Polyunsaturated fats include omega 3 found in certain vegetable oils and omega 6, found in fish and green leafy vegetables.
The authors base their findings on 132 patients with potential or definite amyotrophic lateral sclerosis (ALS), one of the disabling conditions known as motor neurone disease.
Motor neurone disease is thought to be caused by genetic and environmental factors, and diet has been previously implicated in its development.
The patients completed a questionnaire, detailing their regular dietary intake before they became ill of polyunsaturated fats (PUFAs), vitamin E, and a range of other nutrients, among them flavonols, calcium, and lycopene.
The results were compared with those of 220 healthy people and adjusted to take account of other factors likely to influence the findings, including age, sex, energy intake, weight, and smoking habit.
Total energy intake and consumption of dietary supplements were the same in both groups, but intake of total fats differed. The patients with ALS consumed significantly less PUFA and vitamin E than their healthy peers.
The highest daily intake of PUFA of more than 32 g was associated with a 60% lower risk of developing ALS compared with the lowest daily intake of less than 25 g.
Similarly, a daily vitamin E intake of between 18 and 22 mg was associated with a 60% lower risk of developing ALS compared with the lowest daily intake of less than 18 mg.
PUFA and vitamin E seemed to work synergistically, the researchers found, and the results held true even after taking account of other influential factors. No strong associations were found for any of the other nutrients.