Vitamin B12, cobalamin, plays an important role in human health and disease, and a deficiency in B12 can result in physical and mental health problems. Most people get the amount they need through supplements, but animal products like eggs and milk — and even some plants — also serve as good sources. Side effects from this water-soluble vitamin are rare, but it's been known to trigger the sometimes-fatal allergic reaction known as anaphylaxis, so speak with your doctor about it.
Even high doses of vitamin B12 are considered safe, and side effects are rare. There have, however, been cases of people experiencing the allergic reaction known as anaphylaxis after taking B12, underscoring the importance of talking to your doctor before including B12 in your health regimen.
Cobalamin Has Low Bioavailability
Some dietary cobalamin fails to reach your bloodstream. In fact, your ability to process cobalamin decreases as you increase your intake, so a large meal offers only slightly more cobalamin than a smaller meal. In addition, older adults often lose their ability to process cobalamin. All of this contributes to the likelihood of developing cobalamin deficiency.
Dietitians typically recommend getting 2.4 micrograms of cobalamin per day. However, some governments have increased this value to 8.6 micrograms. A person's gender, age and other factors affect these recommendations, and all values assume normal cobalamin processing.
Sublingual Cobalamin Offers Many Benefits
You can get cobalamin supplements in muscular and oral doses. The authors of a June 2016 report in the New Zealand Medical Journal noted the increasing popularity and many advantages of sublingual administration. Placing a B12 tablet under your tongue produces results similar to muscular injections with fewer complications.
A February 2018 paper in Clinical Nutrition also documented the effectiveness of sublingual administration. In this study, a weekly dose of 2,000 micrograms restored circulating cobalamin levels in patients with mild B12 deficiency. Interesting, daily doses of 50 micrograms had an even better effect.
Cobalamin Has Few Side Effects
Taking larger doses of cobalamin can help you overcome bioavailability issues, but whenever you consider upping your dose of a supplement, it's normal to have concerns about safety issues. Fortunately, the authors of a 2018 report in Food Fortification in a Globalized World concluded that even large doses of B12 remain safe, so 2,500 micrograms shouldn't pose a health problem.
Cobalamin Causes Allergic Reactions
While dose size doesn't matter, cobalamin can cause an allergic reaction, as reported in the May 2018 edition of Cureus. An older woman following a vegan diet for five years was prescribed a weekly 1,000-microgram injection of B12 and showed signs of anaphylaxis while receiving the second injection. A 2,000-microgram oral dose was prescribed, addressing the deficiency without side effects. The study noted that very few patients experience cobalamin-related anaphylaxis. Still, you should share any observed side effects with your doctor.
Cobalamin Comes From Many Sources
Because only microorganisms can make cobalamin, you have to get it from your diet or a supplement. Most animal products contain cobalamin. Farm animals offer you the best source of cobalamin, according to a February 2015 report in Nutrition Reviews. Organ meat has the greatest concentration of this vitamin. Dairy products contain considerably less. Vegetables rarely have cobalamin, but some edible seaweeds have it.
Traditional Cooking Changes Cobalamin Content
Food processing can have a dramatic effect on nutrients. For example, traditional cooking methods may cause a 62 percent decrease in cobalamin, according to a 2011 report in the Journal of Nutritional Science and Vitaminology. Modern techniques like vacuum-packed pouch cooking can eliminate this loss.
- Nutrients: Foods and Supplements Associated with Vitamin B12 Biomarkers among Vegetarian and Non-Vegetarian Participants of the Adventist Health Study-2 (AHS-2) Calibration Study
- Nutrients: Vitamin B12-Containing Plant Food Sources for Vegetarians
- National Institutes of Health: Vitamin B12
- Cureus: Anaphylactic Reaction to Cyanocobalamin
- Nutrition Reviews: Vitamin B12 in Meat and Dairy Products
- Journal of Nutritional Science and Vitaminology: Loss of Vitamin B12 in Fish (Round Herring) Meats During Various Cooking Treatments
- Nutrients: Vitamin B12 Among Vegetarians
- Food Fortification in a Globalized World: Efficacy and Safety of Vitamin B12 Fortification
- New Zealand Medical Journal: Sublingual Vitamin B12 Compared to Intramuscular Injection in Patients With Type 2 Diabetes Treated With Metformin
- European Journal of Clinical Nutrition: Treatment of Vitamin B12 Deficiency-Methylcobalamine? Cyancobalamine? Hydroxocobalamin?-Clearing the Confusion
- Clinical Nutrition: Effect of Two Different Sublingual Dosages of Vitamin B12 on Cobalamin Nutritional Status in Vegans and Vegetarians With a Marginal Deficiency