B vitamins are well known for their role in energy metabolism, but new research indicates that they may also have an important role in supporting long-term brain health and cognitive function.
The eight B vitamins are thiamin, riboflavin, niacin, pantothenic acid, vitamin B6, biotin, folate, and vitamin B12. B vitamins are essential nutrients that your body requires to produce energy and metabolize proteins, fats, and carbohydrates, among other vital functions.
Each B vitamin has a recommended dietary allowance or adequate intake level. This number is based on the amount of a nutrient that is needed to prevent deficiency symptoms in about 98 percent of healthy people. However, these recommendations do not necessarily indicate what intake level may be best for optimal health, or in the case of B vitamins, for optimal cognitive function through adulthood.
Long-Term Study Investigates B Vitamins and Cognitive Function
A long-term study observed levels of B vitamin consumption in study participants over a 25-year period to see how varying intake levels influence cognitive function in middle adulthood. The researchers gathered more than 5,000 participants, ranging from 18-30 years old, when the study began in 1985. Despite the long duration, more than 3,000 people remained active participants by the end of the 25-year study.
Researchers recorded the participants’ diet histories, including food and supplements, at the beginning of the study, after seven years, and again after 20 years. In the final year of the study, the participants took standardized tests to measure different aspects of cognitive function including verbal memory, psychomotor speed, and executive function.
B Vitamins and Youthful Cognitive Aging
The participants with higher B vitamin intakes over the course of the study performed better in several areas of cognitive function, although the benefits were influenced by which B vitamins were highest in their usual diets. The two B vitamins that had the strongest impact on cognitive function were niacin and folate. Participants who consumed higher levels of niacin and folate had similar test scores to people who were four to six years younger. Higher levels of vitamin B6 and B12 were also associated with higher scores in cognitive function tests.
The authors of this study concluded that consuming higher levels of the B vitamins, particularly niacin, folate, vitamin B6, and vitamin B12, starting in young adulthood is associated with better cognitive function in middle adulthood. The results of this long-term study highlight the importance of B vitamins for brain health and cognitive function as part of normal aging.
B Vitamins: How Much Do You Need?
The study participants who showed the strongest benefits of cognitive function consumed more than the minimum recommended dietary allowance for each B vitamin on average. However, it’s not true that more is always better for B vitamins. In addition to the recommended dietary allowance, some B vitamins also have a tolerable upper intake level. This is the highest intake of a nutrient that is unlikely to cause a risk from excessive amounts. The upper intake level is typically much higher than the recommended dietary allowance. For example, the recommended dietary allowance for vitamin B6 is 1.3 milligrams per day, while the upper intake level for B6 is dramatically higher at 100 milligrams per day.
Niacin, vitamin B6, and folate are the three B vitamins that have a tolerable upper intake level. Thiamin, riboflavin, pantothenic acid, biotin, and vitamin B12 do not have a tolerable upper intake level as scientists have not identified if there is an amount of these nutrients that is linked to a health risk, although there are no added benefits from consuming extreme amounts.
The results of this study reinforce the importance of getting your B vitamins every day, because study participants with low B vitamin intakes did not perform as well on cognitive function tests as those who met or exceeded the recommended dietary allowance. Getting a bit more than the recommended dietary allowance, especially for niacin, folate, vitamin B6, and vitamin B12, may even provide additional benefits for long-term brain health and cognitive function.
Qin B, Xun P, Jacobs DR Jr, Zhu N, Daviglus ML, Reis JP, Steffen LM, Van Horn L, Sidney S, He K. Intake of niacin, folate, vitamin B-6, and vitamin B-12 through young adulthood and cognitive function in midlife: the Coronary Artery Risk Development in Young Adults (CARDIA) study. Am J Clin Nutr. 2017;106(4):1032-1040. doi: 10.3945/ajcn.117.157834.