Testosterone is the primary sex hormone in men (and anyone with testicles) responsible for sexual development and maturation. It’s what causes facial hair growth and voice deepening during puberty. Testosterone stimulates the growth of muscle, bone, and the production of blood cells. It also helps regulate metabolism, sperm maturation and increases libido (sex drive). As great as testosterone sounds, there are issues with having too much or too little of this hormone. Today we’re going to focus on the causes and effects of low “T.”
Around the age of 40 years, testosterone levels naturally start to decline. However, there are many other dietary and lifestyle factors that can bring testosterone down.
In addition to being associated with an increased risk of cardiovascular diseases1, low testosterone can cause:2
- Decreased bone density
- Lower libido
- Decreased blood cell production which can result in anemia,
- Smaller testicular size
Other than aging, what else causes low testosterone?
Adipose (fat) tissue contains an enzyme called aromatase which converts testosterone into estrogen. When we carry excess adipose tissue in the body (measured as body fat %), there is a vast increase in the conversion of testosterone to estrogen, leading to abnormally increased estrogen levels and a lower testosterone-to-estrogen ratio.3 This can cause hot flashes, irritability and/or depression, and an increase in breast size. The increase in leptin, a hormone associated with obesity, also contributes to a decrease in testosterone production by testicular Leydig cells.4
One study showed that men who had a baseline BMI of 33 to 61kg/m2 had significantly lower testosterone levels and higher estradiol levels. They also had significantly lower sperm counts and lower sperm quality.5
When the men in the above study underwent a 14-week weight loss regimen consisting of dietary changes and physical activity, resulting in a median weight loss of about 15%, there was a significant increase in total sperm count, semen volume and testosterone levels.
Stress activates the hypothalamus-pituitary-adrenal (HPA) axis. This is the hormonal signal pathway from the hypothalamus and pituitary glands situated under the brain to the adrenal glands which secrete our stress hormones. The increase in corticosteroid levels like cortisol can then cause a decrease testosterone levels.3
Phthalates are a group of chemicals and plasticizers used in food processing and packaging, in personal body products, cosmetics, colognes and other fragranced products.
Phthalates have very short half-lives (hours to days) and are excreted from the body via urine and feces. However, they are labelled a “reproductive toxin” by the European Union and are still used regularly in Canada and the US. Phthalates can bind to androgen (testosterone) receptors and affect their function. Higher phthalate levels have been associated with lower testosterone levels,6 and testicular cell death.7
Dietary trans fats and saturated fats
Trans fats and partially hydrogenated oils are found in margarines, peanut butters, theatre-style popcorn, and in baking shortening found in pastries and pie crusts. They increase insulin resistance, inflammation, and the risk of developing type 2 diabetes.
When consumed, saturated and trans fats can accumulate in testicular cells, interfering with testosterone production, sperm production and can cause cell death of testicular Leydig cells.4
Sleep dysfunction and deprivation
Testosterone secretion has its own circadian rhythm. For testosterone this means that levels start to increase when you fall asleep, are highest around waking time, and are lowest during the day. So when you don’t sleep or don’t get enough sleep, you are more likely to have lower levels of testosterone. This has been shown in animal studies where sleep deprivation has led to significantly decreased testosterone levels while also impairing sexual performance (decreased rate of ejaculation).8
This is also related to the effect that stress has on testosterone. The stress hormone cortisol suppresses melatonin (our sleep hormone). If you’re not sleeping (because you’re working or keeping yourself up), or can’t sleep, your melatonin levels will be lower and your cortisol levels higher (cortisol should be at its lowest at night). Keep in mind that exposure to light also suppresses melatonin. This will slow or prevent the release of testosterone from the testicular Leydig cells, decreasing testosterone levels even from short-term sleep loss!8
Another takeaway is that you can’t make up for lost sleep, especially after long-term sleep deprivation and/or chronic stress. That’s not how the body works—lost sleep is lost. This is why it’s so important to avoiding working into the late midnight hours. We need between seven and eight hours of sleep per night. Shift workers in particular have challenged melatonin regulation, which makes light therapy lamps and supplemental melatonin so important in these cases.
Although aging is a primary reason for lower testosterone levels, there are many lifestyle factors that can contribute to low testosterone. To keep levels of this hormone optimal, aim to:
- Ensure adequate sleep (7 to 8 hours per night)
- Maintain a healthy BMI (ideally between 19 to 25, but this may vary depending on your body fat percentage)
- Avoid consuming saturated and trans fats
- Reduce exposure to phthalates and other hormone-disrupting chemicals. This includes those found in body/hygiene products as well as fertilizers and plastics.
- Manage stress. Find a strategy that works for you, such as exercise, acupuncture, meditation and/or breathing exercises, listening to music, or watching something funny that makes you laugh.
- Goodale T, Sadhu A, Petak S, Robbins R. (2017). Testosterone and the Heart. Methodist Debakey Cardiovasc J. 13(2):68-72
- Nassar GN, Leslie SW. Physiology, Testosterone. [Updated 2022 Jan 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526128/
- Sharma R, et al. (2013). Lifestyle factors and reproductive health: taking control of your fertility. Reprod Biol Endocrinol. 11:66
- Suliga E, Gluszek S. (2020) The relationship between diet, energy balance and fertility in men. Int J Vitam Nutr Res. 90(5-6): 514-26
- Hakonsen LB, Thulstrup AM, Aggerholm AS, et al. (2011). Does weight loss improve semen quality and reproductive hormones? Results from a cohort of severely obese men. Reprod Health. 8:24
- Radke EG, Braun JM, Meeker JD, Cooper GS. Phthalate exposure and male reproductive outcomes: A systematic review of the human epidemiological evidence. Environ Int. 2018 Dec;121(Pt 1):764-793
- Amir S, Shah STA, Mamoulakis C, et al. (2021). Endocrine Disruptors Acting on Estrogen and Androgen Pathways Cause Reproductive Disorders through Multiple Mechanisms: A Review. Int J Environ Res Public Health. 18(4):1464
- Lateef OM and Akintubosun MO. (2020). Sleep and reproductive health. J Circadian Rhythms. 18:1