It’s now common to give multivitamins for dogs, but how much do we know about them?
Vitamins are organic compounds and vital nutrients that your dog requires, usually in small amounts. They’re one of the most popular type of dog supplements.
An organic chemical compound is called a vitamin when your dog cannot synthesize the compound in sufficient quantities and therefore requires this to be obtained through the diet.
This means the term “vitamin” depends on the circumstances and your individual dog. For example, ascorbic acid (vitamin C) is a vitamin for humans, but not for most other animals.
Dog supplements today are often given to dogs as preventative measures. Giving multivitamin supplementation is important for the treatment of certain health problems; however, there is little evidence of nutritional benefit when used by otherwise healthy dogs.
Many supplements advertised as multivitamins for dogs also contain other essential nutrients such as dietary minerals, essential amino acids and essential fatty acids. But these other substances are not classified as multivitamins.
What multivitamins for dogs are there?
Thirteen vitamins are universally recognized.
Vitamins are composed of one or more compounds called vitamers. Commonly, the vitamer name is used instead of the vitamin name. The table below lists the 13 vitamins and their vitamers.
Vitamin A – Retinol, retinal, and four carotenoids including beta carotene
Vitamin B1 – Thiamine
Vitamin B2 – Riboflavin
Vitamin B3 – Niacin, niacinamide
Vitamin B5 – Pantothenic acid
Vitamin B6 – Pyridoxine, pyridoxamine, pyridoxal
Vitamin B7 – Biotin
Vitamin B9 – Folic acid, folinic acid
Vitamin B12 – Cyanocobalamin, methylcobalamin, hydroxycobalamin
Vitamin C – Ascorbic acid
Vitamin D – Cholecalciferol (D3), ergocalciferol (D2)
Vitamin E – Tocopherols, tocotrienols
Vitamin K – Phylloquinone, menaquinones
Solubility and toxicity of multivitamins in dogs
The primary section of multivitamins for dogs are often classified according to their solubility, i.e. whether they are soluble in water or fat.
The water soluble vitamins are C and B-complex. The fat soluble vitamins are A, D, E, and K, which are stored by the body in lipocytes (specialised fat storage cells).
Because the body stores fat soluble vitamins, these pose a greater threat than the water soluble vitamins if your dog is over-supplemented.
The water soluble vitamins are not stored within the body, except in very small amounts.
Because the body tissues do not store water soluble vitamins, if over-supplemented, your dog can easily eliminate these from the body in his urine preventing accumulation and a minimal risk of toxic effects.
Functions, roles and deficiencies
Vitamins are classified by their biological and chemical activity, not their structure. They have a wide range of functions.
Some vitamins for dogs act like hormones and function as regulators of the metabolism of minerals (e.g. vitamin D), or regulate the growth of cells and tissues. Others function as antioxidants (e.g. vitamins E and C).
The largest number of vitamins, the B-complex vitamins, are the building blocks of enzymes – the catalysts in metabolism.
For example, biotin is part of enzymes involved in making fatty acids. They may also function as coenzymes for dogs.
Fat soluble vitamins
Vitamin A for dogs
Vitamin A was the first fat soluble vitamin to be discovered. It is found in several forms such as retinoic acid, retinol, retinaldehyde, and in the liver storage form, retinyl palmitate. Vitamin A has many roles and helps your dog with his vision, tissue health, tooth and skeletal development, and reproduction processes.
Deficiency of vitamin A can lead to skin conditions, coat conditions, poor growth, visual problems (especially night blindness).
For those who raise puppies, the role of vitamin A in growth is of particular importance. Lack of vitamin A in puppies directly relates to poor vision, muscle weakness, low growth rates, a poor coat and skeletal and nervous disorders such as hydrocephalus and cleft palate. Female dogs will not ovulate properly and males can become sterile if they are deficient in vitamin A.
Vitamin D for dogs
Vitamin D plays a major role in regulating the calcium and phosphorous levels within the bloodstream. Vitamin D stimulates the kidneys to conserve calcium thereby helping the body to retain this mineral.
Because of this role of conserving calcium, vitamin D is extremely important in bone formation and nerve and muscle control.
Vitamin D is sometimes known as ‘The sunshine vitamin’. Ultraviolet radiation from the sun is needed to convert vitamin D precursors within the body into the active D form. This takes place in the outer skin layers, however, this conversion is inefficient in dogs and supplemental vitamin D must be available in the diet.
Low levels of vitamin D can cause “rickets” which is demineralization of the bones.
Vitamin E for dogs
Vitamin E plays roles in the formation of the membranes surrounding cells, the respiration of cells and the metabolism of fats. It is also considered to be an antioxidant.
Deficiencies of vitamin E can cause cell damage and death in a range of tissues and organs such as muscles, heart, testicles, liver and nervous tissue. It is essential in the maintenance of these.
Vitamin E deficiencies have been well documented in dogs. ‘Brown Bowel Syndrome’ is the term usually used to describe a dog suffering from inadequate vitamin E. These dogs have affected bowels which haemorrhage, ulcerate and gradually degenerate.
Vitamin K for dogs
Supplementing with Vitamin K for dogs is becoming more popular among pet owners.
Good sources of vitamin K1 are green plants and fishmeal is high in Vitamin K2 (and can be synthesized by the bacteria in the intestine). Vitamin K3 (menadione) is a synthetic precursor of the vitamins K1 and K2 and is the most used as an ingredient in supplements.
Vitamin K is not needed in high levels in food supplements because the gut bacteria can manufacture this.
Vitamin K is essential for normal blood functions, particularly clotting.
Water soluble vitamins
Vitamin C for dogs
Vitamin C for dogs acts as an anti-oxidant and is an important nutrient in the synthesis of collagen and cartilage.
Dogs can manufacture their own vitamin C and do not require it in their diet like humans, so the value of supplementing vitamin C remains unclear.
In dogs, vitamin C has been thought to prevent hip dysplasia. It seems highly unlikely that its use will prevent a dog developing this genetically carried trait; however, it may help alleviate the pain arising from the condition.
Vitamin C is also thought to prevent urinary tract infections and bladder stones in dogs.
Vitamin C is unusual in that it is passed through the kidneys totally unchanged and therefore makes the urine acidic. This makes conditions in the bladder much less likely to allow bacteria to live and start infections, or for bladder stones to begin to form.
Vitamin C also plays many important functions in bone formation, both in growth and mineralization. Deficiencies of vitamin C result in the syndrome known as scurvy which in dogs, causes weak bones and swollen joints.
Vitamin B-complex for dogs
Vitamin B-complex consists of a multitude of B vitamins.
Vitamins B1, B2, B3 and biotin participate in different aspects of the production of energy within cells. Vitamin B6 is essential for the metabolism of amino acids, and vitamin B12 and folic acid are required for cell division.
B vitamins are also important in maintaining an environment suitable for neural regeneration.
Deficiency of B vitamins can result in a wide range of conditions such as loss of reflexes and nervous control, retarded growth, loss of appetite, loose stools or diarrhea, poor or dull coat, eye abnormalities and heart failure.
B-complex (in particular B2 and B6) is also essential for the prevention of bladder stone formation in dogs.