Dietary Sources of Vitamin B12
The primary dietary sources of vitamin B12 are animal foods including meat, fish, poultry, eggs, cheese, and milk, as vitamin B12 is not naturally present in plant foods. 1, 2
Animal-Based Sources of Vitamin B12
- Meat and Poultry: Beef, lamb, pork, chicken, and turkey are excellent sources of vitamin B12 1
- Fish and Shellfish: All types of fish and shellfish contain significant amounts of vitamin B12 1, 3
- Dairy Products: Milk, cheese, and other dairy foods provide bioavailable vitamin B12 1, 3
- Eggs: Though absorption is lower (less than 9%) compared to other animal sources, eggs still contribute to vitamin B12 intake 3
Bioavailability of Vitamin B12 from Animal Sources
The bioavailability of vitamin B12 varies by food source:
- Fish meat: approximately 42% bioavailable
- Sheep meat: 56-89% bioavailable
- Chicken meat: 61-66% bioavailable
- Eggs: less than 9% bioavailable 3
Plant-Based Sources
Vitamin B12 is generally not present in plant foods with a few exceptions:
- Certain Algae: Some dried green and purple lavers (nori) contain substantial amounts of vitamin B12 3, 4
- Fortified Foods: Fortified breakfast cereals, plant-based milk alternatives, and nutritional yeast are valuable sources for vegetarians and vegans 3, 5
Important Considerations for Special Populations
Vegetarians and Vegans
People following vegetarian or vegan diets must be particularly vigilant about vitamin B12 intake:
- Vegans require vitamin B12-fortified foods or supplements as no reliable plant sources exist 5
- Regular assessment of vitamin B12 status is recommended for those following vegetarian or vegan diets 5
- Pregnant and lactating vegetarian/vegan women must ensure adequate vitamin B12 intake for their developing babies 5
Elderly Individuals
Older adults may have decreased absorption capacity and are at higher risk of vitamin B12 deficiency:
- Fortified breakfast cereals can be particularly valuable for elderly people 3
- Atrophic gastritis, common in older adults, can reduce vitamin B12 absorption 6
Clinical Relevance
Vitamin B12 deficiency can lead to serious health consequences:
- Pernicious anemia and neurological deterioration 1, 7
- Irreversible damage to the nerves of the spinal cord if left untreated 7
- Increased risk of frailty in older adults 1
For those unable to obtain sufficient vitamin B12 from diet alone, supplementation may be necessary. The recommended daily intake for adults is 4-7 μg/day, with higher amounts needed for pregnant and lactating women (4 μg daily) 8, 7.
It's important to note that certain medications (such as metformin and antacids) and conditions (malabsorption syndromes, gastrointestinal surgery) can interfere with vitamin B12 absorption, potentially necessitating supplementation even when dietary intake appears adequate 6.