Younger women who are obese may have a much higher risk of bowel cancer, according to the latest research.

The link between the disease and obesity in men has already been established, but the evidence until now was not clear in women.

Now, research involving 90,000 women taking part in the Canadian breast screening programme has confirmed the link.

The researchers, from the Albert Einstein College of Medicine in New York, found that women defined as clinically obese were twice as likely to develop the disease, but only before the menopause.

The researchers, writing in the journal Gut, suspect that excess body fat is a source of increased insulin, a hormone which regulates blood sugar levels.

Research has linked this hormone with increased bowel cancer risk.

However, once the menopause has passed, fat tissue is an important source of the hormone oestrogen, which may be protective against this.

Bowel cancer is one of the most commonly diagnosed in the UK.

Cure rates are reduced by the fact that it is often well-advanced by the time that obvious symptoms appear.

There is pressure to introduce a national screening programme for the age groups most at risk.

Folic benefit

More research, also published in the journal Gut suggests that taking folate supplements may cut the risk of developing the disease.

The research, carried out at the Royal Victoria Hospital in Belfast, focused on a small number of patients, who already had pre-cancerous growths, or polyps in their bowel.

Some of them were then given 2mg of folic acid every day for three months, the rest, a dummy tablet with no ingredients.

At four, 12, and 18 weeks, tissue samples were taken, and the cells in them examined for signs of the rapid proliferation which may lead to cancerous growths.

In the folate group, the number of proliferating cells fell significantly - but after the folic acid was taken away, cellular activity began to grow again.

The researchers suggested that folate may help repair cellular DNA after it has been damaged.