Three or more servings of low-fat milk every day raises the risk of Parkinson's, a neurological disorder that affects walking and muscle strength, by around 34 per cent, researchers have discovered.
But people who use the full-fat equivalent don't raise their risk at all, and the same is true if they also consume full-fat versions of cream, cheese, yogurt, butter, margarine and ice cream, say researchers from the Harvard T H Chan school of public health.
They analysed the eating habits and health of 80,736 women and 48,610 men over a 25-year period. During that time, 1,036 of the participants developed Parkinson's.
Although they can't state categorically that low-fat products cause Parkinson's, the researchers say they could be a "modifiable risk factor for the disease"; in other words, they change the biological profile that makes the disease more likely.
The overall risk is still low, the researchers say. Of the 5,830 people who consumed three or more servings of low-fat dairy a day, 60 developed Parkinson's, which represents around 1 per cent of the total, and of the 77,864 people who had less than one serving a day, just 483—or 0.6 per cent—went on to develop the disease.