Women's Guide to Nutrition - Part One (Understanding Nutrition and the Menstrual Cycle)

Stacy Sims, PhD, is an Environmental Exercise Physiologist and Nutrition Scientist. Her long academic and sporting career includes racing at high level in road cycling, XTerra, and IRONMAN triathlons.  Read what Dr. Sims has to say about women-specific nutrition:

Throughout my years of sport, I found that existing sport nutrition guidelines and products out there didn't really work for me.  They didn't work for my teammates, and subsequently they didn't work for my athletes who were reaching high levels in the Olympics, World Cups, etc. . . .  I, however, had the advantage of accessing a lab to answer questions.

The question recurring was it doesn't work for women, but these things work for men. If we look specifically at women's physiology, we are not small men. Our physiology is different. Our metabolism is different. The way we respond to specific nutrition on-a-bike versus recovery off-the-bike is completely different from men, but we've been pigeonholed into being generalized by what's available.

Since the 1980's most of the research has been on men.  Women have been deemed too difficult. We've been told that women are too difficult to be researched in these same studies as men because we have what we call the menstrual cycle.

During the menstrual cycle, estrogen and progesterone go up and down. In the two weeks when estrogen and progesterone are high, we are not at all like men. This interrupts the data collection and the findings in the research. People are driven to perform immaculate research studies which generate strong results. If women are included in these research studies, they're often included in the low hormone phase where we are more like men.  In general, most research is extracted from 18 to 22-year-old, white men. The results are generalized out to the rest of the population, both men and women. For example, a 125-pound woman is completely different from a 155-pound guy. Yet their recommendations for nutrition on and off the bike are the same. It doesn't make sense. All of my research has been done on specific sex differences to see how women are different and how progesterone and estrogen and other factors of the menstrual cycle affect us in our performance.

What happens during the menstrual cycle?

Every month pre-period, we, as women,  feel really bloated, irritable and things just aren't quite right. This is the very tail end of the luteal or high hormone phase. Estrogen and progesterone are the highest. The combination of estrogen and progesterone decreases the plasma volume or the watery part of our blood by about 8%. Our blood is a little bit thicker, so our effective circulation or the amount of blood that can go to our working muscles is decreased, so our power output is decreased.

The other aspect of high estrogen and progesterone levels is our core temperature is up by 0.5 degrees Celsius. Therefore, our time to fatigue or the time it takes for us to get to a temperature at which the muscles stop working is shorter, so our intensity is decreased. Our ability to tolerate heat is decreased. Our ability to go harder longer is decreased just because of this rise in core temperature.

Finally, the third aspect is progesterone is very catabolic. It's very much a breakdown hormone. It breaks down our muscle tissue a little bit faster, which means we have a more difficult time recovering. It also increases our total body sodium losses, so we have less sodium available to go into our sweat. This predisposes us to a clinical condition called hyponatremia. We are a little bit compromised when we think about a few days before a period, but if we back it up even further the two weeks before we start bleeding, this is when estrogen and progesterone start to rise.

How does this affect training?

From a training perspective, there's a two-week period where we are a little bit compromised. We can't get what we need out of our training. As a woman you're thinking, okay, well, all this is kind of shocking and new. Maybe it's not, but if I have two weeks where I have a little bit of a compromised position to get the most out of my training, what can I do about it? Looking specifically at what nutrition does for you come into play. If we know that estrogen and progesterone decrease the amount of water in our blood, we know we need to stay on top of our hydration. We can also think about eating more watery fruits and veggies with a little bit more added salt throughout the day to increase the amount of water that actually is in our bodies available for sweating and for blood circulation.

The other thing to think about is recovery. Progesterone is very catabolic and decreases our ability to build muscle, so having a little bit of protein before and definitely after training knocks that progesterone aspect back and allows our muscles to recover and adapt. The whole idea about going out and training is you're putting your body under stress, and you want your body to recover from this stress to get stronger and fitter. There are a couple of windows that you want to think about.

Before training, you want to have about 10 grams of protein. This increases the amount of amino acids circulating, so you end up with less of a signal to break down muscle tissue from the progesterone. It also jump starts your ability to recover by having these amino acids circulating. After training you have a 30-minute window to have between 20 and 25 grams of really good protein. Preferably we want it to be a fast release like whey and then a slow release like casein. Then you have a longer time of circulating amino acids.  This helps with muscle repair and adaptation.

After that 30-minute window, you have another hour and a half to replace sugars back into your liver and your muscles. If you were to neglect that 30-minute window for protein, your total recovery time is about 90 minutes. We have a shorter window of recovery. This is pretty critical to remember.  Try to adjust eating around training so that you can actually maximize your adaptation and recovery to get another hard session the day after and another hard session the day after. You keep recovering and adapting and getting fitter as you go.

In a race situation and on race day, we don't really have the ability to dictate how our period will affect our racing. We can't really call up the race director and say, "Hey, I can't race today because my period's starting," or "I'm two days before my period starts and my hormones are high." So how do we mitigate these kinds of complications when we're actually racing? If we think about how estrogen and progesterone affect our blood circulation and our metabolism, we want to think about the four or five days before the race and increase our water and salt intake, increase our magnesium intake, and also increase our protein intake.  All of these things help counteract the negative effects of progesterone and estrogen.  So when you show up on race day, you have more body water available for sweating, thermos-regulation and blood circulation. With more amino acid circulating, you don't break down as much muscle tissue and have the ability to generate power and intensity.  On the race course itself, looking at using glucose tablets to raise the amount of blood glucose circulating to hit intensity.

Eating during your menstrual cycle

The two weeks before your period starts, you really need to think about what am I eating, how am I eating, and when am I eating.  Two weeks preceding during the low hormone phase where we're most like men, the general recommendations can hold true except for recovery. The 4:1 ratio about chocolate milk and a lot of the recovery products are still not the right ratio for women. We have a different set point and a different return time to baseline or pre-exercise conditions than men, so we need more protein after exercise.

If you're considering the easy go-to chocolate milk, you really need to add about 20 almonds or a couple of tablespoons of nonfat yogurt to increase the protein intake. One of the best recovery foods is actually nonfat or low-fat Greek yogurt with a little bit of maple syrup or honey.  This provides the protein we need and a little bit of carbohydrate. If we are going with the chocolate milk aspect or some of the typical higher carbohydrate, lower protein recovery drinks, we're being suboptimal in our recovery and being put at a disadvantage because we're following these general guidelines.

Across the board, across the menstrual cycle you really want to think about your recovery as a key cornerstone for gaining adaptations. As you're getting closer to the onset of your period, think of having some protein before and after your training and really think about having watery fruits and veggies and a little bit more sodium in your diet or salt in your diet to kind of offset that drop in your plasma volume and the drop in the effect of circulation of your blood.

In Summary....

• Women's bodies are different from men's, mainly because of how progesterone and estrogen work in a women's body.
• There are a few simple ways to counter act the effects these hormones have on performance.
• 10 grams of protein before exercise
• 20 to 25 grams of protein within thirty minutes after exercise
• Increase hydration and salt intake right before and during your period
• Good recovery options for women: chocolate milk with almonds and yogurt, yogurt with honey or maple syrup,