Serendipity: In a soldier's stomach

AT FORT Mackinac, Michigan, on 6 June 1822, Alexis St Martin found himself on the wrong end of a discharging musket. He was rushed to the army hospital, where a Dr William Beaumont noted that the abdominal wall had been perforated and that through this hole "was pouring out the food St Martin had taken for breakfast".

Although Beaumont saved St Martin, the wound never healed completely and the hole was covered merely by a flappy extension of the stomach lining. This was a considerable inconvenience for St Martin, but for Beaumont it was a lucky accident, because it allowed him to conduct the first real research into digestion.

Beaumont just had to depress the flap with his finger to gain access to the half-digested contents of St Martin's stomach. He could feed him specific foods, and then study their digestion by taking samples directly from the stomach via this accidental valve. St Martin was totally amenable to his new occupation as a living laboratory. Beaumont fed him everything from pig's trotters to tapioca, and made detailed observations.

At one stage Beaumont even extracted gastric juices from St Martin's stomach and applied them to food outside the body. Beaumont then made the remarkable observation that digestion can occur in a bottle, disproving the prevailing theory that digestion required a life force and could occur only within an animal's body. This led him to declare that digestion was a wholly chemical process.

Although Beaumont was largely correct in excluding a life force, digestion is not a wholly chemical process. We now know that the lower gut is home to a range of microbes that aid digestion, and research has shown that what we eat determines the activities of these bacteria, which may be beneficial or harmful.

Our diets have become much richer in sulphur recently, because we eat more meat and artificial preservatives. As a consequence, a strain of sulphur-loving bacteria is now flourishing in our guts. It generates sulphide chemicals, which in turn could harm our digestive system.

In a recent study, 96 per cent of people who suffered from inflammation of the colon had the sulphur bacteria, whereas only 50 per cent of healthy people had them. Sulphur bacteria are also linked to other more serious diseases, including colon cancer. Researchers at Cambridge's Dunn Nutrition Unit are undertaking a major new study to find out the exact impact of sulphur intake and sulphur bugs on our health.

It could be that in years to come we adapt our diet to modify the microbial ecology of the gut, eating certain foods to encourage nice bacteria, and avoiding other foods to starve out the nasty ones. Meanwhile, the advice seems to be to cut down on meat, and increase our intake of fresh fruit, vegetables and fibre.

Simon Singh is the author of `Fermat's Last Theorem' (Fourth Estate, pounds 6.99)