Vitamin B12 Absorption from Eggs

Abstract

The absorption of radiocyanocobalamin incorporated into meat protein in vivo has been studied in normal subjects after ingestion of physiologic doses of vitamin B12 (1). The assimilation of the vitamin equaled or surpassed that observed in controls who ingested comparable amounts of labeled crystalline B12 (2). In contrast, the absorption by normal volunteers of physiologic doses of 6 7 C~ B12 incorporated into eggs by injection into hens in vivo was rather poor when the eggs were in the form of eggnog (3) or scrambled (cooked) (4). The great difference between the assimilation of B,, from meat and from eggs is unknown. One explanation may be the differences in the technique for labeling the B12-containing food (1,3,4).Because the absorption of vitamin B12 from eggnog was slightly superior to that from scrambled eggs a second possibility should also be considered, namely, that the form in which eggs are prepared may influence the absorption of vitamin B12. A study based on this possibility is described in the following report.Materials and Methods. The subjects of this study were 18 healthy volunteers who had gastric acid present as determined by tubeless gastric analysis in 15 and with gastric intubation after betazole hydrochloride stimulation in 3. All subjects had normal serum vitamin B12 concentrations ranging from 200 to 700 pg/ml and normal absorption of aqueous crystalline 57C0 B12. They were served comparable portions of 57C0 B12 eggs cooked in three ways-scrambled, boiled, or fried-and similar portions of aqueous crystalline 57c0 B12. The method for obtaining the 57C0 B12 eggs is described in detail elsewhere (4). The amount of radio-B12 absorbed after ingestion of each of the egg mixtures and of the crystalline 57C0 B12 was measured by stool and urinary excretion tests and 8-hr plasma absorption determina-tions of radioactivity (5-7) as earlier described (4). These values were then compared.The scrambled eggs were prepared two ways, with whole eggs and with yolks only, because most of the vitamin B12 content of eggs is in the latter (8,9). The preparation of both mixtures was identical. The uniformity of the two mixtures was ascertained; the details have been published elsewhere (4).The scrambled egg mixtures contained 0.4-0.5 pCi of 5 7 C~ and 0.56 pg of vitamin B12 for the scrambled whole eggs and 0.5 pg for the yolks. The aqueous crystalline 57C0 B12 contained 0.56 pg vitamin B12 and 0.5 pCi of 5 7 C~. The allotted amount of vitamin B,, was present in 45-56 g of scrambled whole eggs and in 15 g of yolks as determined by Euglena gracilis assay (4, 10). The equal portions of labeled eggs were individually packaged in cellophane bags and stored at -20" until served. Reheating in a microwave oven for 30 sec had no deleterious effect on the vitamin B12 content.The boiled and fried eggs were prepared so that the whites were coagulated and the yolks were still mainly liquid. They were served with a piece of toast and a cup of coffee for breakfast after an overnight fast as were the portions of scrambled wh...

Systematic Review on Daily Vitamin B12 Losses and Bioavailability for Deriving Recommendations on Vitamin B12 Intake with the Factorial Approach

“…Furthermore, we extracted the absolute amount of vitamin B12 that was absorbed. In case this latter estimate was not reported, it was calculated as percent absorbed * ingested dose [9,27,28,29]. …”

“…Currently, the bioavailability of vitamin B12 is generally assumed to be 40 or 50% for healthy adults with normal gastrointestinal functioning [2,4,5,6,7]. This assumption is based on the absorption of labeled vitamin B12 from a few food products, including mutton and chicken meat, rainbow trout, eggs or fortified foods [8,9,10,11,12]. …”

Older Men and Women Efficiently Absorb Vitamin B-12 from Milk and Fortified Bread

“…These percentages compare well with the reported absorbability of vitamin B-12 from meat. Using similar whole body counting or stool counting techniques, 65% is absorbed from mutton, 60% is absorbed from chicken, 39% is absorbed from trout and 24 -36% is absorbed from eggs (Doscherholmen et al 1975(Doscherholmen et al , 1978(Doscherholmen et al and 1981. Our results of high body retention of an extrinsic B-12 label from milk and fortified bread are not surprising given the recent report by Tucker et al (2000), which showed stronger associations between serum vitamin B-12 and intake of vitamin B-12 (by quintiles) from milk and fortified cereal than from other food products in the Framingham Offspring Study.…”

“…In the 1999 Recommended Dietary Allowance report, it was assumed that 50% of dietary vitamin B-12 can be absorbed by healthy adults; however, it was noted that data on vitamin B-12 absorption from specific foods are scanty, and indeed, absorption has been tested only from mutton, eggs, chicken, liver and trout (Doscherholmen et al 1975and 1981, Heysell et al 1966. Nothing is directly known of vitamin B-12 bioavailability from dairy products or from fortified grain products, although a recent epidemiologic study on the Framingham offspring suggested that vitamin B-12 in milk and fortified breakfast cereal may be better absorbed than vitamin B-12 from other food sources (Tucker et al 2000) In the present study, we directly measured vitamin B-12 absorption from water, milk and fortified bread in adult subjects by using extrinsically ( 58 Co) labeled vitamin B-12 and a whole body gamma-ray counter/spectrophotometer.…”

Yolk of the Century Egg (Pidan) Contains a Readily Digestible Form of Free Vitamin B₁₂

“…Thus, foods derived from animals (meat, milk, eggs, fish, and shellfish) are considered to be the major dietary sources of B12 (2). Raw and boiled whole chicken eggs contain 0.9 mg of B12 per 100 g wet weight of the edible portion (3) and most of the B12 is located in the egg yolk (4). The reported average bioavailable levels of B12 in scrambled egg yolks, scrambled whole eggs, boiled eggs, and fried eggs are 8.2%, 3.7%, 8.9%, and 9.2%, respectively (3).…”