One of the most common nutrition problems among geriatric patients is cobalamin (vitamin B12) deficiency. A recent study found that many cases may be going undiagnosed, and that adequate intake of supplemental cobalamin is critical to preventing deficiency. The results are published in the Journal of the American Geriatrics Society.

Screening geriatric outpatients

Researchers in Seattle studied 315 adults aged 65-100 (mean age 77), without previous diagnosis or treatment of cobalamin deficiency, severe anemia, or a life-threatening illness. Detailed information was collected on total synthetic cobalamin intake from all sources, including vitamins, fortified cereals, and liquid nutrition supplements.

Defining cobalamin deficiency

Blood samples were collected, and cobalamin deficiency was defined as a serum cobalamin level </=300 pg/mL and a serum methylmalonic acid (MMA) level >271 nmol/L.

Of the 315 patients screened, 40 (13%) had both serum cobalamin levels and serum methylmalonic acid (MMA) levels meeting these criteria for cobalamin deficiency. According to the authors, this prevalence rate is similar to those found in previous studies of older adults (12-15.8% in other cohorts).

Common causes not always to blame

The two most common causes of cobalamin deficiency in older adults are the loss of gastric cells that secrete acid and intrinsic factor, and a decrease in the ability to absorb cobalamin from food sources. Cobalamin deficiency can be the result of gastric surgery, atrophic gastritis, bacterial overgrowth, or the use of acid-suppressing drugs. In this study population, only 5% of those with deficiency tested positive for anti-intrinsic factor antibodies, and none of those with deficiency had a history of conditions or surgeries that would interfere with food malabsorption.

Protecting with supplemental cobalamin

Of the 315 patients studied, almost half (146, or 46%) were taking a supplemental source of cobalamin, which, in most cases, conferred protection. However, 8% of supplement users were among those found to be deficient. Protection provided by supplement intake appeared to be dose dependent, with only two cases of cobalamin deficiency occurring among the 46 subjects who consumed more than 12 µg daily, and no cases among the 12 subjects who consumed more than 50 µg synthetic cobalamin daily.

The authors suggest that the amount of synthetic cobalamin in a typical multivitamin supplement (usually below 10 µg) may not be enough to confer total protection against deficiency.

Screening crucial

Many of the deficient patients in this study's population had had their cobalamin levels checked previously, but not in the past 3 years (per study exclusion criteria), raising the question, say the authors, as to the optimal frequency to screen for cobalamin deficiency in seniors.

The authors also point out another reason for the importance of cobalamin screening--cobalamin deficiency is linked to hyperhomocysteinemia, a risk factor for atherosclerotic cardiovascular disease.

Practice guidelines

The results of this study suggest that many cases of cobalamin deficiency go undiagnosed and that even patients who do not have the most common causes of deficiency may be deficient. Adequate screening and counseling about supplemental intake may help reduce the prevalence of cobalamin deficiency and related morbidities in seniors.