Vitamin B12: what to know if you eat few animal foods
Nutrition
Key points
- B12 is found in meat, fish, eggs, dairy and fortified foods.
- Vegetarians and vegans have a much higher risk of deficiency.
- Deficiency can cause anemia, fatigue, numbness and memory problems.
- Risk is also higher in older adults and people taking metformin or acid-reducing medicines.
Why B12 is special
Vitamin B12 is needed to make red blood cells and maintain the nervous system. It is made by bacteria and accumulates in animal foods, so plant foods are not a reliable source.
What the research shows
A review of studies found that vegetarians and especially vegans have high rates of B12 deficiency, with risk rising the longer someone follows the diet and the fewer fortified foods or supplements they use (Rizzo et al., 2016).
Risk is also higher in older adults, because absorption declines with age. A large case-control study linked long-term use of acid-reducing medicines (proton pump inhibitors and H2 blockers) to higher risk of B12 deficiency (Lam et al., 2013). Metformin, a common diabetes drug, also lowers B12 levels.
Signs of deficiency
- fatigue and weakness;
- pale skin, shortness of breath (anemia);
- numbness or tingling in the hands and feet;
- problems with balance, memory or mood.
Deficiency develops slowly, sometimes over years, and nerve damage can become permanent.
How to prevent it
- If you are vegan, take a B12 supplement or eat B12-fortified foods (some cereals, plant milks, nutritional yeast) every day.
- Older adults and people on metformin or acid reducers should ask their doctor about testing.
- A plant-rich diet like the one recommended by the EAT–Lancet Commission is healthy, but strictly plant-based diets need B12 planning (Willett et al., 2019).
Frequently asked questions
How much B12 do adults need?
The recommended dietary allowance is 2.4 micrograms a day for adults, 2.6 during pregnancy and 2.8 during breastfeeding.
Do seaweed, mushrooms or spirulina provide B12?
Not reliably. Many contain inactive B12 analogs that do not meet your needs.
Sources
- Rizzo et al. (2016). Vitamin B12 among Vegetarians: Status, Assessment and Supplementation. Nutrients 8(12):767. doi:10.3390/nu8120767
- Orlich et al. (2013). Vegetarian Dietary Patterns and Mortality in Adventist Health Study 2. JAMA Internal Medicine 173(13):1230. doi:10.1001/jamainternmed.2013.6473
- Willett et al. (2019). Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems. The Lancet 393(10170):447-492. doi:10.1016/S0140-6736(18)31788-4
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