It's already everybody's favorite nutritional supplement, linked, however controversially, to preventing the common cold and fighting cancer. But vitamin C recently added a new notch on its belt. The vitamin helps reduce both the physical and psychological effects of stress on people.

People who have high levels of vitamin C do not show the expected mental and physical signs of stress when subjected to acute psychological challenges. What's more, they bounce back from stressful situations faster than people with low levels of vitamin C in their blood.

In one recent study German researchers subjected 120 people to a sure-fire stressor--a public speaking task combined with math problems. Half of those studied were given 1,000 mg of vitamin C. Such signs of stress as elevated levels of the stress hormone cortisol and high blood pressure were significantly greater in those who did not get the vitamin supplement. Those who got vitamin C reported that they felt less stressed when they got the vitamin.

The researchers believe that vitamin C should be considered an essential part of stress management.

Earlier studies showed that vitamin C abolished secretion of cortisol in animals that had been subjected to repeated stress. Cortisol is a hormone released by the adrenal glands in response to stress. Once it gets into the bloodstream, it is responsible for relaying the news of stress to all parts of the body and mind.

Cortisol is the hormone, for example, that triggers the “fight or flight” response to stress. That allows us to spring into action when we sense danger. But like many emergency-alert systems, the stress response comes at a considerable cost. Among other effects, frequent exposure to high levels of stress hormones exhausts the body's physical resources, impairs learning and memory, and makes people susceptible to depression.

In the animal studies, vitamin C fed to rats undergoing stress not only prevented the expected increase in cortisol levels, it prevented the animals from exhibiting the known signs of physical and emotional stress, including loss of body weight. Animals that did not receive vitamin C had three times the level of stress hormones.

The present RDA for vitamin C for adults is 60 milligrams--a far cry from the 1,000 mg found helpful in the stress study. But there's a growing belief that the RDA for vitamin C is vastly outdated. The current RDA was set decades ago and is based on the amount of the vitamin needed to ward off scurvy.

Current thinking looks at vitamin C from the opposite direction: The amount needed to promote health under varying environmental conditions. That appears to be a lot greater than the amount needed to prevent deficiencies.

There's also evidence suggesting that prehistoric humans consumed large amounts of vitamin C in a tropical diet rich in fresh fruits. If so, the physiological constitution we have inherited may require far larger daily doses of vitamin C than the current RDA, perhaps as high as 1,000 mg.

Vitamin C is present in fresh, uncooked fruits and vegetables, especially citrus fruits and red and green peppers. One eight-ounce glass of fresh orange juice provides 97 milligrams of the vitamin.

It's also found in papayas, cantaloupes, strawberries, broccoli, Brussels sprouts, tomatoes, asparagus and parsley. There's no vitamin C in animal food, and a small amount in raw fish.

An unstable substance, vitamin C is destroyed by cooking and exposure to light.

The most commonly consumed nutrient supplement, vitamin C comes in many formulations, but the best may be a time-released preparation that works over the course of a day, as the vitamin works rapidly and is short-acting. Alternatively, vitamin C supplements can be taken at intervals throughout the day.