Like air, vitamins are vital for life. But which vitamins does your best buddy need and can you give too much?

What are vitamins?

Think of vitamins (and minerals) like the key to a locked kitchen. Without that key, the body has the right ingredients for growth and repair, but they're stuck inside a locked room. With the key, everything gels and the body cooks up a storm. In short, vitamins and minerals are necessary for the smooth running of all body systems and without them deficiency diseases occur. 

Vitamins are broadly divided into two groups: water soluble and fat soluble. Why does this matter? Well, water-soluble vitamins are generally more difficult to overdose on because any excess is peed out by the kidneys. But for the same reason, the body is less able to store water soluble vitamins and more likely to need a ready supply or supplement. 

The opposite is true for fat-soluble vitamins. These are stored in the body's fat supplies, and these reserves make it easier to overdose. Some fat-soluble vitamins are harmful when given in large amounts for a long time. 

Fat-soluble vitamins for dogs

Vitamin A for dogs

Just like the porridge in Goldilocks and the three bears, vitamin A for dogs is one that needs to be just right. 

• Not enough vitamin A: The body needs vitamin A to repair itself. Not enough vitamin A results in diarrhea, pneumonia, poor vision, and poor resistance to infection. 
• Too much vitamin A: Over months to years, this causes bones to fuse together into a solid lump, locking the dog inside the cage of a rigid skeleton. 

Many foods are naturally high in vitamin A, plus the body can store this vitamin, so a supplement is rarely needed. The risk of toxicity is low with a healthy diet, because it takes months of over-supplementation for the ill effects to show up. 

Vitamin D for dogs

People call vitamin D the sunshine vitamin. This is because sunlight on human skin makes vitamin D for free—but dogs are different. For one thing, their fur acts like sunscreen and stops this reaction. For another, the wild dogs from which our best buddies evolved ate a meat rich diet. With meat naturally high in vitamin D, dogs didn't need to develop the ability to make it for themselves. 

The best source of vitamin D for dogs is a healthy, balanced diet. Get this right there's no need to give a supplement. But get it wrong (either too little or too much) and it could spell trouble.

• Not enough vitamin D results in painful, weak, bendy bones that snap easily.
• Too much vitamin D causes calcium to be stored in organs such as the heart or kidney, ending in organ failure and death.

Vitamin E for dogs

In the vitamin world, this one is a superhero. Vitamin E is important for dogs because it works as an antioxidant, protecting body tissue from the ravages of pollution and aging. Dogs cant make this vitamin, so it needs to be supplied ready to use in their diet and sometimes given as a supplement or applied to the coat in a treatment shampoo.

• Too much vitamin E: Vitamin E is slightly different to the other fat-soluble vitamins in that overdose is unlikely. However, too much can block the uptake of vitamins A and D, causing them to be deficient.
• Not enough vitamin E: Without this superhero vitamin the skin becomes dry and flaky, the dog can't fight off infections, and their muscles and eyes do not work properly. 

Water-soluble vitamins for dogs

Vitamin B for dogs

The B vitamins are one of the widest groups of vitamins and an umbrella term for a group of similar substances. Like all vitamins, B vitamins for dogs are essential to good health with jobs such as supporting healthy digestion, keeping skin supple and coat shiny, preventing anaemia (a lack of red blood cells), and boosting energy levels.

Vitamin B12 for dogs

Of all the B vitamins, vitamin B12 is singled out for special mention. B12 is super important for the gut to work properly. But there's an irony here, because lack of B12 can cause diarrhea  and diarrhea causes vitamin B12 loss. To break free of this vicious circle, there is a case for a supplement for dogs with an upset tummy. 

Looking at the B vitamins as a whole: 

• Not enough B vitamin leads to a lack of energy, diarrhea, a poor coat, and anemia
• Too much B vitamin is difficult to achieve, as the body pees out the excess

Vitamin C for dogs

Great news! Dogs can make their own vitamin C. This is terrific, as it  is the body's equivalent of a bomb disposal expert to disarm harmful free radicals. This is such an amazing vitamin because it strengthens the immune system, slows aging, and encourages repair. Making vitamin C is a pretty neat trick by Mother Nature, since the body can't store it and needs some fresh every day. 

• Not enough vitamin C: In people, a deficiency causes scurvy. In a healthy dog, this is not likely to happen because the body makes its own supply. 
• Too much vitamin C: This is unlikely to be a problem as the kidneys get rid of it in urine.

Do dogs need vitamin supplements?

A healthy dog fed a well-balanced, good-quality diet has no need for a supplement. However, there are times when a pet vitamin supplement may be a good idea. For example, dogs fighting an infection or those who put a lot of strain on their body (such as high performance or working dogs) may benefit from a vitamin boost. Some health problems, such as liver disease or diarrhea, mean a helping paw may be a good idea—but always discuss this with your vet first

Can vitamin supplements be dangerous?

If your best buddy needs a supplement, skip the human supplement and use one formulated for dogs. People and dogs have different requirements for vitamins, and what suits one could be dangerous to the other. Always stick to the recommended dose, rather than (mistakenly) believing more is better. As you now know, too much of a good thing is a bad idea. 

Choosing a quality dog supplement

When choosing a supplement, look for one made from good-quality ingredients that avoids unnecessary preservatives or colors. Also, check the label for bioavailability. This is a measure of how well the vitamins are absorbed by the body. A product with low bioavailability means it passes straight through the digestive system without getting into the bloodstream (like sweetcorn kernels!) and won’t be of much use.

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