Two supermarket chains confirmed last night they will cut all "trans fats" from their own-brand products, less than a week after scientists warned that even a small amount could endanger health.

Sainsbury's said it would cut the dangerous fat, which raises the risk of heart disease, from its 15,000-strong range of own-brand processed food from January, while Tesco set a date for the end of the year. The announcements follow an article in the British Medical Journal calling for the fats to be clearly listed on food labels, and warning that even small amounts could be bad for health.

Artificial trans fats are found in processed and fried foods, including biscuits, muffins, popcorn and ready-made meals. Formed by a process called hydrogenation - in which vegetable oil is converted into a solid - they give food a better taste and prolong shelf life. Marks & Spencer has stopped using hydrogenated vegetable oil in its food production and other manufacturers are cutting down the trans fat content of processed foods, according to the Biscuit, Cake, Chocolate and Confectionery Association.