Nutrient Information: Vitamin B12

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Nutrient Key Information 
Nutrient Name: Vitamin B12
Nutrient Category: Vitamins and Other Components
Measuring Unit: µg
Nutrient Summary: Vitamin B12 is essential for normal blood formation and body neurological function.
Nutrient Function:

  • Help red blood cell formation and prevent anemia
  • Play the role in nerve cells growth and the nervous system function. It may play a role in preventing brain atrophy which often associated with memory loss or dementia.
  • Vitamin B12 and folate together to help DNA and RNA synthesis of new cells
  • Conversion of food into energy by metabolism of certain fatty acids and amino acids.
  • Vitamin B12 and folate depend on each other for their activation. Vitamin B12 removes a methyl group CH3 from folate and attaches it to itself to activate both Vitamin B12 and folate.

Vitamin B12 is processed in the stomach and the small intestine, and then released into the circulation. To absorb vitamin B12 from foods, there are two steps (vitamin B12 absorption from supplements only needs step #2):
1) Hydrochloric acid and the digestive enzyme pepsin in the stomach separates vitamin B12 from the protein that it's attached to.
2) Then the freed vitamin B12 combines with a protein secreted by the stomach, called intrinsic factor. Now the small intestine's receptors can recognize and absorb the Vitamin B12.

Some people cannot absorb Vitamin B12 well:
1) People older than 50 years old who produce less hydrochloric acid in their stomach.
2) People who eat little or no animal foods.
3) People with autoimmune diseases who cannot produce enough hydrochloric acid and/or intrinsic factor.
4) People with stomach or intestinal surgery who cannot produce enough hydrochloric acid and/or intrinsic factor.
5) People who take some medication which suppresses gastric acid production.

In the body, vitamin B12 is circulated via bile and delivered back to the intestine where it is reabsorbed.

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Food Sources

Foods naturally containing vitamin B12 are primarily animal origin foods. Milk and fish have the greatest B12 bioavailability.

• Fish, such as mackerel, herring, sardines, tuna, trout, salmon
• Dairy products, such as milk (cautious: boiling milk will significantly reduce the Vitamin B12 content)
• Shellfish, such as clams and oyster
• Organ meats, such as beef liver
• Eggs
• Meat, such as beef, pork
• Poultry, such as turkey, chicken drumstick
• Fortified cereals

Attention for vegan diet (pure vegetarian): plant foods have no vitamin B12 unless they are fortified, such as fortified ready-to-eat cereals and meal replacement formulas.

1. 10–30% of people older than 50 years old may be unable to absorb naturally occurring vitamin B12 because of the lower stomach acid secretion caused by the atrophic gastritis. Experts advise people older than 50 to consume foods fortified with vitamin B12 or take Vitamin B12 supplements to meet their daily Vitamin B12 needs.
2. Vitamin B12 can be destroyed by microwave cooking

Sample Foods High in: Vitamin B12
View Additional Food Sources
Food Description Nutrient Amount1 Daily Value%2
Mollusks, clam, mixed species, cooked, moist heat
Category: Finfish and Shellfish Products
98.89 µg 4,120.42%
Beef, variety meats and by-products, liver, cooked, pan-fried
Category: Beef Products
83.13 µg 3,463.75%
Mollusks, oyster, Pacific, cooked, moist heat
Category: Finfish and Shellfish Products
28.8 µg 1,200.00%
Fish, mackerel, Atlantic, cooked, dry heat
Category: Finfish and Shellfish Products
19 µg 791.67%
Fish, tuna, fresh, bluefin, cooked, dry heat
Category: Finfish and Shellfish Products
10.88 µg 453.33%
Milk, reduced fat, fluid, 2% milkfat, with added vitamin A and vitamin D
Category: Dairy and Egg Products
0.55 µg 22.92%
Beef, plate steak, boneless, outside skirt, separable lean and fat, trimmed to 0" fat, all grades, cooked, grilled
Category: Beef Products
7.72 µg 321.67%
Turkey, retail parts, drumstick, meat only, cooked, roasted
Category: Poultry Products
2.53 µg 105.42%
1 Nutrient amount is in 100 gram food
2 Use FDA 2000 calorie diet as Daily Value reference

Additional Nutrient Information
Nutrient Summary Vitamin B12 is essential for normal blood formation and body neurological function.
Deficiency Health Effects Usually vitamin B12 deficiencies are caused by lack of hydrochloric acid (releasing vitamin B12 from foods) or lack of intrinsic factor (enabling vitamin B12 absorption) in the stomach. The common symptom of vitamin B12 deficiency is fatigue or lack of energy. The main problems vitamin B12 deficiency can cause are:

  • Hematological effects: megaloblastic anemia or pernicious anemia. Symptoms include weakness, fatigue, shortness of breath, and palpitations. When anemia is established, some degree of neutropenia and thrombocytopenia may occur.
  • Neurological effects: Neurological complications are present in 75–90% of individuals with vitamin B12 deficiency. Symptoms include tingling and numbness in the limbs, gait disturbances, loss of concentration, memory loss, disorientation, dementia, visual disturbances, insomnia, depression. Even marginal vitamin B12 deficiency impairs memory and cognition.
  • Gastrointestinal effects: Vitamin B12 deficiency is often associated with gastrointestinal complaints, such as loss of appetite, flatulence, and constipation.

Note: Excessive folate intake from supplement may obscure the vitamin B12 deficiency that can result in unrecognized neurological damage.
Effects if Above Upper Limit Due to inadequate data on adverse effects of excess vitamin B12 consumption, a Upper Limit for the vitamin B12 could not be determined.

No adverse effects have been associated with excess vitamin B12 intake from food or supplements in healthy individuals. Apparently only a small percentage of vitamin B12 can be absorbed from the gastrointestinal tract.
External References

Daily Value Age Group Recommended Daily Values
Toddler 1 to 3 years old: 0.9 µg
Child 4 to 8 years old: 1.2 µg
Male 9 to 13 years old: 1.8 µg
Male 14 to 18 years old: 2.4 µg
Male 19 to 30 years old: 2.4 µg
Male 31 to 50 years old: 2.4 µg
Male 51 to 70 years old: 2.4 µg
Male Senior 71 or older: 2.4 µg
Female 9 to 13 years old: 1.8 µg
Female 14 to 18 years old: 2.4 µg
Female 19 to 30 years old: 2.4 µg
Female 31 to 50 years old: 2.4 µg
Female 51 to 70 years old: 2.4 µg
Female Senior 71 or older: 2.4 µg
Female Pregnancy (>18): 2.6 µg
Female Lactation (>18): 2.8 µg
FDA (Based on 2000 calorie daily diet): 2.4 µg

Dietary Reference Intakes The nutrient Dietary Reference Intakes and nutrition facts is from Institute of Medicine of National Academies 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press.
US FDA Nutrition Education Nutrition facts knowledge are based on U.S. FOOD & DRUG Administration Nutrition Education Resources & Materials.
National Institutes of Health Nutrition facts knowledge are based on National Institutes of Health Dietary Supplement Fact Sheets.
Disclaimer The nutrient information provided here should not take the place of medical advice. We encourage you to talk to your healthcare providers (such as your doctor) about your dietary requirements which are best for your overall health. We also recommend you to read organization or professional reference documents or articles mentioned, but not limited to, in this page. Any mentions and reference links in this page don't represent our endorsement of their services and advice.

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