Old age and the diseases that are associated with it are often far from the mind of teenagers, but studies have shown that atherosclerosis (furring up of arteries) and other risk factors for CVD can be found in childhood and adolescence and may predict future CVD risk in adults.
And the new study, published in the current issue of The American Journal of Clinical Nutrition (Vol. 83, pp. 1380-1386), suggests that the introduction of mandatory fortification of certain food with folic acid in the US to reduce birth defects could have the bonus of reducing the risk of CVD for younger generations.
The Child and Adolescent Trial for Cardiovascular Health (CATCH) measured dietary intake of 2695 adolescents (average age 18.3) by means of a 149-item food frequency questionnaire (FFQ), and blood samples were taken to measure serum levels of homocysteine, folate, and vitamins B6 and B12.
The amino acid homocysteine has been linked by epidemiological studies to an increased risk of cardiovascular disease. A meta-analysis in the British Medical Journal (Vol. 325, pp. 1202-1208) of genetic and prospective studies reported that a 3 micromole per liter (mcmol/L) decrease in homocysteine levels was associated with a decrease in the risk of ischemic heart disease of 16 percent.
The researchers found that refined grain intake (fortified with folic acid) had a strong relationship with serum homocysteine levels. When the results were adjusted for age, sex, race, energy intake, smoking, BMI, and vitamins, the highest intake refined grains (between 5.82 to 15.81 servings per day) was associated with a 10 percent reduction of homocysteine levels, compared to the lowest intake group (between 0.07 and 2.49 servings per day).
When the results were adjusted for folate, and vitamins B6 and B12, the relationship between refined grains and homocysteine levels was no longer significant.
Similar results were observed for whole grains, while increasing dairy intake was strongly associated with decreasing homocysteine levels.
Serum levels of folate were positively associated with dietary intake of whole and refined grains, fruit and dairy products.
"Our finding that refined-grain consumption was negatively associated with homocysteine concentrations and positively associated with serum folate concentrations is consistent with our hypothesis," wrote lead author Pamela Lutsey from the University of Minnesota School of Public Health.
"[These results] support the notion that folic acid fortification has a beneficial effect on homocysteine concentrations," she said.
Interestingly, the researchers also found that dietary folate intake was greater for girls than boys (290 micrograms versus 269 micrograms, respectively), and that homocysteine levels were higher in boys than girls (average 6.4 mcmol/L versus 5.1 mcmol/L, respectively).
There are several notable limitations with this study including the use of FFQs, which do not capture information about fortified foods. The authors also could not discern between folate and folic acid in the diet, and so could not adjust the results to reflect relative bioavailabilities.
Studies have shown that folic acid is more easily absorbed from fortified foods (85 percent) and supplements (100 percent) than the folate found naturally in foods (50 percent).
The overall conclusion from this study was that the findings were consistent with the 2005 Dietary Guidelines for Americans, for a varied diet containing grains, fruit, vegetables and dairy products.