Dietary sources of vitamin B12 in older adults: the potential role of dairy

It is estimated that vitamin B₁₂ deficiency impacts up to 40% of older adults when mild deficiencies are considered. Addressing this issue is critical, as even mild vitamin B₁₂ deficiency can have serious and debilitating consequences, such as potentially irreversible neurological damage. While there are numerous possible causes, the impaired absorption of food-bound vitamin B₁₂ is a leading cause of vitamin B₁₂ deficiency in older adults. Vitamin B₁₂ only naturally occurs in foods from animal sources, although certain foods may be fortified. The bioavailability of vitamin B₁₂ has been shown to vary between foods, which may be particularly important for those who are vulnerable due to impaired absorption. 

A longitudinal study of 1,753 older adults (age: 68-84 years) from the Quebec Longitudinal Study on Nutrition and Successful Aging (NuAge) assessed whether dietary vitamin B₁₂ intake (total or from specific food categories) was associated with vitamin B₁₂ status. Data were collected over 4 years using yearly 24-hour food recalls to determine dietary intake and both blood (total serum vitamin B₁₂) and urine samples (methylmalonic acid/creatinine ratio) were used to assess B₁₂ status. Additional considerations were made for age, body mass index, alcohol consumption, renal function, and medication use. Users of vitamin B₁₂ supplements were not included in the analysis.

At baseline, median vitamin B₁₂ intake was 2.9 mcg and 4.0 mcg for women and men aged 71+, respectively. Additionally, 17.6% of participants had vitamin B₁₂ intake below the estimated average requirement of 2.0 mcg set by the Institute of Medicine. The two main dietary sources of vitamin B₁₂ were “dairy products” and “meat, poultry and organ meats”. Across all four study years, 21.8-32.5% of participants had low serum vitamin B₁₂, 12.5-17.0% had indicators of low vitamin B₁₂ via urinary sampling, and 10.1-12.7% had deficiency (based on a cut-off value, using a combination of both biomarkers).

When the combination of both biomarkers was used, higher total dietary vitamin B₁₂ intake was associated with a reduced risk of B₁₂ deficiency in a dose-dependent manner. Greater B₁₂ intake from “dairy products” was associated with a lower risk of vitamin B₁₂ deficiency in all models. This, however, was not the case for the category of “meat, poultry, and organ meats”, which was not associated with vitamin B₁₂ status in any model. Vitamin B₁₂ intake from “fish and shellfish” was linked to lower risk of low serum vitamin B₁₂, but not to urinary measures of B₁₂ or vitamin B₁₂ deficiency (based on the cut-off value). A sensitivity analysis corroborated the link between higher dairy product intake and a decreased risk of both low serum vitamin B₁₂ and vitamin B₁₂ deficiency. 

Overall, these findings support that vitamin B₁₂ naturally encountered in animal foods reduces the risk of vitamin B₁₂ deficiency, with certain foods, such as dairy, having greater effects. In fact, authors suggest that dietary vitamin B₁₂ may prevent deficiency in older adults who do not use supplements or consume vitamin B₁₂ fortified foods. The authors further note that dairy’s positive impact, which they attribute in part to superior bioavailability, is noteworthy: decreased deficiency risk was observed at 2.50 mcg of dairy sourced B₁₂, which can be obtained with 30 grams of Swiss cheese, one cup (250 ml) of milk and ¾ cup (175 ml) of Greek yogurt. The beneficial role of dairy is also mentioned in this study, underscoring that dairy foods contain other key nutrients that also promote healthy ageing, such as calcium, protein, and vitamin D.