People need to include moderate amounts of fat with their uncooked vegetables in order to absorb the beneficial nutrients, new research shows.

U.S. investigators found that when people ate salads with fat-free dressing, their bodies did not absorb alpha-carotene, beta-carotene or lycopene - substances known to protect against cancer and heart disease.

In contrast, when people doused their salads with reduced-fat or regular dressing, their carotenoid levels went up substantially.

These findings suggest that people should include small amounts of cheese, meat, or other sources of fat in their salads or opt for something other than non-fat dressing if they want to get the most out of their veggies, study author Dr. Wendy S. White told Reuters Health.

And if people like to snack on carrot sticks in between meals, consider dipping them in ranch dressing, she added.

However, she cautioned that fat intake is “really a balancing act,” since many Americans currently consume too much fat in their diet.

“We don’t want them drowning their salad in full-fat salad dressing,” said White, who is based at Iowa State University in Ames. “Fat is part of a healthy diet. The key is moderation.”

Carotenoids are red, yellow and orange pigments found in fruits and vegetables. They act as antioxidants, which prevent disease-causing free radicals from damaging the DNA of cells. Long-term damage by free radicals leads to aging and chronic disease.

To investigate whether people need fat with their carotenoids to get their disease-fighting benefits, White and her colleagues asked seven people to eat three different salads on three separate occasions. The salads contained spinach, romaine lettuce, cherry tomatoes and carrots, and were covered in non-fat dressing, reduced-fat dressing (with 6 grams of fat) or full-fat dressing (28 grams of fat).

Reporting in the American Journal of Clinical Nutrition, White and her colleagues found that when people ate the non-fat salads, there was “virtually no absorption of alpha-carotene, beta-carotene or lycopene.”

However, when people used reduced-fat dressing on their salads, levels of these carotenoids increased in their bodies. Full-fat dressing increased carotenoids even further.

In an interview, White explained that carotenoids are “fat-soluble,” meaning they are essentially not absorbed by the body without the aid of fats.

These findings may not apply to cooked vegetables, White noted, for research suggests that people absorb carotenoids more easily from cooked or processed vegetables.

She added that, even without fat, vegetables still contribute other important substances, such as fiber, vitamin C and folate.

But if you can sprinkle uncooked vegetables with a little bit of fat, that might not hurt, she said. “A few tablespoons of bacon bits are not going to ruin anyone’s health.”

SOURCE: American Journal of Clinical Nutrition, August 2004.