According to a new study from the Netherlands, increased intakes of folic acid and vitamin B12 do not prevent cognitive decline in elderly people. Experts criticized that the participants already had a sufficient folic acid status at the beginning of the study.
The randomized controlled trial measured cognitive functioning (e.g., memory, attention and information processing speed) and blood homocysteine concentrations of 2,919 participants with an average age of 74 years who took either 400 micrograms of folic acid and 500 micrograms of vitamin B12 or a placebo every day for two years (1). A data analysis showed that while homocysteine concentrations decreased by 5.0 micromol/L in the group taking the B vitamins, versus 1.3 micromol/L in the placebo group, cognitive test scores did not differ over time between the two groups. However, the memory of participants with the lowest vitamin B12 status improved significantly more compared to those taking the placebo.
The researchers commented that an increased intake of B vitamins may slightly slow the rate of cognitive decline, but the hope that the risk of memory loss and Alzheimer’s disease may be reduced by decreasing homocysteine levels using folic acid and vitamin B12 appears to be unsubstantiated. Experts criticized that while patients with elevated levels of homocysteine were selected for the study, their nutrient status was not considered at baseline. Participants in this study had serum folate concentrations on the high end of normal (about 19 nanomol/L). As nutrient supplementation provides the greatest benefit for those with the poorest nutrient intakes, and ultimately the lowest nutrient status, the new results are no surprise, the scientists said. These data once again highlight the importance of the participants’ nutrient status in designing and interpreting clinical trials in nutrition. An earlier meta-analysis of prospective cohort studies showed a significant association between elevated homocysteine concentrations and an increased risk of cognitive decline (2).