The new study claims that since the advent of folic-acid fortification in food, most people are attaining adequate levels of the B vitamin.
The study, published in the American Journal of Clinical Nutrition, is the first to estimate national levels of folate inadequacy in Canada since the country mandated that folic acid be added to white wheat flour in 1998.
“Understanding folate intakes after folic acid fortification of the food supply will help to establish dietary and supplement recommendations that balance health benefits and risks," write the researchers, led by Dr. Deborah O'Connor of the Hospital for Sick Children in Toronto, Canada.
Folic acid is the synthetic form of folate used in vitamin supplements and added to certain fortified foods including wheat flour and breakfast cereals.
Supplemented folic acid intake is recommended in women of on child bearing age, in order reduce the risk of neural tube defects - birth defects of the brain or spine, including spina bifida.
The recommended daily intake (RDI) of folate ranges between 150 and 300 micrograms (mcg) for children aged between 1 to 13, older teens and adults are advised an intake of 400 mcg.
The upper limits for folate intake are 1,000 mcg per day for adults, and range from 300 to 800 mcg for children and teens, depending on age group.
Since 1998, the U.S. has required manufacturers to add folic acid to enriched flours, breads, cereals, pasta, corn meal and other grain products.
The aims of the new study were to estimate the levels of folate inadequacy and intakes above the tolerable upper intake level (UL) in Canadians.
Based on answers from a national survey of more than 35,000, 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.
Researchers estimated that anywhere from one to four percent of Canadian children are getting too much folate when food and supplement sources are combined. The same was true for up to five percent of adults.
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.
In men younger than 70, folate inadequacy based on food intake only was estimated to be under 7.5 percent, and was virtually non-existent in men younger than 50.
The only group with a prevalence of folate inadequacy the researchers considered high was women older than 70.
According to Dr. O'Connor the findings offer some good news, as she outlined that mandatory folic-acid fortification of white flour has apparently worked well to reduce inadequacies.
O'Connor added that food fortification may have been so effective for certain groups -- children younger than 14 and men - that folic acid from vitamin pills may be unnecessary for them.
The researchers noted that “consideration should be given to removing folic acid from supplements designed for young children and men.”
Dr. O'Connor explained that there are potential risks to getting too much folic acid, including masking potentially harmful deficiencies in vitamin B12.
"There really is no reason to be having folic acid in supplements designed for children and men," she stated.
However, caution over folic acid supplements should not apply to women of childbearing age, who need to keep high levels of folic acid to avoid risks of birth defects, according to O'Connor.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.2010.29696
“Folic acid fortification above mandated levels results in a low prevalence of folate inadequacy among Canadians”
Authors: Yaseer A Shakur, Didier Garriguet, Paul Corey and Deborah L O'Connor