The human body can do incredible things, but with few exceptions, it can't make the vitamins (or at least not in the right quantities) needed for good health.
That includes vitamin B12, an essential nutrient in the vitamin lineup with a number of jobs in the body. Some of its most important functions concern nerve health and red blood cell production.
Your nerves love vitamin B12
Adequate vitamin B12 levels are fundamental for the health of your nervous system. Without this nutrient, your body can't make myelin, which shields nerves and helps them conduct electricity correctly.
If you're chronically deficient in vitamin B12, you may experience the tingling feeling known as peripheral neuropathy, that relentless, pins-and-needle sensation in your hands or feet. And if the deficiency continues, you may eventually have trouble walking without support. Muscle weakness, poor reflexes, and balance problems are all ways that your body tells you it badly needs vitamin B12.
Your red blood cells love vitamin B12, too
Your blood needs vitamin B12 as much as your nervous system does. Without vitamin B12, the body makes red blood cells (RBCs) that are too large, too weak, and unable to transport oxygen. The result is anemia, which can cause major fatigue, dizziness, and shortness of breath.
Your skin may also become pale because there aren’t enough mature RBCs under your skin to give it its normal color. It may even look yellowish, or jaundiced, due to bilirubin, a waste product that forms when RBCs break down.
And that’s just a start. Vitamin B12 deficiency causes many other symptoms: confusion and memory loss, depression, a fast heart rate, mouth and/or tongue pain, nausea, diarrhea, and a loss of appetite.
Are you B12 deficient?
10-20% of the adult population is deficient in vitamin B12. One study showed that around 6% of people under 60 in the USA and UK have a vitamin B12 deficiency. That number jumps to 20% in people aged 60-70 and 30-40% in older people who are institutionalized.
Low or marginal levels are much more common, a staggering 40% of people in Western populations. Unfortunately, "low" could become "deficient" if left unattended. And while the classic hematologic and neurologic symptoms of deficiency may not be present, fatigue and low mood certainly could be.
If you eat food from animal sources, chances are your levels are fine. Vitamin B12 is plentiful in milk, yogurt, meat, eggs, and poultry.
On the other hand, if you're vegetarian or vegan, it's important to eat B12-fortified foods (like cereals, nutritional yeast, and plant milks) or supplement with B12. If you've followed a strict vegan diet for at least a few years, you may develop a deficiency from a lack of dietary intake.
Elderly people are also vulnerable because they're less able to absorb B12. The process requires normal levels of stomach acid, but acid production decreases as people age. If you take gastric acid inhibitors for gastroesophageal reflux disease (GERD) or a peptic ulcer, the same lack of acid could pose a problem.
Crohn’s or celiac disease, weight-loss surgery, gastric surgery, and the lack of certain factors needed for vitamin B12 metabolism, whether due to genetics or other medical conditions, can also interfere with stomach acid production and, therefore, vitamin B12 absorption.
Be safe, not sorry
It can take months, even years, to feel the symptoms of vitamin B12 deficiency. That’s because your liver stores one to two thousand times as much as you typically consume in a day. So, why worry?
Well, you may have noticed how generic the symptoms of vitamin B12 deficiency are. They could be caused by a number of other health conditions so people are often slow to suspect a vitamin deficiency. Additionally, correcting a deficiency doesn’t happen overnight. If those symptoms are due to a vitamin B12 deficiency, once you start correcting the levels, some of the symptoms will take weeks to months to reverse. And some of the neurological deficits are irreversible. Lifelong neuropathy? No, thank you.
If you are in one of the groups at risk for vitamin B12 deficiency—vegans or strict vegetarians, the elderly, people with health conditions or medications affecting the absorption of B12, or already having symptoms of vitamin B12 deficiency—the first thing you can do is talk to your doctor about taking a simple blood test to find out your current levels.
It’s also important to find a reliable source of vitamin B12, especially if you're plant-based. The average adult needs 2.4 mcg of vitamin B12 a day, 2.6 mcg if pregnant, and 2.8 mcg if breastfeeding. However, up to 6 mcg per day may be appropriate for vegans.
If you're supplementing, you'll want to be sure you're taking at least 500 mcg: Your body only absorbs 10 mcg of a 500 mcg supplement. Additionally, a daily dose of 500 mcg has been shown to normalize B12 levels for most people. Higher doses of 1,000 mcg may be necessary for some, though rare.
References
9 Signs and Symptoms of Vitamin B12 Deficiency. Healthline. Retrieved from https://www.healthline.com/nutrition/vitamin-b12-deficiency-symptoms
Ankar, A., Kumar, A. (2021). Vitamin B12 Deficiency. StatPearls [internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK441923/
Burgess, L. What are the symptoms of vitamin B-12 deficiency? (2019). Medical News Today. Retrieved from https://www.medicalnewstoday.com/articles/324265
Carmel, R. (2008). How I treat cobalamin (vitamin B12) deficiency. Blood, 112(6), 2214-21. Retrieved from https://pubmed.ncbi.nlm.nih.gov/18606874/
Gana, W., De Luca, A., Debacq, C., Poitau, F., et al. (2021). Analysis of the Impact of Selected Vitamins Deficiencies on the Risk of Disability in Older People. Nutrients, 13(9), 3163. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8469089/
Hill, M., Flatley, J., Barker, M., Garner, C., et al (2013). A vitamin B-12 supplement of 500 μg/d for eight weeks does not normalize urinary methylmalonic acid or other biomarkers of vitamin B-12 status in elderly people with moderately poor vitamin B-12 status. Journal of Nutrition, 143(2), 142-7. Retrieved from https://pubmed.ncbi.nlm.nih.gov/23236022/
Hunt, A., Harrington, D., Robinson, S. (2014). Vitamin B12 Deficiency. The BMJ, 349, g5226. Retrieved from https://pubmed.ncbi.nlm.nih.gov/25189324/
National Institutes of Health. (2022). Vitamin B12 Fact Sheet for Health Consumers. Retrieved from https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/
National Institutes of Health. (2022). Vitamin B12 Fact Sheet for Health Professionals. Retrieved from https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
Rogerson, D. (2017). Vegan diets: practical advice for athletes and exercisers. Journal of the International Society of Sports Nutrition, 14-36. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28924423/
Vitamin B12 deficiency can be sneaky, harmful. (2020). Harvard Health Blog. Harvard Health Publishing. Retrieved from https://www.health.harvard.edu/blog/vitamin-b12-deficiency-can-be-sneaky-harmful-201301105780
Vitamin deficiency anemia. Mayo Clinic. Retrieved from https://www.mayoclinic.org/diseases-conditions/vitamin-deficiency-anemia/symptoms-causes/syc-20355025
WebMD. Understanding Your B12 Deficiency - Vitamin B12: What to Know. (2021). Retrieved from https://www.webmd.com/diet/vitamin-b12-deficiency-symptoms-causes
