A mild deficiency of zinc will reduce the number of binding sites of androgens and testosterone in the blood become activated and then converted to estrogen in the liver, while the number of estrogen receptors increases. It’s very bad news!
Let’s start with animal studies.
Sure, Zinc deficiency is bad for rats but are these effects the same for human males?
To answer that question, here’s another research. In similar fashion to the two previous studies, this one assessed the effects of dietary zinc depletion on seminal volume and zinc loss, serum testosterone concentrations, and sperm morphology. However, this particular experiment was conducted on young human men.
The men who were a part of this research either had 1.4, 2.5, 3.4, 4.4, or 10.4 mg of Zinc per day. To summarize their results, the group who had the least amount of Zinc (1.4 mg Zn/d) had less semen and serum testosterone compared to the men receiving the highest dose of Zinc (10.4 mg Zn/d).
This next research investigated how exhaustion exercise affects thyroid hormones and testosterone levels in elite athletes who are supplemented with oral zinc sulfate for 4 weeks. These athletes (licensed wrestlers) were also quite young with an average age of 18.7 (+/- 2.4) years old. Moreover, all of them took 3 mg/kg/day of Zinc Sulfate in addition to their normal diets.
Thyroid hormones and testosterone were measured as resting and exhaustion before and after zinc supplementation. Specifically when it comes to testosterone, the results of the research shows that:
- Before Zinc supplementation:
- Resting total testosterone and free testosterone levels were significantly higher than exhaustion levels
- After 4-week Zinc supplementation:
- Resting and exhaustion levels of total and free testosterone were found significantly higher than the levels measured before zinc supplementation
More about Zinc’s effects on Sex Life
Estrogen. Zinc actually inhibits the aromatase enzyme, especially in zinc-depleted individuals, and therefore could decrease estrogen.  (It may also inhibit the conversion of testosterone to DHT, which could help your prostate and hair!) At worst it is another tool in our arsenal to optimize and maintain our estrogen at reasonable levels. And, of course, this may be another reason that zinc is a testosterone booster for some men but not others.
Dopamine. Researchers have found that zinc is one of the most important minerals regulating dopamine.  It turns out that zinc is present in your neuron’s synapses and plays several major roles in neurotransmission. Zinc is known for “inhibiting the uptake” of dopamine, which means that dopamine stays around in your systems (brain) for a longer period of time. And, yes, more dopamine generally means better sex . (Dopamine disorders are associated with migraines, Restless Leg Syndrome and other conditions.)
Depression. Zinc is a proven depression fighter. Several studies have shown that zinc levels tend to be lower in certain types of patients with depression and, furthermore, supplemental zinc has even been shown to help in treatment (25 mg along with an SSRI).  And, recently, researchers created depression (in animals) by inducing a zinc deficiency.
Of course, there is now a strong link established between Depression and Your Sex Life.
Zinc – Side effects and Cautions
Zinc has some powerful properties that can really help us males. Because of this, it is very easy for to get overly enthusiastic. Zinc is extremely powerful and has a definite clinical range, i.e. you can hurt yourself if you overdo it in the ways listed below. Again, stick to the 1-2 RDA range for zinc.
Before you go popping zinc like breath mints, keep in mind that some studies indicate that too much zinc is just as hard on your brain and neurons as too little. Most minerals have a rather tight range and zinc appears to be no exception.
CAUTION: Heart Disease. There was a whole theory of heart disease that centered around the correct balance of copper to zinc.  Admittedly, this theory is outdated, but we can still learn something from it: too much zinc can elevate cholesterol levels and possibly contribute to hyperlipidemia. (You do not want too much copper either: it is very hard on the brain. When it comes to essential minerals, moderation and balance are definite keys.)
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