This excerpt from the Office of Dietary Supplements – National Institutes of Health Fact Sheet on Vitamin B12 discusses why older adults (people over 50) may need to take supplements or use fortified foods to prevent Vitamin B12 deficiency:
Hydrochloric acid helps release vitamin B12 from the protein in food. This must occur before vitamin B12 binds with intrinsic factor and is absorbed in your intestines. Atrophic gastritis, which is an inflammation of the stomach, decreases the secretion of gastric juices, including hydrochloric acid. Less hydrochloric acid decreases the amount of vitamin B12 separated from proteins in foods and can result in poor absorption of vitamin B12. Decreased hydrochloric acid secretion also results in growth of normal bacteria in the small intestines. The bacteria may take up vitamin B12 for their own use, further contributing to a vitamin B12 deficiency. Up to 30 percent of adults aged 50 years and older may have atrophic gastritis, an increased growth of intestinal bacteria, and be unable to normally absorb vitamin B12 in food. They are, however, able to absorb the synthetic vitamin B12 added to fortified foods and dietary supplements. Vitamin supplements and fortified foods may be the best sources of vitamin B12 for adults older than age 50 years.
Caution: Folic Acid and vitamin B12 deficiency
Folic acid can correct the anemia that is caused by vitamin B12 deficiency. Unfortunately, folic acid will not correct the nerve damage also caused by vitamin B12 deficiency [1,36]. Permanent nerve damage can occur if vitamin B12 deficiency is not treated. Folic acid intake from food and supplements should not exceed 1,000 μg daily in healthy individuals because large amounts of folic acid can trigger the damaging effects of vitamin B12 deficiency . Adults older than 50 years who take a folic acid supplement should ask their physician or qualified health care provider about their need for additional vitamin B12.
A further excerpt from the ODS Vitamin B12 Info Sheet discusses the relationship between vitamin B12, homocysteine, and cardiovascular disease. As noted, “clinical intervention trials are underway to determine whether folic acid, vitamin B12, and vitamin B6 supplements can lower risk of coronary heart disease.”
Cardiovascular disease involves any disorder of the heart and blood vessels that make up the cardiovascular system. Coronary heart disease occurs when blood vessels which supply the heart become clogged or blocked, increasing the risk of a heart attack. Vascular damage can also occur to blood vessels supplying the brain, and can result in a stroke.
Cardiovascular disease is the most common cause of death in industrialized countries such as the United States, and is on the rise in developing countries. The National Heart, Lung, and Blood Institute of the National Institutes of Health has identified many risk factors for cardiovascular disease, including an elevated LDL-cholesterol level, high blood pressure, a low HDL-cholesterol level, obesity, and diabetes. In recent years, researchers have identified another risk factor for cardiovascular disease: an elevated homocysteine level. Homocysteine is an amino acid normally found in blood, but elevated levels have been linked with coronary heart disease and stroke. Elevated homocysteine levels may impair endothelial vasomotor function, which determines how easily blood flows through blood vessels. High levels of homocysteine also may damage coronary arteries and make it easier for blood clotting cells called platelets to clump together and form a clot, which may lead to a heart attack.
Vitamin B12, folate, and vitamin B6 are involved in homocysteine metabolism. In fact, a deficiency of vitamin B12, folate, or vitamin B6 may increase blood levels of homocysteine. Recent studies found that vitamin B12 and folic acid supplements decreased homocysteine levels in subjects with vascular disease and in young adult women. The most significant drop in homocysteine level was seen when folic acid was taken alone. A significant decrease in homocysteine levels also occurred in older men and women who took a multivitamin/ multimineral supplement for 8 weeks. The supplement taken provided 100% of Daily Values (DVs) for nutrients in the supplement.
Evidence supports a role for folic acid and vitamin B12 supplements for lowering homocysteine levels, however this does not mean that these supplements will decrease the risk of cardiovascular disease. Clinical intervention trials are underway to determine whether folic acid, vitamin B12, and vitamin B6 supplements can lower risk of coronary heart disease. It is premature to recommend vitamin B12 supplements for the prevention of heart disease until results of ongoing randomized clinical trials positively link increased vitamin B12 intake from supplements with decreased homocysteine levels AND decreased risk of cardiovascular disease.