The term B-complex usually refers to a group of vitamins that includes vitamins B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenate), B6 (pyridoxine), B12 (cyancobalamine) and folate.
Vitamins B1 and B2 are critical for energy production in the cells. Overt deficiencies of vitamins B1 and B2 are known to cause special forms of dermatitis (along with many other problems). Mild deficiencies usually go unnoticed but still may produce some degree of skin damage. People who consume a diet based mainly on processed grains are particularly prone to developing such deficiencies. A few decades ago, the US government mandated that food manufacturers should add B1 and B2 to foods made of white flour. This markedly reduced the incidence of serious B1 and B2 deficiency in the US. Many other governments did the same. Still, mild deficiency (but enough to have some negative effects on the skin and some other organs) does occur, particularly in those who base their diets mainly on processes grains and potatoes. Balancing the diet or modest supplementation is helpful, while excessively high doses of B1 or B2 seem to provide little or no additional benefit.
B12 (cyancobalamine) is essential for a variety of synthetic processes in the cells. The deficiency of this vitamin is particularly detrimental to neurons and rapidly dividing cells, including skin cells. Mild B12 deficiency often goes undiagnosed, producing no overt symptoms. Sometimes, depression may be the only symptom of B12 deficiency. B12 is unique among vitamins in that it is found almost exclusively in foods of animal origin such as meat, poultry, fish, eggs or dairy products. Contrary to some popular beliefs, no active form of B12 is found in algae such as spirulina or fermented soy products. Thus, strict vegetarians are at risk of vitamin B12 deficiency. Healthy young and middle-aged people consuming a balanced non-vegetarian diet are usually not at risk for vitamin B12 deficiency. The absorption of vitamin B12 from food requires intrinsic factor, a protein produced by the stomach. Some older people do not produce enough intrinsic factor due to the atrophy of stomach glands. Certain autoimmune and digestive conditions may also lead to poor absorption of B12. In people whose B12 deficiency is due to poor absorption, neither dietary changes nor oral supplements correct the problem. In such cases, B12 has to be administered as a nasal spray or injected. In contrast to many other vitamins, B12 doses higher than what's required to prevent deficiency may provide extra health benefits.
Folate participates in many of the same biochemical cascades as B12. Just as B12, it is particularly important for rapidly dividing cells, including skin cells. Mild folate deficiency often goes unnoticed. Sometimes, depression may be the only symptom of folate deficiency. Vegetables are the most abundant sources of folate, particularly green leafy vegetables and beans. The only food from animal source rich in folate is liver. Folate can be destroyed during cooking and prolonged storage. The best way to obtain enough folate from the diet is to eat generous amounts of fresh or slightly cooked vegetables. Diet lacking vegetables and fruits puts you at risk for folate deficiency. Certain prescription and over-the-counter drugs interfere with absorption of folate and may cause deficiency.
Vitamin A deficiency causes skin to become dry, fragile and prone to wrinkles. If a person is vitamin A deficient, no skin treatment will work properly. Serious vitamin A deficiency is rather common in the third world and causes a variety of serious health problems. In developed countries, a milder forms of vitamin A deficiency predominate. The main sources of vitamin A are foods of animal origin, particularly eggs, organ meats and whole milk dairy products. Unfortunately, these foods tend to be high in saturated fat and cholesterol. Some plants, such as carrots or broccoli, supply carotenoids which can be converted into vitamin A by the body. Diets lacking foods of animal origin and carotenoid-rich plants may lead to vitamin A deficiency. On the other hand, excessive vitamin A intake (from taking high dose supplements or eating large amounts of liver) may cause serious toxicity and should be avoided.