Testosterone is the main male sex hormone and is associated with masculinizing features such as muscle mass, facial hair, libido, and sperm production.
However, testosterone production is known to gradually decrease in men from the age of 30 (on average) [1].
This eventually leads on to hypogonadism, which is a clinical syndrome that is characterized by low testosterone levels and the presence of low libido, fatigue, and sexual dysfunction [2]. This affects approximately 4-5 million men in the United States alone [3].
This has led a high demand for natural testosterone boosters to keep testosterone levels in the normal range, or even surpass this range, to counteract such symptoms.
Elevating testosterone levels may increase muscular growth, improve nervous system function, and thus resulting in better strength, mood, libido, among other benefits [4].
Recent surveys suggest that people are increasingly seeking herbal and nutrient-based supplements to address hypogonadal symptoms [5].
This is why the supplement market for “testosterone boosters” was introduced, despite a clear lack of regulation by food and drug administrations to ensure safe and effective products.
Unfortunately, testosterone boosters are notoriously know to be produced without rigorous quality control, ingredient standardization, or verification of their apparent benefits.
Many supplement companies have even been found to give financial incentive for their consumers to “promote” these products via online reviews to falsely validate their efficacy.
Despite this, there are actually some supplements with good research behind them regarding increasing testosterone levels, such as:
D-Aspartic Acid
D-aspartate is an amino acid that is present in brain tissue, cerebrospinal fluid, and endocrine systems.
It is mostly associated with the reproductive system such as the adrenal gland, pineal gland, pituitary gland, and the testis [6].
The most important roles of d-aspartic acid is aiding the secretion of hormones in endocrine glands [7]:
- Supports prolactin, oxytocin and vasopressin production
- Suppresses melatonin secretion
- Modulates steroidogenesis and testosterone release in the adrenal gland
Regarding testosterone specifically, it has been reported that d-aspartic acid regulates the release and synthesis of testosterone through multiple pathways of the hypothalamic-pituitary-gonadal (HPG) axis [8].
Some controlled clinical trials have also shown that in healthy adults, ~3 grams of d-aspartic acid supplementation per day can increase testosterone levels by 20-40% after 2 weeks [9].
However, similar trials have not found any changes in hormone secretion or performance with this same dosage after 1 month [10].
The discrepancies between studies can be explained by differences in the participants baseline levels of total testosterone. Quite simply, the lower the initial testosterone levels, the more likely it is that a testosterone-boosting supplement will have a significant effect.
Not to mention that most clinical trials are flawed due to the small number of participants and short durations which makes it hard to assess any changes.
At the very least there is a clear mechanistic benefit to d-aspartic acid in that it can increase testosterone production either directly through leydig cells, and/or indirectly via the hypothalamus-pituitary-testis axis (HPG axis) [11].
Whether this increase in testosterone levels is statistically significant or will make a notable difference to ones health and performance is yet to be determined. Current systematic reviews of the available evidence conclude that the results are too inconsistent and there is a need for more high-quality studies [12].
Vitamin D
Vitamin D is a fat-soluble vitamin produced in the skin when exposed to sunlight. Upon doing so, the “active form” of vitamin D functions as a steroid hormone in the body.
One of its main benefits is that it increases the activity of enzymes that are present in leydig cells, which produce testosterone in the presence of luteinizing hormone [13] [14].
Lab studies have also shown that vitamin D significantly increases testosterone production within testicular models [15].
This is not surprising when analyzing observational studies, as there is a clear sign of low testosterone concentrations related to vitamin D deficiencies.
Controlled clinical studies support the use of vitamin D supplementation in this scenario, with 3 months of vitamin D supplementation increasing testosterone levels in people with clinically low vitamin D levels (<30 nmol/L) [16].
However, other clinical trials suggest that vitamin D supplementation will not necessarily increase these levels in people who are not already testosterone deficient [17] [18].
From this research it is clear that vitamin D deficiencies and testosterone deficiencies usually come hand-in-hand, and vitamin D supplementation will effectively treat deficiencies in either of these markers.
Tribulus Terrestris
Tribulus terrestris is a supplement made from a small leafy plant known as puncture vine.
Animals have noted variable improvements for boosting testosterone levels. Some studies note that 50-100mg per kg bodyweight can increase testosterone production by 30-60% in just 2 weeks [19].
However, most of the evidence only suggests a benefit to normalizing hormonal levels in animals that already have hormonal irregularities [20].
Clinical experiments in humans are lacking, but generally fail to replicate the findings in animal studies [21].
Experts have now started to claim that tribulus terrestris does not possess either direct or indirect androgen-increasing properties [22].
Yet much research is still needed to be conducted on this supplement, and there is reason to believe that its active ingredient called saponin may stimulate androgenic pathways [23].
Theoretically, the stimulation of these pathways may signal for the pituitary gland to secrete more luteinising hormone, which can then cause the testes to synthesize more testosterone [24].
Online reviews of this supplement do not help to clarify the confusion, with public opinion seemingly being split between positive and negative experiences.
This supplement may not work miracles, but it is certainly worth giving a try if boosting testosterone production is your main aim.
Conclusion
Elderly populations have a high prevalence of low testosterone levels, which can be a primary cause of low libido, fatigue, and sexual dysfunction.
Testosterone replacement therapy is an option for this population, however many people do not want to experiment with or risk the side effects of anabolic drugs.
Legal and safe supplemental alternatives to increasing testosterone levels more naturally are d-aspartic acid, vitamin D, and tribulus terrestris.
However, these supplements will only treat testosterone deficiencies and will not impact the levels of healthy adults.