Vegans have lower sperm counts

[Ender]

linka

Soy Linked to Low Sperm Count
Could affect fertility, especially in overweight and obese men, researchers report

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.

[Superman]

Before modern medicine, this would have been nature's way of selecting them out of the gene pool.

[Fingolfin_Noldor]

Yeah I remember reading about that some years back. Which kinda sucks since soy bean milk is pretty nutrious and has less fat in them

[Archaic`]

Wouldn't that be something evolved to keep population numbers down then? If you're more healthy, and living longer, you don't want to be creating quite as many children as quickly as you would otherwise.

[Ender]

Wouldn't that be something evolved to keep population numbers down then? If you're more healthy, and living longer, you don't want to be creating quite as many children as quickly as you would otherwise.

No, this is more likely a "bug" then a "feature", most things are. There is no particular pressure to weed out those who eat soy over meat, so this trait never got pushed out.

[Broomstick]

First of all, the title of this thread is misleading. Nowhere in that article did it define the men studied as vegetarians, much less vegans.

Second - in mankind's pre-industrial situation obesity would have been uncommon, so this effect would have been minimal even among populations that consumed large quantities of soy. Given that regions of the world where soy consumption is quite high - parts of Asia - population is quite high I have to question whether this really has that much effect on fertility, even if it does affect sperm counts.

[FSTargetDrone]

First of all, the title of this thread is misleading. Nowhere in that article did it define the men studied as vegetarians, much less vegans.

Vegans especially (such as myself) seem to be targets of some ridicule/teasing here, so it's not surprising. Really, the subject should be "Overweight Men Who Eat Lots Of Soy May Have Reduced Sperm Count."

Second - in mankind's pre-industrial situation obesity would have been uncommon, so this effect would have been minimal even among populations that consumed large quantities of soy. Given that regions of the world where soy consumption is quite high - parts of Asia - population is quite high I have to question whether this really has that much effect on fertility, even if it does affect sperm counts.

Yes and I think it's important that the whole obesity aspect of this study is not ignored here.

[Knife]

Vegans especially (such as myself) seem to be targets of some ridicule/teasing here, so it's not surprising.

Oh, poor thing.

[Dooey Jo]

I've never heard of an obese vegan. That's a fine thread title there, but yeah, let's mock those gosh darned grass eaters for no reason!

[Knife]

I've never heard of an obese vegan. That's a fine thread title there, but yeah, let's mock those gosh darned grass eaters for no reason!

Why not? Lets mock those that eat too much and become obese as well as those who don't eat except grass and starve.

[Lonestar]

I've never heard of an obese vegan.

Obviously you've never ridden the DC Metro during a "Protest against the World Bank/IMF/Bush Administration" event.

[FSTargetDrone]

Vegans especially (such as myself) seem to be targets of some ridicule/teasing here, so it's not surprising.

Oh, poor thing.

Hey, I'm not complaining, just calling it like I see it. I must admit most of that is directed at the crazy vegans.

[FSTargetDrone]

Why not? Lets mock those that eat too much and become obese as well as those who don't eat except grass and starve.

Rabbits eat grass. We eat tofu!