Iron - should we be having more or less of this key nutrient?

Iron is one of the better known minerals that are needed by the human body in order for it to function correctly. It carries out a number of important roles:

  • It helps transport the oxygen that we breath from our lungs to our tissues and helps us adapt to times of oxygen stress such as being at altitude1.
  • It is needed for our anti-oxidant defenses that slow down aging and our risk of serious chronic disease.
  • It helps us fight against certain types of bacteria as part of an enzyme called myeloperoxidase2.
  • It forms part of the energy producing machinery in our cells.

Am I short on iron?

Iron deficiency is quite common and in particluar can affect the following people:

  • Women with heavier than normal monthly blood loss. In the UK nearly half of pre-menopausal women have ferritin levels below 25ng/ml3, which is considered indicative of low body iron stores. It is a sort of double whammy as on average women need more iron than men before the menopause. Women eat less than men and so end up consuming less iron, although they need more.
  • Athletes, especially long distance runners. Red blood cells can be destroyed by the physical trauma that occurs via compression in muscles under tension or via a foot strike in exercises such as running, jumping and ball sports. The destruction of red blood cells, leads to the release of their iron into the blood serum. While most iron in the serum can be reclaimed, some is lost from the body via urine. There is evidence that in running the foot strike is responsible for about 75% of the red blood cell destruction and that this is made worse if the running surfaces are hard or the shoes are inadequately cushioned4.
  • Vegetarians and vegans. People who avoid meat are at increased risk of iron deficiency as meat is a very good source of iron. The reason is that it contains iron (haem iron) in a form that is more absorbable than iron from plants and dairy produce (non-haem). Typically haem iron is absorbed between 2-15 times better than non-haem iron5.
  • Those affected by certain bacteria. Most bacteria require iron to survive and multiply. When you are infected they will try and use your iron supplies for themselves.
  • People with other causes of chronic blood loss.

Can I consume too much iron?

It is possible to overdose on iron. Doses above 1g can cause acute iron poisoning, which can lead to death of liver tissue, gastrointestinal bleeding, vomiting and ultimately death. Normally this is more than the amount contained in a bottle of iron supplements. Regular daily doses above 50mg should only be taken by those who are trying to increase their ferritin levels.

There are a small number of people who need to be careful with the amount of iron they consume. These include people with the hereditary disorder, haemochromatosis (affecting about 1 in 300 people), all children below the age of 10, people who require regular blood transfusions and those who consume a lot of alcohol. However, most people not in these categories would need to consume a lot to experience adverse health effects. As a rule of thumb it is best to avoid consuming more than 50mg per day unless it has been established that your iron stores are low. If you have low iron amounts up to 300mg should be OK. It is important to keep monitoring your ferritin levels if you are supplementing, as when ferritin levels are within the range 50-200mg/L it is best to reduce iron supplementation to below 50mg/day.

If your iron stores become too high it can be difficult for your body to get rid of them. In this case there are various drugs called chelators that bind to iron, allowing it to be removed from the body. People with haemochromatosis absorb too much iron from their guts and often need regular withdrawals of blood along with chelation therapy to keep their iron levels sufficiently low.

Iron needs and motherhood.

There are a number of misconceptions that are prevalent when it comes to the iron needs of babies. Firstly, breast milk normally contains very little iron, thought to provide the average baby with a daily dose of 0.27mg of iron6The reason for this is that the babies guts are sterile at birth. Bacteria that enter are in a virgin environment in which they could flourish, however, a babies gut is devoid of iron, and most bacteria except for lactobacilli need iron to grow. The lack of iron helps the infant develop immunity. As such recommendations such as the USDA's 1999 advice to give babies up to 6mg/day of iron are plain wrong7.

Since 2001 recomendations for babies aged 0-6months are more reflective of the fact that most babies contain stores of iron at birth that see them through the first 4-6 months, without any additional iron being needed. This is one of the many reasons why formula milk, which often contains iron sulphate leads to worse health outcomes for babies than breast fed milk. If you are using formula it is best to avoid ones providing more than 1mg of iron daily unless you know your baby needs additional iron.

After the age of 6 months a babies gut flora should have developed and their need for iron from their diet escalates very quickly, to more or less adult requirements. However, small size means that children can easily overdose on iron, and supplementing iron to children should not be done unless under medical supervision. You will note that on bottles of iron pills there is normally a warning to keep them out of reach of children.

During pregnancy a woman's requirement for iron is increased, especially during the last 6 months. During this period her blood volume increases and the fetus builds up its iron stores requiring more iron to be provided by the pregnant mother. When breastfeeding, this requirement for iron is much reduced, unless low iron stores or clinical anaemia are estialished. The reason for this is that the baby starts with high iron stores that naturally diminish over the first 4-6 months of life. Breasfeeding mothers often experience delayed menstruation and so their monthly average blood loss can be lower than women who are neither pregnant nor breastfeeding. As an indiciation the guideline intakes for women are: 18-50yo - 18mg, pregnant - 27mg, breastfeeding - 9mg. However, as with all guidelines please remember that the chance you are an average person is actually quite small.

Assessing your iron status

Some medical authorities still assess iron status by measuring the percentage of blood made up of red blood cells (haematocrit), and the amount of a protein called haemoglobin in those cells. Unfortunately, while these two measures can give us an idea about anaemia status, they do not actually tell us everything about iron in our body. For that we need to measure your ferritin levels.

Ferritin levels should be somewhere between 10-200ng/ml for women, and 15-400ng/ml for men, according to some laboratories8. These figures however, are a nonsense for a number of reasons. Firstly, there is no reason that women should have less iron in their bodies than men. The guidline figures are based on levels in the population, not on a level that has been established as optimal for health. Secondly, there is good evidence that for a number of people levels need to be significantly higher than 15mg/L for proper iron metabolism to take place9. For athletes and people suffering from fatigue there is good reason to target having ferritin levels above 50ng/ml.

If you are having your iron levels checked by your doctor make sure that ferritin is measured, as well as haematocrit and haemoglobin. Also find out what the exact ferritin figure is. It is all too easy for the receptionist at your local surgery to let you know that your levels are fine, just because they come within the reference range of your local laboratory. That could be as low as 10ng/ml if you are woman with fatigue. This would be a poor outcome, as a number of women with fatigue are helped when their ferritin levels are restored to above 50ng/ml.

Increasing your iron levels

Not all iron that you consume is absorbed from the guts. In fact the amount absorbed can vary depending on a number of factors. At one extreme babies may be able to absorb as much as 50% of the iron in their mother's milk. At the other extreme less than 1% of iron can be absorbed if iron status is fine and non-haem iron absorption is inhibited by phytates in grains and tannins in tea. As a result of this the amount of iron that you need to consume can be considerably greater than the amount of iron that your body needs. A typical daily need for iron is between 1mg and 5mg. This requirement is likely to be fulfilled by consuming between 10-50mg per day. 

Some nutrients inhibit iron absorption and their consumption needs to be avoided or at least moderated if you want to increase your iron stores. These include:

  • Calcium - dairy produce is not a good source of iron. It can limit absorption of haem as well as non-haem iron.
  • Phytates - found in grains such as bread.
  • Tannins - found in tea.
  • Oxylates - found in spinach and rhubarb.

Some other nutrients assist us absorb iron. They include:

  • Vitamin A - found in liver, green leafy vegetables and coloured vegetables such as carrots and peppers.
  • Vitamin C - found in berries and green vegetables.
  • Copper - found in seeds such as liver, cocoa powder and sunflower seeds.
  • Iron - cooking with iron cookware can increase iron levels markedly over time.

For most people including sources of iron in the diet is a sensible way to maintain iron status. You should remember that iron in animal products is in a highly absorbable form called haem iron. You absorb most of this irrespective of what else you eat in the same meal. Unfortunately for vegetarians and vegans the iron in plants is not absorbed as well as haem iron.

Below I list the typical amount of iron in 100g of foods, including some of those that have high levels.

Haem Iron

  • Liver and kidneys - 10mg
  • Meat: Beef - 3mg, Lamb - 2mg, Pork - 1mg, Chicken - 1mg
  • Seafood and fish: Oysters/Mussels - 6-8mg, Sardines - 2mg, Prawns - 1mg, Fish - 1mg

Non-Haem Iron

  • Nuts: Pistachios - 7mg, Cashews - 5mg, Almonds - 4mg
  • Dairy: Cheese - 0.5-1.0 mg, Yoghurt - 0.1 mg
  • Vegetables: Parsley - 8mg, Spinach - 4mg
  • Powders and drinks - Curry - 75mg, Oxo cubes - 25mg, Ovaltine - 11mg, Cocoa powder - 8mg

Your best bet is to consume liver, meat, seafood and fish. However, if you are vegetarian you need to exercise more judgement. For instance dairy is not a very good source as it does not have a lot to start with, and the calcium in it interferes with the iron absorption. A regular cup of ovaltine or cocoa should help as should cooking in iron cookware. Be careful with spinach as despite the popeye image, it contains fibre and phytates that can reduce iron absorption. Regular handfuls of nuts should help vegetarians and a salad containing plenty of parsley with vitamin C sources such as red peppers should help.


Supplementation should not be considered unless it has been established that your ferritin levels are low. If you have symptoms associated with low iron stores then a target of >50ng/ml ferritin is appropriate. If not a target of >30ng/ml is probably best. The best way to increase your iron stores is probably not with the iron sulphate beloved of the NHS, here in the UK. This supplement is associated with constipation and to a lesser extent nausea and bloating. Preferable supplements include iron conjugated with amino acids such as iron bisglycinate. Another effective solution is liquid floradix (iron gluconate).




3) Health Survey for England 1991: A Survey Carried Out by the Social Survey Division of the OPCS on Behalf of the Department of Health, HMSO. (Series HS no 11) 1993.


5) Nutrition A Health Promotion Approach, Third Edition, Geoffrey P Webb, p313,ISBN10: 034093882X