Dear Osa friends,

Happy summer to you! I’m back from my test prep and am excited to break open a new conversation this week around a sometimes overlooked topic in men’s health: testosterone. We’re going to discuss a few nutritional factors that can affect testosterone levels, in addition to touching on one of our most favorite topics, exercise. Please keep in mind that this is not in any way an exhaustive discussion, but I hope that it gives you some food for thought and maybe even prompts a discussion with your healthcare provider. Enjoy!

Prevalence of low testosterone

Low testosterone, also called “hypogonadism” and defined by a total testosterone level < 300 ng/dL, has been estimated to have a prevalence of roughly 40% in U.S. men over the age of 45¹. A deficit in testosterone has important implications for men’s health because testosterone plays a major role in body composition and energy metabolism–this means that without adequate testosterone, the body has a harder time holding on to muscle and is prone to reduced sensitivity to insulin, poor glucose control, and an elevated lipid profile–all aspects of metabolism syndrome and precursors to type 2 diabetes². Signs of low testosterone include decreased muscle mass, decreased bone density, increased body fat (especially abdominal fat), lack of motivation, fatigue, and decreased libido. Low testosterone and excess body fat together compound metabolic abnormalities because they work in a bidirectional manner: low testosterone promotes fat deposition, and fat cells contribute to lower testosterone via activity of the enzyme aromatase, which converts testosterone into estrogen ²٠³. These issues are further accelerated when symptoms are ignored or accepted them as a “normal” part of aging. (Please refer to my ​post on ageism​ to dig into that topic a bit more).

Actionable Strategies to Preserve Testosterone Production

Strategies to protect testosterone production throughout the lifespan include those things that support metabolic health and provide specific support to hormone synthesis pathways. These include exercise and rest, macronutrient balance and quality, micronutrient sufficiency, and phytonutrients (i.e., those that come from plant foods), which supply a wide array of benefits that include support of a diverse and robust microbiome and inhibition of aromatase. Some aromatase inhibitors are foods we have touched on in past newsletters, such as fiber, soy isoflavones, and lignans from flax seeds.

For today’s discussion, we’re going to zoom in on exercise and rest, and a couple of key micronutrients: magnesium and zinc.

Exercise and Rest

To the extent that exercise improves mitochondrial function and supports metabolic health, it is indeed beneficial for testosterone levels.   However, there is the risk for too much of a good thing: heavy endurance training or any kind of overtraining can dampen testosterone production, as illustrated by cross-sectional studies⁴٠⁵ involving endurance trained athletes which have found lower levels of testosterone in these groups as compared to men who do not engage in endurance training.  Even so, not all studies have reached the same conclusion about endurance training and low testosterone: one study found that “serious leisure” cyclists who trained for at least 8 hours per week had higher testosterone levels than “recreational” cyclists who trained no more than about 30 minutes daily⁶. Factors related to exercise which influence the effect of exercise on testosterone production include energy availability and body fat percentage.  The body makes cholesterol, the precursor for steroid hormones, only when it has sufficient energy.  Over-production of cholesterol is a serious issue which connects metabolic abnormalities with cardiovascular disease; on the other hand, under-production of cholesterol for steroid hormone synthesis can be an issue for athletes–whether professional or recreational–who train at a volume which consistently exceeds their energy intake. 

Weight-bearing exercise is associated with acute (i.e., short-term) increases in free testosterone during and following exercise, which may help support the maintenance and growth of muscle even in elderly men.   One study⁷ found that serum testosterone levels increased similarly during heavy weight-bearing exercise performed twice weekly in both a group of men with a mean age of 40 as well as a group with a mean age of 70.   This study found that participants improved their load-bearing capacity by 16-28% over a 6-month study period with just twice weekly weight-lifting sessions.   Remember when we talked about gains happening during rest?  This is especially important to bear in mind when we’re strategizing to preserve muscle as we age.  If we want to reap the benefits of our exercise, we need to give our bodies ample time to recover and adapt–rest truly is an essential ingredient for your muscle maintenance recipe, and I think this is a message that can be difficult for very active and driven men to internalize.  Hopefully the wisdom that comes with age helps us to value rest as the active process of recovery that it is.

Magnesium

Ah, magnesium. Is there nothing it can’t do? Because of magnesium’s role in hundreds of enzymatic reactions in the body, including any reaction that uses ATP (i.e., energy), it’s not surprising that it affects hormone production. As seasoned readers of the newsletter know, magnesium also plays a central role in glucose control, and deficiency of magnesium has been recognized as a contributing factor to metabolic conditions including type 2 diabetes, which dramatically puts the brakes on testosterone production and skews the ratio of estrogen to testosterone. Magnesium deficiency has also been recognized as a contributing factor in sarcopenia, the age-related decline in muscle quantity and quality. A population-based study⁸ involving men over the age of 65 found a highly significant relationship between serum magnesium and both testosterone and IGF-1, another anabolic hormone. Takeaway: Magnesium is a powerhouse mineral to prioritize for muscle and metabolic health. The RDA for magnesium for adult men is 420 mg, and among the richest sources of this important mineral are leafy greens, nuts, and black beans.

Zinc

Zinc is well-regarded as promoting male fertility including spermatogenesis and testosterone production, and a deficiency in dietary zinc dampens testosterone production even over the short term⁹٠¹⁰. Zinc is also involved in the synthesis of thyroid hormone, which is the key regulatory hormone for metabolic rate and therefore plays an important role in preventing metabolic dysfunction, which (as we have discussed) can be an underlying cause of low testosterone. The RDA for zinc for adult men is 11 mg. Great sources of zinc include oysters and pumpkin seeds; it can also be found in other seafood and animal proteins, and in smaller amounts in whole grains and nuts such as cashews.

References

1. Mulligan, T., Frick, M. F., Zuraw, Q. C., Stemhagen, A., & McWhirter, C. (2006). Prevalence of hypogonadism in males aged at least 45 years: the HIM study. International journal of clinical practice, 60(7), 762–769. ​https://doi.org/10.1111/j.1742-1241.2006.00992.x​​https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1569444/
2. Kelly, D. M., & Jones, T. H. (2013). Testosterone: a metabolic hormone in health and disease. The Journal of endocrinology, 217(3), R25–R45. https://doi.org/10.1530/JOE-12-0455 ​https://pubmed.ncbi.nlm.nih.gov/23378050/​
3. Kalyani, R. R., & Dobs, A. S. (2007). Androgen deficiency, diabetes, and the metabolic syndrome in men. Current opinion in endocrinology, diabetes, and obesity, 14(3), 226–234. ​https://doi.org/10.1097/MED.0b013e32814db856 ​​https://pubmed.ncbi.nlm.nih.gov/17940444/
4. Hackney, A. C., Fahrner, C. L., & Gulledge, T. P. (1998). Basal reproductive hormonal profiles are altered in endurance trained men. The Journal of sports medicine and physical fitness, 38(2), 138–141. https://pubmed.ncbi.nlm.nih.gov/9763799/
5. Arce, J. C., De Souza, M. J., Pescatello, L. S., & Luciano, A. A. (1993). Subclinical alterations in hormone and semen profile in athletes. Fertility and sterility, 59(2), 398–404. https://pubmed.ncbi.nlm.nih.gov/8425638/
6. Fitzgerald, L. Z., Robbins, W. A., Kesner, J. S., & Xun, L. (2012). Reproductive hormones and interleukin-6 in serious leisure male athletes. European journal of applied physiology, 112(11), 3765–3773. https://doi.org/10.1007/s00421-012-2356-2 https://pubmed.ncbi.nlm.nih.gov/22382666/
7. Häkkinen, K., Pakarinen, A., Kraemer, W. J., Newton, R. U., & Alen, M. (2000). Basal concentrations and acute responses of serum hormones and strength development during heavy resistance training in middle-aged and elderly men and women. The journals of gerontology. Series A, Biological sciences and medical sciences, 55(2), B95–B105. https://doi.org/10.1093/gerona/55.2.b95 https://pubmed.ncbi.nlm.nih.gov/10737684/
8. Maggio, M., Ceda, G. P., Lauretani, F., Cattabiani, C., Avantaggiato, E., Morganti, S., Ablondi, F., Bandinelli, S., Dominguez, L. J., Barbagallo, M., Paolisso, G., Semba, R. D., & Ferrucci, L. (2011). Magnesium and anabolic hormones in older men. International journal of andrology, 34(6 Pt 2), e594–e600. https://doi.org/10.1111/j.1365-2605.2011.01193.x  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4623306/
9. Fallah, A., Mohammad-Hasani, A., & Colagar, A. H. (2018). Zinc is an Essential Element for Male Fertility: A Review of Zn Roles in Men’s Health, Germination, Sperm Quality, and Fertilization. Journal of reproduction & infertility, 19(2), 69–81. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6010824/
10. Hunt, C. D., Johnson, P. E., Herbel, J., & Mullen, L. K. (1992). Effects of dietary zinc depletion on seminal volume and zinc loss, serum testosterone concentrations, and sperm morphology in young men. The American journal of clinical nutrition, 56(1), 148–157. https://doi.org/10.1093/ajcn/56.1.148 https://pubmed.ncbi.nlm.nih.gov/1609752/