After 40, testosterone declines in men at approximately 1 to 2 percent per year, and oestrogen begins its perimenopause trajectory in women from the mid-40s onwards. These changes are not reversible through diet. But the rate at which they produce symptomatic effects, and the degree to which other hormones including insulin, cortisol, thyroid hormones, and growth hormone are optimised, is substantially influenced by nutritional status.
Dietary Fat and Testosterone
Testosterone is synthesised from cholesterol. Very low-fat diets consistently produce lower testosterone levels in both men and women. A study of healthy men placed on a low-fat diet for six weeks showed a 15 percent reduction in total testosterone compared to their habitual higher-fat diet period. The specific fats that support testosterone production are saturated and monounsaturated fats from whole food sources including eggs, meat, dairy, and olive oil, rather than polyunsaturated fats from refined vegetable oils.
Key Micronutrients for Hormone Synthesis
- Zinc: required for testosterone synthesis and for the conversion of androstenedione to testosterone; red meat, oysters, and pumpkin seeds are the best sources
- Magnesium: inversely associated with SHBG, which binds and deactivates free testosterone; dark leafy greens, pumpkin seeds, and nuts
- Vitamin D: functions as a steroid hormone precursor; deficiency is associated with lower testosterone in multiple studies
- Iodine and selenium: required for thyroid hormone synthesis; seafood and Brazil nuts are the best food sources
Fibre and Oestrogen Metabolism
The gut microbiome contains bacteria collectively called the estrobolome that metabolise oestrogen conjugates excreted in bile. Adequate dietary fibre maintains a healthy estrobolome that ensures normal oestrogen excretion. Low-fibre diets and dysbiotic microbiomes can increase the recirculation of oestrogen metabolites through enterohepatic recycling, which may contribute to oestrogen dominance symptoms in perimenopausal women.