Some 15 percent of American couples fail to conceive within a year, despite frequent attempts to conceive.
Male infertility plays a role in about half of all cases, and the immediate causes include low sperm production, misshapen or immobile sperm, or blockages that prevent its delivery.
Reports of a steady fall in human sperm quality and quantity, and a rise in testicular abnormalities, arose in the 1990's and continue to generate debate over the quality of the evidence (Carlsen E et al. 1993; Merzenich H et al. 2010).
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Key Points
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University of Illinois studies prove omega-3 DHA is critical to sperm potency in mice.
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The reasons for DHA’s key sperm role hold implications for human brain and eye health.
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Iranian clinical trials show infertile men are low inomega-3s and have unhealthily high omega-6:3 ratios.
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The controversy continues, but rising rates of reproductive problems suggest a generally negative trend ... one in which male infertility, more than female failures, is implicated.
Omega-3 intake is an often-overlooked factor in male fertility. And a new study from the University of Illinois shows one previously unknown reason why.
In addition to low omega-3 intakes, the average American’s diet also features an extreme “omega imbalance” in favor of omega-6 fatty acids.
As we’ll explain, the results of a clinical trial suggest that this dietary imbalance may be responsible for some cases of male infertility.
First, let’s look at the new study in mice, and its implications for reproductive, brain, and eye health.
Novel studies detects critical role for DHA
Dozens of animal studies suggest that omega-3s are essential to fertility in male rodents, horses, pigs, and poultry.
And most of these studies indicate that DHA – one of the two major omega-3s found in human cells and in fish fat – enhances sperm quality and motility.
Over the past two years, researchers at the University of Illinois published studies that highlighted the importance of omega-3s … especially DHA.
In addition to getting it from fish or fish oil, people can make small amounts of DHA from the short-chain omega-3 found in certain plant foods, known as ALA.
To test the effects of DHA on the formation of sperm cells, the University of Illinois team bred groups of mice to lack the gene necessary for the conversion of ALA to DHA (Roqueta-Rivera M et al. 2010).
The sperm of mice that were unable to make DHA from ALA were less mobile and lacked the properties necessary for penetrating an egg cell.
“We looked at sperm count, shape, and motility, and tested the breeding success rate. The male mice that lacked DHA were basically infertile,” said lead author Manabu Nakamura, DVM, Ph.D. (UI 2012)
But when DHA was introduced into the mice's diet, fertility was completely restored. “It was very striking. When we fed the mice DHA, all these abnormalities were prevented,” he said (UI 2012).
Illinois study illuminates unrealized role of DHA in fertility … and beyond
The scientists used 3D microscopy to look at thin slices of tissue in progressive stages of a sperm cell’s development (Roqueta-Rivera M et al. 2011).
As Professor Nakamura explained, “Normal sperm cells contain an arc-like structure called the acrosome that is critical in fertilization because it houses, organizes, and concentrates a variety of enzymes that sperm use to penetrate an egg.” (UI 2012)
The study shows for the first time that omega-3 DHA is essential in fusing the building blocks of the acrosome together.
In the absence of DHA, the vesicles were formed but they didn’t come together to make the arch critical to proper sperm cell structure.
“We could see that the acrosome is constructed when small vesicles containing enzymes fuse together in an arc. But that fusion doesn't happen without DHA,” Nakamura said (UI 2012).
In short, it’s now clear that omega-3 DHA is necessary to construct the arch that turns a round, immature sperm cell into a strong, pointy-headed swimmer with an extra long tail.
In light of their results and the many prior animal studies concerning DHA and male fertility, the researchers concluded that DHA plays a critical role in fertility of all mammals … including humans.
But the implications of their findings extend far beyond fertility.
Sperm findings hold implications for brain and eye health
Because DHA is abundant in the brain and the retina as well as the testes, Nakamura’s team believes that their research findings hold implications for mental and visual health.
As Dr. Nakamura said, “It's logical to hypothesize that DHA is involved in vesicle fusion elsewhere in the body, and because the brain contains so much of it, we wonder if deficiencies could play a role, for example, in the development of dementia. Any communication between neurons in the brain involves vesicle fusion.” (UI 2012)
The Illinois scientists will continue to study sperm. Meanwhile, Nakamura has sent some of his DHA-deficient knockout mice to laboratories where scientists are studying DHA function in the brain and the retina.
Omega-3s improve men’s sperm quality in clinical trial
Last year, Iranian scientists published the results of a clinical trial testing the effects of omega-3 supplements on men’s sperm health (Safarinejad MR 2011).
They recruited 238 infertile men and randomly assigned them to take 1.84 grams of supplemental omega-3s (EPA + DHA), per day, or a placebo, for 32 weeks.
They found significant improvements in sperm count and concentration among men in the omega-3 group.
And they also reported a significant correlation between higher levels of EPA and DHA in seminal fluid, greater antioxidant activity in the fluid, and better scores on key measures of sperm quality.
Interestingly, the higher omega-3-related antioxidant activity seen in the omega-3 group’s seminal fluid was linked to enhanced sperm count, sperm motility, and sperm morphology.
(The biomedical term “morphology” refers to the form and structure of organisms or cells and their specific structural features.)
The Iranians came to an obvious conclusion: “[infertile] men with low levels of EPA and DHA may benefit from omega-3 supplementation.” (Safarinejad MR 2011)
Omega-3 imbalance implicated in male infertility
Two years ago, the same Iranian team published a study that linked the balance between omega-3 and omega-6 fatty acids to male infertility (Safarinejad MR et al. 2010).
They recruited 82 infertile men with abnormal sperm density, movement, morphology, or shape, and 78 fertile men.
The Iranians measured the levels of three major omega-3s (ALA, EPA and DHA) and two major omega-6 fatty acids (LA and AA) in the men’s blood and sperm.
Compared with the infertile men, the fertile volunteers had higher blood and sperm levels of omega-3s.
And compared to the fertile men, the infertile recruits had significantly higher ratios of omega-6 to omega-3 fatty acids.
Additionally, the blood and sperm levels of omega-6 AA in infertile subjects were higher and levels of omega-3 EPA and DHA were lower, compared with the fertile men.
The infertile men also had higher average AA:DHA ratios and AA:EPA ratios, compared with the fertile men
Last, the Iranian team found a strong link between high AA:DHA and AA:EPA ratios and low sperm counts and motility, as well as abnormal sperm morphologies.
As they wrote, “Infertile men had lower concentrations of omega-3s in spermatozoa than fertile men. These results suggest that research should be performed to assess the potential benefits of omega-3 supplementation as a therapeutic approach in infertile men ...” (Safarinejad MR et al. 2010)
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