How much b12 is in an egg
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Vitamin B12 Content in Eggs
Overview of Vitamin B12 in Eggs
Eggs are a notable source of vitamin B12, an essential nutrient crucial for various bodily functions, including red blood cell formation and neurological health. The vitamin B12 content in eggs can vary based on several factors, including the diet of the laying hens and the type of egg.
Vitamin B12 Concentration in Egg Yolks
Research indicates that the vitamin B12 content in egg yolks can range significantly. For instance, one study found that egg yolks contain between 1.3 and 2.6 micrograms of vitamin B12 per 100 grams of yolk, depending on the dietary intake of the hens1. Another study reported that commercially available century eggs (pidan) contain approximately 1.9 micrograms of vitamin B12 per 100 grams of yolk2.
Impact of Hen Diet on Vitamin B12 Levels
The diet of laying hens plays a crucial role in determining the vitamin B12 content of eggs. Hens fed diets supplemented with higher levels of vitamin B12 produce eggs with higher concentrations of the vitamin. For example, hens on a diet containing 8.0 micrograms/kg of vitamin B12 produced eggs with optimal vitamin B12 levels, supporting maximum egg production and hatchability1. Additionally, the transfer efficiency of vitamin B12 from the diet to the egg is about 43%, indicating that dietary fortification is an effective method to enhance the vitamin B12 content in eggs6.
Bioavailability of Vitamin B12 from Eggs
The bioavailability of vitamin B12 from eggs is an important consideration, especially for individuals relying on eggs as a primary source of this nutrient. Studies using labeled vitamin B12 have shown that the bioavailability of vitamin B12 from eggs can range from 13.2% to 57.7%, with an average of 30.2%4. Interestingly, the bioavailability decreases as the total amount of vitamin B12 in the egg increases, reflecting the physiological limits of vitamin B12 absorption8.
Storage and Vitamin B12 Stability
The stability of vitamin B12 in eggs during storage is also a concern. Research has shown that eggs stored for extended periods can lose a significant portion of their vitamin B12 content. For instance, eggs stored for twelve months lost about 27% of their vitamin B123. This highlights the importance of consuming fresh eggs to maximize vitamin B12 intake.
Conclusion
Eggs are a valuable source of vitamin B12, with the content varying based on the diet of the hens and the type of egg. The vitamin B12 content in egg yolks typically ranges from 1.3 to 2.6 micrograms per 100 grams, and the bioavailability of this vitamin from eggs is relatively high, though it decreases with higher vitamin B12 content. To ensure optimal vitamin B12 intake, it is advisable to consume fresh eggs and consider the dietary supplementation of hens.
Sources and full results
Most relevant research papers on this topic
Vitamin profiles of eggs as indicators of nutritional status in the laying hen: vitamin B12 study.
Egg yolk vitamin B12 concentrations rapidly respond to dietary changes in vitamin B12 levels, indicating the laying hen's vitamin B12 status.
Non-RCT
Animal StudyYolk of the Century Egg (Pidan) Contains a Readily Digestible Form of Free Vitamin B12.
The century egg yolk contains a readily digestible form of free vitamin B12, with 52% formed during gastric digestion, while no free vitamin B12 was detected in the egg white.
The Vitamin B12 Content of Fresh and Stored Shell Eggs
Shell eggs stored for 12 months lose vitamin B12, but not choline or biotin, indicating nutrient loss during cold storage.
14C-Cobalamin Absorption from Endogenously Labeled Chicken Eggs Assessed in Humans Using Accelerator Mass Spectrometry
Chicken eggs enriched with 14C-B12 show high bioavailability and provide 20% of the average adult daily B12 requirement, making them a good source of vitamin B12.
Non-RCT
Very Rigorous JournalA Comparison of Production Performance, Egg Quality, and Cecal Microbiota in Laying Hens Receiving Graded Levels of Vitamin B12
Dietary supplementation with 100 or 400 g/kg of vitamin B12 improves eggshell quality, metabolism, and gut health in laying hens, without significantly affecting production performance.
RCTAnimal Study