Why Does My Dog Need Vitamins?  Part Two – The Water-Soluble Vitamins

When we talk about nutrition we tend to focus on the protein and fat requirements of our pets (the carbohydrate requirement gets us all a little hot under the collar) and it stands to reason because they are macronutrients.  What this means is that they are required in larger quantities for optimal bodily function.  But we also have micronutrients, and despite them being required in lower quantities, they are still critical to health.

Under the umbrella of micronutrients, we have vitamins and minerals.  We have some helpful blogs on minerals here:

Why Does My Dog Need Minerals – Part One

Why Does My Dog Need Minerals – Part Two

But, as vitamins are just as important, here at My Pet Nutritionist we thought we’d pop together a blog on why our dogs need them too!

What Are Vitamins?

Vitamins are defined by their physical and physiological characteristics.

Vitamins are needed in minute quantities to function as essential enzymes, enzyme precursors of coenzymes in many of the body’s metabolic processes.

Generally, vitamins are not synthesised by the body and must therefore be provided by food (but our canine companions have a trick up their sleeve with vitamin C for example).

Fat vs. Water Soluble Vitamins

Vitamins are split into fat soluble and water-soluble vitamins. In this blog, we will focus on the water-soluble vitamins.  If you would like to learn more about the fat-soluble vitamins, then check out our blog here:

Why Does My Dog Need Vitamins?  Part One – The Fat-Soluble Vitamins

The Water-Soluble Vitamins

Water soluble vitamins are depleted at a faster rate because of limited storage and are less likely to cause toxicity but more likely to become deficient.

Water soluble vitamins are absorbed by way of active transport, some vitamins require a carrier protein, like with B12 cobalamin (intrinsic factor), where others require a sodium dependent, carrier-mediated absorption pump.

The B Vitamins

The B complex vitamins are all water-soluble vitamins that were originally grouped together because of similar metabolic functions and occurrence in foods. These nine vitamins act as coenzymes for specific cellular enzymes that are involved in energy metabolism and tissue synthesis. Coenzymes are small organic molecules that must be present with an enzyme for a specific reaction to occur, like a key being required for a lock to engage.

The following vitamins are all involved in the conversion of food to energy:

  • thiamine
  • riboflavin
  • niacin
  • pyridoxine
  • pantothenic acid
  • biotin

The following are all important for cell growth and maintenance and/or blood cell synthesis:

  • folate
  • B12 cobalamin
  • choline (it’s not actually a vitamin, but its often grouped with the B vitamins due to their similarities)

Spotlight On…


Known as Vitamin H, for Haar and Haut (hair and skin), we know it more commonly as vitamin B7, or Biotin.

One of the B vitamins, Biotin, helps the body convert food into energy.  Specifically, biotin is involved in gluconeogenesis, which as we know is the synthesis of glucose from non-carbohydrate sources.  Biotin is involved in fatty acid synthesis, which as we know, is key in skin health.

Biotin is also involved in amino acid breakdown.

Deficiency of biotin has been associated with immune depression and reduced collagen synthesis, another key consideration in structural health. Biotin deficiency is rare in those who ingest a varied diet, but symptoms in the dog include alopecia, dull coat, brittle hair and scaly skin.

The use of antibiotics in the dog decreases the bacterial population of the large intestine which increases the dietary requirement for biotin.  Rancid fats also inactive biotin, along with feed rancidity (storage conditions and length).  Chlorine inactivates biotin, so this is of concern if dogs are offered chlorinated drinking water.

Findings Here

Many foods contain biotin, so opt for organ meats, eggs, fish, meat, seeds, and nuts.  Fruits like raspberries also contain biotin, and vegetables like sweet potato.
There are however some concerns that egg whites contain avidin which binds to biotin, making it unavailable for intestinal absorption.  Deficiency has only occurred when over 30% of the diet consists of raw eggs.  So, like all things, moderation is key.

Vitamin B12

Vitamin B12, also known as cobalamin, is critical for a range of functions in the body.

A common deficiency in human vegetarians, disorders of cobalamin metabolism are seemingly increasing in small animal medicine.  The causes of deficiency range from chronic gastrointestinal disease to hereditary disease, but what is clear is the health impact of low levels.

Vitamin B12 is essential for DNA and RNA synthesis and for cellular energy production.  All cells in all bodies need to know what they are doing, and they need energy to do them!

There are no known naturally occurring bioactive forms of B12 in plant sources.  This is because B12 is synthesised by the bacteria in the gastrointestinal tract of animals, and then absorbed by the host animals.  B12 is concentrated in their tissues, which is then eaten by other animals.  Sources of B12 include red meat, fish, dairy and eggs.

B12 can be depleted in times of stress.  This occurs from a range of mechanisms.

Stress is a physiological response; in the presence of a threat, the sympathetic nervous system kicks in for fight or flight.  Energy is diverted to the brain and muscles as these are the parts of the body needed to escape.  Once the threat has been resolved, the parasympathetic nervous system kicks in, returning energy to other bodily functions, which is why it is known as the rest and digest phase.  In times of chronic stress, digestive functions can be significantly altered, which can result in malabsorption of nutrients, in this case B12.

There are also suggestions that gastric acid can vary during times of stress, increasing or decreasing depending on the personality of the host.  Changes in stomach acid secretion can also affect the digestion and absorption of nutrients.

Can Stress Affect My Dog’s Digestive System?

The last mechanism by which B12 levels are affected during times of stress is due to its role in the synthesis of various hormones and neurotransmitters.

B12 is involved in the production of adrenaline and noradrenaline, along with serotonin.  The more they are produced, the more B12 is depleted.  Many human studies have suggested that increased B12 levels demonstrate lower perceived anxiety and stress.

Findings Here


Folate is the natural form of vitamin B9.  Folate helps to form DNA and RNA and is involved in protein metabolism. It plays a key role in breaking down homocysteine, an amino acid that can exert harmful effects in the body if it is present in high amounts. Folate is also needed to produce healthy red blood cells and is critical during periods of rapid growth.

Sources of Folate:

  • dark green leafy vegetables
  • seeds
  • liver
  • seafood
  • eggs

Folic acid is the synthetic version of this vitamin.

Why Does My Dog Need Folate?

Vitamin C

Ascorbic acid, commonly known as vitamin C, has a chemical structure that is closely related to the monosaccharide sugars. It is synthesised from glucose by plants and most animal species, including dogs. When present in foods, ascorbic acid is easily destroyed by oxidative processes. Exposure to heat, light, oxidative enzymes, and the minerals copper and iron all contribute to losses of vitamin C activity.

The body requires ascorbic acid for the hydroxylation of the amino acids, proline and lysine in the formation of collagen and elastin and for the synthesis of acetylcholinesterase.

Collagen is the predominant structural protein in animals and is a primary constituent of osteoid, dentine (tooth support), and connective tissue and so vitamin C is crucial to the health of all of these.

When ascorbic acid is not available, the synthesis of several types of connective tissue within the body is impaired. In animal species that have a dietary requirement for vitamin C like humans, nonhuman primates and Guinea pigs, a vitamin C deficiency results in scurvy. Signs include impaired wound healing, capillary bleeding, anaemia, and faulty bone formation. But what is super interesting, is that except for humans and other animal species like Guinea pigs, all animals, including dogs, are capable of producing adequate levels and therefore do not have a dietary requirement for it.

Ascorbic acid is produced in the liver from either glucose or galactose through the glucuronate pathway. The adult dog produces approximately 40 milligrams per kg body weight of ascorbate each day.

Controlled research studies in the dog have shown they do not require an exogenous source of vitamin C for normal development and maintenance.  There is, however, an interest in utilising vitamin C in the working dog due to the work demands placed upon the body and the high turnover of water.

In addition, vitamin C is thought to reduce cortisol levels in the blood and so as a natural side effect of this, stress is thought to deplete vitamin C levels.  For this reason, there is also interest in increasing vitamin C intake in particularly stressed animals (and humans).

As you can see, water-soluble vitamins have a range of important functions in our pet’s body.  We know the next question you will have is whether your dog may have a deficiency, so check out our blog here:

Does My Dog Have a Vitamin Deficiency?

If you would like to discuss any of your dog’s dietary requirements, then check out our services to see if we can help.

Thanks for reading,

MPN Team    

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