A combination of moderate exercise and dietary supplements may be the best way to cut the risk of heart disease, research suggests.
Exercise is good for health
Scientists at the University of California at Los Angeles found exercise alone helped reduced furring of the arteries.
But the effect was significantly magnified if physical exertion was combined with vitamin supplements.
The study is published in Proceedings of the National Academy of Sciences.
It was carried out in mice, but is thought to be equally applicable to humans.
Atherosclerosis, or furring of the arteries, is caused by the build up of cholesterol plaques which can impede blood flow, and put extra pressure on the heart.
There is some evidence to suggest that over-strenuous exercise may actually exacerbate the problem, but more graduated exercise seems to have a protective effect.
The UCLA team found that moderate exercise alone was enough to benefit mice bred to be prone to heart disease.
However, exercise had a much greater effect on animals that were also given the supplement amino acid L-argenine, and antioxidant vitamins C and E.
Anti-oxidants mop up charged particles called free radicals which can damage the blood vessels.
The combination of exercise and supplements boosted levels of nitric oxide, which is known to protect the arteries and heart from damage.
Lead researcher Dr Louis Ignarro said: "It wasn't just exercise, it was exercise combined with two common dietary supplements.
"This is the first study that shows that if you exercise in addition to taking dietary supplements you have a markedly enhanced production of nitric oxide.
"In science, we like to call it a synergistic effect."
Researchers looked at six groups of eight-week-old mice with high levels of
cholesterol over 18 weeks.
One group was fed a high cholesterol diet alone, and another the same diet
together with vitamins C and E. The third group was given both the antioxidants
and L-argenine as well as the diet.
Some of the mice were put on a swimming regimen, while others did not
Mice from all three groups lost weight when they exercised, and their cholesterol levels lowered.
When they were also given antioxidants and amino acid, they were far less
likely to suffer internal damage to their arteries.
Dr Ignarro recommended a combination of moderate exercise, low fat diet and easily available dietary supplements.
He said: "It works in mice, it'll work in humans."
Dr Tim Bowker, of the British Heart Foundation, said it was already well established that regular physical activity helps improve reduce harmful cholesterol and the risk of atherosclerosis.
He said: "The Heart Protection Study, a major trial part-funded by the BHF in 2002, showed that vitamin supplementation with vitamins C,E or ß-carotene was not protective against cardiovascular disease in people.
"However, it did not test the effect of L-arginine, nor the combination of physical activity with vitamins, which this new study has tested in genetically modified mice.
"Whether the results reported in these mice will apply to people remains unclear.
"What is clear is that physical activity is beneficial for the heart, and people should attempt to incorporate more activity into their daily lives, with or without vitamin supplements."