There are some key physiological differences between males and females that can influence what we should be recommending in terms of nutritional approaches. ADRIAN PENZHORN unpacks ….
Unfortunately most research into sports nutrition uses male participants and we cannot necessarily extrapolate these results to females. Most research into female athletes focuses on eating disorders, which is unfair and not entirely useful as most female athletes do not have an eating disorder. The research is slowly catching up and there are a few key things for us to keep in mind.
Some nutritional needs are influenced by body size, metabolic rate and energy needs at rest and during exercise and for example are greater with larger stores of muscle. Conversely smaller athletes have slower rates and smaller energy expenditures. Naturally this stands to reason that less energy (food) is needed to support training goals.
Body size is also a reason some research leaves us with more questions than answers. Studies show that women have a greater capacity to burn fat when expressed relative to weight, while males will still burn more on average due to the higher energy demand of having to move a larger frame around.
There has been some focus on estrogen and its impact on restricting glycogen (carbohydrate) storage after animal studies showed this. However in human trials it seems if we provide sufficient carbohydrate we can still maximise fuel stores and enhance performance. The tough bit can sometimes be for smaller women
typically eating 3-4 g/kg of carbohydrate but we would be aiming to double this to properly load and that can be quite a bit of food to get through.
During exercise there is no reason to recommend any carbohydrate strategy based on sex – absorption and tolerance are the only limiting factors here. Sweat rates and sweat sodium concentrations are as variable as in males and the fluid needs are again typically based on body weight. For example a 65 kg female athlete would be aiming to keep her fluid losses (weight loss) to 1.3 kg during an event, or less than 2%.
Protein studies also seem to show that women and men who exercise have similar relative needs, around 1.6 g/kg per day. What we do to maximise protein use, recovery and repair is split this into four daily servings. Our 65 kg lady here would be looking for 25 g servings of protein at each meal.
25g protein servings: 3 eggs, 100 g meat or chicken (raw weight), 120 g fish (raw weight), 40 g biltong, 1 scoop protein powder, 400 g yogurt, 200 g cottage cheese, 150 g edamame beans, 150 g tofu, 700 ml milk, 300 g chickpeas/peas, 160 g Quorn
The one micronutrient we need to pay attention to is iron. Female athletes, particularly endurance athletes, are at a higher risk of iron deficiency which can lead to a drop in performance, fatigue, poor recovery and anaemia. A blood test is easy and definitive. For female athletes following a vegetarian diet or calorie restricted diet this is quite important and focusing on iron rich foods a worthwhile addition.
Iron rich foods: liver, kidney, eggs, red meat, seafood, oysters, fortified bread/flour/cereals, molasses, dried legumes, nuts, leafy green vegetables, broccoli, figs, raisins, cocoa
An interesting and evolving bit of research is looking into the influence of the natural variations in hormone levels through the menstrual cycle on responses to training, performance and nutrition. It does seem that certain approaches may be tailored to this in the future so it’s a space worth watching out for.