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Last summer a team of researchers from the Massachusetts Institute of Technology set out to better understand the effects of yogurt on obesity. They were following up on the results of a long-term study from the Harvard School of Public Health that had suggested yogurt, more than any other food, helped to prevent age-related weight gain. The M.I.T. team, led by cancer biologist Susan Erdman and evolutionary geneticist Eric Alm, wanted to replicate the work in mice. The researchers took a group of 40 males and 40 females and either fed the animals a high-fat, low-fiber, low-nutrient diet meant to mimic junk food or fed them standard mouse meals. They then supplemented half of each diet group with vanilla-flavored yogurt.
Their goal was to understand how a probiotic diet affects rates of obesity and its related complications, including cancer. But “the most entertaining aspects of all this were things we didn’t anticipate,” Erdman says.
First, the scientists noticed that the yogurt-eating mice were incredibly shiny. Using both traditional histology techniques and cosmetic rating scales, the researchers showed that these animals had 10 times the active follicle density of other mice, resulting in luxuriantly silky fur.
Then the researchers spotted something particular about the males: they projected their testes outward, which endowed them with a certain “mouse swagger,” Erdman says. On measuring the males, they found that the testicles of the yogurt consumers were about 5 percent heavier than those of mice fed typical diets alone and around 15 percent heavier than those of junk-eating males.
More important, that masculinity pays off. In mating experiments, yogurt-eating males inseminated their partners faster and produced more offspring than control mice. Conversely, females that ate the yogurt diets gave birth to larger litters and weaned those pups with greater success. Reflecting on their unpublished results, Erdman and Alm think that the probiotic microbes in the yogurt help to make the animals leaner and healthier, which indirectly improves sexual machismo.
The findings could have implications for human fertility. In ongoing work, a team led by Harvard nutritional epidemiologist Jorge Chavarro has looked at the association between yogurt intake and semen quality in men. “So far our preliminary findings are consistent with what they see in the mice,” Chavarro says.
This article was published in print as "Mice That Eat Yogurt Have Larger Testicles."
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20 Comments
Add CommentThis study might turn out to be more of an argument for (or against) the use of modern-day dairy products themselves to enhance weight loss or fertility in mice (or humans), than on the effects of pro-biotics. Without having read the study, of course, I have no way of knowing whether the researchers factored in, or ruled out, the other biochemical components present in the (presumably commercially available “vanilla”) yogurt, which might have contributed to the effects they observed. Even if the yogurt they used was completely organic, and not laced with Bovine Growth Hormone, artificial or natural flavorings, or other additives commonly found in commercial yogurt; even if it was not full of carrageenan or pectin (which, I understand, neutralize the pro-biotic actions in yogurt, anyway), the yogurt still would have contained hormones and nutritional components naturally occurring in cow’s milk that mice (or, sometimes, men) might not have encountered in their own natural feeding processes, and which might have contributed to the effects they observed. Before attributing these effects to pro-biotics, I’d like to see what the specific biochemical components in the milk from which the yogurt was made were, which might have caused these dramatic, and, frankly, somewhat scary, changes in fertility, hair-growth, behavior, etc., before assuming the changes were solely as a result of the pro-biotics in the yogurt.
Reply | Report Abuse | Link to thisI am so tired of science journalists who can't convey such basic information as:
Reply | Report Abuse | Link to this(1) What was the control?
(2) Provide the reference for the published article.
Oh... unpublished results. *sigh*
Reply | Report Abuse | Link to thissuggest that Willard Robme try this diet - he needs a pair ...
Reply | Report Abuse | Link to thisI agree with you. I would like to know this information too. I don't know why it is so difficult for SciAm journalists to provide more information, or at least promise to provide more information when it comes available. It's not like this digital magazine is liking for space. If off the shelf yogurt can make our reproductive organs more healthy, maybe we should ban it and take it off the shelves...we don't need to increase our population more.
Reply | Report Abuse | Link to thisAgree whole-heartedly. Just plain laziness. But pretty typical of the typical and predominate American. America's decline is well-deserved.
Reply | Report Abuse | Link to thisAgree, indeed. These kinds of studies are a step away from Nat'l Enquire fodder. Since the hormones secreted from the Pituitary are tropic hormones (make the target glands bigger) and bigger end-organ targets usually mean that stimulation is going on---because the hormone level are low. That's the reason why muscle heads/juicers at the gym have testicles the size of pencil erasers--their equipment needs no pituitary stimulation beause their testoserone levels are superphysiologic. Thus, if the rats had larger gonads it could be because the yogurt made their endogenous testosterone drop and they needed some stimulation to produce some T. That's why in Iodine deficiency people produce goiters (enlarged thyroids) due to the tropic stilmulation of TSH.
Reply | Report Abuse | Link to thisFaking intelligence with negativity won't stand up with crutches and a wall. It's a decent preliminary study - the control group is referenced, and the variable was narrowed to yogurt. Congrats to the mice on the winning team ... can't wait for the advertisements!
Reply | Report Abuse | Link to thisThe proof is always in the (yogurt-based) pudding, but Chavarro's group at Harvard has found that a high intake of saturated fats was negatively related to sperm concentration in adult overweight men...though 2/3 of these were smokers. http://www.ncbi.nlm.nih.gov/pubmed/22416013
Reply | Report Abuse | Link to thisSo, presumably, it's a lower fat yogurt, and the probiotics may not be not what helps mice build bigger balls, as it were. :) IMO, testosterone is underestimated in its importance in obesity in men.
It is no wonder Speedy Gonzales was unavailable for comment.
Reply | Report Abuse | Link to thisI don't know what to think, but my chihuahua loves yogurt and he has nuggets the size of baseballs and a sex drive to match. LOL
Reply | Report Abuse | Link to thisFor me, I just think this research might find something significant while I am not familiar with this field. Or perhaps this paper would lead to some problems about the ethnics.
Reply | Report Abuse | Link to thisI agree with the initial poster. This is sloppy work indeed, with many confounded variables and no real controls. While it *might* be useful as a preliminary “is-there-anything-here-worth-pursuing” type of study, it certainly need not be publicized. But now, with its being “published” in a journal with as much credibility to the man-in-the-street as Scientific American, it is too late. This is indeed a sad commentary on the continued loss of rigor in research and its reporting by poorly-trained writers unable to differentiate between pop science and the real thing. Hmmm… loss of rigor… maybe if we put that entire research team and the SA writers and their editors on an all-yogurt diet, they would do better quality work…
Reply | Report Abuse | Link to thisTHANK YOU Owl905!!!!! I was thinking the same thing. The control group is clearly referred to, as was the fact that the study is yet to be published (repeatedly), but the persons conducting the study and from where were repeatedly referred to as well. It would not be difficult to simply go to MIT's or Harvard's website and look up an email for one of the researchers. I'm sure they'd be more than happy to share any details requested. After all, every scientist would love to see their work replicated to lend it support. Also, this magazine (while I love it) is a lighter form of reading intended to get the average person interested. It's not a Scientific Journal, so not providing specific references in this medium is perfectly acceptable and certainly not a sin. Furthermore, they make no claims that the findings are concrete. They clearly state that the research is in its early phases and yet to be confirmed. Also, in regards to the testosterone debate, that is completely irrelevant and has nothing to do with the reported fact that the mice eating the yogurt/with larger testes were more successful at impregnating the females and produced more offspringand the research has begun to be replicated with humans and so far they found support for it.i seriously don't see what there is to knock here. It appears as if some people are blatantly disregarding the information in front of them in an effort to simply be disparaging, so they can try to feel superior.
Reply | Report Abuse | Link to this"Narrowed to yogurt," but there's yogurt, and then there's yogurt. What KIND of yogurt was it? Had the milk from which it was made been treated with BGH?? What other additives were in the milk/yogurt, which may have been responsible for the changes in behavior and physical characteristics in the mice? Is it the yogurt itself (the chemical changes that come about with fermentation, for example) or what has been added to the yogurt...maybe that's what they should look at next... what components IN the yogurt could cause these changes...
Reply | Report Abuse | Link to thisThat did it, I'm going to have to start eating yogurt now.
Reply | Report Abuse | Link to thisHow they weight mice testicles ?!
Reply | Report Abuse | Link to thisO those MIT pranksters...
My bet is that lactic acid along with epithelia pro-biotic cooperation achieves something in expanded biological space related to epigenetic phenomena which in turn drives phenotypic expression. It is a shame that many modern couples do not know how to behave in order to avoid problems when lazy sperms are in place or other unrelated fertility problem. More should be know about carbon signaling systems as an outcome of genomic capacitance.
Reply | Report Abuse | Link to thisAnd don't forget that synthetic one used in non - organic stuff has much D isomer which is damaging enzymatic activity within both pro bac and a host!
Reply | Report Abuse | Link to thisDid they kill the swaggering mice and took out the testicles to do the measurement?
Reply | Report Abuse | Link to this