Vitamin B12

“[RDA] 19+ years: Male 2.4 mcg, Female 2.4 mcg, Pregnancy 2.6 mcg, Lactation 2.8 mcg … Vitamin B12 is required for the development, myelination, and function of the central nervous system; healthy red blood cell formation; and DNA synthesis … If vitamin B12 is added to fortified foods and dietary supplements, it is already in free form and therefore does not require the separation step … The most common form of vitamin B12 in dietary supplements is cyanocobalamin … Other forms of vitamin B12 in supplements are adenosylcobalamin, methylcobalamin, and hydroxycobalamin … No evidence indicates that absorption rates of vitamin B12 in supplements vary by form of the vitamin … absorption is only about 2% at doses of 500 mcg and 1.3% at doses of 1,000 mcg … typically 500 to 1,000 mcg, in supplements containing only vitamin B12 … Evidence suggests no difference in efficacy between oral and sublingual forms … The FNB did not establish a UL for vitamin B12 because of its low potential for toxicity … vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit … Gastric acid inhibitors include proton pump inhibitors, such as omeprazole (Prilosec) and lansoprazole (Prevacid), and histamine 2-receptor antagonists, such as cimetidine (Tagamet) and ranitidine (Zantac) … They can interfere with vitamin B12 absorption from food by slowing the release of gastric acid into the stomach and thereby lead to vitamin B12 deficiency … Metformin, an antihyperglycemic agent used as first-line treatment for prediabetes and diabetes, might reduce the absorption of vitamin B12 and significantly reduce serum vitamin B12 concentrations … Vegans who consume no animal products and vegetarians who consume some animal products (e.g., dairy products, eggs, or both) but not meat have a higher risk of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods … [pernicious anemia] resulting in failure to produce intrinsic factor and malabsorption of dietary vitamin B12 … Surgical procedures in the gastrointestinal tract, such as for weight loss or to remove all or part of the stomach, can cause a complete or partial loss of cells that secrete hydrochloric acid and cells that secrete intrinsic factor”

“Vitamin B12 is a nutrient that helps keep your body's blood and nerve cells healthy and helps make DNA, the genetic material in all of your cells … Adults 2.4 mcg … Vitamin B12 in dietary supplements isn't attached to protein and doesn't require the first step. However, B12 in supplements does need to combine with intrinsic factor to be absorbed … People over 50 should get most of their vitamin B12 from fortified foods or dietary supplements because, in most cases, their bodies can absorb vitamin B12 from these sources … People with pernicious anemia do not make the intrinsic factor needed to absorb vitamin B12. As a result, they have trouble absorbing vitamin B12 from foods and dietary supplements … Your doctor can test your vitamin B12 level to see if you have a deficiency … Gastric acid inhibitors include omeprazole (Prilosec), lansoprazole (Prevacid), cimetidine (Tagamet), and ranitidine (Zantac) … Metformin might reduce vitamin B12 absorption and lower blood levels of vitamin B12 … Vitamin B12 is also available in a form that's dissolved under your tongue (called sublingual vitamin B12). Research has not shown that any form of supplemental vitamin B12 is better than the others”

“Vitamin B12 … 2.4mcg … DVs are the recommended amounts of nutrients to consume or not to exceed each day”

“4.8 HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5 … Table 4: Vitamins Limits … Nutrient … Maximum Daily Limit … Vitamin B12 0.6mg”

“[KORDEL'S] Vitamin B12 Methylcobalamin 500mcg 120s … [GNC] Vitamin B12 500mcg Tablet 90s … [GREENLIFE] Vitamin B12 (Supports Healthy Red Blood Cells And Immune System Function) 90s”

“NOW Foods, Methyl B-12, 1,000 mcg, 100 Lozenges … Solgar, Vitamin B12, 500 mcg, 100 Tablets … Solgar, Vitamin B 12, Sublingual, 1,000 mcg, 100 Nuggets … Jarrow Formulas, Methyl B-12, Lemon, 1,000 mcg, 100 Chewable Tablets … Nutricost, Vitamin B12, 5,000 mcg, 120 Capsules”