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Iron tablets taken by women during pregnancy may cause bowel cancer

Iron tablets taken by millions may cause bowel cancer, new research suggests.

Even low doses of the chemicals ferric citrate and ferric EDTA, which are commonly found in over-the-counter iron supplements, increase levels of a protein associated with the disease, a study found.

Lead author Professor Scheers, from the Chalmers University of Technology, Gothenburg, said: ‘We can conclude ferric citrate and ferric EDTA might be carcinogenic, as they both increase the formation of amphiregulin, a known cancer marker most often associated with long-term cancer with poor prognosis.’ 

This is not the first time such concerns have been raised, with a study released two years ago suggesting the DNA of cells in blood vessels can be destroyed within 10 minutes of swallowing iron tablets.   

Previous research suggests excessive iron levels ‘switch on’ genetic pathways that lead to bowel cancer.

Around six million iron tablets are prescribed each year in England and Wales alone.

Iron deficiency anaemia is more common in women due to pregnancy and heavy periods increasing the risk of the condition.

Iron tablets taken by millions may cause bowel cancer, new research suggests (stock)


Iron is important for the production of red blood cells, which carry oxygen around the body.

A lack of iron can cause anaemia.

The Department of Health states most people should be able to get all of their iron intake from their diet. 

Good food sources include:

  • Liver (this should be avoided in pregnancy)
  • Meat
  • Beans
  • Nuts
  • Dried fruit
  • Whole grains
  • Dark-green, leafy vegetables, such as kale

How much iron do people need a day?

  • Men over 18: 8.7mg
  • Women aged 19-50: 14.8mg
  • Women over 50: 8.7mg

Women with heavy periods, or those who are pregnant, may require supplements.

Iron intakes of more than 20mg a day can lead to constipation, nausea, vomiting and abdominal pain.

Very high doses can be fatal, particularly in children, therefore iron supplements should be kept out of youngsters’ reach.

Source: NHS Choices 

‘If I needed an iron supplement, I would try to avoid ferric citrate’     

As well as analysing the effects of ferric citrate and ferric EDTA, which is also added to food as a fortifying agent, on human bowel cancer cells, the researchers also assessed the effects of ferrous sulphate.

Results suggest ferrous sulphate, which is also often found in iron supplements, does not lead to higher amphiregulin levels. 

Speaking of the findings, Professor Scheers said: ‘First, we must bear in mind the study was done on human cancer cells cultured in the laboratory, since it would be unethical to do it in humans.

‘But, the possible mechanisms and effects observed still call for caution. They must be further investigated. 

‘Speaking personally, if I needed an iron supplement, I would try to avoid ferric citrate.’

Call for iron supplement labels to be clearer 

The researchers are urging supplement manufacturers to make the type of iron included in the tablets clearer on their labels.

Professor Scheers said: ‘Many stores and suppliers don’t actually state what kind of iron compound is present – even in pharmacies. 

‘Usually it just says “iron” or “iron mineral”, which is problematic for consumers. 

‘Researchers and authorities need to start to distinguish between this form of iron and that form of iron.

‘We need to consider that different forms can have different biological effects.’

Many types of iron supplements are available on the market based on at least 20 different compounds.

Ferric sulphate is one of the most common compounds in these tablets. Ferric citrate is said to be gentler on the stomach.

The findings were published in the journal Oncotarget. 

Women are more at risk of iron deficiency anaemia during pregnancy (stock)

Women are more at risk of iron deficiency anaemia during pregnancy (stock)

Tinned tuna contains up to 100 times more zinc than is safe 

This comes after research released earlier this month suggested tinned tuna contains up to 100 times more zinc than is safe, which could wreak havoc on people’s guts.

The mineral is commonly used to line the inside of cans due to its anti-microbial qualities, which help to prolong foods’ shelf lives.

New findings suggest zinc leaches into food and later becomes lodged in people’s digestive systems, altering their abilities to absorb nutrients.

This may also make their guts more permeable, allowing toxic substances to enter their bloodstreams, according to the researchers.

Study author Professor Gretchen Mahler, from Binghamton University, New York, said: ‘An increase in intestinal permeability is not a good thing – it means that compounds that are not supposed to pass through into the bloodstream might be able to.’

The proposed health condition ‘leaky gut syndrome’, which is not medically recognised, claims disorders such as multiple sclerosis are caused by the immune system reacting to substances absorbed into the bloodstream via a porous bowel.

Excessive zinc intake has been linked to seizures, fever, vomiting and fainting.