This is definitely not another wacky health story in the "shark cartilage cures cancer" tradition. This time the science is serious and, if the direction of current research is confirmed, the implications for the Government's food policy could be huge. The key to it all is a B vitamin called folic acid, until now best known for its ability to prevent neural tube defects such as spina bifida when taken as a supplement by women before and during pregnancy.
Kellogg's now sprays liquid, synthetic folic acid on to its Corn Flakes, Rice Krispies and Special K cereals. The exciting aspect of this otherwise less than appetising stage in the manufacturing process is that folic acid can reduce the blood level of a substance called homocysteine. This matters because high homocysteine counts are known to be closely associated with an increased risk of heart disease.
Homocysteine is an amino acid produced naturally in the body when protein is metabolised. The idea that it could be linked to heart disease first emerged when Dr Kilmer McCully, a pathologist at the Veterans Affairs Medical Center in Rhode Island, investigated the cause of arterial disease and strokes in children with a rare condition known as homocystinuria. Because of a genetic defect, such children are unable to dispose of homocysteine normally and therefore have high levels in their blood.
McCully suggested that a similar process might also be occurring in the general population of adults, not because of any genetic error but because inadequate intakes of folic acid were allowing homocysteine levels to rise too high, become toxic and start damaging artery walls.
Heart disease is in fact much more closely associated with high homocysteine levels than with cholesterol. "Levels of blood homocysteine greater than 14 micromoles per litre are associated with increased risk of arteriosclerosis and the higher the homocysteine level, the higher the risk," suggests Dr McCully. His analysis has now been confirmed by many studies, including the European Concerted Action Project, which found that those people with the highest homocysteine levels were as likely to develop vascular disease as someone smoking 20 cigarettes a day.
While a relationship between homocysteine and heart disease is now widely accepted, there are still doubts about whether elevated homocysteine levels are the direct cause of the problem. It could be that the amino acid is just a marker for some other, still unknown factor that is the real cause of the greater risk.
"Homocysteine is an enigma in relation to cardiovascular disease and nobody yet knows for sure the mechanism linking the two," argues Dr Jacob Selhub, director of the vitamin laboratory at Tufts University, Boston. There have also, as yet, been no long-term, large-scale clinical trials to show that increasing people's intake of folic acid will reduce their risk of developing heart disease.
But there is little doubt that consuming more folic acid reduces homocysteine levels. A recent study at Leeds University suggests that merely eating a bowl of breakfast cereal fortified with 200mg of folic acid every day for 24 weeks lowers the level by 10 per cent.
Dr McCully considers a total daily folic acid intake of 350-400mg to be ideal. (400mg is the level recommended for women who are trying to conceive, and those in up to 12 weeks of pregnancy). But it is difficult to obtain this amount from food, partly because "natural" folic acid is easily lost during both cooking and digestion. Synthetic folic acid is, surprisingly, a far better source, since almost all of it is absorbed by the body. So the best sources of folic acid are vitamin supplements and vitamin-enriched foods, such as Corn Flakes.
Since 1 January 1998, the US Food and Drug Administration (FDA) has required enriched grain products, including breakfast cereals, to be fortified with folic acid at a level that should give the average woman an extra 100mg a day. The FDA's decision was undoubtedly also influenced by the emerging evidence on heart disease. But there are no similar plans for the UK, and those food manufacturers now adding folic acid are doing so voluntarily.
Each year, more than 145,000 people in the UK die of heart disease and the illness costs the health service almost pounds 4bn. Even though not even the most ardent advocate of folic acid claims it constitutes a "magic bullet" for heart disease, if the evidence for its effectiveness hardens, pressure on the Government to follow the FDA's lead will undoubtedly grow. The calls for mandatory food fortification will intensify still further if tentative new evidence linking homocysteine with Alzheimer's disease is also strengthened by further research. In time, a bowl of cereal could well help us snap, crackle and pop for many years to come.