Vitamins & Minerals 101 | Thiamin (B1)
with Savannah Welna of FeedThyDog, Nutrition Advocate

Today we are going to talk about Thiamin (B1)- a very fragile nutrient that is easily at low levels in both commercial and homemade diets! We will discuss the potential role in chronic illness (like diabetes) and how to provide whole food sources of thiamin. Could processed foods and sub-optimal B1 intake be contributing to diabetes in dogs?

Thiamin (Vitamin B1)

Thiamin, Vitamin B1, is a water soluble vitamin that is required in the diet.The dog has limited abilities to store thiamin and is best provided daily.


Thiamin is critical for energy metabolism and plays a special role in carbohydrate metabolism. Specifically, B1 is required in the pentose phosphate cycle- critical for the brain, liver, kidney, and adrenal cortex. 

Deficiencies therefore affect the brain because the brain runs on glucose. In adult dogs, thiamine deficiencies include anorexia, inappetence, mental dullness, vomiting, ataxia, and muscular weakness (to name a few!). Thiamin deficiency starves the brain of glucose.

Thiamin also helps the dog recycle other nutrients!

Thiamin has no known toxicities and is one of the safest to provide in the diet from food or supplements as needed.

Deficiency Risk Factors

Commercial Foods: Low Thiamin & Carbohydrates

Thiamin is extremely fragile. In alkaline environments, thiamin is rapidly destroyed. It is also very sensitive to heat. In commercial pet food (kibble and canned) the majority of thiamin is destroyed and must be supplemented back in. Because thiamin is required for carbohydrate metabolism, processed, low quality kibble or canned food  (or any diet low in thiamin) that do not provide adequate supplemented thiamine can cause disturbances in carbohydrate metabolism and potentially allow glucose to build up in the blood. We know that in humans low thiamin status is observed in individuals with diabetes.

Raw Fish

Thiaminase is an enzyme that breaks down thiamine. It can be found in many different types of fish but cooking reduces the activity. Thiaminase can harm thiamin status even if enough thiamin is fed. Therefore, thiaminase containing raw fish should not be mixed into food that is stored and should not make up a large part of the diet.


Sulfur based preservatives destroy thiamin in food. Generally, homemade feeders do not need to worry about this if you are feeding fresh food that does not use preservatives. Always check for added ingredients as even fresh meat with small amounts of sulfur dioxide can significantly harm thiamin status.

While foods containing products that increase pH result in thiamin destruction, I don’t consider this a major risk for feeders adding fresh food to the diet.

Kidney Conditions and Polyuria

When any condition causes increased urine excretion, thiamin status can be harmed. When large amounts of urine are passed and when the kidneys are unable to reabsorb thiamin, extra must be supplied in the diet.

High Fat Diets

Thiamin is not found in fat. Unbalanced diets that are high in fat and do not supplement thiamin are likely low in this nutrient. This issue is more common in raw/cooked feeders who feed high fat food to low energy dogs.

Practical Applications

While extreme thiamin deficiency results in many of the symptoms outlined above, subtle thiamin deficiency can be harder to catch and is often not on the radar. Given the neurological functions in the brain and the fact that thiamin is extremely fragile, it is not far-fetched to suggest many dogs may not be receiving optimal levels of thiamin. It seems reasonable for those feeding kibble to provide fresh sources of thiamin (below) and for DIY feeders to provide enough thiamine.

Thiamin Shortages in DIY and Commercial Fresh Food Diets

Thiamin can be extremely tricky to get from food and can often be left out in unbalanced commercial and homemade diets. Thiamin is rich in:




-nutritional yeast



-thiamin is relatively higher in many digestible carbohydrates including buckwheat, quinoa, sweet potatoes, grains, and other lower starch options like butternut squash. These should be cooked.

However, even including kidney and liver in the diet will not result in optimal thiamin intake and nutritional yeast is often fortified with undesirable added ingredients.

While meat in general provides thiamin, dogs who have low energy requirements are more likely to need a thiamin supplement. 

Adding to Commercial Food

Canned and kibble foods can be safely topped with lean pork, duck, and heart (multiple protein sources) and some amount of sweet potatoes and squash can provide phytonutrients in addition to B1. Most commercial foods are already high in starch, so focusing more on animal products makes sense.


  1. Identify in food: Most canned and kibble dog foods will be fortified with thiamin. If you are feeding homemade or commercial, identity the thiamin sources- especially DIY feeders or those feeding local raw food blends.
  2. Canned and Kibble: How can you add fresh thiamin to your dog’s diet?
  3. Are you feeding any sources of sulfur based preservatives or fish that contain thiaminase?


NRC Nutrient Requirements of Dogs and Cats

Canine and Feline Nutrition