Literature Review Finds No Indication that Soy Decreases Testosterone Levels
ST LOUIS, July 20 /PRNewswire/ — A new study published by the American Society for Reproductive Medicine finds that soyfoods and soy isoflavone supplements have no significant effect on male reproductive hormone levels in men. The literature review indicates that soy does not decrease testosterone levels.
Led by Jill M. Hamilton-Reeves, PhD, RD, of St. Catherine’s University, St. Paul, Minnesota, researchers assessed the effects of soy protein and soy isoflavones on measurements of male reproductive hormones. Findings, just published online in Fertility and Sterility, a publication of the American Society for Reproductive Medicine, demonstrate no significant effect of soy protein or soy isoflavone intake on circulating levels of testosterone, sex hormone-binding globulin or free testosterone in men.
The comprehensive meta-analysis examined the existing scientific literature including all clinical studies examining soy’s effect on male reproductive hormones published before July 1, 2008. Fifteen placebo-controlled treatment groups with baseline and ending measures were analyzed. Thirty-two reports involving 36 treatment groups were also assessed in simpler statistical models. Studies published after July 1, 2008, which were not included in the meta-analysis, support the conclusions of the meta-analysis.
Reproductive endocrinologist William R. Phipps, MD, of the University of Rochester Medical Center, a co-author of the analysis stated, “As a high-quality source of protein that is relatively low in saturated fat, soy can be an important part of a heart-healthy diet and may contribute to a decreased risk of coronary heart disease.” He noted that some men have been reluctant to consume soyfoods due to concerns about estrogen-like effects of soy isoflavones, often referred to as phytoestrogens. But according to Phipps, “it is important for the public to understand that there is no clinical evidence to support these ideas. After conducting a comprehensive review of the existing literature, we found no indication that soy significantly alters male sex hormone levels.”
Men can benefit from soyfood consumption as a means to meet daily protein requirements and at the same time possibly also reducing their risk of heart disease.
Citing the research study, Lisa Kelly, MPH, RD, of the United Soybean Board, added,
“Soy is often praised for the positive role it can play in the diets of women. But, years of clinical research have shown that men stand to benefit from soy, too. I encourage men to incorporate soyfoods into a balanced and varied diet and talk to their healthcare provider about their own unique nutritional needs.”
SOURCE: United Soybean Board
New research determines that dietary supplements rich in isoflavones may improve the function of arteries in stroke patients
A dietary supplement rich in isoflavones may improve the function of arteries in stroke patients, according to new research from Hong Kong.
The study is said to be the first randomized controlled trial investigating the effects of isoflavone supplements on improving the blood flow in the arm’s main artery in cardiovascular disease patients.
A daily 80 mg dose of isoflavones was associated with a one per cent increase in flow-mediated dilation (FMD), the measure of a blood vessel’s healthy ability to relax, according to findings published today in the European Heart Journal.
“Although the absolute increase in brachial diameter – one per cent – is small, the relative increase actually amounted to about 50 per cent because the mean average FMD in these stroke patients was about two per cent,” explained lead researcher Professor Hung-Fat Tse.
“These findings may have important implications for the use of isoflavone for secondary prevention in patients with cardiovascular disease, on top of conventional treatments,” wrote the authors in their EHJ paper.
Isoflavones from soy have been shown to provide a number of health benefits, including the promotion of heart health and the maintenance of bone health in post-menopausal women.
They have also been studied for their role in cancer prevention and slowing down the ageing process in peri-menopausal women, and isoflavone-rich supplements have proved to be a popular alternative to HRT for those wishing to control menopause symptoms without resorting to drugs.
Professor Tse and his co-workers from the University of Hong Kong recruited 102 stroke patients and randomly assigned 50 to receive daily isoflavone supplements (), and 52 to receive placebo, for 12 weeks.
“The specific dosage of 80 mg/day was chosen because previous studies have shown that isoflavone at this dosage was well tolerated by both men and women without significant side effects,” explained the researchers.
Ultrasound techniques were used to measure FMD at the start and end of the study. At the start, 80 per cent of the patients had an impaired FMD, defined as relaxation of less than 3.7 per cent. At the end of the 12 weeks, however, the patients receiving the isoflavone supplements experienced an improvement of one per cent, compared with the controls.
Moreover, the prevalence of impaired FMD after 12 weeks was only 58 per cent in the isoflavone group, compared to 79 per cent in the placebo group.
“The patients who had a lower initial FMD were found, in general, to respond with a larger absolute increase in FMD after receiving 12 weeks of isoflavone intervention, compared to patients who had a better baseline FMD in the first place,” said Prof Tse.
“These findings suggest that isoflavone reverses endothelial dysfunction in this group of patients with cardiovascular disease. This has important clinical implications, as the benefit of the [intervention] is conferred to the group of patients with the highest risks for cardiovascular events, and this effect persists, even at this rather late stage of the cardiovascular continuum.”
Supplementation with isoflavones was also associated with decreases in the levels of a protein called high-sensitivity C-reactive protein (CRP). This protein is a marker of inflammation and is reported to be an independent predictor of cardiovascular-related events.
“These findings suggested that isoflavone[s] alleviated vascular inflammatory stress and was an important component that mediated the reversal of endothelial dysfunction in this group of patients,” wrote the authors.
The mechanism by which the soy compounds is not totally understood, said Professor Tse. However, the anti-inflammatory effects may be related to the weak oestrogenic effect of the isoflavones. The female hormone oestrogen is known to protect against heart disease, said the researchers.
Despite the promising results of this clinical trial, the researchers stressed that it was too early to make any recommendations in this area.
“At this juncture, regular isoflavone supplement might not be advocated since the benefits and side effects of long-term supplementation are still unknown,” said Professor Tse.
“A balanced diet is still the top priority in promoting health. Diets with higher soy content might be beneficial due to the isoflavone contents. These food products also, in general, have higher contents of polyunsaturated fats, fibre, vitamins and less saturated fat.”
Recent studies have found Colostrum to be three times more effective against flu than the flu vaccine. A trial was conducted comparing colostrum to flu vaccine. The paper titled “Prevention of Influenza Episodes With Colostrum Compared With Vaccination in Healthy and High-Risk Cardiovascular Subjects” evaluated the efficacy of a 2-month treatment with oral colostrum in the prevention of flu episodes compared with anti influenza vaccination. Groups included healthy subjects without prophylaxisand those receiving both vaccination and colostrum. After 3months of follow-up, the number of days with flu was 3 timeshigher in the non-colostrum subjects. The colostrum group had13 episodes versus 14 in the colostrum + vaccination group,41 in the group without prophylaxis, and 57 in nontreated subjects.Part 2 of the study had a similar protocol with 65 very high-riskcardiovascular subjects, all of whom had prophylaxis. The incidenceof complications and hospital admission was higher in the groupthat received only a vaccination compared with the colostrumgroups.
Colostrum, both in healthy subjects and high-risk cardiovascularpatients, is at least 3 times more effective than vaccinationto prevent flu and is very cost-effective.
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Study: San Valentino-Spoltore Vascular Screening Project, Department of Biomedical Sciences, G D’annunzio University, Chieti, Pescara, Italy
Authors: Cesarone MR, Belcaro G, Di Renzo A, Dugall M, Cacchio M, Ruffini I, Pellegrini L, Del Boccio G, Fano F, Ledda A, Bottari A, Ricci A, Stuard S, Vinciguerra G.
ScienceDaily (Mar. 17, 2008) â€” A compound found in soybeans almost completely prevented the spread of human prostate cancer in mice, according to a study published in the March 15 issue of Cancer Research, a journal of the American Association for Cancer Research.
Researchers say that the amount of the chemical, an antioxidant known as genistein, used in the experiments was no higher than what a human would eat in a soybean-rich diet.
Investigators from Northwestern University found that genistein decreased metastasis of prostate cancer to the lungs by 96 percent compared with mice that did not eat the compound in their chowÂ â€” making the study the first to demonstrate genistein can stop prostate cancer metastasis in a living organism.
â€œThese impressive results give us hope that genistein might show some effect in preventing the spread of prostate cancer in patients,â€ said the studyâ€™s senior investigator, Raymond C. Bergan, MD, director of experimental therapeutics for the Robert H. Lurie Comprehensive Cancer Center of Northwestern University.
â€œDiet can affect cancer and it doesnâ€™t do it by magic,â€ Bergan said. â€œCertain chemicals have beneficial effects and now we have all the preclinical studies we need to suggest genistein might be a very promising chemopreventive drug.â€
Bergan and his team have previously demonstrated in prostate cancer cell cultures that genistein inhibits detachment of cancer cells from a primary prostate tumor and represses cell invasion. It does this by blocking activation of p38 MAP kinases, molecules which regulate pathways that activate proteins that loosen cancer cells from their tight hold within a tumor, pushing them to migrate. â€œIn culture, you can actually see that when genistein is introduced, cells flatten themselves in order to spread out and stick strongly to nearby cells,â€ he said.
In this study, investigators fed genistein to several groups of mice before implanting them with an aggressive form of prostate cancer. The amount of genistein in the blood of the animals was comparable to human blood concentrations after consumption of soy foods, Bergan said.
The researchers found that while genistein didnâ€™t reduce the size of tumors that developed within the prostate, it stopped lung metastasis almost completely. They repeated the experiment and found the same result.
They then examined tissue in the animals, measuring the size of tumor cellsâ€™ nuclei to determine if the cells had flattened out in order to spread. â€œWithin a tumor, it is hard to tell where the borders of cells stop, so one way to measure adherence is to look at the size of the nuclei in cells and see if they are wider due to cell spread,â€ Bergan said. â€œAnd that is what we found, demonstrating that the drug is having a primary effect on metastasis.â€
He said that the study also found that mice fed genistein expressed higher levels of genes that are involved in cancer cell migration which, Bergan says, at first might not make sense in light of the studyâ€™s conclusion that genistein almost completely blocked metastasis.
â€œWhat we think is happening here is that the cells we put in the mice normally like to move. When genistein restricted their ability to do so, they tried to compensate by producing more protein involved in migration. But genistein prevented those proteins from being activated,â€ he said. â€œThis is really a lesson for researchers who depend on biomarker studies to test whether a treatment is working. They need to be aware that those biomarkers might be telling only half of the story.â€
Bergan cautioned that much is unknown about use of genistein in preventing cancer spread. For example, it may be that the effects of the compound in people who have eaten soy all their lives is stronger than benefit seen in patients who have only started to use genistein.
â€œThe problem we have faced is that epidemiology studies that found men who eat soy are at reduced risk of prostate cancer death are all associative. They donâ€™t prove anything,â€ he said. â€œThe only way we will find out how promising genistein is will be from conducting clinical trials.â€