, which exercise favorable effects for health, can be found mainly in the blood cells, the lungs, the prostate, the bladder, bones and thymus. Isoflavones stimulate their function even after the level of estrogens has decreased.
The alpha-receptor can be mainly found in the breast tissue, the uterus, the ovaries, the testicles and the liver. In those places, isoflavones protect the receptor against estrogens and help reduce the proneness to tumors.
Regulation of the hormonal balance during menopause
Isoflavones regulate the estrogen levels in the body. Isoflavones play a role when the estrogen level is low. The typical symptoms of the menopause, such as hot flushes and night sweat become less severe. When taking daily 40-50mg of isoflavones, the symptoms of menopause will decrease after 2 to 3. This treatment will also reduce the risk of hormones related tumors, osteoporosis and arterio-sclerosis. In the long term the health benefits are really high.
Other isoflavones actions
Most interest in isoflavones has been generated by their potential hormonal effects. But isoflavones have other physiological effects. There are indications that isoflavones can stop the growth of cancer cells through inhibition of DNA replication and reduction in the activity of various enzymes. Isoflavones also have antioxidant effects and inhibit the actions of various growth factors.
More literature about the action of isoflavones
Setchell KD, Cassidy A. Dietary isoflavones: biological effects and relevance to human health. J Nutr. 1999 Mar;129(3):758S-767S.
Cassidy A, Bingham S, Setchell KD. Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausal women. Am J Clin Nutr. 1994 Sep;60(3):333-40.
Metabolism of isoflavones
Formation of aglycones
Isoflavones occur in foods in the form of glucosides which means that the isoflavones are bound to sugar (conjugated isoflavones). These glycosides are very water soluble. These conjugated isoflavones have to undergo further changes. When ingested, these conjugated isoflavones undergo hydrolysis by glucosidases in the intestine, releasing the principal bioactive aglycones (daidzein, genistein and glycitein). These aglycones may be absorbed and further metabolized to many specific metabolites such as equol.
Influence of diet on isoflavones metabolism
Further metabolism of aglycones seems to be strongly influenced by the diet. A high carbohydrate environment, which causes increased intestinal fermentation, results in more phytoestrogens being transformed in equol. This may be relevant because the potency of equol is higher than that of its plant precursor, daidzein. Also, the intestinal microflora has an effect on the metabolism of isoflavones. When intestinal flora is low (antibiotics, germfree animals, newborn babies) metabolism falls down too. When the dietary intake of fat is high, intestinal microflora has difficulty in synthesizing equol from isoflavones.
Like endogenous estrogens (estradiol), isoflavones are metabolized in the intestines and liver. Absorption happens along the entire length of the intestine and they are secreted in bile and urine. Excretion of isoflavones metabolites can vary strongly between individuals. This may be influenced by the fact that each person has his own specific intestinal microflora population.
Once absorbed equol shows less affinity to be bound to serum proteins and therefore has a greater availability than estradiol. When soy is consumed on a regular basis (50 mg isoflavones/day), plasma isoflavone levels far exceed normal estradiol concentrations. This observation led to the hypothesis that isoflavone would be biologically active, conferring health benefits that could explain the relatively low incidence of hormone-dependent diseases in countries in which soy is a dietary staple.
More literature about isoflavones metabolism
Tsunoda N, Pomeroy S, Nestel P. Absorption in humans of isoflavones from soy and red clover is similar. J Nutr 2002 Aug;132(8):2199-201.