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Iron and your healthOne of the few trace minerals for which the dietary recommendation (Dietary Reference Intakes) hasn't changed over the last couple of decades is Iron (Fe). It was, and still is, at 8mg a day for an average healthy female over 50, as well as an adult male, and 18mg a day for an adult female below the age of 50 (to compensate for periodic losses during menstrual periods).
How do you tell if you are "average" and "healthy" has not been defined. Anyway, iron deficiency has somewhat milder consequences than that of some other key minerals (magnesium, manganese, zinc). It is not to say that it doesn't matter. Prolonged serious iron deficiency will likely result in anemia, due to reduced RBC (red blood cell) hemoglobin content.
Considering that average intake sampled by the U.S. Department of Health and Human Services is around 12mg and 16mg a day for adult females and males, respectively, moderate supplementation should be beneficial, on average, for females below 50 years of age. More so considering that calcium supplementation can significantly reduce iron absorption rate.
As with magnesium, iron deficiency may be caused by manganese deficiency; in addition, the culprit may be magnesium, nickel, copper or zinc deficiency. It also may result from low stomach acid, general malabsorption, or significant blood loss (menstrual cycle in women). Routine blood tests - such is plasma, or serum test, that measures iron's blood fluid level - are unreliable, due to their unpredictable fluctuations. Still, they are commonly used because they are routine, simple and cheap. As a result, many people end up with incorrect iron level assessment and the resulting supplementation recommendation.
This is, of course, undesirable situation, whether it leads into prolonged deficiency, or excessive iron intake.
Iron deficiency can result in a number of symptoms, from fatigue, anemia and gastrointestinal disorders, to "restless leg syndrome" and learning difficulties18.
Free iron is very reactive, in other words, it produces free radicals. In order to prevent this, the body neutralizes iron by placing it in safe protein "boxes" (so called ferritin, or heme molecules). But excessive iron can overwhelm body's protective capability. Longer term excessive iron intake can result in its buildup inside the major organs (liver, heart, pancreas, spleen) and damage to their function.
Worse yet, iron build up in the liver - as a part of the complex combined effect with any of a number of substances processed by the liver (alcohol, medications, food-related and chemical toxins, heavy metals, some herbal supplements) - can precipitate tumor formation18.
It should be emphasized that iron build-up in the body is very unlikely to occur as a consequence of dietary intake alone, even if it is iron-rich. But it suggests that one needs to be careful with significant longer-term iron supplementation.
In other words, don't take longer-term iron supplementation "just in case" - make sure that you really need it, and you are not overdoing it.
This is in particular important for vegetarians - and more so for female vegetarians - who may find it difficult to satisfy their iron needs from food intake alone. Plant iron content is 100% inorganic (free, or non-heme iron). Its average absorption by the body is only about 1/10 (roughly; it can vary from 1/20 to 1/2) the absorption rate of organic, heme iron. The latter makes about 20%-50% of the iron content in animal meat, liver and blood (heme is the deep red non-protein constituent of hemoglobin - the vital constituent of the red blood cell - containing iron; heme iron is sometimes called haem, from haemoglobin, an alternate spelling for hemoglobin).
Since the officially recommended dietary iron intake is based on the average, meat-containing diet, this implies that nominal iron intake for vegetarians should be somewhat higher, as long as it comes from food.
The reason for non-heme iron's lower absorption rate (and that include iron in no-flash animal sources, like eggs and dairy) is that it often comes bound in compounds that need to be broken down before assimilation takes place. Thus it requires more time, slowing down absorption rate (fact that meat enhances absorption of both heme and non-heme iron may be in part due to it causing food to move through the intestine at a slower rate).
However, rather than resorting to iron supplementation, it is better simply to (significantly) enhance absorption of non-heme iron by including vitamin C, or other organic acids such as malic acid and citric acid (which can also be naturally present in plant foods).
If iron supplementation is needed, chelated or water-soluble forms are best tolerated.
Best natural iron food sources are tofu, brewer's and torula yeast, legumes, whole grains and green leafy vegetables.