Iron levels and altitude training

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Altitude training is one of those dark arts where everyone has a different “secret recipe” for what makes it work best. One of the tips you often hear from top coaches is that you need to take extra iron to get the most benefit. It’s a logical suggestion in theory: one of the key goals of altitude training is to increase your levels of iron-rich red blood cells to transport oxygen, so iron is a necessary raw material. But does it actually help in practice?

In PLoS ONE, Australian researchers recently published a retrospective analysis of 178 elite athletes (mostly cyclists, distance runners, and race-walkers) who did altitude training through the Australian Institute of Sport between 2006 and 2014. The training was conducted at altitudes between 1,350 metres and 2,700 metres (4,400 and 8,900 feet), or using the AIS’s altitude house set at 3,000 metres (9,800 feet), lasting two to four weeks.

The athletes received different iron supplements depending on their pre-training ferritin levels (a measure of iron storage). Those with levels greater than 100 micrograms/L got no supplements (n = 15); those with lower levels (average 76 micrograms/L, n = 144) got 105mg of oral iron per day starting one week before altitude and continuing throughout the training camp; those with the lowest levels (average 25 micrograms/L, n = 19) got 210mg of oral iron.

The results were pretty striking: the non-supplemented group increased their haemoglobin mass by 1.1 per cent on average during altitude training; the 105mg group increased by 3.3 per cent; and the 210mg group increased by 4.0 per cent. That seems like fairly strong evidence that iron supplementation is a good idea if you’re headed to altitude for most people (barring conditions like haemochromatosis): after all, 163 of the 178 athletes fell into the category where the AIS felt they needed supplements.

The study design isn’t perfect. It’s possible that the people who had high ferritin levels to begin with (and thus weren’t given iron supplements) also had high haemoglobin levels that were less likely to increase any further at altitude, regardless of whether they took iron supplements. (And similarly, the extra-big improvement of the people who took the highest iron dose may simply be because they were iron deficient, unrelated to the altitude training.)

We also can’t really draw any firm conclusions about what ferritin threshold indicates you need supplements. But the overall picture definitely suggests that extra iron is helpful for a lot people who wouldn’t need supplements at sea level (where a ferritin threshold of 35 micrograms/L is often used for athletes).