Diet is a modifiable male factor for semen quality

Sperm counts have fallen by 50%–60% in developed nations since 1973. The underlying causes are a matter of both active research and heated debate, but worsening diet quality & increasing obesity could, to some extent, explain these trends.

Despite ICSI overcoming the standard IVF limiting factors of sperm number, motility and morphology, some sperm issues still affect the chance of fertilisation and pregnancy.

Why does diet matter?

There are a number of complex steps in the transformation from spermatogonia to mature sperm which may be affected by diet. Spermatozoa lose most of their cytoplasm & grow a tail before leaving the testis. These processes include repeated oxidation reactions & make sperm exceedingly susceptible to oxidative stress. Also, an adequate supply of substrates for DNA production is essential to meet the constant demands for the new DNA in sperm production.

Modifiable male factors affect semen quality. Diet, including types of fatty acids, presence of folate, and a ‘’healthy diet’’ have all been associated with positive changes in semen quality.

Fatty Acids

The fatty acid composition of the sperm cell membrane is highly important for proper sperm function & the sperm cell membrane plays a critical role in key fertilization events, such as capacitation, acrosome reaction, and sperm-oocyte fusion. The amount of Polyunsaturated fatty acids (PUFAs) in the sperm cell membrane increases as the sperm matures (20% of the fatty acid content in mature sperm, compared with only 4% in immature germ cells).

PUFAs cannot be synthesized by humans and must therefore be obtained from consuming nuts, seeds, vegetable oils (Linoleic acids), or seafood (omega-3 PUFAs). In observational studies among fertility patients, higher intake of omega-3 PUFAs has been related to a greater proportion of morphologically normal sperm & fish intake to total sperm count and normal sperm morphology.

Walnuts, which contain large amounts of plant omega-3 fatty acids, have been related to higher sperm parameters. In a randomised controlled trial of young healthy men consuming a typical Western-style diet, men randomised to walnut supplementation of 75 g/d for 12 weeks had improvements in sperm vitality, motility, and morphology compared with control subjects.

Trans fatty acids & saturated fats

Trans fatty acids and saturated fats appear to have the effect on spermatogenesis opposite to that of PUFAs. Like PUFAs, trans fats—which are primarily found in commercially baked and fried foods—accumulate in the testis, but unlike with PUFAs, sperm membrane levels and intake of these fatty acids has been consistently related to poor semen quality, particularly to lower counts.

Nonhuman models suggest that diets supplemented with trans fats result not only in decreased spermatogenesis but can, in a dose dependent manner, decrease production of testosterone, reduce testicular mass, and promote testicular degeneration.

Folates

Folic acid intake affects sperm production as Folates play an important role in spermatogenesis during one-carbon metabolism. This is a biochemical reaction central to the synthesis of DNA, which takes place in the testes. Disruption of this metabolic pathway has detrimental consequences on sperm production.

Multiple trials have shown folic acid supplementation increases sperm concentration & motile sperm. Also, folate intake has been related to a lower frequency of sperm aneuploidy (a study of healthy non-smoking men with the highest folate intake (150 mg/d) had a lower incidence of disomy X, sex nullisomy, disomy 21, and aggregate aneuploidy in their sperm.

In rodent models, folate-deficient diets result in differential sperm DNA methylation at sites associated with cancer and chronic human diseases, decreased pregnancy rates, increased post implantation embryo loss, and increased abnormalities in their offspring.

Antioxidants

Antioxidant supplementation has been used as a factor for sperm defence against oxidative stress for a number of years. However, a recent trial —Males, Antioxidants, and Infertility (MOXI)— found there was no beneficial change in bulk semen parameters (concentration, motility, or morphology) nor any significant change in sperm DNA fragmentation indices in the men taking the supplements.

This could be for a number of reasons:

The formulation chosen may not have been appropriate. Steiner et al. selected the supplements vitamin E, selenium, N-acetylcysteine, and carnitine as their intervention. This reflects a readily available commercial formulation. Coenzyme Q10 was not used (CoQ10 has promising evidence supporting its ability to improve sperm concentration and motility).
There were more men with secondary infertility in the placebo group.
The study excluded men with severe oligozoospermia.

Pesticide Residues

Fruits and vegetables are universally recommended as an essential component of a healthy diet, but are also the main source of pesticide residues in the diet.

Fruits and vegetables with low to moderate pesticide residues, such as onions, avocados, and beans, are positively associated with semen parameters among young healthy men. In men attending a fertility clinic, total fruit and vegetable intake was unrelated to semen parameters, although intake of high-pesticide-residue fruits and vegetables, such as strawberries, spinach, and apples, was associated with poorer semen quality.

On average, men in the highest quartile of high-pesticide-residue fruit and vegetable intake (R1.5 servings/day) had 49% lower total sperm count and 32% lower percentage of morphologically normal sperm than men in the lowest quartile of intake.

Low- to moderate-pesticide-residue fruit and vegetable intake was associated with a higher percentage of morphologically normal sperm.

Diet patterns

Diet patterns have the most consistent association with semen quality. In recent reviews, a healthy dietary pattern, such as the Mediterranean diet or diets with a high intake of seafood, poultry, whole grains, legumes, skimmed milk, fruits, and vegetables, has been consistently associated with better semen parameters & lower sperm DNA fragmentation in studies in North America, Europe, the Middle East, and East Asia.

Unhealthy dietary patterns that were high in fats, red and processed meats, refined grains, sweets and sweetened beverages were associated with poorer semen quality.