Michael S. Donaldson: Metabolic vitamin B12 status on a mostly raw vegan diet with follow-up using tablets, nutritional yeast, or probiotic supplements. (angolul) Annals of Nutrition & Metabolism, XLIV. évf. 5–6. sz. (2000) 229–234. o. doi Idézet a cikkből: „The cobalamin in Red Star nutritional yeast is due to fortification
and does not occur naturally in the yeast.”
Christine VanDoren: A Guide to Vitamin B: Benefits and What Foods to Eat. themanual.com. (angolul) Portland, New York, Chicago, Detroit, Los Angeles, Toronto: Digital Trends Media Group (2022. június 12.) (Hozzáférés: 2022. október 8.) „17. Nutritional Yeast. Unfortified yeast already contains natural B vitamins, minus B12. If you purchase fortified nutritional yeast, you can benefit from synthetic B vitamins, including B12.”