Key Concepts

  • RDA: 1.2 mg/day for adult men and 1.1 mg/day for adult women
  • Excess consumption appears to be non-toxic
  • Food Sources – Enriched foods (breads, cereals), legumes, peas, seeds and nuts
  • B Complex – $0.34/day

Active Form of Thiamin (TPP)

Thiamin pyrophosphate (TPP) is the active form of thiamin in the body. The synthesis of TPP from free thiamin requires magnesium, ATP, and thiamin pyrophosphokinase (an enzyme). This is important because low magnesium levels could disrupt the formation of TPP in the body and disrupt its functions.


Thiamine has a lot of important functions in the body. These include being a co-factor necessary for energy transformation, synthesis of NADP, synthesis of DNA and RNA, and in nerve conduction. if thiamin is not present or not functioning properly, metabolism of carbohydrates and amino acids can be compromised along with cholesterol production and neurotransmitter (glutamate and GABA) synthesis.

Recommended Dietary Allowance (RDA)

The Recommended Dietary Allowance (RDA) for vitamin B1: thiamin is 1.2 mg/day for adult men and 1.1 mg/day for adult women. RDAs for other ages can be viewed here.


Mild deficiencies can occur in as little as four to five days and are characterized by fatigue, insomnia, and headaches. More pronounced deficiencies, which can occur in chronic alcoholism or in developing countries where thiamin intakes are not adequate, can cause beriberi. Dry beriberi results in peripheral neuropathy (burning feet), diminished reflexes, muscle spasms, pain, and tenderness . Wet beriberi can have cardiovascular manifestations including tachycardia (generally a heart rate over 100 bpm), cardiomegaly (enlarged heart), peripheral edema (fluid accumulation causing swelling typically in lower limbs), and congestive heart failure.

Wernicke-Korsakoff Syndrome can also be caused by a deficiency. Symptoms include ophthalmoplegia (paralysis of ocular muscles resulting in abnormal eye movement), ataxia (stance and gait abnormalities), and cognitive abnormalities (memory loss and confusion).


No tolerable upper intake level (UL) is set for thiamin. No well-established toxic effects have been observed for thiamin even in long-term, oral supplementation of nearly 200 times the RDA.

Food Sources

  • Sunflower Seeds, 1 cup – .7mg – 45%
  • Lentils, cooked, boiled, ½ cup – 0.17mg – 14%
  • Green peas (cooked, boiled – ½ cup – 0.21mg – 17%
  • Black beans, boiled, ½ cup – 0.4mg – 27%
  • Acorn squash, cubed, baked, ½ cup – 0.2 mg – 13%
  • Rice, brown, long grain, not enriched, cooked, ½ cup – 0.1 mg – 7%




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