Vitamin B12: What Is It And What Does It Do?

Vitamin B12 What Is It And What Does It Do

Vitamin B12 is needed for producing and maintaining new cells, including nerve cells and red blood cells. It is also needed to help make DNA.


Vitamin B12 is bound to the proteins in food. Once you consume B12, the hydrochloric acid in your stomach releases the B12 from the protein. B12 then combines with a substance called intrinsic factor to be absorbed by the intestines.

How Much Do I Need To Consume?


There is insufficient information to establish an RDA for vitamin B12 for infants. In this case, an Adequate Intake (AI) has been established:

Age Males and Females
0 to 6 months 0.4 mcg/day
7 to 12 months 0.5 mcg/day

The Recommended Dietary Allowance (RDA) for vitamin B12 is:

Age Males and Females Pregnancy Lactation
1 to 3 years 0.9 mcg N/A N/A
4 to 8 years 1.2 mcg N/A N/A
9 to 13 years 1.8 mcg N/A N/A
14 to 19 years 2.4 mcg 2.6 mcg 2.8 mcg
19+ years 2.4 mcg/day 2.6 mcg/day 2.8 mcg/day

What Are Sources Of Vitamin B12?

Vitamin B12 is attached to the proteins in animal foods. Breakfast cereals are fortified with vitamin B12, which is very important for people who do not consume an adequate amount of animal foods.

Food Amount Vitamin B12
Beef, top sirloin, lean, choice, broiled 3 oz 2.4 mcg
Breakfast cereals, fortified ¾ cup 6 mcg
Chicken, breast, cooked ½ breast 0.3 mcg
Egg 1 large 0.6 mcg
Haddock, cooked 3 oz 1.2 mcg
Liver, beef 1 slice 47.9 mcg
Milk 1 cup 0.9 mcg
Mollusks, clam 3 oz 84.1 mcg
Salmon, sockeye, cooked 3 oz 4.9 mcg
Trout, rainbow, farmed, cooked 3 oz 4.2 mcg
Trout, rainbow, wild, cooked 3 oz 5.4 mcg
Tuna, white, canned in water 3 oz 1.0 mcg
Yogurt, plain, skim 1 cup 1.4 mcg


Do I Need To Take Vitamin B12 Supplement?

Studies reveal that the majority of Americans consume an adequate amount of vitamin B12. People who do not consume meat or who have a stomach or intestinal disorder that interferes with absorption may need to take a vitamin B12 supplement. Older adults may have atrophic gastritis and may need to consume additional food sources and/or supplements. There are also some medications that can influence vitamin B12 absorption, including H2 receptor antagonists used to treat peptic ulcers, metformin, and proton pump inhibitors. Your doctor can determine your vitamin B12 levels with a blood test.

What Happens If I Don’t Have Enough Vitamin B12?

An inadequate amount of vitamin B12 can cause pernicious anemia. Signs of vitamin B12 deficiency are fatigue, constipation, weakness, loss of appetite, weight loss, and numbness and tingling in the hands and feet. You may also experience a difficulty in maintaining balance, confusion, dementia, depression, and poor memory. An excess intake of folate can mask the symptoms of B12 deficiency, so it’s important to have your levels checked with blood tests if there is a concern, especially if you consume a vegetarian diet.

Is There Such A Thing As Too Much Vitamin B12?

Currently, there is no Tolerable Upper Limit set for vitamin B12. This does not mean that consuming excessive amounts will provide any additional health benefits. It means that there is a very low potential for toxicity at high levels. The RDA was set for optimal health, so it is best to stick with those recommendations.