We’ve all seen the label on the back of our foods: the Recommended Daily Allowances of all our vitamins and minerals. But the exact processes by which our bodies use vitamins and minerals can be confusing–it can be even more confusing to look at an iron nail and think, “My body needs this?”
Minerals, however, are indispensable for thousands of cellular mechanisms that the body carries out every second. Many people are aware that iron, in my example above, is necessary for binding with oxygen in the lungs, and then carrying that oxygen to the other parts of the body. What many people don’t know is that Zinc is the second-most abundant mineral in the body, and just as important.
Zinc has also shown up on a number of testosterone boosting supplements’ ingredient list. In this article I’ll survey five important studies that may give us clues as to how instrumental Zinc is in the production of this hormone.
✲ Most data of direct testing shows that in Zinc-deficient men, taking high doses of the mineral can have huge impacts on testosterone production.
✲ Some studies, especially of highly active men, found no significantly different testosterone levels in Zinc test groups.
✲ Despite the two outlier studies, practicing doctors have been advised by one study to administer Zinc as a possible treatment for low testosterone.
Studies With Increased Testosterone
Our first study, and the earliest conducted trial, goes back a while, but it’s important to note it for two reasons: the science conducted was sound; the study continues to be cited in the rest of the scientific literature, pointing to its authority.
Researchers in this study not only conducted blood testosterone tests on men taking Zinc supplementation, they also conducted tests on men having their Zinc intake restricted. The results were directly inverse of one another–the Zinc group had increased testosterone, the restrictive group had lowered testosterone.
Building off of that research, later scientists measured for total testosterone and free testosterone, and published their exact figures. In the Zinc test group, total testosterone rose by 32%, free testosterone by 33%. For those data to arrive by accident would take a statistical anomaly to the tune of less than one in ten thousand experiments.
There is a broad swath of more literature, and we’ll get to a review of the aggregate data in our last section. But the rest of the data indicate that these two studies have reliable information. The rest of the data, that is, save for two studies.
Two Studies with Different Results
In the first of our contradictory studies, scientists studied 32 competitive bicyclists, and assigned them to four groups: a Zinc group; a Selenium (mineral) group; a Zinc-Selenium group; and a placebo group. They then had the men perform exhaustive exercises and then compared serum testosterone levels.
While they did find that immediately following exercise the Zinc group had significantly higher testosterone than the other groups, they did not find that those levels stayed high in the days after the exercise.
While this might sound bad for the Zinc fans, regular readers of my articles may have already picked up on two details of this study. One, all of the men were competitive athletes, and may well have already had sufficient Zinc in their diets. Two, there were only 8 men in each group–hardly a large sample size.
The other study was similarly flawed. They found no change in testosterone levels after administering Zinc. Their study, however, only included 14 men; there was no placebo control; all the men were “healthy and active”; and most importantly, they all had Zinc intake between 12 and 23 mg per day! That upper end is more than twice the Recommended Daily Amount.
I’ve included these two studies because they are often cited in other literature as “proof” that zinc supplementation is a fraud. The reader can decide for themselves what to think, but in my opinion, these two studies only demonstrate that in two very limited instances, very active men already taking high doses of Zinc saw no results.
A Last Look
Finally we look at an in-depth review of clinical data that was written by two doctors specifically to address whether Zinc could be used to treat hypogonadism. Hypogonadism is the severe loss of testosterone due to atrophy of the gonad system of testosterone production.
Before we discuss their findings, it is key to note that these doctors reviewed all the scientific literature relevant to their findings, and concluded not only that Zinc was an effective supplement for raising testosterone, but that it might be so effective as to treat an actual illness.
Their concluding findings were that 220 mg of Zinc Sulfate (or 50 mg of the mineral itself) could be an effective adjunct treatment for hypogonadism. They made this recommendation after explaining that the binding of Zinc to important protein receptors and enzyme trigger functions in the gonad system could lead to increased testosterone production, affecting every aspect of male health–from serum testosterone to sperm count.
These findings are also among the latest to be published, meaning the authors have taken into account all the previous studies, meaning that for them, there are no data that can contradict the weight of the other evidence.
In life, and in science, we can often learn as much from hearing the opinion of a dissenter as we can from hearing the majority opinion. Dissent doesn’t mean wrong. But it does mean we need to take what both sides are saying and weigh them against each other.
In this case, we have the overwhelming majority of evidence pointing to a direct relationship between Zinc intake and testosterone production. On the other hand, we have a very limited minority of study data saying that among already healthy men, who are already taking sufficient Zinc, there is no benefit. For anyone looking into the benefits of Zinc supplementation, the question then becomes if the individual thinks they are already getting enough of this important mineral, or if they could use a dietary adjustment.