It’s funny what sticks in your mind sometimes. While a lot of what I learned a 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, forty 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, underpin the traditional advice given to sufferers to eat a diet low in fat. However, despite being well established, new evidence has come to light which suggests that the rationale behind the conventional diet recommended for gallstones is far from rock solid.
At fist glance, it seems to make perfect sense for those wishing to stop or slow the development of cholesterol-composed gallstones to cut back on their intake of supposedly cholesterol-boosting foods such as red meat, eggs and dairy products. However, what is often gets lost in the recommendations regarding dietary control of cholesterol is the fact that great majority of cholesterol in the body does not come directly from the diet, but is made in the liver. One potential stimulus for the production of cholesterol in this organ is the hormone insulin, which is secreted in response to carbohydrates (sugars and starches) in the diet. This means, in theory at least, that it may be an excess of insulin-stimulating carbohydrates, rather than foods rich in fat, that may predispose to gallstone creation.
Evidence for this dietary association has recently come from a study published in July’s edition of the American Journal of Clinical Nutrition (AJCN). This study examined the link between waist size and gallstones risk in almost 30,000 men. Excesses of insulin in the system tend to encourage the deposition of weight around the midriff (so-called abdominal obesity), and increased waist size is believed to be a good guide to a surfeit of insulin in the system. The AJCN study found that compared to men with a waist size of less than or equal to 34 inches, men with a waist size of more than about 40 inches had more than twice the risk of gallstones. Even when 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. The low-fat diet often recommended for this problem is usually high in carbohydrates such as breakfast cereals, bread, potatoes, rice and pasta – all foods that tend to stimulate considerable quantities of cholesterol-inducing insulin. Accompanying this study in the AJCN was another one which casts further doubt on the effectiveness of low-fat diets in management of gallstones. In it, researchers assessed the relationship between nuts (a high-fat food that is usually regarded as verboten for gallstone sufferers) and gallstone risk in women. Women eating 150 g or more of nuts each week had a 25 per cent reduced risk of gallstones compared to those eating little or no nuts.
The fact that nuts tend to induce very modest amount of insulin (and actually help to lower cholesterol levels in the body) may help to explain their apparent ability to ward off gallstones. In some gallstone sufferers, eating foods rich in fat can cause discomfort as these will tend to cause the gallbladder to contract. However, 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.