Recent studies show that, no matter what you eat, testosterone levels drop after a meal. One thing that promotes a dramatic and immediate decline in testosterone levels is consuming high glycemic index or rapidly absorbed carbohydrate sources. Curiously, however, longer acting or complex carbs are known to promote the release of testosterone, probably by opposing the activity of cortisol,which has an inverse effect on testosterone release. Ingesting simple carbs, while inhibiting testosterone, nonetheless does promote anti-catabolic effects in muscle through stimulating an insulin release, which also fosters amino acid uptake into muscle.
Probably the most potent nutrient in promoting testosterone synthesis and release is fat. But not just any dietary fat will do. Polyunsaturated fats, such as those found in fish oil (omega-3) and vegetable oils (omega-6) do nothing to affect testosterone synthesis, although omega-3 fats do seem to promote anabolic effects in muscle though another mechanism. Instead, saturated and monounsaturated fats are the key players in promoting endogenous testosterone production in the body. Studies show that you need to ingest at least 25% of dietary calories as fat to maintain testosterone synthesis in the body. Saturated fat is effective because it's a substrate for cholesterol, which is the raw material from which testosterone is synthesized.
One recent study involved exposing isolated testicular cells from rats to two types of fat. Testosterone is produced mainly (95%) in the Leydig cells of the testes. In this study, the rat cells were incubated with both olive oil, a source of monounsaturated fat, and coconut oil, a source of saturated fat. Both of these fat sources stimulated the activity of two enzymes in the testicular cells (3-beta-HSD and 17-beta-HSD) that are involved in the synthesis of testosterone from cholesterol. The fats also promoted antioxidant activity, which is important since excess oxidation is known to slowly kill off Leydig cells, and may be a primary reason why many men show low levels of testosterone after age 40. Both the olive oil and the coconut oil also promoted the separation of cholesterol from its ester carrier, thus producing higher amounts of free or unbound cholesterol. Free cholesterol shows much higher uptake into the testes for use in testosterone production. Although this study involved animals, not humans, and featured an isolated cell design, all the mechanisms involved are in place in the human body. As such, the effect noted with the exposure of olive and coconut oils on the Leydig cells likely also happens in intact human bodies, although to what degree this is so isn't established. The olive oil was far superior to the coconut oil in this regard. In a 2013 study of healthy human men, extra virgin olive oil was compared to extra virgin argan oil in 60 men, ages 23 to 40. After three weeks, the men showed a 19.9% increase in testosterone levels from the virgin argan oil, and a 17.4% boost in testosterone from the virgin olive oil, underscoring the fact that monounsaturated fat sources can indeed boost testosterone levels. In case you're wondering what "argan oil" is, it's an oil extracted from seeds of the argan tree. It's a popular oil in Morocco, where this study took place. It contains mostly oleic acid, a monounsatured fatty acid, and also linoleic acid, an omega-6 fatty acid.
Other nutrients are also known to be involved in efficient testosterone synthesis. A lack of the trace mineral,
zinc, can itself result not only in a low testosterone level, but also smaller sexual organs. This should not be construed to suggest that ingesting a massive dose of zinc will work like anabolic steroids, or produce penile dimensions that would make a male porno star envious. Instead, it means that without enough zinc in the diet you will not produce optimal levels of testosterone. One study of older men with low zinc levels found that after ingesting zinc supplements for 6 months, the men showed a two-fold boost in their testosterone levels. But note that they started off with nearly deficient levels of zinc. The same study showed then when young men were deprived of zinc for 20 weeks, they showed significant drops in their testosterone levels, thereby illustrating the importance of zinc for maintenance of normal testosterone production. A few years ago, a supplement was introduced that claimed to provide anabolic effects in those who lifted weights. That supplement, ZMA, consisted of zinc, magnesium, and aspartic acid, an amino acid. Although one study with football players did show a rise in IGF-1 after using the supplement, subsequent studies found only those who were low in the contained nutrients in the product, i.e., zinc and magnesium, showed any benefit from it. If your diet is low in zinc, or you don't eat foods that are rich in the mineral, you will get a definite boost in testosterone by ingesting a zinc supplement. This is not likely,however, for most of those engaged in bodybuilding or sports, since most high protein foods, such as meat, dairy, fish, and oysters, all contain a good supply of zinc. If you do opt to use a zinc supplement, don't ingest more than 50 milligrams a day (the daily requirement for a male over age 19 is only 11 milligrams daily), since too much zinc can cause health problems that include lower immune response, lower levels of HDL-cholesterol, and interference with the activity and uptake of the mineral, copper.
Other nutrients may also affect testosterone synthesis and release. One of the most controversial in this regard is
vitamin D. vitamin D is actually a prohormone, since it's converted into an active substance called 25-hydroxy-D in the liver and kidneys. Recent studies suggest that vitamin D may be involved in the synthesis of testosterone. However, not all studies show that D boosts testosterone levels in men and women. Despite this, vitamin D is often included in numerous "testosterone-boosting" food supplements. This isn't a bad idea, since about 85% of people lack sufficient vitamin D, especially if they avoid the sun. The food content of D is very sparse, and it's nearly impossible to get enough D from food sources alone. An upcoming article in
Applied Metabolics will fully discuss the relationships of D to both exercise and testosterone.
Vitamin C also is involved in testosterone synthesis, but since it's probably the most well-known and popular vitamin, few people in the Western world are deficient in it, although many do not ingest optimal levels for health. A good supplemental level is 1,000 to 2,000 milligrams a day, but be aware that an oral dose over 200 milligrams leads to rapid saturation levels of C in the blood, and consequent loss through urination. The trace mineral,
boron, was touted about 20 years ago as a natural "testosterone booster" after a study of older women showed it increased testosterone levels in the women. Later studies of young men involved in weight-training,however, showed no effects of boron on testosterone production in the body. More recent studies show that boron may indeed provide slight increases in testosterone in those who are lacking the mineral, which is found mainly in fruit. But it would be a stretch to refer to it as a legitimate "testosterone booster." A 2012 study of young men engaged in weight-training found that conjugated linoleic acid (CLA) ingested at a dose of 6 grams a day for 3 weeks, significantly boosted levels of testosterone in the men.A more recent rat study showed a similar effect, which you can read about here:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0079686.
