Thiamine or Vitamin B1 is a vitamin involved in the peripheral nervous system. Animals do not synthesize thiamine and thus must obtain it from dietary sources. It is plentiful in plants, but is also found in bacteria and fungi. It is also found in the muscle tissue of animals, particularly pork. Among the best sources are oatmeal, flax, sunflower seeds, brown rice, whole grain rye, asparagus, kale, cauliflower, potatoes, oranges, liver meat and eggs. Lack of thiamine in the diet can lead to beriberi, which is rare, or more commonly Korsakoff's syndrome and Wernicke's encepalopathy, which affect the extremely malnourished and alcoholics.
Some methods of food processing remove or destroy thiamine. Notable among these is polishing rice (the thiamine is in the brown husk) and sulfites used as preservatives.
Some rare genetic diseases affect the body's ability to transport thiamine.
Because of the prevalence of thiamine deficiency in alcoholics, proposals have been put forward to add thiamine supplements to alcohol. However, these efforts have been opposed by labelling laws that prevent alcohol products from either leaving out ingredients or listing ingredients that make it look like it may have health benefits.