Sports medicine experts have observed for years that endurance athletes, particularly females,frequ
ntly have iron deficiencies. Now a new study by a team of Purdue University researcherssuggests tha
even moderate exercise may lead to reduced iron in the blood of women.
"We found that women who were normally inactive and then started a program of moderate exerciseshow
d evidence of iron loss," says Roseanne M. Lyle, associate professor at Purdue. Her study of 62form
rly inactive women who began exercising three times a week for six months was published in thejourn
l Medicine & Science in Sports & Exercise.
"Women who consumed additional meat or took iron supplements were able to bounce back," shenotes. "
ut the new exercisers who followed their normal diet showed a decrease in iron levels."Iron deficie
cy is very common among women in general, affecting one in four female teenagers andone in five wom
n aged 18 to 45, respectively. But the ratio is even greater among active women,affecting up to 80
ercent of female endurance athletes. This means, Lyle says, that "too many womenignore the amount o
iron they take in";. Women of child-bearing age are at greatest risk, since theirmonthly bleeding
s a major source of iron loss. Plus, many health-conscious women increase their riskby rejecting re
meat, which contains the most easily absorbed form of iron. And because women oftenrestrict their
iet in an effort to control weight, they may not consume enough iron-rich food, and areliable to ex
erience a deficiency.
"The average woman takes in only two thirds of the recommended daily allowance for iron," notesanot
er expert. "For a woman who already has a poor iron status, any additional iron loss from exercisem
y be enough to tip her over the edge into a more serious deficiency," notes the expert.
Exercise can result in iron loss through a variety of mechanisms. Some iron is lost in sweat, and,
orunknown reasons, intense endurance exercise is sometimes associated with bleeding of the digestiv
system. Athletes in high-impact sports such as running may also lose iron through a phenomenonwhere
small blood vessels in the feet leak blood.
There are three stages of iron deficiency. The first and most common is having low iron reserves, a
ondition that typically has no symptoms. Fatigue and poor performance may begin to appear in thesec
nd stage of deficiency, when not enough iron is present to form the molecules of blood protein that
ransport oxygen to the working muscles. In the third and final stage, people often feel weak, tired
andout of breath - and exercise performance is severely compromised.
"People think that if they're not at the third stage, nothing is wrong, but that's not true," says
ohn L.
Beard, who helped design the Purdue study. "You're not stage 3 until your iron reserves go to zero,
andif you wait until that point, you're in trouble."However, most people with low iron reserves don
t know they have a deficiency, because traditionalmethods of calculating the amount of iron in bloo
(by checking levels of the blood protein thattransports oxygen) are not sufficient, Beard states.
nstead, it's important to check levels of a differentcompound, which indicates the amount of storag
of iron in the blood. While active, child-bearing agewomen are most likely to have low iron stores
he notes, "Men are not safe, especially if they don't eatmeat and have a high level of physical ac
ivity." (An estimated 15 percent of male long distance runnershave low iron stores.) Beard and othe
experts say it's advisable for people in these groups to have ayearly blood test to check blood ir
n reserves.
If iron levels are low, talk with a physician to see if the deficiency should be corrected by modif
ingyour diet or by taking supplements. In general, it's better to undo the problem by adding more i
on-rich foods to the diet, because iron supplements can have serious shortcomings. Supplements mayp
oduce a feeling of wanting to throw up, and may be poisonous in some cases. The best sources of iro
,and the only sources of the form of iron most readily absorbed by the body, are meat, chicken, and
fish.
Good sources of other forms of iron include dates, beans, and some leafy green vegetables.
"Select breads and cereals with the words 'iron-added' on the label," writes sports diet expert Nan
yClark. "This added iron supplements the small amount that naturally occurs in grains. Eat these fo
dswith plentiful Vitamin C (for example, drink orange juice with cereal or put a tomato on a sandwi
h) toenhance the amount of iron absorbed." Clark also recommends cooking in iron pans, as food can
eriveiron from the pan during the cooking process. "The iron content of tomato sauce cooked in an i
on potfor three hours showed a striking increase, the level going up nearly 30 times," she writes.
nd peoplewho are likely to have low iron should avoid drinking coffee or tea with meals, she says,
incesubstances in these drinks can interfere with iron being absorbed into the body.
"Active women need to be a lot more careful about their food choices," sums up Purdue's Lyle. "Ifyo
pay attention to warning signs before iron reserves are gone, you can remedy the deficiency before
t really becomes a problem."