Mild iron deficiency may drain endurance: study

[Guest guest]

Mild iron deficiency may drain endurance: study

Last Updated: 2004-04-01 15:51:16 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Some women who are short on iron may be

short on endurance as well, even when they do not have full-blown

anemia, new study findings suggest.

On the bright side, researchers report, getting enough iron may help

correct the problem.

Their study of 41 women who were moderately iron deficient found that

iron supplements helped boost fitness among those with more depleted

iron stores in their body tissue.

Brownlie and his colleagues at Cornell University in Ithaca, New

York, report the findings in the American Journal of Clinical Nutrition.

Iron-deficiency anemia occurs when the body has too little hemoglobin,

an iron-containing protein in red blood cells that carries oxygen.

Anemia is well known to cause fatigue, pale skin and breathlessness

during exercise, but the effects of less severe iron deficiency are not

as clear.

Animal studies have suggested it can sap endurance, but human studies

have not consistently shown this, according to Brownlie's team.

To study the question, the researchers looked at whether iron

supplements would help modestly iron-deficient women get more out of

exercise training. They had 41 iron-depleted -- but not anemic -- women

between the ages of 18 and 33 take either iron supplements or placebo

pills for six weeks. All of the women spent the last four weeks of the

study training on stationary bikes five days a week.

Brownlie and his colleagues also looked specifically at a measure called

serum transferrin receptor (sTfR) concentration, which indicates the

iron status of the body's tissues. A higher concentration means greater

iron deficiency in the tissue.

The researchers found that iron supplements appeared to help women with

signs of " overt " tissue iron depletion make greater fitness gains during

their exercise regimen.

In contrast, the supplements provided no fitness benefit to women with

normal sTfR levels, who improved their endurance regardless of whether

they took iron or not. This suggests that their degree of iron depletion

had not been limiting their endurance in the first place, according to

Brownlie's team.

The findings also indicate that a person's sTfR levels can help

distinguish diminished iron levels from a more problematic iron

deficiency, the researchers note. If iron depletion is impairing

fitness, they conclude, supplements may help correct the problem.

Iron supplements can, however, cause side effects such as abdominal

pain, nausea, constipation and diarrhea, and experts advise consumers to

consult a doctor before taking iron supplements.

They also recommend that people look at their diets before turning to

pills; good food sources of iron include red meat, lentils and other

legumes, spinach and iron-fortified cereals and grains.

The current study was partially funded by a grant from Mead

Nutritionals, a Bristol-Myers Squibb company that makes dietary

supplements.

SOURCE: American Journal of Clinical Nutrition, March 2004.

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org