What we eat may influence our health by changing specific genes, researchers believe.
Nutrients may switch different genes on and off
Several studies in rodents have shown that nutrients and supplements can change the genetics of animals by switching on or off certain genes.
It is not clear whether foods do the same in humans, but an article in New Scientist says there is good reason to believe they do.
In the future, diseases might be reversed by diet in this way, it says.
While many disorders in humans are caused by mutations to DNA, a few, including some cancers, occur when genes are switched on or off.
There are thousands of genes in the body, but not all of them are active.
Scientists have been looking at what factors might control gene activity and have found some evidence to suggest that diet is important.
In a recent animal experiment, adult rats were made to behave differently by injecting them with a specific amino acid called L-methionine.
Researchers are studying DNA methylation
After the injections, the animals were less confident when exploring new environments and produced higher levels of stress hormones.
The change to their behaviour occurred because the amino acid altered the way the rat's genes were expressed.
L-methionine altered a gene for glucocorticoid that helps control the animal's response to stress, Moshe Szyf and his team from McGill University in Montreal, Canada, told a meeting on environmental epigenomics in November in Durham, North Carolina.
It added chemical tags, known as methyl groups, to the gene by a process called methylation.
The researchers are now looking to see if they can cause a positive rather than a negative behavioural change in animals using a naturally-occurring chemical called trichostatin A (TSA).
TSA causes the opposite effect to L-methionine on genes, stripping them of methyl groups.
Dr Szyf said his work showed how important subtle nutrients and supplements can be.
Animal research has also shown that a mother's diet can affect the level of DNA methylation and hence gene expression in offspring.
Professor Ian Johnson at the Institute of Food Research is investigating whether colon cancer in humans might be triggered by diet through DNA methylation. His team is studying healthy people before this cancer starts.
He said: "It's quite a strong possibility that nutrients might cause DNA changes. We think diet may have a role to play as a regulator in genes.
"Ultimately one would want to chose diets that would give you the most beneficial pattern of DNA methylation in the gut. But it is too early to say that we know the dietary strategy to do that.
"We need much more research.
"Genes regulate all the processes in the body and things that change gene expression, therefore, may be linked to a number of health issues other than cancer too."
He said one nutrient that scientists believe might influence methylation is folate or folic acid.
A deficiency in folate levels has been linked to an increased risk of developing some adult cancers, including breast and colon.