Get oiled up! Why dressing helps you get maximum nutritional benefit from your salad

OK, so the summer is on its way out, but I couldn’t resist the opportunity to report on a recent study which supports the idea that there is real nourishment to be had from salad-munching. Research conducted at UCLA and Louisiana State University on more than 17,500 men and women has found that consumption of salad and raw vegetables correlates with higher concentrations of key nutrients including folic acid, vitamins C and E, lycopene and alpha and beta carotene in the bloodstream [1]. The findings of this study suggest that eating just one serving of salad or raw vegetables per day significantly boosts the likelihood of meeting the recommended daily intake of certain key nutrients.
For those keen to do whatever they can to get the maximum nutritional value from salad, my advice is to eat it with an oil-based dressing. In the accompanying article, you can read about research which has found that oil actually enhances the absorption of nutrients from vegetables, specifically ‘carotenoid’ nutrients such as lycopene, alpha-carotene and beta-carotene.

Observer Column – 15th August 2004
The fact that we have finally been treated to some decent sunshine is likely to be reflected in our enhanced appetite for summer salads. Few would doubt that dishes based on raw, fresh vegetables offer a good deal from a nutritional perspective. However, where flavour is concerned, I reckon what turns a good salad into a really great one is the dressing. Unfortunately, conventional wisdom dictates that the oily nature of traditional dressings does not bode well for our waistlines or weight, and such fat-phobia has spawned an ever-expanding number of low-in-fat and even ‘fat-free’ dressings to be found on our supermarket shelves. The promise here seems to be that the reduced-fat content of these dressings will help to ensure a reduced-fat content of our dresses, suits and jeans.

However, contrary to popular belief, review studies have found that long-term low-fat eating is quite ineffective for the purposes of weight loss. This, however, is not the only reason why it may not pay to splash out on reduced fat dressings. Research has revealed that fat can actually enhance the nutritional value of the food we eat it with. Specifically, studies have shown that fat aids and abets our ability to extract and absorb so-called carotenoid nutrients such as beta-carotene (found in many green, yellow and orange fruits and vegetables) and lycopene (found primarily in tomatoes).

The role that fat plays in the extraction of carotenoids from food was most recently assessed in a study published this month in the American Journal of Clinical Nutrition (AJCN) [2]. Researchers measured the levels of three carotenoids (beta-carotene, alpha-carotene and lycopene) both before and after the consumption of a mixed salad accompanied by either a fat-free, reduced-fat or full-fat dressing. Researchers found that eating salad with dressing free of fat did not lead to a significant rise in the levels of any of the carotenoids measured. However, when the salad was consumed with a reduced-fat dressing, there was appreciable rises in the levels of all three nutrients. What is more, the full-fat dressing boosted carotenoid levels significantly higher than the fat-reduced variety.

The explanation for this phenomenon is not known for sure, though it has theorised that fat assists the release of carotenoids from food and eases their passage through the gut wall into the bloodstream. Whatever the precise mechanism, the effect undoubtedly has the potential to bring significant benefits to our health: carotenoids have been found to an array of beneficial biochemical actions for the body, and a mass of evidence now exists which suggests that they have considerable cancer-protective properties.

When it comes to choosing an oil on which to base a dressing, my preference is to go for cold-pressed extra virgin olive oil. Olive oil is rich in so-called monounsaturated fat which studies show can bring benefits for the heart and circulation. This oil is extracted with minimal processing and no application of heat – factors that are believed to help preserve the healthy properties innate to this oil. Olive oil, shaken or stirred with some vinegar or citrus juice, makes not only a tasty but healthy addition to our food. For those of us looking to get maximum nutritional value from the food we eat, I advise making sure salad is appropriately dressed for dinner or lunch.

1. Su LJ et al. Salad and Raw Vegetable Consumption and Nutritional Status in the Adult US Population: Results from the Third National Health and Nutrition Examination Journal of the American Dietetic Association. 2006;106(9):1394-1404

2. Brown MJ, et al. Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. Am J Clin Nutr 2004;80(2):396-403.

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