How Low Fat Can You Go?

From the WebMD Archives

May 19, 2000 -- You can forget using the excuse that you need fat to absorb certain vitamins so that's why you can't start that low fat diet. While it's true that some fat is needed to absorb fat-soluble vitamins, it's a very small amount, according to a study in the May issue of The American Journal of Clinical Nutrition.

Vitamin E and carotenoids -- such as alpha- and beta-carotene and lutein -- are all antioxidants. Antioxidants scarf up free-radicals, which are unstable molecules in the body that can damage cells, leading to heart disease, cancer, and other chronic diseases.

Dutch researchers found that only limited amounts of fat are needed for optimal absorption of vitamin E and alpha- and beta-carotene.

In nature, lutein is found in spinach, broccoli, and green peas, but for experimental purposes, the authors used a slightly different form of lutein, called lutein "esters." While their study showed that slightly more fat was needed to absorb this lutein esters, they speculate that far less is necessary to absorb the type of lutein found in food.

Lead researcher Annett Roodenburg tells WebMD that at the moment, lutein is not considered essential, but some experiments have shown that inadequate amounts of it may lead to an age-related eye disease known as macular degeneration.

Researchers at the Unilever Health Institute in the Netherlands placed four groups of 14 to 15 volunteers on low fat diets for two, seven-day periods. Each group received a different supplement of 50 mg of vitamin E; 8 mg of alpha- and beta-carotene; 8 mg of lutein ester; or a placebo mixed in either a low-fat (3 grams) or high-fat (36 grams) spread with their evening meal. Blood tests to measure how much of the nutrient had made the long and complex journey into the blood stream were done after each of two experimental periods.

The researchers found there was no significant difference in the blood concentrations of vitamin E or the carotenes when the supplements were given with the low fat or high fat diets. In nature, vitamin E is found in many fats and oils. "Nature does not incorporate fat-soluble nutrients into foods without fat," writes Maret G. Traber, PhD, in an editorial accompanying the study. But she points out that manufacturers might do what nature doesn't, citing vitamin E-enriched fat-free mayonnaise or vitamin D-enriched fat free milk as examples.

Roodenburg says the proliferation of fat-free foods was one of the reasons she and her colleagues were prompted to do the study.

The study results indicate that we don't need to be concerned about lowering our fat intake to the 25 to 30% fat range, Traber tells WebMD. She served on the National Academy of Sciences panel on antioxidants and is associate professor at the Linus Pauling Institute at Oregon State University in Corvallis.

Even going as low as 10% won't hinder your absorption of fat-soluble nutrients, says Alice Lichtenstein, DSc, professor of nutrition at Tufts University. If you eat a 2000-calorie, 10% fat diet, you're still getting 22 grams of fat, which is way above 6.5 grams of fat consumed by those in this study's low fat diet, Lichtenstein tells WebMD, "It's important to consume a nutrient-rich diet, and under normal circumstances, vitamins and minerals will be absorbed."

The unexpected result was that the increase in lutein concentration was significantly larger when the supplement was taken in the high fat spread than the low fat one. The reasons may be that lutein ester supplements were used and not the kind of lutein found in foods.

"Theoretically, you wouldn't need more [fat]," Lichtenstein says. "All you can tell from this experiment -- and they demonstrated it very nicely -- is that you don't get as high a percentage absorption [of lutein] at a lower fat intake. But that doesn't mean that the person is not getting enough to cover all the biological needs," she says.

Vital Information:

  • Although the body needs some fat to absorb certain nutrients, such as vitamin E and alpha- and beta-carotene, the amount of fat needed is very small, according to a recent study.
  • One expert comments that nature doesn't put fat-soluble nutrients into foods without fats, but food manufacturers do.
  • More fat is necessary to absorb lutein, according to study results, but lutein was taken as a supplement and may require less fat when it's consumed in foods.