Your parents knew what they were talking about when they told you to eat your vegetables, though they probably should have specified which ones.

A new study has found that diets rich in orange and dark green veggies like carrots, green beans and sweet potatoes may result in less disease and a longer life.

Researchers believe that the potential for a longer, disease-free life is due to the alpha-carotene in those foods, which, like beta-carotene, is a carotenoid antioxidant and may stop oxidative damage to cells and DNA.

"Because of the multiple constituents within these vegetables, there is a plethora of benefits of getting them in the natural food forms and eating plenty of them," nutritionist Douglas Husbands told AOL Health. "That should be one of the foundations of people if they want to live a healthy and long life."

Dark green vegetables like beans, spinach, kale, bok choy, swiss chard and collard greens are rich in folates and many other essential nutrients, Husbands said -- and eating them doesn't only boost your own health but that of future generations.

"They work to turn on many good genes and turn off many bad genes," he said. "Studies are continuing to show that dark green vegetables most definitely can influence a healthier life and potentially a longer life also. The research on this is just overwhelming."

Dr. Chaoyang Li of the Centers for Disease Control and Prevention and his colleagues based their findings on the previously-established link between good health -- including less cancer and heart disease -- and eating certain fruits and vegetables.

Li told Reuters Health that his team wanted to find out specifically what components in vegetables have benefits and how they work. Recent studies have suggested that beta-carotene pills have no concrete positive effects, he said.

The researchers looked at data on more than 15,000 people participating in a wide-scale national nutrition survey. The subjects had given blood samples, as well as information on their medical histories and lifestyles at the start of the 14-year study.

By the end of the study period, almost 4,000 participants had died. Li and his colleagues determined that the more alpha-carotene the subjects had in their systems at the beginning of the survey, the lower their chances of disease and death, Reuters reported. Those with the highest amounts of the antioxidant in their blood had as much as a 39 percent lower risk of dying than participants with the lowest levels of alpha-carotene.

The findings, published this week in the Archives of Internal Medicine, stayed the same even after researchers took other risk factors into account, including age and smoking. They also remained steady when the rates of death due to cancer and heart disease were analyzed.

But the study results don't provide solid evidence that alpha-carotene is what leads to a longer life and less disease, according to the authors.

"Alpha-carotene may be at least partially responsible for the risk reduction," Li told Reuters. "However, we are unable to rule out the possible links of other antioxidants or other elements in vegetables and fruits to lower mortality risk."

Husbands said it isn't just alpha-carotene that is responsible for the health benefits seen in the research. "You can't simplify it or (see) one carotenoid as a magic bullet because you're going to get spurious results," he told AOL Health. "It's the mix."

Howard Sesso of the Harvard School of Public Health said it's difficult to differentiate between the benefits of alpha-carotene and beta-carotene since carrots and some of the other vegetables in question tend to contain both.

"Alpha-carotene has a lot of overlapping chemical properties with beta-carotene, as well as the same perceived mechanisms of effect," he told Reuters Health. "It's hard to disentangle the two from each other. They tend to travel together."

Li said there have been previous lab experiments showing that alpha-carotene is a more potent preventer of brain, skin and liver cancer than its beta relative, according to Reuters. No matter what is behind the findings, Sesso said they're hopeful.

"We don't know how this is going to translate into practice yet, but it is encouraging," he said. "If nothing else, these results reinforce the point that there is likely little downside to increasing your fruit and veggie intake."

And there is little debate about the enormous health benefits of vegetables, particularly the dark green and orange variety, according to Husbands."That's some of the cheapest health care people can buy," he said.

By Catherine Donaldson-Evans published in AOL.COM, 11/20/2010.

Knowing is not enough; we must apply. Willing is not enough; we must do. Johann Wolfgang von Goethe