Fish Tales: Does Seafood Consumption Increase Fecundity?

For couples trying to conceive, a diet rich in seafood may prove to be advantageous in their efforts to start a family. According to a new study, just two servings of fish per week not only improved various biological markers but also increased the number of times the couples were intimate. 

This past May, a study appeared in The Journal of Clinical Endocrinology & Metabolism that said greater seafood intake among couples trying to get pregnant was associated with higher sexual intercourse frequency and fecundity, bringing hope to couples who may be having trouble conceiving.

The authors of the paper wrote in their conclusion that couples achieved these results when they consumed eight or more servings of seafood per cycle, or about two servings per week. Seafood, of course, is an important source of protein and other nutrients for women who are or may become pregnant but concerns about mercury levels in fish have led some women to avoid seafood altogether when trying to conceive.

According to the lead author of the paper “Seafood Intake, Sexual Activity, and Time to Pregnancy,” Audrey Gaskins, ScD, of Harvard T.H. Chan School of Public Health in Boston, Mass., while seafood is a recommended component of many healthy eating patterns, in the context of fertility it’s largely been studied as a potential source of harm, given that it could be a source of exposure to toxicants such as organochlorines, dioxins, and mercury.

The Food and Drug Administration and the Environmental Protection Agency says that 90% of the fish eaten in the U.S. is low in mercury and safe to eat. And although the agencies recommend two to three servings of lower-mercury fish per week, 50% of pregnant women still eat far less than the recommended amount. Gaskins lays out a few reasons for that second statistic: The first is the aforementioned concern about environmental contamination and fear of exposure, especially to methyl mercury. “A great example of this is in January 2001 there was a well-publicized federal advisory recommending that pregnant women limit consumption of certain fish because of concerns about mercury contamination,” she says. “Not surprisingly, subsequent research showed that after the dissemination of these federal recommendations, pregnant women reduced their consumption of fish, including tuna, dark meat fish, and white meat fish.”

Beyond that, seafood is usually more expensive than other sources of protein, which prices out a lot of people, so they go for cheaper options like chicken and beef. “The third reason which also comes up frequently is that many people just don’t like the taste of seafood,” Gaskins says.

Despite all this, research is starting to show the benefits of a seafood-rich diet when it comes to fertility. “A few recent studies have found reproductive benefits with higher marine long-chain omega 3 fatty acid intake, of which seafood is the primary source, which led us to wonder whether seafood intake, when looked at as a whole, was good or bad when it came to fecundity and what we should be recommending to couples trying to get pregnant,” Gaskins says.

Angling for Couples

In a prospective cohort study, Gaskins and her colleagues followed 500 Michigan and Texas couples from the Longitudinal Investigation of Fertility and the Environment (LIFE) Study for one year to determine the relationship between seafood intake and time to pregnancy. Participants recorded their seafood intake and sexual activity in daily journals.

The researchers chose to recruit couples from these two states because they comprised individuals residing in four Michigan counties with reported exposure to persistent organochlorine chemicals (i.e. Berrien, Calhoun, Ingham, Kalamazoo) and 12 counties in Texas (i.e. Aransas, Brazoria, Calhoun, Chambers, Fort Bend, Galveston, Harris, Jefferson, Matagorda, Montgomery, Nueces, and Orange) with presumed exposure to persistent environmental chemicals.

“Moreover, we were particularly interested in couples with ties to the angler community as they would be more likely to consume seafood from these local water ways,” Gaskins says. “The original aim of the cohort was to assess the effect of environmental chemicals, specifically persistent chemicals such as PCBs, on fertility. Since seafood is one potential route of exposure to persistent chemicals, we collected information on this variable.”

The researchers found that 92% of couples who ate seafood more than twice a week were pregnant at the end of one year, compared to 79% among couples consuming less seafood. The association between seafood and faster time to pregnancy was not completely explained by more frequent sexual activity, suggesting other biological factors were at play. These could include effects on semen quality, ovulation or embryo quality.

Correlation Does Not Equal Causation

Gaskins says that several previous studies have found positive associations between omega fatty acid intake and seafood intake and semen quality parameters, lending support to the idea that higher seafood intake could increase the quantity and quality of sperm. Among women, dietary intake of docosapentaenoic acid (which is found in seafood) was associated with a lower risk of anovulation, and dietary intake of total marine omega-3 polyunsaturated fats was associated with increased luteal-phase progesterone concentrations, suggesting beneficial effects of seafood on ovulation and menstrual cycle function.

“A few recent studies have found reproductive benefits with higher marine long-chain omega 3 fatty acid intake, of which seafood is the primary source, which led us to wonder whether seafood intake, when looked at as a whole, was good or bad when it came to fecundity and what we should be recommending to couples trying to get pregnant.” – Audrey Gaskins, ScD, Harvard T.H. Chan School of Public Health, Boston, Mass.

Finally, two separate infertility cohort studies have shown that embryo quality measures were improved among women with higher fish intake, supporting a favorable role of seafood intake on early embryo development.

Another interesting finding in this study was the daily odds of sexual intercourse were 39% higher when both partners consumed seafood on the same day, supporting the popular theory that seafood is an aphrodisiac. But Gaskins is cautious here; correlation doesn’t equal causation.

When asked about the biological reason for this association, she says that the short answer is they’re not sure. Shellfish like oysters are high in zinc, and studies have shown that in humans, dietary zinc intake has a positive correlation with testosterone levels and in rats that zinc therapy improves sexual competence. “However,” she says, “given that we did not measure zinc intake in our study and zinc is found in many other foods other than seafood, we felt uncomfortable making this link. It is also possible that couples who consume higher amounts of seafood together share more meals and thus more time together (including nights) which may be a behavioral explanation for the association we observed with sexual activity.”

Going Back for Seconds

But there’s still work to be done. For example, the researchers point out that they weren’t able to obtain daily dietary assessments from participants since it would have been too burdensome. Therefore, they couldn’t evaluate whether the men and women who ate more seafood also had a healthier diet. In their study, however, seafood intake was not associated with income or education which led them to believe that seafood may not be as tightly correlated with a healthy diet in this population (as it is in others).

“If we were to study a population which primarily consumed predatory fish, which tends to be high in environmental chemicals, we might find that overall, the detriments of consuming seafood (because of exposure to these toxicants) far outweigh the potential reproductive benefits. Future research will have to evaluate this further.” – Audrey Gaskins, ScD, Harvard T.H. Chan School of Public Health, Boston, Mass.

Gaskins also says that they do not have a good biomarker of seafood intake and therefore they have to rely on self-reported intake when doing research. “There are proxies for seafood intake that we can measure in the blood — for example, levels of long chain omega 3 fatty acids, which are derived from seafood, but this is not a perfect biomarker as people can consume these long chain omega fatty acids from supplements as well,” she says.

And in their conclusion, Gaskins and her team write that further research is needed to study that effects of eating predatory fish, which tend to have higher levels of environmental chemicals and mercury and could actually produce adverse health effects. Predatory fish such as swordfish and sharks have higher concentrations of these chemicals because of bioaccumulation which starts when algae absorbs small quantities of these chemicals at the beginning of the food chain.

“In the U.S., the majority of fish that we eat is from non-predatory fish which limits our potential exposure to high levels of environmental chemicals,” Gaskins says. “Therefore, we’re likely getting most of the benefits of fish and very few of the potential downsides due to environmental contamination. However, if we were to study a population which primarily consumed predatory fish, which tends to be high in environmental chemicals, we might find that overall, the detriments of consuming seafood (because of exposure to these toxicants) far outweigh the potential reproductive benefits. Future research will have to evaluate this further.”

For now, Gaskins and her team conclude that their research suggests that both men and women should aim to consume at least two servings of low-mercury seafood per week for the maximum fertility benefit. “Furthermore,” she says, “we saw no detrimental effect of higher seafood intakes on fecundity in men or women suggesting that couples may see benefits of seafood intake above and beyond the two servings per week suggestion.”

— Bagley is the senior editor of Endocrine News. In the August issue, he wrote about managing acromegaly patients after they’ve been successfully treated or even cured.

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