Dark green vegetables like asparagus are a better source of folate than synthetic folic acid tablets.
The National Institutes of Health has wrapped up a state-of-the-science conference on multivitamin use and the prevention of chronic disease. Recommendations from experts vary, as does the scientific certainty. Four researchers who participated in the conference answer questions about which vitamins they recommend and why:
Dr. Meir J. Stampfer, Professor of Epidemiology and Nutrition, Harvard School of Public Health
How much is known about the health benefits of vitamins?
The list of vitamin supplements for which we have proven benefits is very short. But the list of supplements for which there are possible benefits is pretty long. You have to weigh the cost, risks and benefits while we're still waiting for clinical evidence.
Many people believe that natural supplements are always safe. Are there risks?
You can get too much of certain nutrients. For example, pre-formed vitamin A. It's not too hard to get to a level that's actually bad for you, which can increase the risk of fractures and birth defects. The vitamin companies have been responsive to this new data and have begun replacing pre-formed vitamin A with beta-carotene (which the body converts to vitamin A), which does not have the toxicity. We can't lose sight of the idea that just because it's natural doesn't mean it's necessarily safe. Tobacco and asbestos are natural, yet they are not safe.
What sort of individual variations exist in terms of how people absorb and use vitamin supplements?
We have a lot to learn about absorption (of nutrients). There are genetic and gender differences. For instance, African Americans need more vitamin D because of skin pigment. Older people need extra B12 because they don't make enough stomach acid, which you need to liberate B12 from food. Iron is another example. The body doesn't have a good way to get rid of iron except through blood loss, so postmenopausal women, and men, do not need to take an iron supplement.
What, in your view, is the overall importance of vitamin supplements in a healthy lifestyle?
Vitamins are a minor part of staying healthy. They pale compared to a healthy diet and daily physical activity. The multivitamin is the extra insurance.
Maret Traber, Ph.D. Professor, Linus Pauling Institute, Oregon State University
The latest news on vitamin E has been mixed with several negative findings. Is there any evidence that vitamin E supplementation is beneficial to any segment of the population?
The data from the large Women's Health Initiative trials found that women over 65 were protected against death from heart attacks by taking a vitamin E supplement. My studies at Oregon State show that vitamin E can reverse oxidative stress, (which can lead to disease).
Are there individual variations in absorption of vitamin E supplements?
We look at what you have to eat with the vitamin E pill in order to make it work. Vitamin E is fat soluble, so you actually need to eat a fair amount of fat, say a couple of teaspoons of cream cheese with your bagel, to absorb optimally the vitamin E in a capsule.
Dr. Irwin Rosenberg, Senior Scientist and Professor, Tufts University
Are there other examples of nutrients that need to be taken with fat in order to be absorbed properly?
Your body can't convert beta-carotene into vitamin A unless there's some fat in your diet. Each vitamin is different. Each has its own pattern. Take, for instance, folic acid. There are different variants of folate. Folic acid is not a natural form of folate. It's synthetic. In the body, folic acid must be converted to natural folates that are active in the metabolic systems. The absorption is a little different and passage across membranes is different. We're not certain that folic acid gets across the blood-brain barrier as well as one of the natural forms of folate. So with each vitamin, we have to look at these variations.
Is it better to get vitamins and nutrients through diet, when possible?
I'm very much in favor of using diet as the preferred source of vitamins. I try to eat fish three to four times a week and I try to buy the fatty, oily fish rich in the marine omega-3 fatty acids. This has to do with not just cardiovascular health, but also brain function and anti-inflammatory functions.
Even though my research is about the vitamins that control homocysteine (an amino acid found in the blood that at high levels can contribute to cardiovascular problems) ... I don't take extra folate supplements because we're getting a fair amount of folate in the diet through fortification of flour. I do try to eat a diet rich in the B vitamins.
Dr. Johanna M. Seddon, Director, Epidemiology Unit, Massachusetts Eye and Ear Infirmary
Several studies have suggested that increasing the consumption of dark green, leafy vegetables appears to offer some protection against macular degeneration? Do you recommend vitamin supplements of the nutrients found in these foods?
I don't take lutein or zeaxanthin supplements, but I eat a lot of foods that contain them, including spinach and fish and nuts several times a week. The lutein and zeaxanthin supplements are high-dose vitamins intended for people who already have signs of macular degeneration.