Kedelai Kurangi Jumlah Sperma?

[markosprawira]

KOMPAS.com - Jumlah sperma ikut menentukan kualitas kesuburan seorang pria. Seorang pria dianggap subur bila ia memiliki lebih dari 20 juta sperma per milimeter cairan mani. Agar kuantitas sperma tetap terjaga, sebaiknya calon ayah mengurangi konsumsi kedelai.

Penelitian yang dilakukan terhadap 99 pria yang bermasalah dengan kesuburan menunjukkan, mereka yang mengonsumsi makanan berbahan kedelai setiap hari, mengalami penurunan jumlah sperma.

Hal tersebut disebabkan karena senyawa kimia yang disebut isoflavon yang ada di dalam kedelai. Isoflavon mirip dengan hormon estrogen. Meningkatnya jumlah estrogen akan membuat persentase lemak tubuh meningkat (itu sebabnya wanita memiliki lemak tubuh lebih tinggi). Padahal, berat badan berlebih akan menyebabkan berkurangnya kesuburan.

Selain itu, kedelai juga diketahui bisa mengurangi penyerapan zinc oleh tubuh. Bagi pria yang sedang merencanakan kehamilan, zinc sangat dibutuhkan untuk meningkatkan jumlah sperma dan kadar hormon testoteron.

Kendati demikian, bukan berarti semua makanan berbahan kedelai harus dihindari. Yang penting adalah menjaga agar jumlah kedelai yang dikonsumsi tidak berlebihan. Pasalnya, sejumlah studi yang meneliti kaitan antara kedelai dan kesuburan menunjukkan penurunan jumlah sperma bila kedelai yang dikonsumsi berlebihan.

Sebagai contoh, dalam sebuah studi terhadap mencit menunjukkan, konsumsi kedelai dalam jumlah rendah (sekitar 2mg/kg berat badan) selama 90 hari, tidak menyebabkan pengurangan sperma. Baru setelah dosisnya ditambah menjadi 20 mg/kg atau 100 mg/kg, terjadi pengurangan.

Untunglah kadar kedelai dalam makanan tidak terlalu tinggi. Sebagai contoh 1 cangkir susu kedelai mengandung 30 mg, 1/2 cup kacang kedelai mengandung 47 mg, tempe sekitar 37 mg, serta tahu 20 mg. Jadi, bila berat Anda kira-kira 79 kilogram, maka pengurangan jumlah sperma baru terjadi bila Anda mengonsumsi sektiar 1.600 - 8.000 miligram kedelai.


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[FZ]

Men don't need to fear soy foods
Guest contributor: Karen Collins, M.S., R.D., C.D.N.
Karen Collins holds a B.S. degree from Purdue and an M.S. degree from Cornell, both in nutrition. When she's not writing or speaking, she conducts a private nutrition practice in Jamestown, New York.

It's no wonder that men who have read the recent stories circulating about soy are confused. Some stories claim that soy foods, such as tofu and soy milk, can lead to breast growth or reduce testosterone levels. Other stories tout the benefits of soy, suggesting soy may help protect against prostate cancer.

Women have wondered for years whether phytoestrogens affect their health, from menopausal hot flashes to breast cancer. Now men are left to wonder about soy foods possible unwanted effects.
Soy studies don't show harm

Soy contains compounds called isoflavones that are known as phytoestrogens, which are weak plant versions of the hormone estrogen. Fears that the amount of phytoestrogens in moderate amounts of soy foods could stimulate men's breast tissue or reduce their testosterone are not based on sound research.

A study of children fed soy protein formula for more than six months showed no hormonal effects. A study of men in their 50s and 60s found that the men who ate soy foods twice a day for three months showed no change in testosterone levels, but had a 14 percent drop in levels of PSA (an indicator of prostate growth used in screening for prostate cancer).

Concerns about lowering sperm count and affecting fertility also do not seem to hold up in human studies of realistic dietary consumption.
Soy and prostate cancer

Whether soy foods offer protection from prostate cancer is still an open question. One recent analysis that combined results from many studies found that men who consumed the most soy foods or the isoflavones they contain were 26 percent less likely to develop prostate cancer. Yet studies overall suggest that men may differ in their response to soy.

Asian populations tend to show a much greater drop in prostate cancer risk with soy foods than Western populations. Japanese men with highest consumption of soy or blood levels of isoflavones have shown 40 to 60 percent lower risk of prostate cancer than those with lowest consumption or blood levels.

Yet European studies on the effect of soy are inconsistent.

The difference between Asian and Western populations could stem from several sources, such as the bacteria in our gut. All people carry millions of useful bacteria in thier digestive tracts that help metabolize food, yet different populations (and people) carry varied types of bacteria.

Some bacteria break down food isoflavones into a compound (equol) that is linked with lower prostate cancer risk. Overall, Asian populations show a higher proportion of equol-producers, which could be one reason why soy is more often linked with prostate protection in these groups.

The type of soy food also makes the research challenging. Fermentation may change how easily our bodies absorb isoflavones, which means that fermented soy foods (miso, tempeh, natto) may have a different effect on prostate cancer risk than non-fermented soy foods (soy milk, tofu and edamame). Some studies suggest that the effect of soy foods may depend on its interaction with other food compounds; the lycopene from tomatoes is one such interaction under study.

While we wait for more answers about the possible protection from soy, men can feel safe eating one or two servings of soy foods daily. Soy foods are nutritious, low in saturated fat, and men have consumed them for generations without harm. However, until we know more about isoflavone safety, research does not show benefit or safety of consuming large amounts of isoflavone supplements in hopes of achieving protection.

(This article was provided by the American Institute for Cancer Research in Washington, D.C. A registered dietician is available to respond to questions about diet, nutrition, and cancer at the free AICR Hotline at 1 (800) 843-8114 during business hours.)