Vitamin B12: Everything you need to know

Vitamin B12

Vitamin B12 is an essential vitamin which plays a major role in some vital functions of your body like production of red blood cells and DNA as well as the nerve tissue development and brain function.

Among many other micronutrients, Vitamin B12 is one of those nutrients that can easily be ignored to intake in the right amount in your daily diet. However, it can lead to severe problems when deficient.

Vitamin B 12 deficiency is one of the most common vitamin deficiencies worldwide: For instance, prevalence in the United Kingdom and United States is around 6% in people aged less than 60 years, and closer to 20% in those aged more than 60 years.

What is Vitamin B12?

Vitamin B12 is also known as cobalamin. It’s an essential water soluble micro-nutrient, same as all other B vitamins.

Microorganisms in the natural environment synthesize it and thus, we can obtain it only through our diet. Moreover, the most common source of vitamin B12 is animal proteins. But there are plenty of options for vegans to stay on top of your vegan B12.

It can exist in 4 forms; hydroxocobalamincyanocobalaminmethylcobalamin, and adenosylcobalamin, collectively called “cobalamins”.

Vitamin B 12 which is attached to proteins are separated in the stomach from its protein with the help of hydrochloric acid in the stomach. Then the vitamin part combines with a protein made in the stomach called intrinsic factor and is absorbed by the body.

Recommended intake values of Vitamin B12

According to National Institutes of Health (NIH) , U.S, the recommend dietary allowance (RDA) of vitamin B12 for those who are over the age of 14 years is 2.4 micrograms (mcg) and it varies for children and infants below that age.

Pregnant women should be sure to consume 2.6 mcg, and lactating women 2.8 mcg.


RDA (Recommended dietary allowance)

0–6 months

0.4 mcg

7–12 months

0.5 mcg

1–3 years

0.9 mcg

4–8 years

1.2 mcg

9–13 years

1.8 mcg

14+ years

2.4 mcg

There are no evidence to suggest that you can have any toxic reactions or abnormalities by having an excess of Vitamin B12. However you should always consult a physician before taking supplements.

Sources of Vitamin B12

As we now know the required amounts, the next important question is, how to fulfill this requirement. If you do not have B12 deficiency already, it is best to fulfill the recommended daily value, through food.  That is to say, you should not progress to supplements or sublingual preparations as tablets unless you do not have the deficiency.

Vitamin B12 is naturally found in abundance in animal products and milk products. But there are a plenty of options for vegans to fulfill their daily requirements as well. Therefore it is advisable that vegans pay extra attention for this matter as deficiency of this vitamin is very common among vegans. To clarify, here we have sorted through some food sources that are rich in vitamin B12 and their percentage daily values according to The U.S. Department of Agriculture’s (USDA’s) Food Data Central Web site that lists the nutrient content of many foods and provides a comprehensive list of foods containing vitamin B12 arranged by nutrient content and by food name.

Food sources that are rich in vitamin B12 and their percentage daily values
Food Micrograms (mcg)
Per serving Percent DV*
Clams, cooked, 3 ounces 84.1 3504
Liver, beef, cooked, 3 ounces 70.7 2946
Trout, rainbow, wild, cooked, 3 ounces 5.4 225
Salmon, sockeye, cooked, 3 ounces 4.8 200
Trout, rainbow, farmed, cooked, 3 ounces 3.5 146
Tuna fish, light, canned in water, 3 ounces 2.5 104
Nutritional yeasts, fortified with 100% of the DV for vitamin B12, 1 serving 2.4 100
Cheeseburger, double patty and bun, 1 sandwich 2.1 88
Haddock, cooked, 3 ounces 1.8 75
Beef, top sirloin, broiled, 3 ounces 1.4 58
Milk, low-fat, 1 cup 1.2 50
Yogurt, fruit, low-fat, 8 ounces 1.1 46
Cheese, Swiss, 1 ounce 0.9 38
Beef taco, 1 soft taco 0.9 38
Breakfast cereals, fortified with 25% of the DV for vitamin B12, 1 serving 0.6 25
Ham, cured, roasted, 3 ounces 0.6 25
Egg, whole, hard boiled, 1 large 0.6 25
Chicken, breast meat, roasted, 3 ounces 0.3 13

*DV- Daily Value

The separation step with hydrochloric acid is not required in the fortified foods as they are available in the free form and not attached to proteins as in animal food.


Dietary Supplements

In addition to oral dietary supplements, Vitamin B12 is available in sublingual preparations as tablets or lozenges. In these, it is most commonly present as cyanocobalamin or methylcobalamin. Our body readily converts cyanocobalamin to the active forms methylcobalamin and 5-deoxyadenosylcobalamin.

These supplements are often marketed with the fact that they have high bioavailability of Vitamin B1. But in the other hand, the presence of intrinsic factors in our stomach highly limits the absorption of this vitamin.

Prescription medication

The most common and widely used form of prescription medicine of Vitamin B12 is an intramuscular injection. However, it is typically used to treat deficiency caused by pernicious anemia and other conditions that result in B12 malabsorption and severe deficiency. In addition, it is also available in the form of a nasal spray or a gel, and some people prefer it more in place of the injection.


Vitamin B12 deficiency

Unfortunately, vegetarians or vegans and the elderly are the groups that mostly suffer with Vitamin B12 deficiency. You’re at risk of deficiency if you don’t get enough from your diet or aren’t able to absorb enough from the food you eat. However, above are not the only groups that are at risk of Vitamin B12 deficiency. Next we will look into the identified groups that are at risk of this deficiency.

 Who are at risk of Vitamin B12 deficiency?

Following are some groups that can be deficient of B12.

  • The elderly
  • Individuals with gastrointestinal disorders like, celiac disease and Crohn’s disease
  • Individuals with pernicious anemia
  • Those who’ve had gastrointestinal surgery that removes the part of the bowel that absorbs B12
  • People on the drug metformin for diabetes
  • Pregnant and lactating women who follow strict vegetarian diets and their infants
  • People following a strict vegan diet
  • Individuals taking long-term antacid drugs for heartburn

If you’re not sure whether you are deficient of this Vitamin, you can test your blood to check vitamin B12 level in your blood, with the advice of your doctor.

Vitamin B12 deficiency symptoms

You might see symptoms of Vitamin B12 deficiency even with the slightest decrease in the normal levels.

  • Weakness, tiredness, or lightheadedness
  • Heart palpitations and shortness of breath
  • Pale skin
  • Depression, memory loss, confusion
  • A sore tongue
  • Constipation, diarrhea, loss of appetite, or gas

If untreated, it may lead to severe symptoms such as:

  • Nerve problems like numbness or tingling, muscle weakness, and problems walking
  • Vision loss
  • Mental problems like depression, memory loss, or behavioral changes

In worst cases, permanent brain and nerve damages may occur and some people might even develop mania, psychosis and dementia.



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