Vitamin B1

What Is Thiamine (Vitamin B1)?

Thiamine was the first B vitamin to be identified, which is why it is B1. It dissolves in water, and the body keeps only a small store of it, about half in the skeletal muscles. Half of that store is used up in 9 to 18 days, so thiamine has to come in steadily from food or supplements.

What Thiamine Does

Inside cells, thiamine becomes thiamine diphosphate (also called thiamine pyrophosphate), a helper for the enzymes that break down glucose and some amino acids. One of them moves the products of glucose into the cycle that makes most of a cell's energy; another builds the sugar the body uses for DNA and RNA.

The brain relies heavily on glucose for energy, so the brain and nerves are among the first to suffer when thiamine runs out. That is why the signs of deficiency are mostly confusion, memory loss, numbness and weakness rather than anything visible on the skin.

Thiamine in Pork, Beef, and Chicken

Among meats, pork stands alone. A cooked pork chop has 0.644 mg of thiamine per 100 g in the Caltide food library, steak 0.071 mg and chicken breast 0.086 mg. Gram for gram, pork has about nine times the thiamine of beef, and one 90 g chop gives about half of what an adult needs a day.

Why White Bread Is a Source of Thiamine

Milling white flour removes the bran and germ, and most of the grain's thiamine with them. In the United States and several other countries, white flour is then enriched: thiamine is added back, with riboflavin, niacin, folic acid and iron. That is why a bagel has 0.57 mg of thiamine per 100 g and bread 0.51 mg, more than oats.

Enrichment is also how riboflavin (B2) and niacin (B3) reach many diets, and why beriberi, once common where people lived on polished white rice, is now rare wherever enriched grains are eaten.

Who Is Most Likely to Be Low in Thiamine

Alcohol is the main cause of thiamine deficiency in richer countries. Heavy drinking lowers intake, blocks absorption in the gut and raises losses in urine. The result can be Wernicke encephalopathy (confusion, unsteady walking and eye movement problems) and later Korsakoff syndrome, a lasting loss of memory.

Other groups at higher risk are older adults, people with diabetes or HIV, and people who have had weight-loss (bariatric) surgery, which reduces how much food is eaten and absorbed.

Common Thiamine Mistakes

Counting on red meat. Beef is rich in many nutrients, but thiamine is not one of them. Pork, seeds, beans and grains are where it is.

Pouring the water away. Thiamine leaks into cooking water and breaks down with long heating. Steaming, or using the water in a sauce or soup, keeps more of it.

Thinking the body has reserves. Unlike vitamin A or B12, thiamine is not stored for months. A few weeks of eating very little, as in heavy drinking or after surgery, is enough to run short.