A year ago, running coach and veteran marathoner Kathy Pugh was preparing for the Marine Corps Marathon. But despite a tried-and-true training program, it wasn't going well.
"I just didn't have the energy," Pugh says. "I was struggling and felt like I never wanted to do a marathon again."
What had happened?
As Pugh found out through a blood test, she was iron-deficient, something that's not all that unusual for premenopausal women, particularly athletes.
"It's quite common for female athletes to have iron deficiency," says Nancy Clark, a Boston-based sports nutritionist and author of the "Sports Nutrition Guidebook."
"And it really affects performance."
Exactly how prevalent iron deficiency is among female athletes isn't known, but Clark says it could be as high as 50 percent. In the general premenopausal female population, the prevalence is roughly 9 percent. A 2011 study of female collegiate rowers in New York state found 10 percent were anemic and 30 percent had low iron stores.
(Anemic refers to low hemoglobin, for which the most common reason is low iron. But you can be iron-deficient without being anemic — as was true for Pugh.
Clark attributes iron deficiency among female athletes to monthly blood loss (true for most premenopausal women) and an added demand on iron stores through high-intensity training as well as a focus on lean, vegetarian and natural foods.
But wouldn't "lean, vegetarian and natural" be a good thing?
"Absolutely, but if you are vegan, especially as an athlete, you have to make sure you are getting what you need nutritionally," says Lisa Lilienfield, a doctor with the Kaplan Center for Integrative Medicine in McLean, Va., whose expertise includes women's health and sports medicine.
Iron can be taken as a supplement but is readily available in our food — especially in red meat and seafood (in particular, clams). It is also abundant in green-leafy vegetables such as spinach and in beans and fortified cereals.
And so, Clark says, the trend among female athletes and other health-conscious consumers to move away from red meat and to give up fortified foods in favor of natural foods creates a "perfect storm" for iron deficiency.
"Female athletes tend to be very health- and weight-conscious," she says. "And when they want to lose weight, they'll give up things like hamburgers and steaks," as well as processed food, she says.
For example, good ol' Grape Nuts — a fortified ("processed") cereal has 90 percent of the recommended daily allowance for iron, while the natural Kashi Go Lean Crunch has 8 percent.
The recommendation for the general female premenopausal population is 18 mg of iron per day. Lilienfield suggests that should be higher — in the range of 20 mg or higher — for female athletes.
"I would recommend that female endurance athletes get screened so they can see if they need iron supplementation," Clark said. Note: Too much iron is not healthful, either, so it's important to know the right level before taking any iron supplementation.
Pugh says she can relate to both parts of Clark's perfect storm: She moved away from red meat and tried eating all-natural foods for the year leading up to the 2013 Marine Corps Marathon.
"I was doing my green smoothies and eating nutritional yeast — I felt like I was the picture of perfect health, and yet I felt tired," Pugh says.
For women who want to get more of their iron from plants, one possibility is to consume greens or beans together with vitamin C, which improves iron absorption, Lilienfield says.
For example, says Pugh, who is now also a trained health coach with the Institute for Integrative Nutrition: "You could have your salad with a lemon vinaigrette."
It's also worth limiting consumption of foods that inhibit the uptake of iron, she says, including calcium and coffee and tea.
So, what are some of the signs — aside from lack of energy — of low iron, and why is iron important in sports?
One is the desire to chew ice, says Clark (the medical term is pacophagia). In addition, "being cold all the time, feeling depressed and feeling tired," can be signs of iron deficiency.
Iron is essential for successful athletic performance since it helps carry oxygen to cells throughout the body. But when athletes feel overtired from workouts they often assume they need to lose weight — and in doing so they often deplete their iron stores even more.
"Athletes in endurance sports will notice it the most," Clark says. "But iron deficiency could impact all sports."
And she adds that iron deficiency is a "needless" problem, "since it's totally preventable. I see it as an education problem."
Pugh says she definitely has learned what works better for her these past few months. Her diet still consists of mostly natural foods and lots of greens, but she has added some red meat once a week or so — and says she thinks there is a link to her feeling better.
"Maybe it's just a coincidence, but I feel much more energetic, and I have no trouble sleeping, which was also an issue last year," Pugh says.