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What Female Athletes Need to Know About Fueling

By Heidi Strickler | March 26, 2019, 10:47 a.m. (ET)

Women's nutrition

Women have historically been excluded from research studies in sports science because our hormones are “too difficult and variable to study.” In fact, when all 2015 publications from the three leading sports science journals were analyzed, women made up only 3 percent of the 254,813 participants in 188 studies. This means that most of the nutrition and training research marketed to athletes (including women) has not been tested in women.

So why does this matter? 

If our hormones are different enough that you can’t use us in research, what makes you think that the data from men can be applied to women? 

A Woman on a Man’s Diet 

Since beginning my career as a Registered Sport Dietitian, I have had female clients complain about their lack of weight loss compared to their male partners on the same diet. This difference stems from the role of female hormones; from an evolutionary standpoint our bodies are not wired to thrive in an extreme or chronic low carbohydrate state, which is how many diets promise results. Some women experience success on low carbohydrate, high fat (LCHF) diets, but our biology does not support it for long term health. Severe long-term carbohydrate restriction (less than 120 grams of carbohydrate per day) increases cortisol, which signals fat storage and causes hormonal disruption and menstrual dysfunction. If fat loss and/or improving metabolic efficiency are your goals, women see the greatest benefit from periodizing their carbohydrate intake, with short strategic blocks of low carbohydrate availability around specific training (1). Outside of these blocks, women in training should keep carbohydrate intakes greater 120 grams daily from fruit, vegetables, legumes, and whole grains.

Know Your Flow 

A standard menstrual cycle lasts 28 days, although 24 - 38 days is “normal.” A women’s cycle is divided into the “low hormone” follicular phase, from your first day of bleeding (day 1) until ovulation (day 14), and the “high hormone” luteal phase, days 15 through 28. Although other hormones are involved, the two primary hormones are estrogen and progesterone. 

Days 1-13: The Follicular “Feel Awesome” Phase

During this phase women are most like men because hormones are at their lowest. While most women complain when a competition falls during their period, this is actually the time when our performance peaks. 

Nutrition Tips During Your Period (Menses): 

Prostaglandins increase inflammation, so supplementing with 1,000 - 5,000IU of vitamin D per day may be helpful based on your blood work results. Eating foods high in omega-3 fats, such as oily fish, walnuts and chia seeds, may also help to reduce inflammation.

Iron and magnesium are lost in the blood (which is why we crave chocolate!). Consume iron-rich foods, such as red meat, shellfish, spinach, legumes and whole grains with a source of vitamin C to maximize the absorption rate. Try supplementing with 250 milligrams of magnesium daily during your period, which can also reduce cramps

Digestive issues are one of the most common menstrual symptoms. Try eating more foods rich in Vitamin B6 such as meat, eggs, chickpeas, peanuts, potatoes, and bananas. If you choose to supplement, aim for 50-100 milligrams per day. 

Nutrition Tips for Days 10-12: 

A brief spike in estrogen just before ovulation causes loose tendons and ligaments and increases risk for injury. Ensure you are consuming adequate protein, plus collagen and vitamin C, to help strengthen these tissues.

Hydration Tips

Drink to thirst throughout the day and add electrolytes into your water during training. Avoid fructose and maltodextrin-based sports drinks, because women have fewer fructose receptors than men, which means that added fructose has greater likelihood to cause stomach issues. 

Days 15-28: The Luteal “Lousy” Phase

After ovulation (Day 14), progesterone and estrogen rise and peak on days 21 - 25, which is when your physiology really fights against you. Days 26 - 28 see a sharp hormonal drop, signaling uterine contraction, cramping and bleeding. 

Estrogen spares carbohydrate, so we rely more on free fatty acids for energy during exercise because we can’t access our stored carbohydrate. Carbohydrate intake during endurance exercise becomes more important and something along the lines of glucose tablets (or something similar) can be taken before each hard set during interval training. 

Estrogen and progesterone are catabolic, which means they increase muscle breakdown. Adequate daily protein intake maintains the production of serotonin and melatonin, helping boost mood and stimulate sleep. Women also need 25-35 grams of high-quality protein within 30 minutes of exercise. High-leucine sources, such as whey, are best. If you don’t consume whey, try 3 grams of a branched chain amino acid (BCAA) supplement both before and after training. 

BCAAs also reduce sugar cravings and mental fatigue in the week before your period.

Vitamins and Minerals: 

- Bloating before your period is caused by a water shift from blood vessels to cells. Adding salt to your food will help re-establish fluid balance. 

- You can supplement with 250 - 300 milligrams of magnesium and 1 gram of omega 3’s daily leading up to your period. 

Hydration Tips

Women are at greater risk for hyponatremia during the luteal phase due to the following effects of high estrogen and progesterone:

- Decreased thirst, so you take in fewer fluids 

- Increased core temperature by 0.5 degrees Celsius, so it takes longer for you to sweat and cool off

- Decrease in blood plasma volume by 8%, so your blood is less efficient at delivering oxygen and nutrients and clearing lactic acid

- Increased sodium losses because progesterone competes with aldosterone

- Increased blood vessel vasodilation, which results in greater heat absorption when exercising in the heat

For daily hydration, add 1/16 tsp salt to a 20oz water bottle, and 1/8-1/4 tsp during training. Consuming cold drinks on the bike or run can also help. 

Finally, I recommend women perform a sweat rate test during each phase of their menstrual cycle to gauge losses. Instructions on conducting your own sweat rate test can be found here. 

Celebrate Your Cycle and Kick Butt

As women, our menstrual cycle and hormones do not have to be a source of confusion or a reason to stop training. Once you understand why you feel lousy, hot or can’t sleep during the month, or why you can’t recover, or why you bonk on the bike, you can create a nutrition and training plan that produces more consistent results. Periodizing your nutrition and training throughout the month is critical for both short term performance success and long-term health, and it needs to be different than the men in your life. Knowledge is power, now go kick ass.  

Heidi Strickler, RD, CSSD, METS I, ISAK I is a Registered Sports Dietitian with eNRG Performance. An avid endurance athlete, triathlete, and ultra-runner herself, she has a passion for providing nutrition coaching to endurance athletes. She also specializes in plant-based nutrition, female physiology, and collegiate athlete nutrition. In July, she will graduate with a Master’s degree in Sports Nutrition from Liverpool John Moores University in England, United Kingdom. Find out more about Heidi at


1. Stellingwerff, T. (2017) Body Composition Periodizaton in an Olympic-Level Female Middle Distance Runner Over a 9-Year Career. International Journal of Sport Nutrition and Exercise Metabolism. DOI: 10.1123/ijsnem.2017-0312