Eggs As a Source of Bioavailable Vitamin B12
Obesity and Metabolism Research Unit
2009 Annual Report
1a.Objectives (from AD-416)
The objective of the research is to determine the bioavailability of vitamin B12 from chicken eggs. The term bioavailability refers to the percentage of a nutrient, in this case vitamin B12, within a food that is actually absorbed into the body during the digestive process. This is contrasted with the percentage of the nutrient that passes through the digestive tract and is excreted without being absorbed by the body. The hypothesis to be tested is that a high percentage of the vitamin B12 in egg is bioavailable, thus indicating that eggs are a good source of dietary vitamin B12.
1b.Approach (from AD-416)
Egg enriched with vitamin B12 labeled with a radioactive tag (carbon 14) will be cooked and fed to healthy human volunteers. The amount of the carbon-14 labeled vitamin B12 that is excreted in the stook (unabsorbed vitamin B12) will be compared with the amount of carbon-14 labeled vitamin B12 that appears in the blood and urine (absorbed vitamin B12). From these measurements, the fraction or percentage of vitamin B12 absorbed (bioavailability) will be calculated. The study will be carried out in 10 human volunteers and the mean bioavailability of vitamin B12 from egg will be calculated and reported. Documents Trust with the American Egg Board. Log 32483.
Eggs labeled in vivo with 14C-vitamin B12 were obtained by feeding the labeled vitamin to hens. The eggs were scrambled and doses containing approximately 2 ug of the vitamin were fed to 10 human subjects. Plasma samples were collected hourly for the first 12 hours then every 24 h for 9 days. Urine and feces were collected throughout. Analysis of plasma 14C shows that the vitamin was absorbed, with a peak around 10 hours after consumption. Large amounts of radioactivity appeared in urine during the first 48 hours. Analysis of 14C in the fecal samples is in progress and required to quantify the bioavailability of the vitamin. The project will be completed in FY 2010.