In the diet, B12 comes from meat, fish, dairy, other animal products, and fortified breakfast cereals. As many as one-quarter of the elderly may have mild B12 deficiency. Strict vegetarians, who avoid meat, and vegans, who avoid all animal products, are also at risk of B12 deficiency.
"This is an unexpected finding. We thought we had already learned everything about the absorption of vitamin B12," said co-author Jacob Selhub, director of the Vitamin Metabolism Laboratory at the USDA Human Nutrition Research Center on Aging at Tufts University. He has conducted many of the studies linking B12 status in the elderly with cognitive impairment, anemia, and bone marrow density and osteoporosis.
Anything in the stomach that affects the normal acidity and digestive processes, ranging from infections to acid reflux medicine to aging, may also interfere with B12 absorption, studies suggest. B12 is first separated from food by stomach acid and then escorted from there by a protein called intrinsic factor to the small intestine, where the complex is absorbed and B12 is released into the blood.
Until further studies are conducted, the most plausible explanation is the potential preventive effect of the gene variant on factors known to cause B12 malabsorption, such as H. pylori infection, the researchers say.
Hazra and her colleagues had been investigating the genetic and epigenetic links between colorectal cancer and adenoma and the B-vitamin pathway, also known as the one-carbon metabolism pathway, including folate, vitamins B6 and B12, and homocysteine. Ultimately, she hopes to identify different gene variants that work together and create a nutrigenomics predictor score to assist in future individual cancer prevention strategies.
Evaluating more than 528,000 genetic variants, the strongest signals came from variants
|Contact: Christina Roache|
Harvard School of Public Health