We have long appreciated the role of particular vitamins in contributing to the physical structure of the body. There’s vitamin D for healthy bone turnover, and vitamin C for hydroxylation of proline and lysine, required for the synthesis of collagen. Vitamin B12 is another of these key factors, and it contributes to the building and maintenance of myelin, the protective covering that surrounds neurons. Severe B12 deficiency results in a number of signs and symptoms that affect multiple body systems. Among these are the hematological changes categorized as pernicious and megaloblastic anemias, decreased methylation and elevated homocysteine, and compromised neurological function. The last of these is especially concerning, because some of the adverse effects may be irreversible, even upon repletion of B12 stores.

One group commonly at risk for B12 insufficiency is the elderly. Many older people may be taking stomach acid blocking medication, which will inhibit the body’s ability to absorb this vitamin. Additionally, due to decades of guidance from government nutrition authorities to reduce consumption of foods rich in saturated fat and cholesterol, people may be avoiding some of the primary dietary sources of B12, including red meat (liver, in particular), egg yolks, and shellfish. (Older people might also steer clear of these foods if they find them more difficult to chew, and reduced stomach acid will make them harder to digest, as well.)

It is especially troubling that older people may be deficient in this nutrient, because B12 is critical for healthy cognitive function. It is well known that a B12 deficiency can result in memory loss, disorientation, and dementia. It would be tragic if some older patients were misdiagnosed as having Alzheimer’s disease when the cause of changes in their cognition and behavior was actually a vitamin deficiency. Researchers say that low vitamin B12 status “is an important risk factor for loss of brain volume in older community-dwelling adults. These findings suggest that plasma vitamin B12 status may be an early marker of brain atrophy and thus a potentially important modifiable risk factor for cognitive decline in the elderly.” (Emphasis added.)

Compared to patients with other types of dementia, Alzheimer’s disease patients have lower levels of B12 in their cerebrospinal fluid. The resulting reduced availability of methyl groups is believed to lead to decreased synthesis of myelin, membrane phospholipids, and the neurotransmitter  —all of which would have disastrous consequences for cognitive function. After recognizing that elevated plasma homocysteine was associated with cognitive decline in older adults, researchers who set out to determine whether it was insufficient folate or insufficient B12 that was responsible, found that it is B12 that influences healthy cognition. A doubling of holotranscobalamin (bioavailable or “active” B12) concentration was associated with a 30% slower rate of cognitive decline, whereas a doubling in homocysteine or methyl-malonic acid (markers for B12 insufficiency) was associated with greater than 50% more rapid cognitive decline.

Other groups that may be at risk for low B12 status are vegetarians and vegans, since the most concentrated sources of this nutrient are animal proteins. Lacto-ovo vegetarians may get sufficient amounts from eggs and dairy products, but those who avoid animal-sourced foods altogether may have difficulty remaining nutrient replete without careful supplementation. Children of strictly vegetarian parents have experienced developmental difficulties resulting from decreased myelination due to B12 deficiency. These include severe psychomotor retardation, frontoparietal cranial atrophy, and the more general catch-all, “failure to thrive.” Most disturbing is that even when hematological signs of deficiency are corrected, there may be some degree of long-lasting neurocognitive defects later in child development. Researchers familiar with B12 deficiency in infants emphasize that strict vegetarian parents should be made aware that some of the resulting compromises in development during fetal and neonatal life may be irreversible, and, thus, it would be wise to take precautions to ensure adequate maternal B12 levels during pregnancy and breastfeeding.

 NOTE: Many of you have heard me talk about “Aunt Sadie” who beginning in the 1950’s gave B12 injections to our entire family and everyone else who lived in the neighborhood.  She had a booming B12 practice.