Is heated food more harmful than previously thought?

illustration photoThis comes from the recent doctoral dissertation of Camilla Svendsen from the Norwegian Institute of Public Health.

Many new substances are formed during heat treatment of food that are not present in the raw material. Many of the new substances are completely harmless while others may be hazardous to humans. Both acrylamide, which is found in potato products, cracker/crisp bread and coffee and food mutagens which are formed during heating of meat and fish, have both been shown to cause cancer in various organs in animals.

HMF – a barely studied substance

A substance that has been studied only to a limited extent is 5-hydroxymethylfurfural (HMF), which is formed when sugar-containing food or drinks are heated or dried. HMF is considered to be harmless, but can be converted by enzymes to a harmful substance in the body.

Previous research about HMF suggests that it may increase the development of colon cancer in rats. Humans are probably more able than rodents to metabolise these substances in the intestinal tract Both HMF and other food processing mutagens might be more harmful to us than previously assumed.

Caramel, prunes and coffee all contain large amounts of HMF. Smaller amounts are found in a variety of other foods such as milk, bread, biscuits, jam, brown cheese, etc.

Colon cancer is a disease with high mortality with 3000 new cases annually in Norway. HMF and carcinogenic compounds formed during heating of meat (heterocyclic amines), can be converted into substances that can damage DNA and cause cancer.

Man and Mouse

As humans and mice have different enzymes, it is conceivable that normal mice are not a suitable model to assess the cancer risk to humans. Svendsen therefore tested HMF and a known food mutagen in “human-like” mice that have the same enzymes as humans.

The “human-like” mice had more than a doubling of the incidence of colon tumours after exposure to the food mutagen compared to normal mice, but not after they were exposed to HMF. The intake of HMF has been estimated in 50 Norwegians and the substance has also been investigated in a mouse model particularly sensitive to development of intestinal cancer. It was shown that HMF gave a small increase of tumours in the intestines of mice, but only at high doses.

We ingest an average of about 6 milligrams HMF each day, which is 1000 to 10 000 times higher than for other harmful substances formed during heat treatment. Despite this, the possible cancer risk to humans by consumption of HMF is presumed to be low.