Monounsaturated fats are good for salads – and brains too, researchers find

By: Dr. Andrew Craig

It’s not often that two stories with peanut implications come along that appeal to both culinary and neurological interests. But the practical implication from two recent U.S. studies is just that: to be good to your salads (absorb more vitamins from salad vegetables¹) and your brains (safeguard cognitive health in older adults²) use more monounsaturated oils. The good news is that peanut oil for salads and peanuts for everyday eating fit the bill perfectly.

In the first study, Purdue University researchers funded by the USDA compared a high monounsaturated salad oil (canola) with a high polyunsaturated oil (soybean) and a high saturated fat salad dressing based on butter. Each dressing was studied and compared in terms of its effect on the absorption of carotenoids (antioxidant chemicals related to Vitamin A) from identical salad vegetables. Carotenoids are found in vegetables including carrots, sweet potatoes, spinach, kale, collard greens, papaya, sweet peppers and tomatoes.

The Purdue team found that the type of fat in the salad dressing made a difference to how well the carotenoid vitamins were absorbed by the body, compared to the amount of oil used in the dressing. By analysing blood samples from the study participants, they found the monounsaturated oil dressing required the least amount of oil (and therefore fewer calories) for the highest level of vitamin absorption. Both the polyunsaturated and the saturated fat based dressings required higher amounts of oil (and more calories) to get the same absorption benefit.

The practical conclusion is that a salad dressing using a high monounsaturated oil, such as American peanut oil, would achieve this effect in terms of maximising absorption of carotenoids and other fat soluble vitamins and nutrients from salad vegetables. That’s good to know because American peanut oil is perfect for combining with herbs, spices and other ingredients for a flavourful salad dressing.

And while you are munching on your healthy peanut-oil dressing salad, spare a thought for the benefits you are giving your brain, especially if you are an older person and female. That’s because Harvard researchers funded by the National Institutes of Health, using the massive database of the Women’s Health Study, found that what mattered for cognitive health, memory and retaining mental capacity for women over 65 was the type of fat they consumed, rather than the overall amount of fat. The 6,000 women in this study undertook three tests of mental function every two years over a testing span of four years, and also completed dietary questionnaires. Researchers then compared the types of fat in the foods they reported eating most frequently with how they scored on the cognitive tests.

They found that women who ate the most monounsaturated fats had better patterns of cognitive scores over time, compared to women who ate more saturated fats. This finding could have significant public health implications in terms of a simple dietary approach to reduce or slow the onset of mental decline in older people. Peanuts and peanut oil, avocados, most other nuts and seeds are good monounsaturated fat sources which would fit this pattern of consumption for maintaining brain health. And they also make good salad ingredients, too.

For more information on the salad oil and carotenoid story, Purdue University has a YouTube video interview with Professor Ferruzzi. To learn more about the Harvard study about cognitive protection for older women, see this story from Brigham and Women’s Hospital in Boston.

Dr. Andrew Craig is a health education consultant working with the American Peanut Council in London

Sources:, Globe and Mail and Telegraph-Journal

¹ Goltz SR et al. “Meal triacylglycerol profile modulates postprandial absorption of carotenoids in humans” Molecular Nutrition & Food Research, June 2012; 56 (6): 866–877.
² Okereke OI et al. “Dietary fat types and 4-year cognitive change in community-dwelling older women”. Annals of Neurology, July 2012; 72 (1): 124–134.