Why do you feel tired even though you are not anemic?

When blood hemoglobin levels drop and you become anemic, you may feel dizzy or short of breath. However, some people may feel fatigue unrelated to hemoglobin even though they are not anemic. Anthony Broy, an assistant professor of medicine at Harvard University, explains why this is due to a lack of iron.

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???? Why does iron-deficiency-cause-fatigue, even in the absence of anemia?

I have often equated iron with hemoglobin and oxygen-carrying capacity.

But there is so much more to it!

— Tony Breu (@tony_breu)

July 2, 2022

It has been observed since the 1800s that even if hemoglobin levels are normal, iron deficiency can cause fatigue. And these symptoms are alleviated by administration of iron.

A randomized controlled trial in 1960 found that women with hemoglobin levels above 12 g per dL were given iron or placebo, and those who received iron showed greater improvement in symptoms. It was confirmed that iron administration reduced the feeling of fatigue. More recent data support the idea that iron administration to people who are not anemic but who are iron deficient reduces fatigue.

In addition, studies of polycythemia vera, in which an increase in red blood cells and white blood cells is seen due to abnormalities in hematopoietic cells, have confirmed the phenomenon of causing a feeling of fatigue despite a high hemoglobin concentration.

'In short, iron does more than just carry oxygen,' Broy said of these findings. He explained that this is due to the fact that iron plays an important role in many important human enzymes, especially those required for mitochondrial function.

A 1976 study of motor performance in normal and iron-deficient rats found that iron-deficient rats had inferior running performance compared to control animals, which was improved by iron administration. I did. At this time, the level of α-glycerophosphate dehydrogenase, an iron-containing enzyme present in mitochondria, was also changing.

These findings can explain the effectiveness of iron in the treatment of heart failure. 'One study estimates that 6.5% of all human enzymes are iron-dependent. Iron supplementation helps improve heart failure,' said Broy.