Vitamin B12
Vitamin B12, also called cobalamin, is involved in the formation of red blood cells and is essential for the functioning of the nervous system. It also plays a role in the production of RNA and DNA, as well as in the metabolism of amino acids and fatty acids.
Vitamin B12 is absorbed into the gut in a two-step process. First, stomach acid separates the vitamin from the food proteins it is attached to. Then, the vitamin binds to a substance made in the stomach called intrinsic factor. Both of these steps must take place for absorption to occur.
Other names
- Cobalamin
Sources
Since plant-based foods generally do not contain vitamin B12, the best sources of this vitamin are the following:
- Offal
- Meat
- Poultry
- Seafood
Dairy products also contain vitamin B12, but in smaller quantities. Fortified foods, such as plant-based beverages and some nutritional yeasts, are another good source of this vitamin. Tempeh and some seaweeds contain small amounts of B12, but in most cases, it is in a form that our bodies can't use.
Vitamin B12 is stable during cooking, meaning that it is not destroyed by heat.
Approximate vitamin B12 content
| Food | Portion | B12 content |
|---|---|---|
| Beef liver, cooked | 75 g | 62.4 mcg |
| Veal kidneys, cooked | 75 g | 27.8 mcg |
| Clams, cooked | 75 g | 14.6 mcg |
| Oysters, raw | 75 g | 12.1 mcg |
| Mackerel, salted | 75 g | 9 mcg |
| Canned sardines, with bones | 75 g | 6.6 mcg |
| Trout, cooked | 75 g | 5.6 mg |
| Grain-fed veal, cooked | 75 g | 2.5 mcg |
| Canned light tuna | 75 g | 2.3 mcg |
| Food | Portion | Content |
|---|---|---|
| Whole eggs, fresh | 2 large | 2 mcg |
| Lamb, cooked | 75 g | 1.9 mcg |
| Beef, roasted | 75 g | 1.9 mcg |
| Swiss cheese | 50 g | 1.8 mcg |
| Cow's milk | 250 mL | 1.4 mcg |
| Fortified almond or oat beverage | 250 mL | 1.1 mcg |
| Fortified soy or rice beverage | 250 mL | 1 mcg |
| Red Star brand nutritional yeast | 2 g* | 1 mcg |
* 1 tsp of powder or 2 tsp of flakes
Recommended dietary allowance (RDA)
The RDA for vitamin B12 is the daily vitamin B12 intake required to meet the needs of most healthy individuals.
Vitamin B12 Requirements
| Age | Men | Women |
|---|---|---|
| 1-3 years | 0.9 mcg | 0.9 mcg |
| 4-8 years | 1.2 mcg | 1.2 mcg |
| 9-13 years | 1.8 mcg | 1.8 mcg |
| 14-18 years | 2.4 mcg | 2.4 mcg |
| Age | Men | Women |
|---|---|---|
| > 19 years | 2.4 mcg | 2.4 mcg |
| Pregnancy | 2.6 mcg | |
| Breastfeeding | 2.8 mcg |
Deficiency
The main effects of vitamin B12 deficiency are as follows:
- Pernicious macrocytic anemia:
- Fewer, abnormally large red blood cells
- Decreased concentration of hemoglobin in the blood
- Potentially irreversible neurological damage
Vitamin B12 deficiency anemia can develop gradually. Symptoms (pale skin, weakness, and fatigue) may be mild despite severe anemia. Tingling or loss of sensation due to nerve dysfunction may also be present. More severe deficiency may result in confusion.
Deficiency can be caused by the following:
- Not eating enough foods rich in vitamin B12
- Malabsorption
- People over the age of 50, especially those with low stomach acid, have more difficulty absorbing vitamin B12 effectively. If their dietary intake of this vitamin is insufficient, these individuals may develop a deficiency.
- People who take medications that suppress stomach acid, who have had certain surgeries, or who have specific health problems are also at greater risk of vitamin B12 deficiency.
Because this vitamin is stored in the liver, symptoms of deficiency may take several years to appear. In addition, folic acid supplements can mask the symptoms of anemia, which can delay their detection and increase the risk of neurological problems.
Toxicity
No cases of vitamin B12 toxicity have been reported.
Supplements
Moderate consumption of foods rich in vitamin B12 is sufficient to prevent deficiency in most people.
Since older adults tend to have more difficulty absorbing vitamin B12 from dietary sources, it is recommended that individuals over the age of 50 incorporate foods fortified with vitamin B12 into their daily diet or take B12 supplements.
Vegetarians and vegans who do not consume any animal products are at greater risk of deficiency and should be particularly careful to incorporate fortified foods into their diets or take supplements.
Vitamin B12 supplements are available in the form of injections (into the muscles or skin) and oral tablets.
Always watch your diet:
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