Most people have heard that a high-fibre diet reduces the likelihood of bowel cancer –– for years it's been the accepted wisdom. However, a study in 1999 called this wisdom into question and received a large amount of publicity, much of it suggesting that fibre was no longer relevant. That's far from the case.
What the study found was that people who ate the most fibre had the same risk of colon cancer as those who ate the least. Two things could explain the results:
- First, none of the groups of people studied ate the amount of fibre recommended as a minimum amount (30 grams) –– the highest amount eaten was 25 grams a day. This may simply not have been enough to work.
- Second, what we really know is that a diet high in fruits, vegetables, whole grains and legumes is linked to a reduced colon cancer risk. But it may not be the fibre.
Instead it could be other things in these foods that are protecting you from cancer if you eat enough for example, antioxidants or other plant chemicals. And there are thousands of them. The evidence for fibre and prevention of breast cancer is also inconclusive –– but it's hopeful.
In any case, eating at least the minimum amount recommended is good for many aspects of your health, so fibre is still very important.
The evidence that fibre protects you from heart disease is very strong. Not all of fibre's protective powers come from soluble fibre reducing your cholesterol levels, although this is an important way fibre helps your heart.
Other ways it may act are by:
- Slowing your rate of digestion, which lowers insulin levels. Extra insulin can raiselood pressure, reduce the amount of 'good' cholesterol (HDL) in your blood and increase your risk of diabetes, all of which can increase the risk of heart disease.
- Helping you to lose weight. High-fibre meals are usually more filling, so you eat fewer calories.
- Reducing the risk of blood clots. Some chemicals formed by bacteria when they break down soluble fibre may reduce blood clots, which would lower the risk of heart attacks and stroke.