Ovalbumin and egg yolks, mixed separately in vitro with radiocyanocobalamin (57 Co-vitamin B12), were served to normal volunteers in a cooked form. Ovalbumin, and to a lesser degree, egg yolks were observed to inhibit vitamin B12 absorption. This observation explains the rather poor assimilation of vitamin B12 from eggs labelled in vivo with 57 Co-vitamin B12.

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...

Chicken meat labeled in vivo with radio-B12 was ingested by normal volunteers. The absorption, measured by the fecal excretion method, was similar to that reported for crystalline radiocyanocobalamin and for mutton, but exceeded that from eggs. Parenteral injection of 1000 microgram of nonlabeled vitamin B12 did not interfere with the absorption of the radio-B12 from the meat. The urinary radioactivities, which were as low as those after oral administration of radioactive hydroxocobalamin and vitamin B12 coenzyme, suggested that the radio-B12 was present in meat in coenzyme form or was converted into the stable hydroxoform during the process of cooking and digestion. Patients with pernicious anemia showed insignificant urinary radioactivities in a standardized urinary excretion test using chicken meat whereas subjects with simple gastric achlorhydria and partial gastrectomy had subnormal values although their absorption of crystalline radiocyanocobalamin was normal. The subnormal serum vitamin B12 concentration seen in these latter subjects may, therefore, be due to impaired assimilation of vitamin B12 from food.

Serum vitamin B12 (B12), maximal gastric acid output (MAO), and B12 absorption were determined in 82 subjects, age 32 to 85 years, who had normal absorption of radiocyanocobalamin. In 46 of the patients the gastric intrinsic factor (IF) was also measured. Serum B12 concentration and MAO varied widely in all age groups from abnormally low to definitely normal. The mean values for serum B12 and MAO, however, declined very similarly with advancing age owing to an increased incidence of low values for these two measurerment in the aged. There was no significant fall in the mean B12 absorption or IF secretion as a function of old age. Achlorhydric and hypochlorhydric patients invariably had lower mean serum B12 concentrations than those with adequate MAO. Conversely, patients with normal MAO all had normal serum B12 levels. Serum B12 concentration, although correlating with both MAO and IF secretion, showed a closer relationship to the former than to the latter. These findings suggest that the stomach, aside from producing the IF, plays an important role in maintaining a normal serum B12 concentration.

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