Link Between Saturated Fats and Low Sperm Count – Misleading?

Researchers from the Harvard Medical School published their findings in the journal Human Reproduction. The claims being made from this study are that a diet high in saturated fats causes a lower sperm count. However, there are some interesting things about the data set that need to be taken into account.

Saturated fats are long fatty acid molecules ranging from 4 carbons to 18 (stearic acid – found in grass fed meat). Fatty Acids between 12 and 16 carbons long (lauric, myristic and palmitic acid) are all atherogenic – they increase cholesterol and the risk of atherosclerosis.

There is a common misconception that saturated fats are bad for you that stems from the fact that people believe them to all be atherogenic. As already stated, only three of the common saturated fatty acids do indeed cholesterol – which can be lowered by following the tips in this article.

saturated fat structure

Saturated Fat Structure vs Unsaturated Fat

The research is being interpreted (by various news outlets) as saying that anyone who eats a diet high in saturated fats will have lower sperm counts. However, a cursory glance at the study itself shows that 71% of the test subjects were obese.

Why is that significant?

Obese people have larger and more abundant adipocytes (the cells that form adipose tissue), adipocytes are loaded with an enzyme known as aromatase which is the chief culprit in the transformation of testosterone into estrogen.

Estrogen is involved in a negative feedback loop with the hypothalamus – when the hypothalamus detects high levels of estrogen it slows down testosterone production by limiting LH and FSH release from the pituitary gland.

The chain is known as the HPGA (hypothalamus-pituitary-gonadal axis) or HPTA (hypothalamus-pituitary-testicular axis).

When LH and FSH (primarly FSH) levels fall, sperm production begins to decline – this is why men become less fertile as they age and why men on testosterone replacement therapy have a difficult time conceiving – due to diminished FSH levels.

Now, if those men were already obese it is likely that they already have a lower sperm count due to high circulating estrogen and lower FSH. When fed a diet of saturated fats (which has been shown to increase testosterone (here and in other instances), as steroid hormones are derived from lipids) their estrogen levels are likely to rise even more due to conversion of testosterone to estrogen. This will further lower FSH levels.


Only one useful piece of information can be extracted from this study:

“Higher intake of omega-3 polyunsaturated fats was related to a more favorable sperm morphology. Men in the highest third of omega-3 fatty acids had 1.9% (0.4–3.5%) higher normal morphology than men in the lowest third (Ptrend = 0.02).”

This suggests to us another reason to supplement with Omega 3 fatty acids – which can be purchased here! Could this be a possible fertility treatment?

Further research is planned and the researchers hope to be able to repeat the results. Hopefully they use a healthier group of participants and show us what a diet high in saturated fatty acids does to sperm quality and concentration. That information would be useful for couples trying to conceive.

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