Nutrition for women – what do we really know? Most studies are done on men but what impact do hormone fluctuations have on nutrition needs for optimal fuelling and recovery.

Us women are complex beings. So complex in fact that most researchers don’t want to touch (or study) us, with the result being that women are seriously underrepresented in sports nutrition research (indeed nutrition research in general). This is mainly due to our hormones and the fluctuations throughout the monthly cycle as well as other changes such as at menopause, puberty or from the effects of synthetic contraceptives, which make it hard to standardize results in scientific studies. In addition, the subject of hormones, menstruation and ‘women’s issues’ in the sports world is still considered somewhat of a taboo subject. Not only does it still make many men squeamish, embarrassed or fall under TMI, but most women are too reluctant to talk.

The upshot of this is that not only are sports nutrition guidelines generalised for women, based on results comprised mostly from research on young adult males, but even anecdotal evidence and experiences are not well shared. So what do we really know when it comes to sports nutrition and women? And do we need to tailor this advice based on the phase of their cycle (or other hormone status)?

The truth is there are several ways in which changes in hormone levels (whether during monthly fluctuations, oral contraceptive pills (OCPs) or whether due to more permanent life cycle changes such as puberty and menopause), can affect how we as women respond to food, and our ability to metabolise, tolerate, synthesise, store and utilise nutrients. 

What’s the story with hormones?
Hormones are messenger chemicals in the body. They are released by particular cells and circulate throughout the body either stimulating or inhibiting functions of various cells and organs and regulating activity depending on demand at the time. While we all know about hormones and their relation and importance to reproduction as part of the endocrine system, what is less considered is their effect on other body systems from the brain and nervous system, the skin, the gastrointestinal system and even the skeletal and muscular systems. 

While there are many hormones that come into play in regulating menstrual cycle, the two key ones are estrogen and progesterone. Although women’s cycle length can vary, even when regular for simplicity, they are often referred to as being 28 days (or one month) long. A monthly cycle can really be simplified into two phases, the follicular phase (also known as the low hormone phase) which follows on from menstruation and in which the two hormones remain in relatively low levels, before a sharp surge in estrogen which precedes ovulation. The luteal phase (high hormone phase) sees both estrogen and progesterone rise, with progesterone the dominant hormone. This is the time where many women experience symptoms of Premenstrual Syndrome (PMS). 

OCPs increase hormone levels, and although tend to even out fluctuations mean that and you are always in a high hormone phase. For some women oral contraceptives can improve symptoms while for others symptoms are worsened. Menopause changes things again as hormone levels plummet. This reduction has negative consequences for muscle synthesis and recovery, ability to tolerate heat and a greater propensity towards body fat storage.

PMS and effect on athletic performance: real or imagined?
For many busy female athletes with race schedules, monthly periods are often seen as a nuisance. For others the effects can be debilitating, making life a misery for days or even weeks every month. Yet despite widespread reports of women suffering generally as well as on the sports field, there is actually very little scientific evidence that the menstrual cycle has any demonstrable effect on athletic performance. “I call BS on that” says Amanda Stevens, pro triathlete and Ironman Champion who goes as far as planning out her entire race calendar for the year based on her monthly cycle, discarding races that fall in an unfavorable part of her cycle. 

Dr Cristina Beer, an integrative GP specialising in nutritional medicine and who has treated her share of Olympic and recreational athletes agrees: “I have seen this to not be the case”. The classic symptoms include bloating and water retention, cravings, increased appetite, mood and energy changes, alterations to sensations of pain. 

“In its extreme form, mood changes during this period can be so significant that the condition, labeled premenstrual dysphoric disorder, is treated with antidepressant medication for just two weeks before the menstrual period.” Dr Beer warns. 

Others turn to oral contraceptives in the hope they will not only make planning for races and training easier, but also reduce or eliminate negative hormonal symptoms. However, this is not always the case, “going on a low-dose oral contraceptive pill sometimes seems to improve symptoms and thereby perceived or real performance,” Dr Beer said. “For other women, the pill seems to worsen symptoms of bloating, fluid retention, and feelings of sluggishness.”

Menstrual symptoms can be manipulated somewhat by nutrition. Stevens underwent a complete overhaul of her dietary regime (flipping her traditional high carb diet to a low carb, high fat diet for other health and performance reasons) has helped with lessening monthly symptoms. “In general my PMS systems are much improved. The pain/cramps used to be intolerable for the first two days. I still get cramps but not to the same extent.  My flow is much shorter now too. Other symptoms of breast tenderness and crampy upper quads are still there but much improved and I have only slight weight gain.”

Other nutritional changes might also help lessen the severity of symptoms: “I often advise reducing sodium for the second half of a menstrual cycle,” shares Dr Beer. “I also advise increasing foods rich in vitamin B6 and natural tryptophan if mood changes are an issue.”

Menstrual symptoms might be an obvious potential performance crippler, but there are less obvious physiological changes such as fuels burnt for energy, shifts in fluid and sodium and gut function.

Effect on metabolism:
Hormone fluctuations influence metabolic rate and ratios of substrates (fat or carbs) used for energy. During the follicular phase, resting metabolic rate declines somewhat and the body shifts to higher levels of muscle glycogen usage and insulin sensitivity also increases. This means that you might need to pay attention to supplementing with extra carbs during high intensity workouts. Be aware though that this is also the time when women are more prone to experience PMS symptoms including cravings and an increase in appetite. Serotonin production also drops leading to the potential for lowered mood and this prompts instinctual cravings for high carb foods. The issue is, like many instances of increased hunger (such as in hard training), appetite can be over and above actual energy needs. This can lead to a tendency to overcompensate, consuming more than we need, worsening some symptoms and also hampering any body fat losses.

During the luteal phase, the body shifts to rely more heavily on fats for fuel as opposed to muscle glycogen. In theory this may be the optimal time for endurance sports, but this glycogen sparing mode might make it more challenging to reach higher intensities. At this time of the menstrual cycle (before a period starts) calories are burnt at a faster rate than at any other time.  This is something that Stevens, a medical doctor by training has seen directly, “my metabolism shifts more toward sugar burning a few days before and during my period with a steady, although slight, rise in blood glucose and decrease in ketones. The biggest difference with the sugar shift is during training.  I feel a bit sluggish and don’t seem to be quite as efficient in burning/utilising fat.  I usually need to take in more calories (especially with longer workouts) and the effects of the sugars don’t last as long, leading to more peaks and valleys in energy levels.”

What this means is that if you are racing (or have a key workout to complete) during the first half of your cycle, then you might need to pay extra attention to your pre-workout fuel. During the second high hormone phase then consider supplementing with carbs and proteins during and after workouts. Nutrition researcher, exercise physiologist and co-founder of Osmo, Stacy Sims, recommends women consider adding branched chain amino acids to ‘dampen the breakdown effects of progesterone’ on muscle during this high hormone phase of their cycle. 

Effect on hydration and sodium:
Both estrogen and progesterone influence the feedback systems that control and regulate thirst, as well as fluid and sodium intake and output. The overall effect of estrogen is to increase plasma volume and retain water, hence the bloating and water retention often seen premenstrually. During the second part of the month – the luteal phase – progesterone increases your core temperature, muscle breakdown and also causes your body to lose sodium and fluid with a resultant drop in blood plasma volume, earlier fatigue and ultimately a performance decline. This in effect thickens blood, slowing blood flow and leading to faster fatiguing muscles and reduced tolerance to working out in the heat. During this time women should pay attention to hydration to try and maintain higher plasma volumes associated with greater hydration and performance. According to Dr Sims, additional sodium during this phase will help boost blood plasma levels and bolster performance. 

Effect on GI tract:
In general, women have greater incidence of GI issues and a greater prevalence of GI distress during exercise.

Women are more likely to identify as having food intolerances and sensitivities. Research shows that there is an increase in GI symptoms including abdominal pain, changes in bowel patterns, bloating in women pre-menstruation and also pre-menopause, reflecting times of low ovarian hormone levels. Interestingly, there are receptors in the GI tract for estrogen and progesterone, reflecting this interaction between gut function, sensation and intensity of intestinal pain and the sex hormones. Women suffering from IBS also report a decline in symptoms after menopause, when hormone levels also decrease. Small bowel transit time is faster in the luteal phase than the follicular phase, while gastric emptying and colonic emptying rate remain the same. Hormones associated with OCPs can affect gut function linked to food intolerances and sensitivities with some women reporting onset or worsening of symptoms when they either started or ceased using an OCP. 

Women may also be increasing risk of GI distress during races and training by trying to follow generalised (male focused) sports nutrition guidelines. As more efficient fat burners, we actually need less carbs per hour than our male counterparts. Guidelines recommend 60-90g of carbs per hour for longer endurance exercise (like an Ironman or a half) but trying to reach these high levels of carbs during an event may just be too much for our GI systems to cope with. Instead try backing things off and aim for somewhere in the range of 40-60g.

On the flip side a poorly functioning GI tract – frequent IBS or damage caused by inflammation – can impact on proper hormone function and production, in effect setting up a negative looping feedback.

If you suffer from frequent or monthly related GI issues then it’s worthwhile tracking intake to help determine if you have any underlying food intolerances and sensitivities and help improve gut function and reduce or eliminate symptoms. If symptoms are linked purely with monthly fluctuations and certain foods, then it should be relatively simple to avoid these culprits around race time.

What’s the conclusion?
Being a female athlete is great but hormones can also throw in many more challenges, some of which are unexpected and unpleasant. When it comes to hormones and implications for sports nutrition, research is still very much in its infancy. Especially if you suffer through hormonal related symptoms, it might be worthwhile tracking food and hydration and mapping against symptoms and monthly cycle to see if any patterns emerge. Even those without obvious PMS may notice patterns emerge in optimal fuelling for performance and recovery based on the different phases of a cycle. The reality is that even with greater research, every female is going to be unique in hormonal responses and any dietary interventions and that most success will come as a result of trial and error (and likely a bit of luck as well).


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– Pip Taylor