With the advent of folic-acid supplementation of certain foods, few Canadians are now getting too little of the B vitamin, a new study estimates -- in findings that question the need for children and men to get additional folic acid from vitamins.

The study does not challenge the need for women of childbearing age to take folic acid supplements, researchers say, since they need extra amounts of the vitamin to reduce the risk of having a baby with neural tube defects -- birth defects of the brain or spine, including spina bifida.

Nor should women older than 70 feel a need to cut back on folic acid: they were the one group the study found to have a high rate of inadequate folate/folic acid intake. (Folate is the natural form of the B vitamin, found in foods such as spinach, asparagus, dried beans and peas, and orange juice; folic acid is the synthetic form used in vitamin supplements and added to certain fortified foods, including wheat flour and breakfast cereals.)

The study, published in the American Journal of Clinical Nutrition, is the first to estimate the national level of folate inadequacy in Canada since the nation mandated in 1998 that folic acid be added to white wheat flour to help prevent neural tube defects.

Researchers used data from a national survey of more than 35,000 Canadians to create statistical models estimating the prevalence of folate inadequacy in different age groups of women, men and children.

Inadequacy means that a person is not getting enough total folate -- from food and supplements -- to meet the average nutrient needs for his or her age and sex, and may run the risk of becoming deficient in the vitamin over time.

Based on survey answers, the researchers estimated how much folate and folic acid individuals were consuming in foods, and how much additional folic acid they were getting from vitamin supplements.

Overall, the estimates found folate inadequacy to be low -- and close to zero among children younger than 14 - with most people getting sufficient folate and folic acid from food sources alone.

Among men younger than 70, folate inadequacy was estimated to be under 7.5 percent -- and virtually non-existent in men younger than 50 -- based on food intake only.

Among elderly men and women age 70 or younger, folate inadequacy was relatively uncommon, being less than 20 percent, based on food intake alone. And within that category, just 10 percent of women ages 19 to 30 were estimated to be getting inadequate amounts of the vitamin from foods alone.

The only group with what the researchers considered a high prevalence of folate inadequacy -- greater than 20 percent -- was women older than 70: even with intake from folic acid supplements along with food, 25 percent of women in this age group were estimated to have folate inadequacy.

Taken together, the findings offer some good news, according to senior researcher Dr. Deborah L. O'Connor of the Hospital for Sick Children in Toronto. Mandatory folic-acid fortification of white flour has apparently worked well, she told Reuters Health.

TOO MUCH FOR SOME?

In fact, O'Connor said, fortification may have been so effective for certain groups -- namely, children younger than 14 and men -- that folic acid from vitamin pills may be unnecessary for them.

There really is no reason to be having folic acid in supplements designed for children and men, she said.

That's because there are potential risks to getting too much folic acid, O'Connor explained. High folic acid intake can, for example, mask and worsen any deficiency in vitamin B-12 (although that should not be a problem if people are taking a supplement that also contains B-12, O'Connor noted).

Studies have also found an association between high folic acid intake and increased risks of certain cancers, such as colon and prostate cancers. Those studies did not, however, prove that folic acid was the reason for the elevated risks.

O'Connor said that no one should panic about the possibility of getting extra folic acid from their multivitamins. But she suggested that parents who are concerned about overdoing the nutrient look for children's multivitamins that contain either no folic acid or relatively low amounts. The same advice goes for men using multivitamins.

The recommended daily intake of folate from all sources is 150 micrograms (mcg) for children ages 1 to 3; 200 mcg for ages 4 to 8; and 300 mcg for ages 9 to 13. Older teens and men are advised to get 400 mcg.

The upper limits for folate intake -- the levels beyond which adverse effects might occur -- are 1,000 mcg per day for adults and range from 300 to 800 mcg for children and teens, depending on age group.

In this study, the researchers estimated that anywhere from 1 percent to 4 percent of Canadian children got too much folate when food and supplement sources were combined. The same was true for up to 5 percent of adults, depending on their sex and age group.

WOMEN STILL NEED MORE

The caution on folic acid supplements does not, however, apply to women of childbearing age, according to O'Connor.

While the study found that relatively few women between the ages of 14 and 50 had inadequate folate intakes that put them at risk of outright deficiency, that does not mean they were getting enough folate to cut the risk of neural tube defects in their babies should they become pregnant.

Only an estimated 18 percent of women in that age range were getting at least 400 micrograms of folic acid per day from fortified foods and supplements combined; experts recommend that women get 400 mcg of folic acid, in addition to any naturally occurring folate from food, to help prevent neural tube defects.

O'Connor said that it's important for women who might become pregnant to keep taking supplemental folic acid.

As for women who are older than 70, it is not clear why they still had a high prevalence of folate inadequacy even with supplement use taken into account. O'Connor said that more research is needed to see whether any change in official recommendations for these women will be necessary. (As with adult men, older women are advised to get 400 mcg of total folate each day.)

The findings could also be relevant beyond Canada, according to O'Connor. She noted that studies from the U.S. have indicated that folate inadequacy is similarly low -- but that, as in Canada, only a minority of women of childbearing age get the recommended amounts of folic acid from supplements.

Since 1998, the U.S. has required manufacturers to add folic acid to enriched flours, breads, cereals, pasta, corn meal and other grain products.

Canada Medicine