Eating processed meats such as bacon, ham and sausages can increase the risk of heart disease and diabetes, according to research published yesterday.

Processed meats are already linked to a higher chance of developing bowel cancer, but a review of worldwide research has now shown a link with other conditions.

The work, by the Harvard School of Public Health in the US, found that people who eat 50g of processed meats daily have a 42 per cent higher risk of heart disease and a 19 per cent increased risk of Type 2 diabetes. Unprocessed red meats, such as beef, pork or lamb, do not raise the risk.

Men in the UK eat an average of nearly 50g of processed meat a day, whereas women eat just 24g.

Experts examined 20 worldwide published studies involving more than a million people. Writing in the journal Circulation, the authors said: "Consumption of processed meats, but not red meats, is associated with higher incidence of coronary heart disease and diabetes mellitus (Type 2).

"These results highlight the need for better understanding of potential mechanisms of effects and for particular focus on processed meats for dietary and policy recommendations."

The authors defined processed meat as any meat preserved by smoking, curing or salting, or with chemical preservatives added to it. Examples include bacon, salami, sausages, hot dogs and processed deli or luncheon meats. The effects held true even when lifestyle factors which might affect the results were taken into account.

The lead author, Renata Micha, a research fellow in the department of epidemiology, said: "When we looked at average nutrients in unprocessed red and processed meats eaten in the United States, we found that they contained similar average amounts of saturated fat and cholesterol.

"In contrast, processed meats contained, on average, four times more sodium and 50 per cent more nitrate preservatives. This suggests that differences in salt and preservatives, rather than fats, might explain the higher risk of heart disease and diabetes seen with processed meats, but not with unprocessed red meats."

Salt is known to increase blood pressure, which increases the risk of heart disease, but studies on animals have also shown that nitrate preservatives can cause a build-up of hard deposits in the arteries and reduce the body's ability to handle sugars, which can increase the risk of heart disease and diabetes.