Vitamins B1 (thiamin), B2 (riboflavin), B3 (niacin), and B5 (pantothenic acid) are four essential B vitamins that the body must consume from the diet, in addition to vitamin B3, which can also be synthesized from the amino acid tryptophan.

Studies have found that a deficiency of thiamin leads to a reduction in oxidative metabolism. Biochemical consequences include a failure to produce ATP, lactic acidosis due to increased production of lactic acid, and decreased synthesis of neurotransmitters such as acetylcholine, glutamate, aspartate, and GABA.

Inadequate dietary intake of riboflavin manifests as a clinical deficiency after several months of deficiency. Symptoms include sore throat, hyperemia, edema of oral and mucous membranes, cheilosis, and may progress to loss of hair, inflammation of the skin, anemia, a swollen tongue, cataract development, malabsorption, and impaired nerve function.

Niacin deficiency was first described in 1735 and first referred to as “pellagra” (“rough skin”) in 1771. Pellagra became characterized as a “3 Ds” or “4 Ds” disease, referring to the three common symptoms (dermatitis, dementia, and diarrhea) and possibly culminating in death (the 4th D). It is mainly due to a monotonous diet (especially unprocessed corn) that leads to an insufficient intake of vitamin B3.

Since vitamin B5 is present in a variety of foods, vitamin B5 deficiency is generally rare but could be observed in severely malnourished people and animals.

Hrubša, M., Siatka, T., Nejmanová, I., Vopršalová, M., Kujovská Krčmová, L., Matoušová, K., … & Oemonom. (2022). Biological properties of vitamins of the B-complex, part 1: Vitamins B1, B2, B3, and B5. Nutrients, 14(3), 484. [Link]