The Food and Drug Administration has given its backing to research by manufacturers Proctor & Gamble rebuffing claims that eating olestra - which is found in snacks such as crisps - can lead to cancer, heart disease and blindness.

A Harvard study had stoked public concern by alleging olestra consumption would lead to thousands of cancer deaths.

The claims are based on olestra's tendency to block absorption of carotenoids and vitamins A,E,D and K.

Carotenoids are plant pigments found in yellow and red vegetables, which are converted into vitamin A in the liver.

But an FDA advisory panel that approved the use of olestra more than two years ago has accepted there are no nutritional deficiencies linked to olestra.

Random decrease

The P&G study found some decrease in carotenoids among people who were heavy olestra consumers but the decline seemed to be random.

FDA spokesman Thomas Wilcox said: "The carotenoid decrease does not appear to be associated with olestra ingestion."

In the P&G study, Indianapolis area consumers were followed for up to a year.

They were asked about what snacks they ate, and whether they were eaten at the same time as fruits and vegetables.

A second study found no link between olestra and blindness.

Their blood was then tested for key nutrients and carotenoids. The researchers will continue to monitor the Indianapolis group and others at several new sites until 2001.

Nutritional deficiency

When olestra was approved in 1996, the FDA and P&G agreed that bolstering it with vitamins A, E, D and K would offset any nutritional deficiency.

The FDA recommended against adding carotenoids, a conclusion backed by the National Cancer Institute (NCI) and the National Eye Institute.

Olestra is a cooking oil made from soybeans or cottonseed which mimics the taste of conventional fatty oils but cannot be absorbed by the body.

Boon for dieters

The product has been touted by P&G as a boon for dieters trying to reduce their fat intake.

All foods made with olestra carry a label required by the FDA saying the product "may cause abdominal cramping and loose stools."