Vitamin B1 in Food: A Practical Guide

Vitamin B1 (i.e. thiamine) is an essential nutrient that enables you to use the energy from the food you eat, particularly carbohydrates, for use in the brain, nervous system.   

Thiamine deficiency symptoms 

Severe thiamine deficiency (known as Beriberi), while rare today, can affect the nerves, leading to decreased muscle strength and heart failure.  Low levels of thiamin are common in people with diabetes, Alzheimer’s, hypertension, liver failure and HIV/AIDS.  

Thiamine deficiency is also common in alcoholics due to inadequate intake of nutrients and inflammation of the stomach which leads to a reduction in the body’s ability to absorb vitamins.  Thiamine supplementation is often used as part of their rehabilitation and recovery.  

Availability of thiamine in the food system

Nearly 20% of US residents are understood to not be aching their minimum intake of vitamin B1.  If it were not for fortification, this would be as high as 50%.  

Thiamin availability in the diet increased in 1939 after the commencement of widespread fortification of refined white flour to address thiamine deficiency.   

While whole grains contain thiamine, refining removes the bran and wheat germ which contains the majority of the thiamine from the grain.  As shown in the chart below, after the introduction of fortification, our average intake is slightly above the EAR and RDI (data from USDA Economic Research Service).   However, this is still well below our optimal stretch target that aligns with optimal satiety.

Processing losses 

Food processing causes significant losses of thiamine, including: 

  • roasting of meat (40 to 60%), 
  • milling of flour (60 to 80%), 
  • baking of bread (5 to 15%), and 
  • the cooking of vegetables (60 to 80%).   

Storage and losses in the body

Due to the limited storage capacity for thiamine in the body, thiamine deficiencies can develop in as quickly as two weeks of a nutrient-poor diet.  

How much thiamin do you require each day?

Our satiety analysis of data from Optimisers indicates that there is a signficant satiety response to a diet that contains more thiamine.  When people consume food that contains more vitamin B1, they tend to eat around 20% fewer calories.  

The average thiamin intake of Optimisers is 1.9 mg/2000 calories, which is near twice the Estimated Average Requirement of 1.0 mg/day and the Daily Recommended Intake of 1.2 mg/day.   

Stretch target for Vitamin B1

Someone aiming to optimise their micronutrients could set a stretch target as shown in the table below (i.e. 4.4 mg/day for women or 5.5 mg/day for men from foods).   

nutrient averageEAR RDIstretch (men)stretch (women)
thiamin (B1) (mg)

Thiamine toxicity and overdose 

There is no known upper limit for vitamin B1 as the kidneys quickly excrete excess dietary thiamine in the urine.  

Bioavailability of thiamine 

Little is known about the bioavailability of thiamine (e.g. from plants vs animal-based foods).  

Availability in the food system

As shown in the nutrient fingerprint below, shows that thiamine is reasonably easy to obtain from a nutrient-dense diet.  Foods that are high in thiamine tend to be lower in fat.  This makes sense given we require twice as much thiamine to metabolise carbohydrates compared to fat.  

Thiamine rich food sources 

Popular foods that contain more thiamine per calorie are mainly non-starchy green vegetables (and liver).

  • asparagus  
  • lettuce
  • flax seeds
  • green peppers
  • cabbage
  • zucchini
  • liver
  • parsley
  • kale 
  • broccoli  
  • cauliflower 
  • oranges
  • cucumber
  • grapes
  • garlic

For a more complete list, check out the Top 101 Foods High In Vitamin B1 (Thiamin) which shows the foods highest in vitamin B1 per serving. If your goal is weight loss, you should switch to ‘nutrients per calorie.

Nutrient Optimiser

If you ensure you’re getting enough Vitamin B1 (along with ALL the other essential nutrients), we’d love you to check out Nutrient Optimiser

We have designed Nutrient Optimiser to be the quickest and easiest way to optimise your nutrition at the micronutrient level.  

You can select from our database of five hundred recipes to plan your meals for the coming week to ensure you will get the nutrients you need to thrive. 

Then, if you are able to track your current diet for a few days, Nutrient Optimiser will identify the foods and meals that you need to fill your macro and micronutrient gaps.