Sources
Thiamine occurs in all natural foods, although in smell amounts.Vitamin B1 main sources are: seafood, green peas, spinach, pork, beef, beef liver, wheat bran, sunflower seeds, peanuts, egg-yolk, beans, soybeans, whole-grain, enriched cereals, bread, and legumes.

Vitamin B1 vitamins are also available supplements, usually compounded with B-complex vitamins or in multivitamin supplements.

Deficiency of vitamin B1
Deficiency of Vitamin B1 will result in beriberi. Symptoms include swelling, tingling or burning sensation in the hands and feet, confusion, difficulty breathing due to fluid in the lungs, and uncontrolled eye movements (termed as nystagmus).

Wernicke-Korsakoff syndrome is a brain disorder caused by thiamine deficiency. It involves neural damage in the central and peripheral nervous systems and is generally caused by undernourishment accompanied by regular alcohol consumption. Korsakoff syndrome is characterized by memory loss. High doses of thiamine can slightly improve faulty muscle coordination, but rarely improves the memory loss.

Cataracts - people with plenty of protein and vitamins B1 in their diet are less likely to develop cataracts.

Heart failure - Thiamine deficiency may contribute to the development of congestive heart failure (CHF). Eating a balanced diet, including thiamine, and avoiding stuff that depletes this vitamin is essential, particularly for those at the initial stages of CHF.

Alzheimer's disease - Although not fully proven, but assumed that thiamine deficiency can lead to this disease because of the effect it has on the brain and the symptoms that people develop when deficient in thiamine. Deficiency may also lead to extreme fatigue, irritability, constipation, edema (fluid retention) and an enlarged liver.

Symptoms of Vitamin B1 deficiency

Poor memory, Poor coordination of body parts, Weak and sore muscles, Changes in heart beat, Mood swings accompanied by irritability, Stressful breathing, Loss of appetite, Gastrointestinal disturbances, Tingling sensation in feet, Nervousness, Numbness of the hands and feet, Severe weight loss. In extreme cases, it can even lead to wasting and death.