Some of the most exciting news in nutrition these days involves folic acid, a B vitamin that probably plays a role in preventing birth defects, vascular disease, colon cancer and possibly dementia.
Folate, often called folic acid or folacin, is in most vegetables and fruits, especially legumes and dark leafy vegetables. Frozen orange juice is a very convenient source, and several cereals, such as Total and Product 19, have added 400 micrograms, the Recommended Daily Allowance.
Many researchers believe that getting folate into the diet is so important that the Food and Drug Administration has proposed adding it to flour, as already is done with some other vitamins and minerals.
The Centers for Disease Control and Prevention and the Pub-lic Health Service support that initiative. Others, including leading folate researchers, are cautious about endorsing supplementation and food fortification before enough information is in. Although it seems relatively harmless, no one knows exactly how much folate is needed.
The importance of folate in guarding against neural tube birth defects has been recognized for several years. Women who have low blood levels of it during the first three weeks of pregnancy face a far greater risk of producing babies with anencephaly (the absence of a brain) or spina bifida (incomplete development of the back and spinal cord).
Folate also can control the blood levels of homocysteine, an amino acid that, like cholesterol, may be a risk factor for heart disease and stroke. Studies show that many people with clogged blood vessels also have higher than normal levels of homocysteine.
Other research shows that elevated homocysteine may be related to cognitive disorders, particularly in older people, and that a deficiency in folate could tie in with the development of colon cancer.
The immediate, quick-fix reaction to all this from dietitians, government bureaucrats and especially vitamin sellers has been to advocate pumping more folate into the diet.
For instance, Dr. Godfrey Oakley, chief of the birth de-fects branch at the CDC, is so concerned that he routinely hands out bottles of folic acid pills to brides at weddings.
Other researchers, though they believe folate may help prevent disease, are wary of recommending indiscriminate use, including enriching pasta and flour products. “The evidence seems overwhelming that homocysteine is tied to vascular disease and that B vitamins can lower it,” says Paul Jacques, associate chief of the epidemiology program at the Depart-ment of Agriculture’s Nutri-tion Research Center on Aging at Tufts University in Boston. “But I’m still slightly skeptical that homocysteine is the cause.”
Most of the studies are based on large population groups or are not long-term, he says. “The question is: Does elevated homocysteine predate the increased risk of vascular disease or vice versa?”
If homocysteine is the culprit, Jacques asks, at what level does it cause trouble? Is it connected to genetics? How much folate is needed to lower it to a safe level? Is it 400 micrograms? Or 1,000 mcg, which is the FDA’s recommended maximum limit? Or 5,000 mcg–the amount one group of subjects is getting in a cancer study?
“We know that by giving super doses of folic acid we can get a reduction in homocysteine,” says Jacques, who is trying to determine what the optimum blood level of homocysteine should be.
“We don’t benefit by increasing folate levels helter-skelter,” he adds.
“We are dealing with a public health issue here, and we are dealing in ignorance. People are rushing ahead. I’m concerned that the results won’t be definite if we go in (with recommended dosages) too fast.”
Jacob Selhub, director of the USDA center’s vitamin and metabolism laboratory, is trying to determine how much folate the body actually uses and exactly what the RDA should be. Current figures are more or less an educated guess, he says.
“It’s very complex,” Selhub says. He is trying to calculate how much folate the body absorbs from a given foodstuff so that people will know how much of what kind of food they need to eat.
“Some people think that by just eating certain vegetables they will get their folacin,” Selhub says. “But they take sources such as spinach or Brussels sprouts and boil them, thus causing the vegetable to lose its folacin into the cooking water. People aren’t aware of things like that.”
Does that mean Selhub would prescribe folic acid in pill form?
“Up to 10 years ago, if you asked me whether or not you should supplement, I would have said, You don’t seem anemic, you don’t show signs of vitamin deficiency. No.’
“Now I realize there is a gray area between overt deficiency and complete sufficiency. We call it inadequate status’ or subclinical deficiency.’ That place may be related to chronic diseases, particularly in aged people.”
Selhub’s job, then, is to find an RDA that will control homocysteine and prevent neural tube defects, ideally without resorting to supplements, if for no other reason than it is difficult to get people to take pills every day.
On the other hand, “it may be hard to eat enough food to get the right intake,” he says.
Another difficulty with folic acid supplements or fortification: Folate can mask symptoms of vitamin B12 deficiency, which can cause neurological damage, particularly in old people. Some researchers suggest that this risk can be avoided either by more precise testing for B12 deficiency or by fortifying folic acid supplements with large amounts of B12, just in case.
Selhub has a simpler solution, though not one most people seem willing to heed: Make your diet conform to the USDA Food Guide Pyramid.
Because the pyramid recommends five to nine daily amounts of fruits and vegetables, Selhub says, those who follow its suggestions “probably would be getting not just the folate they need, but other vitamins and minerals as well.”
GETTING YOUR FOLATE FROM FOOD
Most vegetables and fruits are sources of folate. Dairy products and meats, with the exception of organ meats and eggs, are poorer sources. Following are some products with significant amounts. Folate is measured in micrograms, or millionths of a gram. The Recommended Daily Allowance is 400 micrograms.
The following items are 1/2 cup servings and are cooked unless otherwise specified:
– 180 to 300 micrograms (mcg)
Fortified cold cereals such as Product 19, Total, Quaker Extra, lentils, roasted soybeans, any food that according to its Nutrition Facts label provides 45 percent or more of the Daily Value for folic acid.
– 100-179 mcg
Asparagus, broccoli, spinach, pinto beans, navy beans, chickpeas, kidney beans, black beans, black-eyed peas, avocado (1 raw), any product that according to its Nutrition Facts label provides 25 to 40 percent of the Daily Value for folic acid.
– 60-90mcg
Great northern beans, split peas, white beans, turnip greens, collard greens (frozen), Brussels sprouts, beets, orange juice (6 ounces from frozen).
– 30-59mcg
Green peas, okra, cantaloupe (raw), lettuce, cos or romaine (raw), corn, pineapple juice (6 ounces), tomato juice (6 ounces), orange (raw).
Source: U.S. Department of Agriculture composition tables
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Steven Pratt’s e-mail address is SMPratt @aol.com
