The T Protocol: Testosterone and your Micro's

The T Protocol is a complete review of what is known to optimise Testosterone in Men.

Originally intended as a single resource, it has grown into a series of posts on key areas that Men need to address in order to realise the natural Testosterone levels that are their birth right.

Intuitively, Men seem to know that their diet must affect their Testosterone levels. But, there is a ton of misinformation to cut through on this topic before we can get to what is known, and what is simply conjecture.

This post will focus on how the micronutrients obtained through diet can affect your Testosterone levels. Micronutrients are the Vitamins and Minerals present in your food and drink. Sadly, poor diet and lifestyle choices can leave you lacking in many of the Micronutrients essential for healthy Testosterone levels.

Let us scrutinise some of the key Micronutrients that can help to optimise Male Testosterone levels.

Vitamin A and Testosterone

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In researching this article, it was clear The Weston Price Foundation had thought deeply about Vitamin A and the health connotations of getting an optimal amount in your diet. They had also considered the implications of Vitamin A for Male Health, and that always encompasses Testosterone in some way:

Their work was so compelling, little else need be done but share the important points:

“Abundant animal research indicates the importance of vitamin A to the production of testosterone. Vitamin A crosses the blood-testis barrier in its alcohol form as retinol, where it is stored in the Sertoli cells and converted as needed to its more biologically active form, retinoic acid. Experiments with rats show that greater concentrations of vitamin A in the testes increase basal testosterone secretion, as well as transferrin, which is responsible for the transport of iron; and a variety of growth factors including IGF-binding protein 4 (which transports IGF), androgen-binding protein (which transports androgens), transforming growth factor-beta (which causes cell growth but suppresses cancer) and steroidogenic acute regulatory protein (which is responsible for the transport of cholesterol into the mitochondria for its conversion to steroids). Vitamin A also decreases estrogen production in the male testes. Rats that are deficient in vitamin A experience decreased testosterone until the accessory sex organs atrophy, indicating that vitamin A not only aids in, but is essential to, testosterone production (Livera 2002).”

“One experiment using guinea pigs, which corroborates the many experiments done with rats, found a decrease in plasma testosterone associated with a deficiency in vitamin A. (Nayyar 2000). A human study comparing the dietary intakes of 155 pairs of male twins found a correlation between testosterone levels and vitamin A intake (Bishop 1988).”

“The most compelling study is one that assigned 102 teenage boys with short stature and delayed puberty into four groups: a control, a testosterone-supplemented group, a vitamin A- and iron-supplemented group, and a group that received both testosterone and the nutritional supplementation. All treatments were effective in inducing growth and puberty, whereas the control group did not gain weight or begin puberty in the same period of time. What is most amazing is that the degree of growth acceleration was similar in the testosterone-treated group and the vitamin A-treated group. Pubertal onset occurred in 9-12 months in the testosterone group, and by 12 months in the vitamin-A group (Zadik 2004).” (https://www.westonaprice.org/health-topics/vitamin-a-the-forgotten-bodybuilding-nutrient/)”

Brossaud et al (2017) also note that Vitamin A is critical for the formation of Male Gonads and aside from night blindness, one of the major symptoms of deficiency is infertility. Vitamin A is also involved in the production of steroid hormone synthesis.

They even go as far as to suggest that athletes ingesting enough quality Vitamin A may achieve similar results to those supplementing with precursors of Testosterone!

Dosage

Vitamin A is toxic in high enough doses. That said, Vitamin A poisoning is rare. A single dose of 300,000IU or 60,000IU/day for several weeks would be necessary to induce poisoning. Official RDA for this vitamin is 5,000IU/day, The Weston Price Foundation multiply this by ten!

It is important to note that diabetics, people with thyroid disorders and infants cannot covert carotenes (plant vitamin A) into an active form. Children are also poor converters and strenuous exercise, high protein intake (sound familiar Men?), zinc deficiency and excessive polyunsaturated acid intake all hinder conversion of carotenes to Vitamin A.

The simple remedy is to eat quality animal sources of vitamin A several times per week.

Sources

Liver (Beef) 3oz, 22,000IU

Cod Liver Oil, 1 Tsp, 20,000IU

Butter (Grass Fed) 1 Tsp 355IU

Oily Fish 3oz, 730IU

1 Egg 300IU

Boron and Testosterone

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Before investigating micronutrients for Testosterone enhancement, Boron seemed to be just another element on the periodic table. It doesn’t even have an Recommended Daily Amount (RDA) because its functions in the human body are so poorly understood.

Then I discovered a small study showing that acute Boron supplementation (10mg’s per day for 7 days) increased T nearly 30% whilst decreasing Oestrogen AND reducing markers of inflammation (Naghii 2011).

Suddenly, Boron was more interesting!

The findings of Naghii et al have been reproduced. Mjilkovich et al 2004 supplemented 13 men with 6mg’s of Boron for 2 months, resulting in a similar approximate 30% increase in T.

Could this be true, for a mineral that hasn’t even got an RDA?

Potentially, yes. Boron has recently been proven to be an important trace mineral because it is;

·      Essential for the growth and maintenance of bone

·      Greatly improves wound healing

·      Beneficially impacts the body’s use of Oestrogen, Testosterone, and vitamin D

·      Boosts magnesium absorption

·      Reduces levels of inflammatory biomarkers

·      Raises levels of antioxidant Enzymes

·      Protects against pesticide-induced oxidative stress and heavy-metal toxicity

·      Improves brain electrical activity, cognitive performance, and short-term memory in elders

·      Influences the formation and activity of key biomolecules

·      Has demonstrated preventive and therapeutic effects in a number of cancers, such as prostate, cervical, and lung cancers and multiple and non- Hodgkin’s lymphoma

·      May help ameliorate the adverse effects of traditional chemotherapeutic agents

(Pizzorno 2014)

Which begs the questions, how much Boron is optimal, where can I get it from, and is it safe?

Dosage

In the studies conducted to date, none of boron’s beneficial effects appear at intakes of less than 3 mg/d. An upper limit of 20 mg/d for individuals aged 18 years or older has been established, but as we will see, it would be almost impossible to get near that amount under normal dietary circumstances. The absence of studies showing harm, in conjunction with the substantial number of articles showing benefits, support the consideration of boron supplementation of 3 mg/d (Pizzorno 2015).

Americans’ daily dietary intake of boron was estimated to be approximately 1 mg/d in 1999. This is sadly lacking. Both animal and human data indicate that an intake of less than 1.0mg/day inhibits the health benefits of boron (Nielsen 2014).

This creates a situation whereby many people fail to attain 1mg/day of Boron, but need to really hit 3mg/day to realise the benefits of general health, and in the afore mentioned studies, 6mg/day or more was used to demonstrate a beneficial impact on Testosterone.

Let us take a look at the best natural sources of Boron and see how much it is possible to get from an optimised diet.

Sources

Raisins 2.5-4mg/100g

Almonds 2.3mg/100g

Avocado 2mg/100g

Brazil Nuts 1.7mg/100g

Red Wine Approx. 1mg/100ml

As demonstrated, achieving over 6mg of Boron per day can prove tricky if you are trying to optimise your Testosterone levels by also manipulating your macronutrients. For example, 200g of raisins per day may well get you over the 6mg of Boron demonstrated to increase T, but it also contains around 150 grams of carbs. Similarly, 250g per day of Almonds would get you around the 6mg dose, but that amount also contains 122.5 grams of fat and lots of Polyunsaturated fat, which as we have seen before, can reduce T levels.

In this context, it seems that supplementation would allow for maximal flexibility in diet planning. 

An intake of 4 g/day of boric acid was reported without incident, but more than this is considered toxic in more than a few doses. Intakes of more than 0.5 grams per day for 50 days cause minor digestive and other problems suggestive of toxicity (Nielson 1997).

So 6mg per day is well within safe limits and is a cheap supplement for Testosterone enhancement.

 

Vitamin D and Testosterone

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Vitamin D is essential for robust health. With regards to Testosterone levels, it is notable that the testis, the pituitary gland and the hypothalamus all have Vitamin D Receptors and Vitamin D is involved in the regulation of gonadal function (Wang 2015).

Several studies have investigated the association between Vitamin D levels and Testosterone. Vitamin D and Testosterone are positively related, although the relationship between the two is yet to be fully elucidated (Lerchbaum 2017).

The major source of vitamin D for humans is sunlight exposure and several factors influence this. The interested reader is directed to Nolick, 2011 for an in-depth look at an evolutionary perspective on Vitamin D.

One can extrapolate just how important Vitamin D is to humans from the fact that early human populations migrating out of Africa evolved de-pigmented skin in response to living at higher latitudes (Luxwolda 2012). This means light skinned individuals can create Vitamin D around 5 to 6 times faster than dark skinned individuals.

What is notable from the literature, apart from the poor quality of most of the studies designed to investigate Vitamin D levels and Testosterone, is that the effects on Testosterone appear most obviously in individuals who are deficient. Nimptsch (2012) showed, in a large cohort of patients, that the association between T and Vit D occurs most strongly at lower levels, below approximately 75-85nmol/l. (Note, this level is more than double what government recommendations state are ‘sufficient’). Wentz (2015) showed a high prevalence of poor vitamin D status in male military personnel. Those men with the lowest vitamin D levels had significantly lower Testosterone concentrations, compared to the men with the highest Vitamin D levels.

Pilz (2011) showed 3332 IU of Vitamin D per day, given to a randomised group of Men for 1 year, increased their testosterone around 25% and doubled their vitamin D levels. A control group had no change in their T levels.

With this in mind, and given the multitude of health benefits of Vitamin D, optimising your levels of Vitamin D levels is a sensible course of action.

 

Dosage

The Vitamin D Council guidelines provide the most sensible advice on dosing. Most Government RDA’s are simply urinating into a stiff breeze.

Exposure to sunlight (UVB light) triggers synthesis of vitamin D in the skin, producing up to 10,000 to 25,000 IUs of vitamin D in one erythemal dose of UVB radiation. The Vitamin D Council considers this the preferable and choice method in elevating and maintaining blood levels since it is the natural and traditional method for humans. More specifically, the Vitamin D Council makes the following recommendations:

On days that individuals do not sunbathe, the Vitamin D Council recommends the following daily maintenance doses:

·       Children: 1,000 IU per 25lbs of body weight.

Notes: Recommendation applies up to 125 lbs.

·       Adults: 5,000 IU (including pregnant and breastfeeding mothers)

Notes: If the mother is sufficient, then the weaning infant does not need to supplement.

·       Upper limit: 10,000 IU

Notes: If dosing at 10,000 IU/day or higher, the Vitamin D Council recommends 25(OH)D testing every 3 months for the first year, every 6 months thereafter.

Individuals suffering from Obesity, IBD and other GI disorders may need 2-3 times the amount of Vitamin D to correct a deficiency.

Whilst it would be remiss to endorse dangerous sunbathing practises, it has been estimated that for every person who dies from non-melanoma skin cancer, as many as 500-600 lives could be saved from cancers of the colon, prostate and breast (Nolick 2011). Sensible, moderate, sun exposure regimens should therefore be exercised.

What blood levels of Vitamin D to aim for?

Blood testing for Vitamin D is simple and widely available. This allows for easy monitoring of one’s own levels if insufficiency is expected.

Traditional living peoples in Africa (Masai and Hadze tribes) had Vitamin D blood leves of 71-171nmol/l with an average of 115nmol/l. None of the populations had values below 58nmol/l and the highest value recorded was 171nmol/l. It should be noted these values are similar to those obtained from Caucasian people working outdoors in summer months. (Luxwolda 2012). To put this in perspective, The Vitamin D council recommends:

Maintaining serum levels of 50 ng/ml (equivalent to 125 nmol/L*), with the following reference ranges:

·       Deficient: 0-40 ng/ml (0-100 nmol/l)

·       Sufficient: 40-80 ng/ml (100-200 nmol/l)

·       High Normal: 80-100 ng/ml (200-250 nmol/l)

·       Undesirable: > 100 ng/ml (> 250 nmol/l)

·       Toxic: > 150 ng/ml (> 375 nmol/l)

(https://www.vitamindcouncil.org/for-health-professionals-position-statement-on-supplementation-blood-levels-and-sun-exposure/)

This is a long way from the Government recommendations.

“The Scientific Advisory Committee on Nutrition (SACN), the committee of independent experts that advises Government on matters relating to diet, nutrition and health, reviewed the scientific literature to ascertain whether current vitamin D recommendations were still appropriate. In the resultant report, Vitamin D and Health, SACN has published new recommendations sufficient to maintain a blood vitamin D level of at least 25 nmol/L in the vast majority (97.5%) of individuals in the UK.

The Recommended Nutrient Intake (RNI) proposed by SACN for all people aged 4 and above is 10 µg/day. For infants and younger children, data are insufficient to set an RNI. Instead, as a precaution, a ‘Safe Intake’ of 8.5-10 µg/day has been set.”

Talk about pontificating! 10ug is equivalent to around 400IU. Not enough to get someone with low blood Vitamin D levels anywhere near ancestral levels.

For ensuring optimal Testosterone levels, based on the available evidence, it is likely you will need to maintain a level of over approximately 75-85 nmol/l. Given how cheap vitamin D supplements are, and since sun exposure is free (although weather dependent) this should be simple to achieve.

 

Magnesium and Testosterone

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Magnesium (Mg) is a critically important mineral, involved in energy production and operating as a cofactor in over 300 enzymatic reactions.

With regards to Testosterone, animal models have shown the importance of Mg in supporting the gonads and enhancing steroidogenic enzymes, with concurrent increases in serum T levels (Maggio 2014).

In human studies, the results are mixed, but several examples of Magnesium supplementation increasing anabolic hormone status exist.

In the often quoted study by Brilla and Conte (2000), a Zinc and Magnesium formulation, known in sports supplement circles as ZMA, increased Testosterone over an 8 week period in football players training during pre-season.

Later studies with ZMA failed to reproduce this result, although with far less strenuous training protocols (Wilborn 2004).

Other investigators have noted interesting results using large doses of Mg in athletic populations. Using a dose of 10mg/kg of Mg, Cinar et al (2010) achieved a significant increase in both total and free T levels after 4 weeks in both sedentary and athletic individuals. The effects were further compounded in the exercise plus supplementation group.

Testosterone levels are strongly related to antioxidant capacity, and Mg deficiency decreases antioxidant capacity. Additionally, Mg is able to reduce the affinity of T for binding with SHBG (We have briefly addressed SHBG in previous posts).

In addition to the potential for increasing Testosterone, Mg has also been shown to decrease cortisol and inflammatory cytokines in athletes. Golf (1998) showed Mg reduced cortisol in a double blind placebo controlled trial in triathletes. Further, it is known that Magnesium deficiency increases activity of the HPA axis (the ‘stress’ axis that works in opposition to the HPG axis producing Testosterone) activity in animal models. Dmitrasinovic (2016) demonstrated a reduction in the HPA axis activity in rugby players with 500mg of Mg daily for 4 weeks, including an interesting reduction in IL-6, an inflammatory cytokine.

Intake of Mg is associated with a better anabolic hormonal profile. In a cohort of almost 400 older men, magnesium levels were strongly, positively and independently associated with total testosterone and total IGF-1 (Maggio 2011)

Numerous studies have shown that typical Western diets contain only usually 30-65% of the RDA for Magnesium. Even just 100 years ago, diets contained around double the Magnesium content (Altura 2016).

Overall Mg status is determined by dietary intake, absorption, tissue uptake, utilisation and loss via sweat and renal excretion.

In athletic populations, due to higher calorie intake and often better quality diets, Males usually achieve adequate Magnesium intake. However, this situation is not the case for athletes in sports where weight categories mean calorie restriction is necessary (Maggio 2014).

There is currently no widely available, accurate method for assessing the total Magnesium levels in the body. As such, serum Mg levels are usually checked (normal ranges between 0.75-0.95 mmol/l or 1.7-5 mg/dl).

Dosage

The numerous health benefits of adequate Mg intake, as well as its potential to optimise T, make briefly analysing your diet and ensuring sure enough Mg is consumed is a sensible course of action.

The RDA for an adult Male is 420mg/day (Volpe 2016). Since many of the quoted studies use at least this on top of dietary intake, it may be of benefit to consider a Mg supplement.

Sources

Grains and Legumes are often touted as good magnesium sources. Given that the Phytate content of both can reduce Mg absorption by up to 60% (Bohn 2008), it seems pertinent to consider alternative sources for dietary optimisation.

Spinach, 1 cup, 157mg of Magnesium

Dark Chocolate, 1 square, 95mg of Magnesium (now you know where that chocolate craving comes from!)

Swiss Chard, cooked, 150mg of Magnesium

Almonds, 1 ounce, 75mg of Magnesium

Selenium and Testosterone

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Mounting evidence in the literature supports the importance of Selenium (Se) for human health. Insufficient Se is associated with several disease states such as cancer, diabetes, cardiovascular and immune system disorders.

Selenium (Se) status and individual selenoproteins are also important regulators of hormonal homeostasis during development and adulthood (Kohrle 2016)

Simply supplementing with this element to improve health is not so simple. Even sub-toxic doses may have a negative health impact, for example, by increasing the risk of type 2 diabetes (Roman 2013).

Se is essential for normal Testicular development and Se levels have been seen to correlate with T levels in some populations of Men (Oluboyo 2012). In a double-blind, placebo controlled, randomised study of over 400 Men, Se supplementation of 200 ug of Se per day significantly increased T levels (Safarinejad 2009).

Caution should be taken however, as Rayman (2017) notes:

“Our recent randomised controlled trial in Denmark, a country of low-moderate Se status, showed significantly increased mortality with a Se dose of 300 µg/d after five years of treatment and a further ten years of follow-up…The crucial factor that needs to be emphasized with regard to the health effects of Se is the inextricable U-shaped link with status: while additional Se intake may well benefit people with low status, those of adequate-to-high status may be affected adversely and should not take selenium supplements.”

This is especially true for males: The available experimental and clinical data indicate that in general, males are more responsive to acute changes in the Se supply, their Se status responds with faster kinetics and stronger amplitude to inflammatory stimuli, and likewise they seem more sensitive to adverse health effects upon surplus Se intake (Schomberg 2016)

Indeed, Neek (2011) observed no effect of Se supplementation (at 200ug per day) on T levels in subjects who consume a Se sufficient diet.

This noted, it appears that inadequate Se levels will affect Testosterone, but more in this instance is not always better. Thus it seems pertinent to ensure an optimum intake through diet, with caution that supplementing with high doses of Selenium may be potentially harmful.

Dosage

Recommended daily intake levels range from 50-60mcg to a sensible upper limit of 400 micrograms per day for adults (Roman 2013).

Selenosis (toxicity due to high Se intake) may occur at >850mcg per day, although the US environmental protection agency defined an intake of 1262mcg as the level at which Selenosis occurs.

Sources

Brazil nuts 1oz 544mcg (several times the RDA)

Sardines 3oz 45mcg

Grass fed beef 3oz 33mcg

Liver 1oz up to 42 mcg

Zinc and Testosterone

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Dietary zinc deficiency is prevalent in the developing world, where common side effects associated with it are growth retardation and testicular hypofunction (Prasad 2003). Moderate Zinc deficiency is common even in developed countries, and is associated with hypogonadism in Men (Prasad 1996)

Zinc can increase Testosterone through several mechanisms. Leydig cell synthesis of T is dependant on adequate dietary Zinc, which is a vital factor in their activation (Chang 2011, Hunt 1992). Zinc enhances production of cAMP and consequently testosterone in animal models. Additionally, Zinc may increase the conversion of androstenedione to testosterone in the periphery tissues. Zinc also interferes with the metabolism of testosterone by decreasing its hepatic clearance and reducing hepatic 5 alpha-reductase activities. (Neek 2011)

Several studies link Zinc and Testosterone levels.

Low T patients increased their T and DHT upon administration of an oral zinc supplement (Netter 1981)

Fuse et al., reported a correlation between zinc concentration and plasma testosterone concentration and other investigators have shown that seminal plasma zinc levels are directly proportional to Testosterone (Kothari 2016).

Dietary zinc restriction in normal young men was associated with a significant decrease in serum testosterone concentrations after 20 weeks of zinc restriction. (Prasad 1996)

(Interestingly, this dietary restriction of zinc was induced by feeding them texturized Soy products!)

Zinc supplementation of marginally zinc-deficient normal elderly men for six months resulted in an average doubling of serum Testosterone levels (Prasad 1996)

Prasad et al concluded that Zinc status appears to represent an important determinant of serum total testosterone levels.

Compared to consuming 10.4mg/day of Zinc, volunteers receiving 1.4mg/day had decreased serum T and decreased semen volume (Hunt 1992).

In another study, Chang et al 2011 noted subjects in a normal testosterone group had a significantly higher Zn level compared to subjects in a low testosterone group.

Whilst the results of the Brilla and Conte study (2000) investigating a Zinc and Magnesium formulation have not been reliably reproduced, ZMA supplementation was shown to increase T in college football athletes in pre-season training, as mentioned in the Magnesium section.

Interestingly, Zinc also inhibits the Aromatase enzyme from converting Testosterone to Oestrogen.

It is clear that maintaining optimal levels and intake of Zinc are important for Testosterone and incidentally, Male fertility. This is especially important where poor intake or absorption of Zinc is suspected, or under circumstances of high Zinc loss. For example, 9% of the daily RDA was lost via sweat in a 2 hour exercise bout in Men (DeRuisseau et al 2002)

Dosage

Phytates in cereals markedly reduce the absorption of Zinc, as noted previously with Magnesium. The ideal sources of Zinc therefore avoid these. The body also lacks a storage mechanism for Zinc, so intakes must meet requirements consistently.

The RDA for a Male is around 10mg per day, although active individuals may require more.

Sources

Oysters 100g contain 78mg Zinc (over 500% the RDA!)

Dark Chocolate 100g contains 7mg Zinc

Eggs 100g contain 5mg Zinc

Beef 100g contains 4.5mg Zinc

Liver 100g contains 4mg Zinc

Conclusions...

Micronutrient intake can significantly impact your Testosterone levels.

Fortunately, when the above evidence is considered, the dietary strategy required to optimise micronutrient intake for Testosterone is simple.

Liver emerges as one of the best Testosterone supporting foods. A few ounces of Liver will provide Vitamin A, Zinc, and Selenium in abundance. It is also cost effective, even when sourced through a reputable butcher from grass fed animals.

The much derided association between red meat and manliness appears to be in some part well justified. Even just 8oz of steak provides enough Selenium and Zinc to cover a Mans daily needs.

Dark chocolate is also an interesting food stuff, being so rich in Magnesium. It provides a portable Magnesium source when 'greens' are not available. Alongside Spinach and other leafy green sources, healthy Magnesium intake should be achievable.

Of the micronutrients listed, the two most likely to require supplementation are Boron and Vitamin D.  These are cheap and easily sourced, and alongside the other sources listed, place optimal micronutrient intake within easy reach of Men seeking to maximise their Testosterone levels.

Now, if you’ll excuse me, I am off to catch some sun, before dining on livers, steak and greens, with top drop of red wine…for the Boron content of course!

Please leave a comment, and I cannot help but ask:

Have you got the Minerals!?

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References

Altura BT et al (2016) Genotoxic Effects of Magnesium Deficiency in the Cardiovascular System and their Relatioships to Cardiovascular Diseases and Atherogenesis, Journal of Cardiovascular Disease and Diagnosis, S1

Bishop, et. al., “The effect of nutritional factors on sex hormone levels in male twins,” Genet Epidemiol. 1988;5(1):43-59.

Bohn T (2008) Dietary Factors Influencing Magnesium Absorption in Humans, Current Nutrition and Food Science,4, 000-000

Brilla LR and Conte V (2000) Efect of a Novel Zinc-Magnesium Formulation on Hormones and Strength, JEP online, 3,4, Oct 2000

Brossaud J et al (2017) Vitamin A, endocrine tissues and hormones: interplay and interactions, Endocrine Connections, R121-130

Cinar V et al (2010) Levels of Athletes and Sedentary Subjects at Rest and afer Exhaustion, Biol Trace Elem Res, 140:18-23

Chang CS et al (2011) Correlation Between Serum Testosterone Level and Concentrations of Copper and Zinc in Hair Tissue, Biol Trace Elem Res, 44:264-271

DeRuisseau KC et al (2002) Sweat iron and zinc losses during prolonged exercise, Iny J Sport Nutr Exerc Metab, Dec; 12(4):428-37

Dmitrašinović G et al (2016) ACTH, CORTISOL AND IL-6 LEVELS IN ATHLETES FOLLOWING MAGNESIUM SUPPLEMENTATION, J Med Biochem, 35:375-384

Golf SW, Bender S, Gruttner J. On the significance of magnesium in extreme physical stress. Cardiovasc Drugs Ther 1998:12:197-202

Holick MF (2011) Vitamin D: Evolutionary, Physiological and Health Perspectives, Current Drug Targets, 12, 4-18

Hunt CD et al (1992) Effects of dietary zinc depletion on seminal volume and zinc loss, serum testosterone concentrations and sperm morphology in young men, Am J Clin Nutr, 56:148-57

Kohrle (2016) Selenium and Endocrine Tissues, Selenium, 389-400

Kothari (2016) Zinc levels in Seminal Fluid in Infertile Males and its Relation with Serum Free Testosterone, Journal of Clinical and Diagnostic Research, May, Vol 10(5), 5-8

Livera, et al., “Regulation and Perturbation of Testicular Functions by Vitamin A” (Review), Reproduction (2002) 124, 173-180

Lerchbaum E et al (2017) Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial, J Clin Endocrinol Metab, 102: 4292-4302

Luxwolda MF et al (2012) Traditionally living populations in East Africa have a mean serum 25-hydroxyvitamin D concentration of 115nmol/l, Br J Nut, 108, 1557-1561

Luxwolda MF et al (2013) Vitamin D status indicators in indigenous populations in East Africa, Eur J Nutr, 52:1115-1125

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Maggio M et al (2014) The Interplay between Magnesium and Testosterone in Modulating Physical Function in Men, International Journal of Endocrinology, 10.1155/2014/525249

Naghii MR et al (2011) Comparative effects of daily and weekly boron supplementation on plasma steroid hormones and proinflammatory cytokines, J Trace Elem Med Biol. 2011 Jan;25(1):54-8. doi: 10.1016/j.jtemb.2010.10.001. Epub 2010 Dec 3.

Nayyar, et. al., “Alterations in binding characteristics of peripheral benzodiazepine receptors in testes by vitamin A deficiency in guinea pigs,” Mol Cell Biochem. 2000 Aug;211(1-2):47-50

Neek LS et al (2011) Effect of Zinc and Selenium Supplementation on Serum Testosterone and Plasma Lactate in Cyclist After an Exhaustive Exercise Bout, Biol Trace Elem Res, 144:454-462

Netter A et al (1981) Effect of Zinc Administration on Plasma Testosterone, Dihydrotestosterone, and Sperm Count, Archives of Andrology, 7:1, 69-73

Nielsen F H. (1997) Boron in human and animal nutrition. Plant and Soil. 193 (2): 199–208. doi:10.1023/A:1004276311956.

Nielsen FH (2014) Update on human health effects of boron, J Trace Elem Med Biol. Oct;28(4):383-7. doi: 10.1016/j.jtemb.2014.06.023. Epub 2014 Jul 5.

Nimptsch K et al (2012) Association between plasma 25-OH vitamin D and testosterone levels in men, Clinical Endocrinology, 77(1):106-112

Miljkovic D et al (2004) Up-regulatory impact of boron on vitamin D function -- does it reflect inhibition of 24-hydroxylase? Med Hypotheses. 2004;63(6):1054-6.

Oluboyo AO et al (2012) Relationship between serum levels of testosterone, zinc and selenium in infertile males attending fertility clinic in Nnewi, south east Nigeria, Afr J Med Med Sci. Dec;41 Suppl:51-4.

Pilz S et al (2011) Effect of Vitamin D supplementation on testosterone levels in Men, Horm Metab Res, Mar;43(3):223-5

Pizzorno L (2015) Nothing Boring about Boron, Integr Med, Aug; 14(4): 35-48

Prasad AS (1996) Zinc status and serum Testosterone levels of healthy adults, Nutrition, 12: 5

Prasad AS (2003) Zinc deficiency has been known for 40 years but ignored by global health organisations, BMJ, 326, 409-410

Rayman M (2017) Selenium Intake And Status In Health & Disease, Free Radical Biology and Medicine, November, 112:1, 5

Roman M et al (2013) Selenium biochemistry and its role for human health, Metallomics, 10.1039/c3mt00185g

Safarinejad MR and Safarinejad S (2009) Efficacy of Selenium and/or N-Acetyl-Cysteine for Improving Semen Parameters in Infertile Men: A Double-Blind, Placebo Controlled, Randomized Study, The Journal of Urology, 181, 741-751

Schomberg L (2016) Sex-Specific Differences in Biological Effects and Metabolism of Selenium, Selenium, 377-388

Volpe SL (2016) Magnesium and the Athlete, Nutrition and Ergogenic Aids, Current sports Medicine Reports, 1537-890X/1404/279-283

Wang N et al (2015) Vitamin D is assocated with Testosterone and hypogonadism in Chinese men: Results from a cross-sectional SPECT-China study, Reproductive Biology and Endocrinology, 13:74

Wentz LM et al (2015) Vitamin D Correlation with Testosterone Concentration in US Army Special Operations Personnel, Journal of Military ad Veterans’ Health, 24,3

Wilborn CD et al (2004) Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolism and Catabolism, I Int Soc Sports Nutr, 1(2):12-20

Zadik, et. al., “Vitamin A and iron supplementation is as efficient as hormonal therapy in constitutionally delayed children,” Clin Endocrinol (Oxf). 2004 Jun; 60(6):682-7.