Does bracken cause cancer?

Recently, ‘bracken causes cancer‘ has become a hot topic on the online communities. Food safety experts agreed and suggested to eat less bracken, it contains rich ptaquiloside, especially in its leaves. “Traditional dishes do not mean they are safe,” they said.

This crops up in the press from time to time. Mainly because bracken is known to cause bladder cancer and stomach cancer in cattle that have been grazing on it.

There have been fears that it could cause cancer in people

  • Directly, from being eaten
  • Through getting into cow’s milk
  • Through getting into the water supply
  • From the release of bracken spores into the air

Bracken is eaten in Japan, Korea and China, by aborigines in Australia and in some areas of North America, where it’s called ‘fiddlehead greens’. We don’t really eat it in the UK, so it isn’t likely to cause cancer that way. There are some studies that have suggested there may be an association between eating bracken and stomach cancer or cancer of the food pipe (oesophagus) but this is not clear.

If bracken were to get into milk or the water supply, it is possible that it would be carcinogenic (cancer causing). But in the UK, milk is produced by large dairies that get supplies from a wide area. Most of this would be unaffected by bracken. It is unlikely that any carcinogenic effect would be strong enough to affect people drinking the milk. Similarly the mains water supply would not contain very much bracken contaminated water.

Studies have shown that bracken spores can cause cancer in mice. This is a long way from saying they can cause cancer in humans. The mice were given the spores to eat. And they were exposed to amounts that most of us are not likely to come into contact with.

Some people need to take extra precautions. Bracken spores are released in hot, dry weather. So people who work in areas where bracken is widespread are advised to wear face masks in hot weather, as they will spend a lot of time in contact with the spores. Similarly, farmers whose cattle feed on bracken are advised not to drink their cow’s milk. However, we couldn’t find any studies that have looked into the cancer risk of inhaling bracken.

Certainly for most of us, it is unlikely that bracken is a major cause of cancer. Certainly it is far less important than smoking and diet, the risk factors over which we have the most control.