Brazil nuts have been hailed as a tasty way of building up the immune system and even protecting against cancer.
But the health-boosting mineral they contain may also push up cholesterol levels and raise the risk of heart disease, researchers claim. The findings came in a study suggesting that a high level in the blood of selenium - a trace mineral found naturally in Brazil nuts, grain, fish and meat - increases cholesterol levels.
Those found in tests to have the highest level of the mineral in their blood were regularly taking dietary supplements containing selenium. However, eating large quantities of Brazil nuts and selenium-rich foods might have the same effect.
Researchers at Warwick University say they have discovered that high selenium levels are 'associated' with a 10 per cent rise in cholesterol. The warning emerges from data on 1,042 people aged 19 to 64 who took part in the UK National Diet and Nutrition Survey between 2000 and 2001.
In those with blood selenium concentrations higher than 1.20micromoles per litre, the levels of total cholesterol were raised by an average of 8 per cent. Levels of a 'bad' type of cholesterol associated with heart disease were increased by 10 per cent.
The study did not take account of the health of individuals or whether they were taking cholesterol-lowering drugs.