John Briffa: Stone age

It's funny what sticks in your mind sometimes. While a lot of what I learnt at medical school has long evaporated from my grey matter, I do remember the dictum often trotted out by my teachers that gallstone sufferers are typically female, 40 and fat. The knowledge that gallstones are more common in those carrying excess weight, coupled with the fact that the majority of stones are composed of cholesterol, underpins the traditional advice given to sufferers to eat a diet low in fat. However, new evidence suggests that the rationale behind this advice is far from rock solid.

What often gets lost in the recommendations is the fact that most cholesterol does not come from the diet, but is made in the liver. One potential stimulus for the production of cholesterol is the hormone insulin, which is secreted in response to carbohydrates (sugars and starches). This means, in theory at least, that an excess of insulin-stimulating carbohydrates may predispose to gallstone creation.

Evidence for this dietary association has come from a recent study in the American Journal of Clinical Nutrition which examined the link between waist size and gallstones risk in 30,000 men. Excesses of insulin encourage the deposition of weight around the midriff (abdominal obesity), and increased waist size is believed to be a good guide to a surfeit of insulin. The study found that, compared to men with a waist size of less than or equal to 34in, men with a waist size of more than 40in had more than twice the risk of gallstones. Even with overall weight taken into account, this association between waist size and gallstone risk remained.

This study appears to raise some questions about standard anti-gallstone advice. A low-fat diet is usually high in carbohydrates such as cereals, bread, potatoes, rice and pasta - which stimulate considerable quantities of cholesterol-inducing insulin. In another study in the AJCN, researchers assessed the relationship between nuts (a high-fat food usually regarded as verboten for gallstone sufferers) and gallstone risk in women. Women eating 150g or more of nuts each week had a 25 per cent reduced risk compared to those eating little or no nuts.

The fact that nuts tend to induce very modest amounts of insulin (and actually help to lower cholesterol levels) may help to explain their apparent ability to ward off gallstones. In some sufferers, eating foods rich in fat can cause discomfort, as these tend to cause the gall bladder to contract. But as long as they do not provoke symptoms, the evidence suggests that nuts are a cracking good food for those seeking to protect themselves from gallstones.

Dear John

My husband has a problem with waking at night (usually around 4am). He feels anxious and finds it difficult to drop off again. He is vegetarian, a keen hill runner and eats a lot of bread and pasta for energy.
Fiona Cummins

My experience in practice tells me that waking in the night is very often related to dips in blood-sugar levels. Should they fall low in the small hours, the body secretes stress hormones (such as adrenaline), which raise sugar levels by stimulating the conversion of glycogen (a type of starch) into glucose. Adrenaline tends to increase feelings of arousal, alertness and perhaps anxiety. While your husband will need a fair amount of carbohydrate to fuel his hill running, having bread and pasta at supper can cause peaks in blood sugar, which may be overcompensated for, leading to low blood sugar in the early hours. Slower-releasing carbs that might be better, especially at supper, include beans, lentils and fruits such as oranges and apples. A bedtime snack such as fresh fruit and a few nuts may pick up blood sugar levels and reduce the risk that they will drop off later.

Nutrition news

Infection with the human immunodeficiency virus (HIV) may eventually lead to the development of acquired immunodeficiency syndrome (Aids), with potentially fatal consequences. In theory, improved nutritional status may enhance the function of the immune system and delay progressions from HIV infection to Aids. In a recent study published in the New England Journal of Medicine, more than 100 pregnant women infected with HIV were assigned to be treated with a either a multivitamin (containing vitamins B1, B2, B3, B6, B12, C, E and folic acid), a supplement of vitamin A and betacarotene, the multivitamin plus vitamin A and betacarotene, or a placebo (inactive medication) for an average of 71 months. Compared to those taking placebo, those taking the multivitamin were found to be 29 per cent less likely to die or progress to the most severe form of Aids at the end of the study. Supplementation with vitamin A and betacarotene, however, did not seem to confer any benefit. This study suggests that supplementation with B vitamins and vitamins C and E may help slow the progression of HIV to Aids.

· john.briffa@observer.co.uk

Thanks to guardian.co.uk who have provided this article. View the original here.