New research shows the nutrition requirements of men and women aren't the same
Over the last few decades, a lot of research has gone into nutrition and how it affects running performance. Unfortunately, the majority of that research has been done on males, and it is only recently that sports scientists have begun looking specifically at the nutritional needs of female athletes. Not surprisingly, these requirements do differ from those of their male counterparts. Much more research needs to be done, but here’s what we know so far.
Males vs. females
Thanks to their higher levels of testosterone, male runners tend to have more muscle mass and a lower body fat percentage. They also typically have a higher VO2 max than female runners. This 2009 study explains that on average, women have six to 11 per cent more body fat than men because of their higher levels of estrogen, which reduces the body’s ability to burn energy after eating. This results in more fat storage around the body, presumably to prime women for childbearing.
Muscle tissue is more active than fat tissue, and so the more muscle you have, the more calories you need to sustain yourself. Because females typically have higher amounts of body fat and less muscle mass, they typically require fewer calories than males, even outside of the context of running. Throw running into the mix, and you begin to see even more difference between the nutritional needs of male and female athletes.
Vitamins and minerals
Female runners need to pay particularly close attention to three nutrients: iron, calcium and vitamin D. Of course, these are important for male athletes as well, but the female menstrual cycle can affect the status of these nutrients, and throw them out of whack if you’re not careful.
Iron is required for the transportation of oxygen throughout the body and for energy production, and a deficiency can negatively impact your performance, energy levels, recovery and immune function. Females are at greater risk of iron deficiency as a result of menstruation, so their requirements are higher than males’. The recommended daily intakes of iron are as follows:
Males 19-70+: 8 mg/day
Females 19-50: 18 mg/day
Females 50+: 8 mg/day
Female athletes also tend to be at a greater risk for lower bone density than male athletes, which means they need to pay more attention to both their calcium and vitamin D intake. While the calcium recommendations for the general population are the same for men and women (1,000 mg to 1,200 mg/day, depending on your age), a recent study recommended that females who are at risk for lower bone density should consume 1,500 mg/day to optimize their bone health. Studies have also shown that women tend to have a lower vitamin D status, and since it is not widely available in the diet, supplementation may be necessary. Dosage recommendations vary, so female runners should talk to their doctor or dietitian before adding a supplement to their daily routine.
Females can forget fasting
In May we spoke with Dr. Stacy Sims, who explained that female physiology makes women much better at regulating their metabolisms based on how much or how little they eat. For this reason, she says fad diets (like paleo or keto) and fasted training can work well for men, but is more stressful for female bodies than beneficial, and should be avoided. She recommends that women always eat before a workout (even if it’s just a small snack) and that they concentrate their carbohydrates around their workouts to improve performance and kickstart the recovery process.
Yes, protein is important for both male and female athletes, but new research suggests that physiological changes throughout their menstrual cycles may impact female athletes’ protein needs. Although more research is needed in this area, new recommendations encourage women to increase their protein intake during the follicular phase (day 1-16), because this is the time when estrogen levels are rising, which creates an anabolic (muscle-building) effect. During this time, female runners should aim to consume 1.6 grams of protein per kg of body weight each day.
Don’t skimp on the calories
This holds true for both male and female athletes, although female athletes tend to run the risk of under-fuelling more than males. As an athlete, there is little value in trying to add more protein to your diet, eat according to your menstrual cycle (for females) or do anything to optimize your micronutrient status if you’re not meeting your basic energy needs. At the end of the day, the most basic requirement for your body to run well is to have enough energy, so skimping on calories will prevent you from reaching your full athletic potential.
posted Thursday November 25th
by Brittany Hambleton