Basics of Nutrition: Vitamin Guide for Dog and Cat Owners

Vitamins may be tiny in amount, but they play an enormous role in keeping our pets healthy. Unlike proteins, fats, or carbohydrates, vitamins are not used as energy sources or building blocks. Instead, they work as essential helpers—acting as enzymes, enzyme precursors, or coenzymes in many of the body’s metabolic processes.

Because most vitamins cannot be produced by the body, they must come from food. Pet nutrition experts divide vitamins into two main groups:

• Fat-soluble vitamins: A, D, E, and K

• Water-soluble vitamins: C and the B-complex group

Let’s take a closer look at why these nutrients are so vital for your dog or cat.

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Fat-Soluble Vitamins

These vitamins are absorbed along with dietary fat and stored mainly in the liver. Since they accumulate, overdosing can be toxic—especially with vitamins A and D.

Vitamin A

• Functions: Vision, bone growth, reproduction, skin and tissue health.

• Deficiency signs: Night blindness, skin problems, poor growth, and weakened immunity.

• Sources: Fish liver oils, milk, liver, egg yolk, carrots, sweet potatoes.

• Special note: Dogs can convert plant carotenoids (like beta-carotene) into vitamin A, but cats cannot—they require preformed vitamin A from animal-based foods.

Vitamin D

• Functions: Regulates calcium and phosphorus, crucial for strong bones and teeth.

• Deficiency signs: Rickets in young pets, osteomalacia (soft bones) in adults.

• Sources: Fish liver oils, egg yolk, liver, sunlight.

• Special note: Cats and dogs cannot make enough vitamin D from sunlight alone—dietary sources are essential.

Vitamin E

• Functions: A powerful antioxidant that protects cells from damage and supports immune health. Works closely with selenium.

• Deficiency signs: Reproductive failure, muscle weakness, or (in cats) fat inflammation known as pansteatitis.

• Sources: Wheat germ, soybean, corn, and sunflower oils.

Vitamin K

• Functions: Essential for blood clotting and bone health.

• Deficiency signs: Excessive bleeding or delayed clotting.

• Sources: Green leafy vegetables, liver, some fish meals.

• Special note: Gut bacteria in pets help produce vitamin K, but antibiotic treatments may reduce this supply.

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Water-Soluble Vitamins

Unlike fat-soluble vitamins, these are not stored in the body (except for vitamin B12). They are absorbed quickly and excreted in urine, which means deficiencies develop faster—but toxicities are rare.

B-Complex Vitamins

The B-group vitamins help the body use food for energy, support cell growth, and maintain nerve and blood health.

• Thiamin (B1): Important for carbohydrate metabolism and nervous system function.

• Riboflavin (B2): Helps release energy from food and supports skin and coat health.

• Niacin (B3): Aids fat, protein, and carbohydrate metabolism. Dogs can make niacin from tryptophan, but cats cannot.

• Vitamin B6 (Pyridoxine): Essential for protein metabolism and hemoglobin synthesis.

• Pantothenic Acid: Supports energy production through the citric acid cycle.

• Biotin: Important for skin, coat, and fatty acid metabolism.

• Folic Acid: Necessary for DNA synthesis and red blood cell production.

• Cobalamin (B12): Vital for nerve function and red blood cell health; stored in the liver.

• Choline: Supports fat metabolism, cell membranes, and neurotransmitter function.

Vitamin C (Ascorbic Acid)

• Functions: Supports collagen formation, wound healing, and antioxidant defense.

• Special note: Dogs and cats can produce their own vitamin C, so dietary supplementation is usually unnecessary.

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Vitamin Deficiency and Excess

Because vitamins are so powerful, balance is key:

• Deficiencies may lead to poor growth, weak bones, skin and coat issues, anemia, or neurological problems.

• Excesses—especially of fat-soluble vitamins A and D—can cause bone abnormalities, organ stress, and other toxic effects.

This is why commercial pet foods are carefully formulated to meet vitamin requirements without under- or over-supplementation.