Despite fresh concerns over soy bean safety, a recent study suggests it may boost assisted reproduction success report BEN UKWUOMA and CHUKWUMA MUANYA.
CAN a meal of soy bean boost fertility? A recent study published in the medical journal Fertility and Sterility suggests high doses of soy-derived estrogens does not only boost fertility, but can improve pregnancy rates in women undergoing in vitro fertilisation (IVF) and embryo transfer.
This contradicts previous study, which suggests that a chemical in soy bean can damage the male reproductive organs of the unborn child and increase the risk of long-term developmental damage in their children.
Commonly called soja bean or soya bean, soybean is scientifically called Glycine soya or Glycine max and belongs to the plant family Fabiaceae.
A botanist at the University of Lagos, Akoka, Associate Prof. Toyin Ogundipe, describes soybean as a yearly leguminous plant, native of Asia, economically the most important bean in the world.
Ogundipe says: "The soybean is an erect branching plant resembling, in its early growth, ordinary field or navy beans. Varieties range in height from less than 30 centimetres (12 inches) to more than two metres (7 feet). The deep roots are responsible in part for the great resistance to drought offered by soybean.
"The seeds are usually yellow, green, brown, or black, but may be bicoloured. No truly white or red seeds are known. The commonest bicoloured patterns are green or yellow, with saddle-like patch of black or brown extending down on each side of the helium, or seed scar. Most commercial varieties range in seed size from 2,500 to 3,500 seeds per 0.45 kilogrammes (one pound)".
Soybean is reported to contain compounds called phytoesrogens or isoflavones that have been found to mimic the effects of the female sex hormone oesrogen.
These effects, according to assisted reproduction technique expert at The Roding Medical Centre, Victoria Island, Lagos, Dr. Faye Iketubosin, may help to prevent a range of conditions including the unpleasant symptoms of menopause.
"Phytoestrogens", according a Botanist and Dean of Student Affairs University of Lagos, Prof. Dele Olowokudejo, is the name given to a family of plant compounds that have both estrogenic and anti-estrogenic properties. Flaxseed, soy and alfalfa, he said, are examples of plants containing phytoestrogens. "Unlike other legumes, soy is very high in protein and lower in carbohydrates. This makes soy a natural dietary replacement for animal protein", Olowokudejo says.
Research indicates that these plants, and isolated lignans (proteins) from these plants, have many protective effects in the body.
Hundreds of research studies demonstrate that soy foods are safe and have a moderating influence on both estrogen and testosterone.
There is some evidence to suggest that the more the food has been processed to be drug-like, the more likely there could be adverse effects. Therefore, nutritionists insist that eating soy beans in chill, putting ground flax seed in smoothie, or having a tofu scramble for breakfast, is preferable to taking capsules of isolated soy proteins.
Typical soy products, according to a nutritionist at Nigerian Institute of Medical Research (NIMR), Yaba, Lagos, Dr. Rosemary Anyanwu, include: "Edamame - the Japanese name for fresh soybeans. The soybeans (either fresh or frozen) are boiled in their pods with salt then chilled and served as an appetiser. Soy flour - dried and ground soybeans. This product can be difficult to digest.
"Soy milk - Soy milk is made simply from dried soybeans and water. It is an excellent replacement for milk. Use it fresh to drink, or pour over cereal, or in most recipes that require milk. This is a great, easily digestible way to increase your soy intake.
"Miso - Is a fermented soybean paste the consistency of peanut butter. Use it as a seasoning or as a broth or soup (common in Japanese restaurants) as well as for sauces, dips or marinades.
"Tofu - Tofu is soybean curd. It has a naturally bland flavour but has the ability to easily take on the flavour of other ingredients cooked with the tofu.
"Soy sauce - Soy sauce and tamari are made of soybeans, salt and water. Soy sauce contains a wheat product called koji. Tamari contains no wheat. Soy sauce is used as a flavour enhancer. For the best flavour purchase, a high quality soy sauce or Tamari product, which has been well aged. Some of the very inexpensive brands may have a very harsh flavour.
"Dried and roasted soybeans - Soybeans can be dried and roasted and used as a snack food. These can be very difficult to digest.
Anyanwu, however, notes that not all soy products are healthful and readily digestible. "Products should be carefully selected to enhance your daily nutrition."
Indeed, Italian researchers have found that women who took 1,500 milligrams of soy isoflavones per day, along with progesterone injections, had significantly greater rates of implantation, on-going pregnancy and delivery than women given progesterone injections with placebo.
Lead researcher, Dr. Vittorio Unfer, of the Obstetrics and Gynecology Centre in Rome and colleagues report that progesterone injections after egg retrieval are standard practice, but the role of estrogen supplementation has been controversial.
They conducted the current study to determine if high doses of plant estrogens, previously shown by the researchers to have estrogen-like effects on the uterine lining of postmenopausal women, could help support implantation of the early embryo.
The researchers randomly assigned 213 women to take soy supplementation or inactive placebo supplements after egg retrieval. The women continued to take the daily supplement until a pregnancy was confirmed or ruled out. Among women given the supplements, 25 per cent of the embryos transferred achieved implantation, compared to 20 per cent among women given placebo.
Clinical pregnancy was seen in 39 per cent of women on the soy estrogens and 21 per cent of those on placebo. The rate of successful delivery per pregnancy was 30 per cent among women who took the active supplement compared with 16 per cent for women given the placebo.
Larger studies are necessary before plant-derived estrogens can be routinely recommended for in vitro fertilisation and embryo transfer, the researchers write. "Nevertheless, our findings suggest new avenues for future fertility research and treatment," they conclude.
Iketubosin, however, insists that more studies are needed before soy bean could be recommended in assisted reproduction treatments. "This is a new finding, and we must approach it with caution. With more studies confirming this one, we may then be in a better position to say soy bean actually enhances fertility.
"But one thing is certain, diet plays a crucial role in fertility."
He continued: "I have looked at the association between soya bean products and infertility. There is an interesting report from Queen's University Belfast linking large consumption of soya products to poor sperm quality.
"The offending agent is oestrogen, soya beans are very rich in oestrogen, which as you is the female hormone. Consuming large quantities of oestrogen by men affects their sperm quality. This has become noticeable now because a lot more people are eating fast foods and packaged dinners as a result of our very busy lifestyles.
"More worrying, however, is the fact that if young boys are fed with a diet consisting of large proportions of fast foods rich in soya products, it may have a permanent effect on their future reproductive ability. Examples of the offending foods are pizzas, vegetarian burgers and packaged dinners such as steak and kidney pies."
The solution, according to Iketubosin is to eat freshly prepared foods, fruits and vegetables. "Fast foods to be consumed in moderation.
"In the Nigerian context we do not have an over dependence on fast foods. Most Nigerians eat freshly prepared foods regardless of the social status in society. Hence this study may not be applicable to the average Nigerian but university students and children of the affluent should take note as these are the groups that tend to indulge in the fast food craze."
Meanwhile, eating soya-rich foods could reduce a woman's risk of developing breast cancer, researchers have found. A study has found women who eat soya-rich diets have less "high risk" dense breast tissue.
It had been suspected that the high consumption of foods such as tofu and soy bean or milk in countries such as China and Japan contributed to the countries' low breast cancer rates. But there had been no conclusive scientific evidence to back up the theory.
The amount of soy bean a woman eats may have an effect on breast tissue and in turn may potentially reduce her risk of breast cancer.
Dr. Stephen Duffy, from Cancer Research UK, the National University of Singapore and the U.S. National Cancer Institute looked at the results from two studies carried out in Singapore.
The first looked at the women's diet; the second used mammograms to assess the density of their breast tissue. It has previously been shown that dense tissue is associated with an increased risk of breast cancer.
Four hundred and six women took part in both studies. The women who ate the most soya were 60 per cent less likely to have the "high risk" breast tissue than women who had the least soya in their diet.
The benefit could from a chemical in soy bean called isoflavone, which mimics the action of the female sex hormone oestrogen, though such "plant oestrogens" are not as strong as the oestrogen produced by the body. Being exposed to the plant oestrogens appears to lengthen a woman's menstrual cycle.
Previous studies have indicated that the fewer menstrual cycles a woman has in her life, the lower her risk of breast cancer.
Meanwhile, soy bean may protect women against the cancer risk linked with hormone replacement therapy (HRT), scientists have claimed.
However, they warn that the wrong balance between soy bean consumption and HRT dosage may have the opposite effect and increase the risk.
HRT has been associated with a higher than normal incidence of breast or uterine cancer. This is because oestrogen, the female sex hormone that is given to women undergoing HRT, can trigger the development of cancerous tumours.
Soya contains plant versions of another female sex hormone, called phytoestrogens, which are thought to block the action of oestrogen on breast and uterus cells.
Prof. Mark Cline, from Wake Forest University Baptist Medical Centre in Winston-Salem, North Carolina, U.S., showed that soy bean could protect postmenopausal monkeys from developing cancer.
Hormone replacement therapy induced a proliferation of cells - a precursor of cancer - in the breasts and wombs of the monkeys. But when they were fed soy bean of the sort found in tofu and dietary supplements the cells stopped multiplying so rapidly.
"These data indicate that soy supplements may decrease breast and endometrial (uterine) cell proliferation and therefore could decrease cancer risk in these tissues," said Cline, who presented his findings at the yearly meeting of the American Association for the Advancement of Science in Anaheim, California.
However, Cline warned that tests in rats whose ovaries had been removed revealed that when the animals were given low doses of oestrogen replacement, the addition of natural soya to their diet increased breast cell proliferation.
At higher HRT doses, however, soya reduced cell proliferation in both the breast and uterus. Cline said further work was needed to explore the basic mechanisms by which soya phytoestrogens affected the incidence of breast cancer.
"Widespread consumption of phytochemicals in the human diet and as supplements make it imperative that we understand their effects, particularly as they relate to differing developmental and functional stages of the breast," he added.
He drew attention to the fact that Asians living in their native country had far lower cancer rates than Americans, probably because of their diet, which contained a high proportion of vegetables, including soya.
American-born children of Asian immigrants had a 60 per cent higher risk of developing breast cancer than people who had moved to the U.S. from Asia and were now eating Western diets.
This implied that dietary effects protecting against breast cancer may occur early in life. However, the degree to which the anti-cancer properties of vegetables could be attributed to phytoestrogens was unclear.
Cline said: "The benefit of soya phytoestrogens is clearer for dietary exposures early in life and for pre-menopausal women. The benefit for older women and breast cancer survivors remains to be determined."
