VITAMIN B1 (Thiamin)

Vitamin B1 is a water-soluble vitamin and a member of the B complex. Thiamin is essential for the energy production from carbohydrate and fat. The active form (coenzyme), thiamin pyrophosphate, serves as an enzyme helper in the breakdown of glucose (blood sugar) and in the Kreb’s cycle, the central energy-yielding pathway of the body. Thiamin is also required in the PENTOSE phosphate pathway, a sequence of enzymes that converts glucose to the smaller sugars and energy and liberates hydrogen atoms for biosynthesis. These energy-yielding pathways are critical for normal function of peripheral nerves, skeletal muscle and heart muscle, among others.

Severe thiamin deficiency causes BERIBERI. Though rare in the United States, this disease occurs all too frequently in malnourished populations in developing nations who rely on white flour and white rice that are not enriched with thiamin. When beriberi affects primarily the nervous system, it is called “dry”‘ beriberi. Degeneration of insulation (myelin sheath) around nerves of the central nervous system occurs, leading to nerve irritation, pain, numbness and, in extreme cases, paralysis and muscle wasting. Beriberi produces a staggering gait, numbness of legs and retarded growth. Mental symptoms such as disorientation, hallucinations and depression occur as well. These symptoms usually respond to thiamin supplementation, and thiamin is also important in treating polyneuritis (nerve inflammation) associated with pregnancy and ALCOHOLISM. Thiamin deficiency can masquerade as SENILITY. Alcoholics may exhibit the mental confusion typical of beriberi. Thiamin supplementation alone does not seem to affect mental processes and memory if thiamin deficiency is not involved.

An alternate course results in “wet” beriberi, seen as problems with the heart and circulation (abnormal heart rhythm, low blood pressure, elevated levels of blood lactic acid, edema [water retention] of the legs, heart muscle weakness and, ultimately, heart failure). This form of beriberi usually responds quickly and dramatically to thiamin supplementation.


The RECOMMENDED DIETARY ALLOWANCE (RDA) for thiamin for men is 1.5 mg and for non-pregnant women 1.1 mg, and based upon an allowance of 0.5 mg per 1,000 calories consumed daily. The requirement increases with pregnancy and lactation. Because of the prevalence of alcoholism in the United States, thiamin deficiency is not uncommon. Symptoms of moderate deficiency include FATIGUE, apathy, nausea, irritability, depression, slowed wound healing, loss of appetite, indigestion and constipation. Moderate deficiency symptoms can be caused by crash dieting, alcohol abuse or liver disease. People relying on highly processed foods are at risk, for example, elderly people; low-income persons; teenagers relying on sweets, soft drinks and low nutrient foods; and pregnant women. Consuming large amounts of sugar as found in sweets and soft drinks increases the need for thiamin. Also at risk are patients on kidney dialysis or who are sustained for long periods by intravenous nutrients.

Factors That Increase Thiamin Requirements

  • Alcohol. Thiamin assimilation is blocked by alcohol consumption. Alcohol use also injures the small intestine and reduces its ability to absorb thiamin. Alcohol decreases thiamin conversion to thiamin pyrophosphate and depletes tissues of this coenzyme.
  • Thiamin antagonists. Raw SEAFOOD, such as shrimp, carp, herring, mussels and clams, and YEAST contain thiaminase, an enzyme that degrades thiamin. Eating a large amount of live yeast can reduce thiamin ABSORPTION. Cooking seafood destroys this enzyme.
  • Heat-stable anti-thiamin factors have been isolated from several sources. Fermented fish contain factors that limit thiamin uptake. Tea, coffee and even decaffeinated coffee reduce thiamin absorption.
  • Baking soda. Cooking with baking soda destroys thiamin.
  • Cigarette smoking. Smoking adversely affects thiamin uptake and use by tissues.
  • Medications. Antacids and barbiturates may interfere with thiamin uptake.

Foods that contain ample thiamin are wheat germ; meats (pork, beef, ham, and organ meats); nuts (pecans, peanuts, and walnuts); brewer’s yeast; fortified cereals and grain products. Thiamin is used to enrich flour, breads and cereals, a practice that has eliminated the widespread thiamin deficiency that existed prior to enrichment programs. Heating food and processing destroys this fragile vitamin. The higher the cooking temperature, the greater the loss. However, microwave cooking does not seem to increase thiamin loss. Thiamin is relatively non-toxic. Very high doses rarely lead to headaches, mental instability, irritability or weakness. Some people are allergic to thiamin injections usually due to the preservatives in the solution.

Seear, Michael, et al., “Thiamine, Riboflavin and Pyridoxine Deficiencies in a Population of Critically III Children,” Journal of Pediatrics, 121:4 (1992), pp. 533-38.