Thiamine hides in whole grains, legumes and fortified cereal at levels that meet the RDA with room to spare, and the deficiency risk list runs through alcohol use disorder and bariatric surgery, not what's on the plate.
Vegan Brief·Evidence last reviewed August 22, 2026
This is a summary of the cited evidence, not medical advice.
Black beans, 1/2 cup0.4 mg thiamine (33% of the DV)
RDA, adults1.1-1.2 mg/day
Main deficiency causeAlcohol use disorder, not diet
01
The short version
Thiamine, also called vitamin B1, keeps cells converting food into usable energy. It has a short half-life, so the body needs a steady supply rather than a stockpile.
Primary source 01 / 03
This vitamin plays a critical role in energy metabolism and, therefore, in the growth, development, and function of cells.
The RDA is 1.2 mg a day for men and 1.1 mg for women. Whole grains sit at the center of the federal food list, alongside legumes and fortified cereal, which is exactly what a plant-based plate tends to be built from.
02
Grains and beans do the work
Fortified breakfast cereal can supply the full Daily Value in one bowl. Black beans provide a third of it in half a cup, and whole wheat macaroni, brown rice, sunflower seeds and oatmeal each add smaller but genuine amounts. White rice loses most of its thiamine in milling unless it is enriched, which is worth checking on a label.
Primary source 02 / 03
Food sources of thiamin include whole grains, meat, and fish.
The deficiency disease is beriberi, and it is genuinely rare in a developed country with a varied diet. Where it shows up, the cause is almost never a food group being missing.
Primary source 03 / 03
In highly industrialized countries, chronic alcohol use disorders appear to be the most common cause of thiamin deficiency.
NIH's other named risk groups are older adults, people with HIV, people with diabetes and people who have had bariatric surgery. None of that is diet-type specific, and none of it points to routine supplementation for someone eating whole grains and legumes regularly.
Vitamin B6 on a vegan dietVitamin B6 turns up in chickpeas, potatoes and bananas in amounts that rival or beat meat, and the federal government's own list of at-risk groups never once mentions diet type.
Niacin (B3) on a vegan dietNiacin comes from brown rice, peanuts and fortified grains directly, and the body has a second route: it converts spare tryptophan from any protein, plant or animal, into niacin on its own.
Pantothenic acid (B5) on a vegan dietPantothenic acid is in almost everything on a plate, plant or animal, and the deficiency record is so thin that the only confirmed human cases came from deliberate starvation experiments.
Frequently asked
Can vegans get enough thiamine from food alone?
Yes. Whole grains, legumes and fortified cereal are the main food sources, and they line up closely with a typical plant-based plate. Fortified cereal alone can supply the full Daily Value.
What causes thiamine deficiency if diet isn't usually the cause?
NIH's fact sheet points to chronic alcohol use disorder as the leading cause in industrialized countries, along with older age, HIV, diabetes and bariatric surgery. None of these are tied to eating plant-based.
The primary sources
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