Vitamin B-12 (also known as cobalamin) is one of the eight B-complex vitamins. The best food sources are meat and shellfish, but you can get small amounts from dairy and eggs.
It's been speculated that plant sources, like spirulina, tempeh, and seaweed, have vitamin B-12. But, researchers found that these foods actually contain B-12 analogues. These analogues structurally look like B-12, but don't perform the same functions.
You need it to make DNA and RNA, and to maintain healthy nerve cells. It also works with other B vitamins in order to make red blood cells, and to produce S-adenosylmethionine (SAM-e). SAM-e is a powerful antioxidant that relieves depression and elevates mood.
The Food and Drug Administration's (FDA) recommended Daily Value (DV) is 6 mcg. You can see from the numbers below that you need to eat quite a bit of dairy and eggs each day to meet their recommendation.
(mcg per serving)
|1 egg, hard boiled||1.11|
|Milk - 1 cup||0.9|
|Yogurt - plain, 1 cup||1.4|
If you don't eat enough dairy and eggs, you're over 50 years old, or have a digestive disorder, you need to supplement.
Up to 30 percent of people over 50 have less pepsin and gastric acid in their stomachs. And when your body doesn't have enough of these stomach secretions it absorbs less vitamin B-12.
A study tracked 174 healthy people living in Germany and the Netherlands. The results showed 92% of the Vegans, and approximately 66% of the vegetarians in the study, had a deficiency. Only 5% of the meat eaters were deficient.
The good news is studies show supplements and fortified cereals do a good job in preventing deficiencies. And, they're safe.
"No adverse effects have been associated with excess vitamin B-12 intake from food and supplements in healthy individuals". - The Institute of Medicine
Symptoms of a deficiency include fatigue, weakness, nausea, lightheadedness, stomach discomfort, memory loss, and constipation or diarrhea. But, in mild cases the symptoms are not noticeable.
What's more, the National Institute of Health warns that, "Large amounts of folic acid can mask the damaging effects of vitamin B12 deficiency." Foods that are high in folic acid include leafy green vegetables (like spinach and turnip greens), fruits (like citrus fruits and juices), dried beans, and peas.
And, since the liver can store up to five years worth of B-12, it's a while before a deficiency will even start to surface.
The only way to know whether you have a deficiency is to get a blood test.
USDA Nutrient Database, http://www.nal.usda.gov/fnic/foodcomp/search/
NIH Clinical Center website, http://ods.od.nih.gov/factsheets/VitaminB12.asp
NIH Clinical Center website, http://ods.od.nih.gov/factsheets/folate/
Katherine L Tucker, Sharron Rich, Irwin Rosenberg, Paul Jacques, Gerard Dallal, Peter WF Wilson and Jacob Selhub, "Plasma vitamin B12 concentrations relate to intake source in the Framingham Offspring Study," American Journal of Clinical Nutrition, Vol. 71, No. 2, 514-522, February 2000.
Asok C Antony, "Vegetarianism and vitamin B12 (cobalamin) deficiency," American Journal of Clinical Nutrition, Vol. 78, No. 1, 3-6, July 2003.
Vesanto Melina, Brenda Davis, The New Becoming Vegetarian, (Healthy Living Publications)
Marie A. Boyle, Sara Long, Personal Nutrition, Brooks Cole
Brenda Davis, Vesanto Melina, Becoming vegan: the complete guide to adopting a healthy plant-based diet, United States: Book Publishing Company