Vitamin B1 (Thiamin): Reference and Dietary Sources

In this article, we identified Dietary sources of B vitamins (specifically, for Vitamin B1, or Thiamin, these are grains, meat, and fish), provided reference values, and described testing methods, benefits, and toxicity. Nutri-IQ recommends to Wellness Practitioners to check nutritional status with our Nutritional Balance Assessment Tool in order to holistically recognize and close nutritional gaps.


In this article, we describe:

  • the major purposes of this specific nutrient in the human body, 
  • its experimentally confirmed health uses, 
  • conventional ways to estimate nutrient status,
  • nutrient’s toxicities and deficiencies,
  • experimentally confirmed and approved levels of the nutrient intake for different demographics,
  • dietary sources of the nutrient.


Thiamin (Vitamin B1) is one of B complex vitamins. It naturally present in some foods, added to some food products, and available as a dietary supplement. This vitamin plays a critical role in energy metabolism and, therefore, in the growth, development, and function of cells.

B Complex vitamins are all water soluble and are not stored very well in the body. Thus, they are needed daily through diet or supplement to support their many functions. Deficiencies of one or more of the B vitamins may occur fairly easily, especially during times of fasting or dieting for weight loss or with diets that include substantial amounts of refined and processed food, sugar, or alcohol.

B complex vitamins are fairly easily digested from food or supplements and then absorbed into the blood, mainly from the small intestine. When the amount of Bs taken exceeds the body’s needs, the excess is easily excreted in the urine, giving it a dark yellow color. 

About 80% of the approximately 25–30 mg of thiamin in the adult human body is in the form of thiamin diphosphate (TDP; also known as thiamin pyrophosphate), the main metabolically active form of thiamin. Thiamin status is often measured indirectly by assaying the activity of the transketolase enzyme, which depends on TDP, in erythrocyte hemolysates in the presence and absence of added TDP. The result, known as the “TDP effect,” reflects the extent of unsaturation of transketolase with TDP. The result is typically 0%–15% in healthy people, 15%–25% in those with marginal deficiency, and higher than 25% in people with deficiency.

A very neat tool Heart Disease Risk Analysis estimates risk of cardiovascular disease by assessment of levels of Vitamins A, D, E, C, B1, B12, Folate, Magnesium, Potassium, Zinc, and Selenium. One may want to take supplements or change the diet to bring the body back to homeostasis, if it is not too late.

Thiamin toxicity is rare as the body exerts excess amount with urine. People with alcohol dependence; older adults; patients with HIV/AIDS; people with diabetes; and those who underwent geriatric surgery are at risk for thiamin inadequate status. Thiamin deficiency can be a contributing factor to heart failure and Alzheimer disease.

Thiamin might play a role in:

  • Wernicke-Korsakoff encephalopathy syndrome,
  • Diabetes  decreasing glucose levels in patients with type 2 diabetes or impaired glucose tolerance,
  • Heart failure improving net change in left ventricular ejection fraction,
  • and Alzheimer’s disease as thiamin deficiency might play a role in the development of it.

Assessment of nutritional balance brings cost-effective immediate answers when your client:

  • Feels stressed, tired, depressed
  • Takes prescription meds but cannot alleviate symptoms
  • Wants to achieve optimal wellness, prevent chronic disease, and manage aging process

Nutri-IQis a unique tool that helps Wellness Professionals to easy and conveniently identify clients’ nutritional gaps as possible causes for clients’ complaints.

Recommended Dietary Allowances (RDAs) for Thiamin 

Birth to 6 months*0.2 mg0.2 mg  
7–12 months*0.3 mg0.3 mg  
1–3 years0.5 mg0.5 mg  
4–8 years0.6 mg0.6 mg  
9–13 years0.9 mg0.9 mg  
14–18 years1.2 mg1.0 mg1.4 mg1.4 mg
19-50 years1.2 mg1.1 mg1.4 mg1.4 mg
51+ years1.2 mg1.1 mg 

Food Sources of Vitamin B1

Food sources of thiamin include whole grains, meat, and fish. Breads, cereals, and infant formulas in the United States and many other countries are fortified with thiamin. The most common sources of thiamin in the U.S. diet are cereals and bread. Pork is another major source of the vitamin. Dairy products and most fruits contain little thiamin. About half of the thiamin in the U.S. diet comes from foods that naturally contain thiamin; the remainder comes from foods to which thiamin has been added.

Heating foods containing thiamin can reduce their thiamin content. For example, bread has 20%–30% less thiamin than its raw ingredients, and pasteurization reduces thiamin content (which is very small to begin with) in milk by up to 20%. Because thiamin dissolves in water, a significant amount of the vitamin is lost when cooking water is thrown out. Processing also alters thiamin levels in foods; for example, unless white rice is enriched with thiamin, it has one tenth the amount of thiamin in unenriched brown rice.

Some studies do show that thiamin absorption increases when intakes are low.

Selected Food Sources of Thiamin

(mg) per
Fortified white parboiled rice, long grain, ½ cup1.4117
Fortified breakfast cereals, 1 serving1.5100
Enriched Egg noodles, cooked, 1 cup0.542
Broiled pork chop, bone-in, 3 ounces0.433
Cooked trout, 3 ounces0.433
Black beans, boiled, ½ cup0.433
English muffin, 10.325
Blue mussels, cooked, 3 ounces0.325
Bluefin tuna, 3 ounces0.217
Macaroni, whole wheat, cooked, 1 cup0.217
Acorn squash, baked, ½ cup0.217
Brown rice, cooked, ½ cup0.18
Whole wheat bread, 1 slice0.18
Orange juice from concentrate, 1 cup0.18
Toasted sunflower seeds, 1 ounce0.18
Beef steak, trimmed and braised, 3 ounces0.18
Plain yogurt, low fat, 1 cup0.18
Oatmeal, cooked with water, ½ cup0.18
Boiled yellow corn, 1 ear0.18
2% Milk, 1 cup0.18
Cooked barley, 1 cup0.18
Cheddar cheese, 1½ ounces00
Roasted chicken, 3 ounces00
Sliced Apple, 1 cup00
  • *DV = Daily Value.
  • The DV for thiamin used here 2 is 1.2 mg for adults and children age 4 years and older.
  • Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.


  1. Elson Haas. “Staying Healthy with Nutrition”
  2. U.S. Department of Health & Human Services:

Comments are closed.

Translate »