Bioavailability of vitamin B12 in algae and other foods

In the typical diet of Western countries in general, and of Italy in particular, the most common food sources of vitamin B12 are foods of animal origin, such as meat, milk, eggs, fish and fishery products. East Asia and Southeast Asia, an important source of vitamin B12 is represented by seaweed, a characteristic ingredient of local cuisines.

For several years now, scholars have been wondering about the bioavailability of dietary vitamin B12, which in turn depends on the intestinal absorption capacity of the substance and its metabolic activity. In 1991 [1] a rather well-known study in which the supplementation of algae (nori and spirulina) in children with plasma vitamin B12 deficiency proved ineffective in correcting the values ​​of MCV (mean corpuscular volume of red blood cells). All this despite the fact that the levels of vitamin B12 in the blood had increased; on the other hand, the children who had received the supplementation of vitamin B12 from animal sources (Fish) or from specific vitamin B12 supplements, showed significant improvements in this blood index.

For what has been said, it is not enough to rely on the vitamin B12 values ​​reported in the nutritional tables; rather, it is necessary - at least in broad terms - to know which foods are in which the bioavailability of the vitamin is poor.

Since the intestinal absorption of vitamin B12 is strictly dependent on the availability of intrinsic factor (produced by the stomach), and since in physiological conditions this system becomes saturated for doses of vitamin B12 equal to about 1.5-2.0 μg per meal, higher quantities of vitamin B12 significantly decrease the bioavailability of the excess vitamin content.

According to a more recent study [2], the bioavailability of vitamin B12 in healthy adult subjects averages around:

42% for fish meat

56% –89% for sheep meat

61-66% for chicken meat

56% –89% for cooked mutton

Vitamin B12 contained in eggs appears to be poorly absorbable (<9%) when compared to that present in other animal sources.

Significant losses of vitamin B12 (~ 33%) were recorded after cooking the meat.

In the same study it is reiterated once again that:

Most of the blue-green algae (cyanobacteria such as "spirulina algae or" Klamath algae) used in food supplements contain pesudovitamin B12, which is inactive in humans. Therefore, these supplements are not suitable for supplementing food-borne vitamin B12 , as they mainly contain it in a poorly bioavailable form.

Several researches have shown, for example, that the vitamin B12 contained in the "spirulina algae and in the Klamath algae" is not bioavailable in mammals [4,5, 8]. A more recent study reinvigorates the bioavailability of vitamin B12 contained in the "Klamath algae [9]

On the other hand, it seems that other types of algae, such as nori algae, can prevent the deficiency of this vitamin in the vegan population [3]. Hypothesis confirmed by the isolation of only the active forms of vitamin B12 in dry extracts of eukaryotic microalgae (Chlorella sp. And Pleurochrysis carterae) [6, 7]. Vitamin B12 contained in the seaweed Porphyra umbilicalis was shown to be bioavailable to laboratory mice.

Sources of vitamin B12 and related bioavailability

Foods Bioavailability * Vitamin B12 content (μg / 100 g) MEAT ANIMALS Cooked Mutton 56%–89% 2.6 Cooked Chicken 61%–66% 9.4 COW MILK 65% 0.4 EGG Chicken eggs, cooked < 9% 1.3 FISHING PRODUCTS Oysters ND 46.3, 28.1 Mussels ND 15.7, 10.3 Clams ND 37.0, 52.4 FISH MEAT Skipjack tuna, dark muscle ND 158.5 Yellowfin tuna, dark muscle ND 52.9 Rainbow trout, cooked 42.0% 4.9 EDIBLE ALGAE Porphyra umbilicalis (Purple laver) ND 32.3, 77.6 Nori seaweed (Green laver) ND 63.6, 31.8 Chlorella ND 200.9–211.6 Klamath seaweed ND 100 * Intake of less than 2 μg of vitamin B12 per meal in humans

Bibliography:

[1] Dagnelie PC, van Staveren WA, van den Berg H. Vitamin B-12 from algae appears not to be bioavailable. Am J Clin Nutr. 1991 Mar; 53: 695-7. Erratum in: Am J Clin Nutr 1991 Apr; 53: 988.

[2] Watanabe F. Vitamin B12 sources and bioavailability. Exp Biol Med (Maywood). 2007 Nov; 232: 1266-74. Review.

[3] Suzuki H. Serum vitamin B12 levels in young vegans who eat brown rice. Nutr Sci Vitaminol (Tokyo). 1995 Dec; 41: 587-94.

[4] Watanabe F, Katsura H, Takenaka S, Fujita T, Abe K, Tamura Y, Nakatsuka T, Nakano Y. Pseudovitamin B12 is the predominate cobamide of an algal health food, spirulina tablets. J Agric Food Chem 47: 4736–4741, 1999.

[5] Herbert V, Drivas G. Spirulina and vitamin B12. JAMA 248: 3096–3097, 1982.

[6] Watanabe F, Takenaka S, Katsura H, Miyamoto E, Abe K, Tamura Y, Nakatsuka T, Nakano Y. Characterization of a vitamin B12 compound in the edible purple laver, Porphyra yezoensis. Biosci Biotechnol Biochem

[7] Miyamoto E, Watanabe F, Ebara S, Takenaka S, Takenaka H, ​​Yamaguchi Y, Tanaka N, Inui H, Nakano Y. Characterization of a vitamin B12 compound from unicellular coccolithophorid alga (Pleurochrysis carterae). J Agric Food Chem 49: 3486–3489, 2001

[8] Miyamoto E, Tanioka Y, Nakao T, Barla F, Inui H, Fujita T, Watanabe F, Nakano Y. Purification and characterization of a corrinoid-compound in an edible cyanobacterium Aphanizomenon flosaquae as a nutritional supplementary food.

[9] Effect of a Klamath algae product ("AFA-B12") on blood levels of vitamin B12 and homocysteine ​​in vegan subjects: a pilot study. Baroni L, Scoglio S, Benedetti S, Bonetto C, Pagliarani S, Benedetti Y, Rocchi M, Canestrari F. Int J Vitam Nutr Res. 2009 Mar; 79: 117-23.