WEDNESDAY, July 23 (HealthDay News) -- Eating half a serving of soy food a day lowers sperm concentrations and may play a role in male infertility, particularly in obese men, Harvard University researchers report.

The reason for this relationship between soy and sperm count isn't clear. However, researchers speculate that soy increases estrogen activity, which may have a negative affect on sperm production and also interfere with other hormonal signals.

"There have been a lot of interest in estrogen and isoflavones in particular and a potential relationship to fertility and other reproductive disorders," said lead researcher Dr. Jorge Chavarro, a research fellow in the department of nutrition at the Harvard School of Public Health.

Research in animals has shown that isoflavones and estrogen can have a potentially negative affect on reproduction, including decreased fertility, Chavarro said. However, there is very little evidence of how these findings apply to humans, he said.

The new research, he added, lends support to how results of animal studies apply to humans. But Chavarro considers the findings preliminary and inconclusive. "It's way too early to say stop eating soy foods," he said. "It's not time to worry about whether you're eating too much soy. There's not enough information to conclusively say that. "

His report was published in the July 24 online edition of the journal Human Reproduction.

For the study, Chavarro and colleagues collected data on 99 men who attended a fertility clinic for evaluation. The men were asked about how much of 15 soy-based foods they ate in the past three months.

The foods men were asked about included tofu, tempeh, tofu or soy sausages, bacon, burgers, soy milk, cheese, yogurt, ice cream and other soy products like roasted nuts and energy bars.

Because different foods have different levels of isoflavones, half a serving of soy is equal to about one cup of soy milk or one serving of tofu or soy burgers every other day, Chavarro noted.

Chavarro's team found that men who ate the most soy had 41 million fewer sperm per milliliter of semen compared with men who did not eat soy foods. Normal sperm counts range between 80 million and 120 million per milliliter, according to a press release from the journal, a monthly publication of the European Society for Human Reproduction and Embryology.

In addition, the researchers found that the link between soy and sperm concentration was stronger among overweight and obese men. Overweight and obese men produce more estrogen than thinner men, and soy may increase those estrogen levels even further, they speculated.

Moreover, the link between soy and sperm concentration was strongest in men with higher sperm concentrations. Men who have normal or high sperm counts may be more susceptible to soy foods than men with low sperm counts, Chavarro said.

Infertility expert Dr. Hossein Sadeghi-Nejad, an associate professor of urology at UMDNJ New Jersey Medical School and Hackensack University Medical Center, agreed that soy may be one factor affecting fertility, especially in overweight and obese men.

"When patients are overweight, the fat tissue converts male hormones to more female hormones," Sadeghi-Nejad said. "So, it is possible that the combination of this estrogenic source [soy] and the extra internal estrogen that is caused by the conversion of androgen to estrogen through the fat has a more deleterious effect in that group of patients."

In addition, Sadeghi-Nejad noted that although sperm counts decreased most among men who have the highest counts, that should not affect fertility, since sperm counts were still in the normal range.

"But this is a good reminder that if you have an overweight patient, with abnormal semen parameters, and a very high soy intake, it may be wise for them to decrease this factor," Sadeghi-Nejad said.

More information

For more about obesity and infertility, visit the Obesity Action Coalition.

you should read about infant soy formulas
the level of phytoestrogens in a day's worth of "milk" for one baby, was equivalent to estrogen levels in 2-3 birth control pills. You wonder how little boys on that diet even manage to produce any sperm at all

ZombieKitten said:

It is kind of scary since hormones control so much...not just sperm.

shanti0608 said:

really creepy

they never talk about its effect on baby girls, but I think it must be just as detrimental to them, we just don't know the long-term implications yet

soy is in everything too these days, isn't it one of the biggest crops in the world? and GM in the states. It finds its way into nearly all processed food products because it is so cheap.

sadly it looks like GM is catching on.
http://www.gmo-compass.or..._2007.html

shanti0608 said:

those countries listed there are desperate economies that will do anything. very sad

It is very tragic.

Have we just discovered something about Phil?

Anyway, I have been saying this for ages, nobody ever bloody listens to the scientists until they want somebody to blame. I have always kept my soy intake low, we don't know enough about phytoestrogens yet.

PREDOMINANT said:

I've been hearing about this for years (I guess it just depends on what one reads )
Do you think the effects can be as equally detrimental for women? I imagine, like a few were saying up above that there is a negative effect on little girls.

If you people take away my soy, then I've got nothing.

OK, then I've got wheat gluten, but still.

Unfermented soy is just bad, bad, bad. It contains a lot of phytic acid, which is a nutrient inhibitor and can cause intestinal distress. Soy has been implicated in early puberty in girls and feminization of boys because of the phytoestrogens it contains. (My sister told me she was giving her sons soy milk because she was concerned about the effects of pasteurization and homogenization on dairy milk and I congratulated her on going from bad to worse.)

It's funny that, in the above article, they talked about the lower sperm counts and mentioned that it's especially a problem for overweight men - but didn't mention that the soy might also be responsible (in part) for their obesity.

Cool.
Cheaper than male birth control.
More tofu!!!!!

You know how it's been said that eventhough you CAN make a baby there are just some people who SHOULDN'T???





Seriously, just proves more and more that EVERYONE needs to be aware of what they are eating and where it comes from.

applekisses said:

Yep, me too. Moderation is the key.

PREDOMINANT said:

Never touch the stuff mate

applekisses said:

Early onset menarche . Problem is there there are very few good studies, if one looks at population studies there doesn't seem to be any detremental affect in eastern cultures where soy has been used for decades (centures). So we are only just starting to see the effects of soy in western diets.

Genesia said:[quote]Unfermented soy is just bad, bad, bad. It contains a lot of phytic acid, which is a nutrient inhibitor and can cause intestinal distress. Soy has been implicated in early puberty in girls and feminization of boys because of the phytoestrogens it contains. (My sister told me she was giving her sons soy milk because she was concerned about the effects of pasteurization and homogenization on dairy milk and I congratulated her on going from bad to worse.)

It's funny that, in the above article, they talked about the lower sperm counts and mentioned that it's especially a problem for overweight men - but didn't mention that the soy might also be responsible (in part) for their obesity.[/quote]

Or that the obesity was the actual cause of low sperm count?

PREDOMINANT said:

I don't get that either. Could it be that our western bodies just need to adjust over some generations?

applekisses said:

It's a couple of things. First, people in eastern cultures eat far less soy than you might think. It is not a main source of protein there (as it is for many people in the west), it is something they eat occasionally. They also eat more fermented soy - tempeh, natto, miso, etc. - which does not have the detrimental effects of unfermented soy. Asians do not drink soy milk or eat soy yogurt or soy ice cream or what have you.

Because of western food processing, there is now soy in practically everything except food that is sold in its natural state. I am a label-reading freak - and try to avoid soy wherever possible.

low count?
Hooray, soy can also be used as a contraceptive.
Honestly, dairy farmers will try anything to get people to continue buying their product.
Milk is for calves. I think Prince once said that and I believe that. Lactose and my body aren't friends so I'll just risk cancer and a low sperm count for the rest of my life.

dseann said:

Ummmmm...what makes you think soy is only used as a dairy substitute?

Genesia said:

Didn't say it was. I use it as a dairy substitute.

At first, I thought the title said " Sony Linked to Low Sperm Count"

dseann said:

No...but you made a crack about the above story being a plot of dairy farmers...which it isn't.

I read/heard alot of things that cause low sperm count.This is a new one that I have heard.

Genesia said:

yeah what you said.
Eastern cultures don't have it bulking up everything, and they eat it fermented.

well then people. soy is the solution for the problem of over population.

dseann said:

this comment makes the pope upset

Genesia said:

I do think so. Are you sure they aren't behind some of the hype?

ehuffnsd said:

He'll get over it ... or die with his ire eventually anyway.