Vitamin B12

Vitamin B12

Sources of vitamin B-12

deficiency of vitamin b-12

Vitamin B12 is a nutrient.

Functions of vitamin B-12:

Vitamin B12 helps in keeping the blood cells and body’s nerves healthy. It also helps in making DNA which is the genetic material of the cells. Consuming vitamin B12 also helps in preventing a specified type of anemia termed as megaloblastic anemia which makes people weak and tired.

Steps required for the absorption of vitamin B-12:

Body requires two steps to absorb vitamin B-12 from food. In the first step stomach HCl is separates vitamin B-12 from the protein food which contains vitamin B-12. In the second step separated vitamin B-12 combine with the intrinsic factor which is a protein made by stomach. In this form now, vitamin B1-2 will be absorbed by the body. Some people suffer from a condition named pernicious anemia. People suffering from this condition are unable to make intrinsic factor. Due to deficiency of intrinsic factor they are unable to absorb vitamin B-12 from all dietary supplements and foods.

Daily Requirements of vitamin B-12:

Amount of vitamin B-12 required depends upon age. For different age groups average daily recommended amounts in mcg are listed below:


Life StageRecommended Amount
Birth to 6 months0.4 mcg
Infants 7–12 months0.5 mcg
Children 1–3 years0.9 mcg
Children 4–8 years1.2 mcg
Children 9–13 years1.8 mcg
Teens 14–18 years2.4 mcg
Adults2.4 mcg
Pregnant teens and women2.6 mcg
Breastfeeding teens and women2.8 mcg



Sources of vitamin B12:

Naturally vitamin B12 is found in wide variety of animal foods. Vitamin B12 is also added to some fortified foods. Vitamin B12 will not be present in plant foods until or unless they are fortified. Recommended amounts of vitamin B12 can be obtained by eating a variety of foods such as:

  • Clams and beef liver which are considered as a best source of vitamin B12.
  • Foods containing vitamin B12 such as meat, fish, poultry, milk, eggs and other dairy products.
  • Vitamin B12 fortified foods such as some cereals of breakfast, nutritional yeast and other food products. Product labels can be checked to find out that vitamin B12 is present or not.
  • Vitamin b12 natural sources
       Food        Milligrams
(mg) per
Clams, cooked, 3 ounces84.11,402
Liver, beef, cooked, 3 ounces70.71,178
Breakfast cereals, fortified with 100% of the DV for vitamin B12, 1 serving6.0100
Trout, rainbow, wild, cooked, 3 ounces5.490
Salmon, sockeye, cooked, 3 ounces4.880
Trout, rainbow, farmed, cooked, 3 ounces3.558
Tuna fish, light, canned in water, 3 ounces2.542
Cheeseburger, double patty and bun, 1 sandwich2.135
Haddock, cooked, 3 ounces1.830
Breakfast cereals, fortified with 25% of the DV for vitamin B12, 1 serving1.525
Beef, top sirloin, broiled, 3 ounces1.423
Milk, low-fat, 1 cup1.218
Yogurt, fruit, low-fat, 8 ounces1.118
Cheese, Swiss, 1 ounce0.915
Beef taco, 1 soft taco0.915
Ham, cured, roasted, 3 ounces0.610
Egg, whole, hard boiled, 1 large0.610
Chicken, breast meat, roasted, 3 ounces0.3


Dietary supplements of vitamin B12:

Almost all multivitamins are composed of vitamin B12. Vitamin B12 dietary supplements are also available. Vitamin B12 is also available with other nutrients like folic acid and other B vitamins. Amount of vitamin B12 in a specific product can be checked by the supplement facts label.

Sublingual forms of vitamin B12 is also available in the market but there is no evidence regarding better absorption of sublingual forms than vitamin B12 pills which are swallowed.

Vitamin B12 in prescription form can also be administered as a “shot”. This form of vitamin B12 is usually used to treat deficiency of vitamin B12. Nasal gel form of vitamin B12 as a prescription medicine is also available to use in the nose.

People suffering from vitamin B12 deficiency:

People living in the united states mostly get enough amount of vitamin B-12 from the foods they consume. But vitamin B-12 is not absorbed properly in some people. As a result, 1.5% and 15% of public suffer from deficiency of vitamin B-12. Tests can be performed by the doctors to check the deficiency of vitamin B12.

Some groups that feel trouble in absorbing or getting enough amount of vitamin B12 are discussed below:

  • Older adults who don’t have enough amount of HCl in their stomach are unable to absorb naturally present vitamin B-12 in food. People with age group of above 50 should consume dietary supplements or fortified foods to get sufficient amount of vitamin B-12. because their bodies have ability to absorb vitamin B-12 from these sources.
  • People suffering from pernicious anemia are unable to synthesize intrinsic factor which is required by the body to absorb vitamin B-12 also suffer from vitamin B-12 deficiency. Usually this condition is treated by using vitamin B-12 shots. However, vitamin B12 oral doses in a very high amount might also be effective in treating this condition.
  • People who have undergone gastro-intestinal surgery, like surgery for weight loss or those suffering from digestive disorders like crohn’s disease or celiac disease. These conditions limit or decrease the absorption level of vitamin B12 in the body.
  • Vegetarians or vegans who consume little or no animal food suffer from vitamin B12 deficiency. Naturally vitamin B12 is found only in animal foods, women who breast feed their babies or pregnant women when strictly follow vegetarian diet their babies will not get enough amount of vitamin B12 as a result they will be deficient in vitamin B12.
  • symptoms of vitamin b12 deficiency

Effects of vitamin B12 deficiency:

Deficiency of vitamin B12 results in weakness, tiredness, loss of appetite, constipation, megaloblastic anemia and weight loss. Problems associated with nerves such as tingling and numbness in feet and hands can also occur. Some other symptoms caused due to deficiency of vitamin B12 include balance problems, confusion, depression, poor memory, dementia, and soreness of tongue or mouth. Deficiency of vitamin B12 can also cause nervous system damage even in people who don’t suffer from anemia, so it is very important to treat the vitamin B12 deficiency as soon as possible.

Vitamin B12 deficiency signs in infants include failure to thrive, movement problems, megaloblastic anemia, delayed reaching to three typical developmental milestones. Megaloblastic anemia can be prevented by using large amounts of folic acid because it will hide the deficiency of vitamin B12. But folic acid is not helpful in preventing the nervous system progressive damage which is also a result of vitamin B12 deficiency. So, healthy adults should not consume folic acid more than 1000 mcg per day.

Health effects of vitamin B12:

Scientists are studying the Health effects of vitamin B12 some of these are discussed below:

Heart diseases:

Supplements of vitamin B12 along with vitamin B6 and folic acid don’t help in reducing the risk of getting heart disease. These vitamins actually involved in reducing blood levels of homocysteine due to this reason scientists thought that these vitamins might be helpful. Homocysteine is a compound that is associated with an increased risk of having a stroke or heart attack.


People having high levels of homocysteine in the blood suffer from dementia in their older age. If vitamin B12 is used along with vitamin B6 or folicacid it will help in lowering homocysteine levels in patient’s blood but scientists are not clear about that whether these vitamins actually help in preventing or treating dementia.

Athletic performance and energy:

Supplements of vitamin B12 are often promoted through advertisement that they are a way to elevate endurance or energy. With exceptance or vitamin B12 deficient people, there is no evidence regarding the elevation of energy or improvement in athletic performance by using vitamin B12 supplements.

Harmful effects of vitamin B-12:

vitamin B12 is not involved in causing any harmful effects.

Interactions of vitamin B-12 with other medicines:

vitamin B-12 show interactions with some medicines and in certain cases medicines can lower the levels of vitamin B12 in the body. Examples of some medications that interfere with the use or absorption of vitamin B-12 in the body include:

  • Chloramphenicol (Chloromycetin®) which is an antibiotic utilize for the treatment of certain types of infections.
  • Inhibitors of proton pump like lansoprazole (Prevacid®) and omeprazole (Prilosec®) that are used for the treatment of peptic ulcer diseases and acid reflux.
  • H2 receptor antagonists, of Histamine like ranitidine (Zantac®), famotidine (Pepcid®) and cimetidine (Tagamet®) which are used for the treatment of peptic ulcer diseases.
  • Drug used for the treatment of diabetes such as Metformin.

It is therefore highly recommended that you should discuss with, pharmacist, and other health care providers about any dietary supplements and medicines you take. They will better guide you if dietary supplements might interact or interfere with your prescription.

Healthful eating and vitamin B-12:

Foods containing vitamins, minerals, dietary fiber and other substances are benefit for health. However fortified foods may also provide a good option. Furthermore, for a balanced diet one should be refer to the Dietary Guidelines for Americans and the U.S. Department of Agriculture’s MyPlate.


This fact paper by Office of Dietary Supplements gives a piece of knowledge that should not replace the medical prescription. We foster you to communicate with your healthcare adviser (doctor, pharmacist, dentist etc.) for your interest in, queries about, or use of supplements and what could be best for your health.