P-071 The dichotomy of micronutrients in male fertility: doses matter - striking the right balance for optimal reproductive health
Authors: Moazamian A , Hug E , Villeneuve P , Bravard S , Geurtsen R , Saez F , Aitken R  J , Gharagozloo P , Drevet J 
Published: July 2024

Study question

What is the impact of escalating doses of common water-soluble antioxidant nutrients on semen parameters and fertility in healthy (CD1) and stressed (Gpx5-/-) mice?

Summary answer

High-dose supplementation of previously “thought-to-be-safe” common water-soluble antioxidant nutrients can cause significant DNA damage/impaired fertility in healthy mice.

What is known already

In assisted conception, men increasingly take preconceptual antioxidant supplements (even if they are generally healthy) to enhance the likelihood of a successful pregnancy. Recent published reviews suggest 79% of male fertility supplements include ingredients at dosages exceeding Food Safety Authorities’ Recommended Dietary Allowances (RDAs). While many fertility experts question the efficacy of such supplements, most still carry the notion that “dietary ingredients”, regardless of the doses given, pose little safety concerns. Moreover, without established RDAs for many natural substances such as carnitines, supplement makers often subscribe to the “more is better” philosophy, potentially compromising safety in their product formulations.

Study design, size, duration

This study evaluates escalating doses of common water-soluble antioxidant nutrients (Vitamin C, Zinc, Folate, and Carnitines) on redox status, semen parameters, genetic integrity, and fertility in healthy (CD1) and stressed (Gpx5 -/-) mice over 28 days. The treated groups (n = 6) were compared against pooled controls (n = 24). We analyzed the doses of these ingredients in commercial fertility supplements against our new “safety profiles” to highlight potential overdosing risks and asses the broader safety implications.

Participants/materials, setting, methods

Experimental ingredient exposure dosages were based on current US-FDA RDA/I declarations, commercial popularity, and/or use in clinical fertility settings. Animal dosage conversion calculations were based on standard pharmaceutical methodologies. Assessments of male mouse redox status and reproductive function included general sperm parameters (count, motility, viability, acrosome integrity), DNA parameters [oxidation (8-OHdG staining), fragmentation (TUNEL), decondensation (Toluidine Blue)], and blood analysis (total antioxidant capacity, glutathione, malondialdehyde). Pregnancy outcomes were assessed in Carnitine fed, CD1 mice.

Main results and the role of chance

In CD1 mice, escalating doses of individual micronutrients had minimal effect on semen parameters, except for a significant sperm count increase at the highest Carnitine dose. However, there were considerable adverse effects on sperm DNA integrity and blood plasma redox state. The high-dose Carnitine group notably exhibited reduced pregnancy rates, in terms of both impregnation and total pups born, compared to controls. Yet, there were no differences in the number of pups born or resorptions, per pregnant female, between the high-dose Carnitine group and controls.

In GPX5-/- mice, general semen parameters were mostly unaffected. Intriguingly, Carnitine positively influenced sperm DNA integrity in this model, underscoring the established link between micronutrient deficiency, oxidative stress, and semen quality.

In the analysis of 34 random male fertility supplements, almost every product contained at least one ingredient at a dose that was harmful according to our study. Alarmingly, 88% had at least two such ingredients, 68% had three or more, and roughly 33% contained four or more at doses considered unsafe.

Limitations, reasons for caution

Carnitines’ pungent odor may have affected the mating efficiency of carnitine exposed CD1 males. Due to synergy of action, antioxidants administered individually, even at the same dose, may exert a different biochemical profile than when in combination with other ingredients (as in most commercial formulations).

Wider implications of the findings

The majority of male fertility supplements often combine aggressive doses of antioxidant nutrients. Our results highlight the potential dangers that may arise from their use and provide a clear warning to fertility experts against routinely recommending random, unsubstantiated supplements, especially in the absence of prior oxidative stress assessment.

Trial registration number

not applicable