Nutrition Notes

Zinc - One of the Major Influencers of Male Fertility

There are many determinants that are critically important for the proper function of the reproductive system. Lifestyle behaviors, dietary patterns, foods, and individual nutrients are crucial factors. One essential antioxidant nutrient in particular - zinc - tops the list. Zinc is most well-known for its role as a common cold remedy. As mentioned in a previous article, zinc is well known for its role in male reproductive health and fertility. Zinc status is one of the many factors influencing male fertility, a deficiency being correlated with reduced ability to conceive.   

According to a recent systematic review, male factors account for approximately 25% of all infertility cases, and strong adherence to a healthy diet (including zinc-rich foods) is associated with improved semen quality and fecundability rates. Zinc helps protect sperm from the harmful effects of oxidative stress, reported in the International Journal for Vitamin and Nutrition Research to be a causative factor in 30-80% of cases of reduced male fertility. When subfertile men with asthenozoospermia (reduced sperm motility) were given supplemental zinc, the total antioxidant capacity of semen increased, and oxygen sensitivity and catalase activity were restored to proper ranges. Novel findings in a recent study reveal that zinc has a distinct role as a second messenger in the signaling pathway vital for fertility by inducing physiological changes in sperm during the critical period when transcription is inactive.

The recommended dietary allowance for men over the age of 19 is 11mg per day.  As mentioned above, zinc “promotes sperm quality through antioxidant and anti-apoptotic properties” and “acts as a cofactor of metalloenzymes involved in DNA transcription and protein synthesis critical to spermatogenesis.” In addition to research demonstrating zinc’s protective effects on sperm structure, the seminal fluid concentrations of zinc are markedly higher in fertile men compared to subfertile, and structural sperm abnormalities, hypertrophy, and hyperplasia of the fibrous sheath are all associated with zinc deficiency.

Oysters top the list (74 mg per serving) with more zinc per serving than any other food. Other good dietary sources of zinc include shellfish, red meat and poultry, and specific types of beans, nuts, and seeds such as chickpeas and pumpkin seeds. However, due to the phytic acid present in grains, legumes, nuts, and seeds that bind to zinc inhibiting its absorption in the body, animal sources are much more bioavailable than plant sources. Thus, patients who eat primarily vegetarian or vegan diets may be at risk for deficiency and may require as much as 50% more zinc than omnivores. According to research, compared with normal zinc consumption, volunteers with severe zinc depletion resulted in significantly reduced semen testosterone levels and total semen volume. 

Patients should consult with their medical professionals if taking acid-lowering medications as hydrochloric acid (HCl) and vitamin B12 are necessary for zinc absorption. Those who suffer from insufficient gastric acid most likely have trouble breaking down dietary proteins leading to even lower zinc absorption. Heavy alcohol users or those with gastrointestinal disorders causing malabsorption are at risk for zinc deficiency and need to consult with their doctor about ways to increase zinc status. A helpful laboratory marker to test zinc status in patients is alkaline phosphatase. According to functional medicine ranges, levels lower than 70 IU/L may be an indicator of zinc deficiency.

Patients would benefit from avoiding diets high in processed meats, alcohol, sugar-sweetened beverages and trans-fats as they are detrimental to overall semen parameters affecting fertility outcomes. Instead, educate patients to opt-in for diets rich in grass-fed and pasture-raised meats, wild-caught fish and shellfish, monounsaturated fats, and fresh vegetables and fruits rich to boost antioxidant status overall and testicular health.