Iron | Nutritional Advice El Mondo

There are two types of iron in food: haem and non-haem iron.
In animal products, 40% of the total iron content is haem iron and 60% non-haem iron.
Plant foods contain only non-haem iron, which is found naturally in wholegrain cereals and breads, dried beans and legumes, dark green leafy vegetables, dried fruits, nuts and seeds.
The darker the flesh, the higher the iron content. This means beef contains more iron than lamb and pork.
In humans, iron is an essential component of proteins involved in oxygen transport.
Iron is also essential for the regulation of cell growth and differentiation.
The recommended daily allowance (RDA) is 10-20 mg per day.
A deficiency of iron limits oxygen delivery to cells, resulting in fatigue, poor work performance and decreased immunity.
Excess amounts of iron (>50-75 mg iron per day) can result in toxicity and even death.
Symptoms of acute toxicity may occur with iron doses of 20-60 mg/kg of body weight.
The amount of total iron available from a mixed diet (including meat) is estimated at 18%, whereas the amount of total (non-haem) iron available from a vegetarian diet is considered to be about 10%.
Non-haem iron predominates in all diets comprising some 90%-95% of total daily iron intake.
Haem iron provides 10%-15% of total iron in meat-eating populations.
Haem iron and non-haem iron are both absorbed in the small intestine, but via different mechanisms.
Haem iron is absorbed through the gut wall intact, regardless of how much we need.
Non-haem iron absorption is more carefully controlled, as it is more readily absorbed when the body has need for iron, a protective measure for iron overload.
Haem is the most bioavailable source of iron ranges from15%-35%.
The bioavailability of non-haem iron is low, only 1%-10% of the dietary load is absorbed.
Non-haem iron bioavailability is influenced by various dietary components that either enhance or inhibit its absorption.
However, haem iron bioavailability is not influenced by dietary components.
The main inhibitor of non-haem iron absorption is phytate, or phytic acid, which is usually found in legumes, nuts, wholegrain cereals and unprocessed bran. Processing the wholegrain removes much of the phytate content, but also removes other beneficial nutrients such as iron and zinc.
The most significant enhancers of iron absorption are meat proteins and vitamin C (both synthetic and dietary), which can enhance absorption up to sixfold in those who have low iron stores.
Vitamin C acts by reducing ferric iron to the more soluble and absorbable ferrous form.
Normally only 2-2.5 mg of body iron is lost each day, which means the body only needs 2-2.5 mg iron from diet to compensate the daily loss.
Taking into account the bioavailability of 18% from a mixed diet and 10% from a vegetarian diet, the RDA will be 10-20 mg.
Body iron content is approximately 4.0 g in men and 3.5 g in women. In adults, most body iron is present in hemoglobin (60-70%) in circulating erythrocytes where it is essential for oxygen transport and in muscle myoglobin (10%).
The remaining body iron (20-30%) is found primarily in storage pools located in the liver and reticulo-endothelial (macrophage) system as ferritin and hemosiderin.
Only about 1% of body iron is incorporated in the range of iron-containing enzymes and less than 0.2% of body iron is in the plasma transport pool where it is bound to transferrin.
A serum ferritin concentration of 1 microgram/L is equivalent to about 10 mg of iron stored in the body.
Non-heme iron, the type in dietary supplements, comes in either ferrous (Fe²⁺) or ferric (Fe³⁺) forms. Ferrous salts are more bioavailable and absorbed in higher amounts than ferric iron.
There are many forms of iron supplements which contain different amounts of elemental iron:
1 gram of ferrous gluconate = 120 mg elemental iron (12% iron).
1 gram of ferrous sulfate = 200 mg elemental iron (20% iron).
1 gram of ferrous fumarate = 330 mg elemental iron (33% iron).
Iron facilitates fat oxidation in the food industry. Therefore, it is very difficult to fortify food with iron. The best form of iron for food fortification is FeEDTA.
The tolerable upper intake level (UL) for iron is 50-75 mg per day.

Scientific studies on the relationship between iron and disease prevention:
Review articles of randomized, placebo-controlled double-blind clinical trials (RCTs) will answer the following question:
"Is taking dietary supplements make sense?". Yes at a positive conclusion and no at a negative conclusion.

Review articles of cohort studies or case-control studies will answer the following question:
"Should I change my diet?".