Nutrient deficiencies from wheat/grain consumption are common, especially deficiencies of positively-charged minerals magnesium, calcium, iron, and zinc, due to the presence of phytates that block their absorption. But deficiency of vitamin B12 can also occur for other reasons unrelated to grain phytates and, if not corrected, can lead to symptoms such as fatigue and mental fogginess, as well as some real health problems.
Gastrointestinal absorption of vitamin B12 can be tenuous because it requires the participation of two factors/sites: so-called intrinsic factor produced by the parietal cells of the stomach to bind B12 from food or supplements and a healthy distal ileum (just before the colon) for absorption. Disruption of the health at either site will therefore impair vitamin B12 absorption and lead, over time, to deficiency. Wheat and grains can disrupt health at both sites.
Wheat germ agglutinin from wheat, rye, barley, and rice can block intrinsic factor, while gliadin from wheat and proteins from related grains (secalin in rye, hordein in barley) provokes formation of antibodies against both intrinsic factor and stomach parietal cells, leading to autoimmune destruction. People with Crohn’s disease are especially vulnerable to vitamin B12 deficiency, since the distal ileum is inflamed in this condition and may require months to years to recover the ability to absorb B12.
Vitamin B12 deficiency is suggested by symptoms such as impaired mental performance/clarity, deteriorating nervous system function, low energy, an enlarged liver, a cherry red tongue, and a specific form of anemia called macrocytic anemia due to abnormally enlarged red blood cells (signaled by a high mean corpuscular volume, or MCV, value on a CBC). You may recall that removing grains, restoring vitamin D, and cultivation of healthy bowel flora can reverse autoimmune inflammation. Unfortunately, some organs, such as the thyroid or the beta cells of the pancreas, are poor at recovering once autoimmune damage has been inflicted, and there is little hope of recovering organ function. The same can be true for autoimmune damage to the stomach’s parietal cells that produce intrinsic factor: remove the original cause of damage (gliadin and related proteins), but parietal cells may not recover. This means long-term dependence on vitamin B12 supplementation, with blood levels dropping when supplementation ceases.
Vitamin B12 deficiency is identified by measurement of cobalamin or holocobalamin on a blood test, as well as an increased level of methylmalonic acid that can detect milder degrees of deficiency. When restoring vitamin B12, aim to achieve cobalamin and holocobalamin levels in the upper half of the reference range, as levels in the lower half of cobalamin and holocobalamin levels can still be associated with persistent problems including neuropathy, impaired balance, and memory. For the majority, oral (or sublingual, i.e., beneath the tongue, if poor absorption is suspected) supplementation with higher doses in the 500 to 1000 mcg per day range get the job done; rarely are injectable forms required. Because vitamin B12 is most plentiful in animal products such as meat, liver, and eggs, vegans and vegetarians should consider lifelong B12 supplementation. The best form of B12 is methylcobalamin, rather than the more common cyanocobalamin, as the methyl- form is better absorbed and sidesteps the question of potential cyanide toxicity with the cyano-form.
You can also appreciate how deep the fictions surrounding “healthy whole grains” can be. We are told over and over again that whole grains are filled with fiber and B vitamins, but not told that numerous deficiencies can develop, including B12 deficiency, regardless of how much is added to grains to compensate. Notice that grains are the only foods that are “fortified” with B vitamins?