On Jul. 23, 2025, research at Tufts and elsewhere has revealed the eight essential nutrients that make up the suite of B vitamins also known as the B complex influence a vast spectrum of human health and disease, including cognitive function, cardiovascular health, gastric bypass recovery, neural tube defects, and even cancer.

“It’s hard to study the B vitamins in isolation,” says gastroenterologist Joel Mason, senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) and professor at the Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy and Tufts University School of Medicine. “Four of these B-vitamins cooperate as co-factors in many critical activities in cells in what we call ‘one carbon metabolism’.” 

One carbon metabolism is a series of pathways that allow for the transfer of single-carbon units to cells for essential processes such as DNA synthesis, amino acid metabolism, and more. It’s their role in all these crucial biological functions that make the B vitamins so important—and so challenging to tease out how they contribute positively and, perhaps negatively, to human health.

Eight essential nutrients make up the suite of B vitamins also known as the B complex. Research at Tufts and elsewhere has revealed that these B vitamins influence a vast spectrum of human health and disease, including cognitive function, cardiovascular health, gastric bypass recovery, neural tube defects, and even cancer.

“It’s hard to study the B vitamins in isolation,” says gastroenterologist Joel Mason, senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) and professor at the Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy and Tufts University School of Medicine. “Four of these B-vitamins cooperate as co-factors in many critical activities in cells in what we call ‘one carbon metabolism’.” 

One carbon metabolism is a series of pathways that allow for the transfer of single-carbon units to cells for essential processes such as DNA synthesis, amino acid metabolism, and more. It’s their role in all these crucial biological functions that make the B vitamins so important—and so challenging to tease out how they contribute positively and, perhaps negatively, to human health.

“The risk of dementia and late-stage Alzheimer’s begins to increase when one is 75 years old or older, but evidence suggests that some of the pathological changes associated with dementia and Alzheimer’s may start to develop 20+ years before clinical symptoms and diagnosis occurs,” says Jacques. “This study should give us a good handle on whether B₁₂ is related to cognitive decline and dementia. If so, hopefully we can identify a simple, inexpensive intervention that could be started years in advance and before real damage occurs.”