OK, I’m laying it out for you here…this post will be a little long (I’ve named it The Beast). But I had to share the great information I got when I spoke to Dr. Jorge Chavarro, MD, for Sunday’s On Nutrition column. I could only fit a fraction of what he told me into the column, so here’s the rest.
Chavarro is assistant professor of nutrition and epidemiology at Harvard School of Public Health and assistant professor of medicine at Harvard Medical School. He’s also co-author of The Fertility Diet
. While Chavarro’s research suggests that diet is an important factor in infertility due to ovulation problems, he points out that improved nutrition does not have an effect on infertility due to diseases of the fallopian tubes or other physical causes of tubal blockage. It also does not help with male infertility due to obstructions or genetic factors.
Chavarro said his team’s initial research looked at whether dietary factors that had previously been linked to diabetes or insulin resistance are also related to ovulatory infertility
. In many cases, they are.
- Fats: “The bottom line is that there are some types of fat that are better than others for fertility as well as cardiometabolic health. Monounsaturated fat tends to be more protective.”
- Carbohydrates: “The type of carbohydrate matters. A lower-glycemic load is better. You can get to a high glycemic load by consuming a lot of carbohydrates or high glycemic index carbohydrates.”
- Protein: “Different types of protein exert different effects on how much insulin you release. Women with higher intake of protein from animal sources, especially red meat, were at higher risk of infertility. Women with more plant proteins have lower risk.”
- Non-heme iron is associated with lower risk of infertility. (Heme iron comes from animal foods, non-heme iron comes from plant foods.)
- Folic acid is associated with low risk of infertility. This is one of the most consistent findings in the diet-fertility research, Chavarro said, and part of the increasing evidence that folic acid may have additional reproductive benefits beyond preventing neural tube defects. What about natural folate from foods, such as dark leafy greens? “This is one case where supplements are better,” he said. “Natural folate is harder to absorb, would be very difficult to get to the beneficial level with natural folate.”
Fertility, PCOS and Diabetes
As mentioned, Chavarro started by looking at possible dietary common ground between type 2 diabetes, insulin resistance and fertility. This is significant, and not at all random. Diabetes and polycystic ovary syndrome (PCOS) have insulin resistance in common, and PCOS is not only a huge risk factor for later development of type 2 diabetes, but it is the most common cause of ovulatory infertility.
The Food For Fertility program encourages a Mediterranean-style, anti-inflammatory diet (chronic inflammation can also interfere with fertility) that hits all the points that Chavarro and others have uncovered in their research. It appears to me making a difference.
Both Dr. Angela Thyer, MD
, of Seattle Reproductive Medicine
and registered dietitian Judy Simon, MS, RDN, CD, CHES
, said that they see many, many infertility patients who have PCOS. Simon said the women in her classes, as well as her other fertility patients, are less likely to develop gestational diabetes, and more likely to have healthy pregnancies, because they are eating better and moving more.
The real baddy, it turns out, is trans fats (bad for the heart, bad for sperm). A 2011 study
that Chavarro co-authored measured the levels of trans-fats in 33 men undergoing infertility evaluation. The higher the levels of trans-fats found in the sperm membrane, the lower the sperm count.
What makes this finding even more remarkable is that the sperm samples were collected in late 2008-early 2009…after trans-fat labeling went into effect and the level of trans-fats in the food supply were already on the decline. A similar study among young, healthy men in Spain
found a similar association, again despite the decline in food supply.
Chavarro: “When did the men ingest the trans fats? Had they been lingering in the sperm for decades?”
A large systematic review of clinical trials involving men seeking infertility treatment found we found was that antioxidants were related to improved semen quality. Chavarro said the take home message is that something in those supplements is doing something, but the current research doesn’t allow for detailed conclusions. He said what qualified as a antioxidant has been poorly defined in some studies, and no two clinical trials tested the same intervention (i.e., specific dosage, combination of antioxidants, etc.). Replication of results is an important test of whether those results are valid.
“We have no idea what supplements or at what doses,” he said, adding that carotenoids
do appear to have some positive impact on sperm morphology. “That’s an area that needs more research.”
Sugar-Sweetened Beverages (SSBs)
A recently published study round that SSB intake was associated with lower sperm motility
. Men with the highest intake were the most likely to have reduced motility—and the highest intake was only an average of 1.3 servings per day! Chavarro said they thought that SSB intake might also be associated with a higher body mass index (which could mean that it was excess body fat that was really affecting sperm motility), but it wasn’t
, which means that, in this study, BMI didn’t make a difference. He said the men in this study were young, which may be a factor, and that more research needs to be done.
Milk & Dairy
Chavarro said that low-fat dairy is associated with higher sperm counts
. “That’s actually not that surprising. One of the well-known effects of dairy products is to stimulate growth. Probably any factor affecting or how fast cells divide would influence spermatogenesis.”
Interestingly, his research suggests that women with higher intakes of high fat dairy
have lower risk of infertility. “That’s the one finding that I’m a little skeptical about,” he said.
Chavarro also said that there is still much research that needs about the interactions between food and fertility. “Even as much as we now know, we know very little about hownutrition affects fertility.”
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Photo source: Centers for Disease Control and Prevention