Continuing with factors that can impact an individual’s nutrition requirements: Gender. I will say upfront that this is not an article designed to tell you what to eat as a man or a woman. It is an article to flag some key factors of growing interest in the field of sports nutrition, particularly with respect female athletic nutrition.
I doubt I am surprising anyone when I say that men and women are not the same.
Considering physiology: Men typically have larger fast versus slow twitch muscle fibres, larger heart and lung volumes, and lower levels of essential body fat (even after accounting for differences in body size!). Women typically have larger slow versus fast twitch muscle fibres, and have a higher proportion of their muscle mass in the lower part of their body.
And hormonally: Men have higher testosterone from puberty onwards (albeit it declines slowly with age), whereas women experience cyclical patterns of high oestrogen, progesterone and other hormones from puberty to the menopause.
Most sports nutrition research has been performed in men. So I think it is reasonable to assume that the broad gender requirements of males has been implicitly accounted for in sports nutrition guidance. Although it should be noted there is still much we don’t know!! It should also be noted that research on the impact of varying levels of testosterone within the normal physiological range (we aren’t talking about those on the juice!) on muscle mass, energetic capacity and performance continues.
But what about women? Women have been studied less. Partly because in the past there was less female participation in sport. But partly because females are harder to study. Hormone cycles impact many physiological responses. This means if you study a group of women all at different stages of their cycle you can end up with a right mess of results! And then there are women on hormonal contraceptives and post-menopausal women, both of whom can have different results again! It is possible to identify the stage a women is at in her cycle, or whether she is on contraceptives, or if she is post-menopausal, and analyse the results of studies with this in mind. This is done, but it makes research more complicated and you typically need a higher number of participants to get meaningful results from any one hormone ‘stage’. So it is done less!
We know that a lot of the sports guidance developed from male research clearly does apply to women … because we get positive results when our female athletes follow variations of it. But without studying it, we don’t know that there are other approaches, or added dietary tweaks or supplements that could further enhance female performance at one or more stage of her hormone cycles.
What of research that has been performed in women? Well, the short answer is ‘equivocal’. There is conflicting evidence out there in the studies that have been performed, which is likely because different studies have or have not correctly identified where a woman is in her hormone cycle, have used women of different trained status (and we know trained and untrained individuals can respond differently to the same nutrition intervention), have used different training protocols and so on. In other words, the results may differ because factors other than nutrition have differed between studies.
Based on the research that has been performed to date, a few things that do appear to emerge from multiple studies with respect female athletic performance and associated nutrition:
Muscle strength: Oestrogen and progesterone levels do not appear to impact muscle strength. This means muscle strength is not expected to be impacted by fluctuations specifically in these hormones across the monthly menstrual cycle, after the menopause, or with short term ingestion of oral contraceptives containing these hormones.
Anabolic response: There is some evidence there is a reduced anabolic response when progesterone is high, which might mean that whilst existing muscle strength is not impacted there may be less muscle mass and potentially strength development over this time.
Protein: Having said this, women appear to utilise protein more or less equivalently to men, and thus it is thought that guidance on protein intake apply to women as well as men.
Carbs: This is complex! The shorter answer is, we still have a lot to understand. There is evidence that women metabolise carbohydrates differently at different stages of the hormone cycle and post menopause. This is a vast topic in itself and so too big to cover in this blog. But get in touch with me if you want to chat about it!
Hydration: Hormone levels impact water and salt retention and therefore risk of both dehydration and hyponatremia. When hormone levels are high, women are at highest risk of hyponatremia.
Iron: Women have higher requirements for iron, when menstruating. As athletes typically already have higher iron requirements than sedentary populations this is likely to be a particular focus for female athletes.
Calcium: Women must also have a greater focus on calcium and therefore also vitamin D intake to maintain strong bones. Oestrogen supports calcium uptake and maintenance of bone mineral density. Post menopause, when oestrogen levels decline this should be an area of focus for female athletes. It is also significant when we consider Relative Energy Deficiency Syndrome (RED-S), which encompasses the female athletic triad. Males can suffer this too, but it is thought to be more prevalent in females. It is where females take in too little energy for the sports they do, resulting in low energy availability (LEA) for core bodily functions. Persistent LEA can lead to cessation of hormone cycles and menstruation. Low oestrogen can result in loss of bone mineral density, as for post-menopausal women and increase fracture risk in female athletes. LEA in males does not seem to have the same effect on bone mineral density, likely because the control is not so dependent on high oestrogen levels.
So there you have it. Women are not small men, and men are not large women! There is still much to learn about both. Just a few special considerations highlighted above. Get in touch if you are interested in chatting more on this topic!