Lack of iron is one of the most common mineral deficiencies world-wide, so I read with despair the recent headlines suggesting that iron levels found in supplements ‘could damage the body within just 10 minutes’. This study does not reflect what happens in the human body as the researchers added an iron solution to blood vessel lining cells grown in a laboratory. Not surprisingly, these cells rapidly showed signs of damage as iron on its own is a toxic pro-oxidant. We know that. It’s why iron rusts so readily in the presence of oxygen.
The human body is a bit more sophisticated than that. Within the circulation, iron is bubble-wrapped in an array of protective carrier proteins (including haemoglobin, ferritin and transferrin) to which it is tightly bound and unavailable for interaction with endothelial lining cells. Only a tiny amount of iron remains unbound and this is buffered by other antioxidant components of the circulation, including dietary antioxidants, which were not present in this study.
Worldwide, lack of iron is the most common nutritional disease, with most cases going unrecognized. It is a major health concern and if your doctor has suggested that you need iron supplements, please don’t stop taking them because of these recent headlines.
How Iron Absorption Is Regulated
Your intestines have a clever mechanism to ensure you only absorb as much iron as you need from your diet – whether in food or supplements. This system works on the fact that gut lining cells are shed every three to five days. Iron absorbed from the gut (mostly in the duodenum) is stored in these gut lining cells (enterocytes) bound to ferritin protein and, once the ferritin is saturated, no more iron is absorbed from the intestinal lumen.
Iron can only leave these storage cells and enter the circulation if it is passed on to another iron-binding protein (transferrin) in your circulation. If your circulating transferrin saturation is optimal however – because your iron levels are good – iron can’t pass from the gut lining cells into the circulation, and instead is naturally shed within a few days as the enterocytes are shed and replaced. This highly tuned process helps to ensure that the amount of iron in your circulation does not rise too high. It also accounts for the fact that higher dose iron supplements can cause intestinal side effects such as nausea, dark motions, diarrhoea or constipation.
How Much Iron Is Absorbed?
Males typically absorb an average of 6% total dietary iron, while women of child-bearing age absorb around 13% due to their higher needs to replenish that lost during menstruation.
This mechanism is not fully mature in infants, however, for whom an iron overdose is highly toxic. Iron is among the most common causes of serious poisoning in children (keep all supplements out of their sight and reach). A few people also inherit an ability to bypass this mechanism and absorb too much iron, causing a condition known as haemochromatosis.
Symptoms Of Iron Deficiency
Women are more at risk of iron deficiency than men, because of blood loss during menstruation. This can result in a low-grade iron deficiency that is enough to impair immunity and cause tiredness and poor work performance, reduced fertility and headache without causing frank iron-deficiency anaemia.
If unrecognised and allowed to progress, lack of iron quickly leads to the production of red blood cells that are significantly smaller and paler (due to lack of haemoglobin) than normal. This iron-deficiency anaemia is associated with generalized skin itching, concave brittle nails, hair loss, sore tongue, cracking at the corners of the mouth, profound exhaustion, reduced appetite and difficulty in swallowing. The affected person will look very pale with a fast pulse, dizziness, shortness of breath and can lead to angina and even a heart attack.
Food Sources Of Iron
Diet should always come first, and good sources of iron include shellfish, red meats, sardines, wheatgerm, wholemeal bread, egg yolk, green vegetables, dried fruit, bread made from fortified flour, and fortified breakfast cereals. Haem iron (found in meat products) is absorbed two to three times more efficiently absorbed into your gut lining cells than inorganic iron from plant sources such as spinach, enriched cereals and supplements.
To make things slightly more complicated, inorganic iron exists in two oxidation states: ferrous (Fe2+) and ferric (Fe3+) which have separate uptake mechanisms. Ferric iron – the form in which most plant-derived iron is obtained – is less well absorbed due to low solubility at the pH found in your small intestines. Vitamin C increases absorption by converting ferric iron to ferrous iron. Avoid over-boiling vegetables as this decreases their iron availability by up to 20 per cent as well as destroying any vitamin C present.
Iron Deficiency Is Common
UK iron intakes have fallen over the last 30 years due to decreased meat consumption and energy intake. Those who are most vulnerable to iron deficiency anaemia include:
• Infants if exclusively breast-fed
• Menstruating women
• Pregnant women
Those following a plant-based diet
• People with a high intake of phytates from unleavened bread (which blocks iron absorption)
• People with gastro-intestinal diseases
• The elderly.
If your doctor has recommended that you take iron supplements, it is important to keep taking them.
If you decided to take an iron-containing multivitamin yourself, because you don’t eat much in the way of iron rich foods, don’t let this study put you off taking them. However, if you have persistent symptoms such as tiredness or fatigue, do seek medical advice to find out the cause. This is especially important if you are female and experience heavy or prolonged periods. Your doctor can confirm whether or not you have iron deficiency through a blood test to assess your red blood cells, and to measure levels of your iron storage protein, ferritin. Iron deficiency anaemia is not a diagnosis you should make on your own.
If you eat plenty of iron-rich foods then select a multivitamin that does not contain iron as you will absorb all that you need from your food.
Iron Supplements Dose
The EU RDA for iron is 14 mg for adults, while the US DV is 18mg. The upper safe level for long-term use from supplements is just 17mg per day. Higher doses are prescribed for short-term use when iron-deficiency is confirmed, and are best taken under medical supervision.
Children’s use of iron supplements should always be closely supervised by a doctor as it can be toxic.
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