Vitamins
Vitamin A is found in both animal and plant-based foods. It is a fat-soluble vitamin and can be balanced over time in a properly formulated diet.
The form found in animal products is called retinol. Different forms are found in plant products; however, beta-carotene refers to the provitamin A form found in plants.
Cats cannot utilize beta-carotene, but dogs can efficiently convert beta-carotene into vitamin A. There is no risk of toxicity for beta-carotene, and when a dog's vitamin A needs are met, beta-carotene can be used as an antioxidant in the body.
Retinol is a form of vitamin A that has high bioavailability and is easily utilized by the body. While there is a safe upper intake limit for retinol, no such upper limit has been established for beta-carotene.
Liver and fish liver oils are the most common and richest sources of vitamin A in the form of retinol.
Functions: Vision, bone development, reproduction, immune system functions, and maintenance of epithelial tissue health.
Deficiency Symptoms: Growth retardation, reproductive problems, impaired epithelial integrity, dermatoses (skin problems), fetal abnormalities, impaired immune system function, and weight loss. Deficiency is particularly harmful to offspring. Skin problems may also occur in adults.
Symptoms of excess: Skeletal abnormalities, fetal abnormalities, and various signs of hypervitaminosis A observed in clinical studies. A safe upper intake limit for vitamin A has been defined; however, a precise limit for adults is not clear.
Sources: Fish liver oil, liver, and egg yolk.
Vitamin D is a fat-soluble vitamin. Despite being fat-soluble, maintaining a balance of this nutrient over time can be challenging due to the varying amounts found in foods and the required intake of fat.
The form of vitamin D that should be given to pets is vitamin D3, not D2.
Vitamin D is critical for maintaining normal calcium and phosphorus levels in the blood and for sustaining a healthy skeletal system. It also supports calcium absorption in the intestine, therefore it is directly related to calcium intake.
Ensuring adequate vitamin D intake through diet can sometimes be challenging. Mackerel, salmon, and sardines are among the richest natural sources. Dogs cannot synthesize sufficient vitamin D from sunlight, so supplementation is also a frequently preferred option.
Eggs can contribute vitamin D to the diet, but they do not provide sufficient amounts of vitamin D on their own.
Functions: Regulating calcium and phosphorus balance, supporting bone development and maintenance of bone tissue, aiding calcium and phosphorus absorption in the intestines, maintaining bone mineralization and normal skeletal development.
Deficiency Symptoms: Rickets, osteomalacia, and nutritionally related secondary hyperparathyroidism may occur. These conditions generally lead to weakening of the skeletal system and deterioration of bone health.
Symptoms of excess calcium: Hypercalcemia (increased calcium in the blood), bone resorption (destruction of bone tissue), and calcification in soft tissues.Sources: Fatty fish, some fish liver oils, egg yolks, and liver. However, using only liver or only eggs is not sufficient to meet vitamin D requirements without creating an excess of other nutrients in recipes.
Vitamin E is a fat-soluble vitamin. While its most important form is d-alpha tocopherol, it exists in a total of eight different forms, and it is beneficial to include other tocopherols in the diet as well.
Vitamin E is an important antioxidant, particularly preventing oxidation caused by polyunsaturated fatty acids (PUFAs). Therefore, the need for vitamin E increases as the amount of PUFAs in the diet increases. It also works with selenium to support the glutathione system, the body's main antioxidant.
Plant-based foods and some vegetable oils contain vitamin E; however, because these oils have a high PUFA content, they can also increase the need for vitamin E. Therefore, for example, wheat germ oil is not considered a good source of vitamin E due to its PUFA content.
Obtaining sufficient vitamin E solely through food can be challenging, and supplementation is often a preferred option. While the risk of toxicity is unknown, very high doses of d-alpha tocopherol may reduce other tocopherols and, in excessive doses, may exert an oxidative effect, impacting vitamins A and D as well. When choosing a supplement, d-alpha tocopherol and mixed tocopherols should be preferred, and synthetic d-alpha tocopherol should be avoided.
Functions: Protection of cell membranes, strong antioxidant defense, prevention of free radical damage, and reduction of cellular oxidative stress in conjunction with selenium.Deficiency Symptoms: Reproductive problems, skeletal muscle degeneration, retinal degeneration. Some studies have also reported edema, loss of appetite, and depression-like symptoms in cases of deficiency.
Symptoms of Excess: It is not toxic, but high doses can increase the need for vitamins A and D. Very high doses of d-alpha tocopherol can cause other tocopherols to be removed from circulation and may have a blood-thinning effect. Therefore, vitamin E should be used in moderation.
Sources: Supplements, some oils, and some plant-based foods.
Vitamin K is a fat-soluble vitamin and comes in three forms:
K1 (phylloquinone)
K2 (menaquinone)
K3 (menadione) – is a synthetic form and does not occur in nature.
Vitamin K is best known for its role in blood clotting. However, studies in mammals suggest it may also play a role in preventing soft tissue calcification and maintaining insulin sensitivity.
Most vitamin K1 can be synthesized by gut bacteria, so meeting the recommended daily intake (RDA) is often not necessary. Also, vitamin K levels may not be listed in the nutritional analysis of many foods.
Raw food diets consisting of meat, bones, eggs, and dairy products generally provide sufficient vitamin K2. In healthy cats and dogs, most of their vitamin K needs can be synthesized by gut microorganisms. However, this does not mean that no vitamin K needs to be obtained from the diet. In cats, however, fish-heavy diets may affect vitamin K synthesis, so vitamin K supplementation may be necessary in some cases.
Functions: Blood clotting, synthesis of prothrombin and other clotting factors in the liver.
Deficiency symptoms: Prolonged clotting time and bleeding (hemorrhage).
Signs of Overdose: There are no reported signs of toxicity or overdose.
Sources: Green leafy vegetables and liver.
Functions: It functions as part of the coenzyme thiamine pyrophosphate. It plays a role in the utilization of carbohydrates for energy, fat synthesis, and the metabolism of fatty acids, nucleic acids, steroids, and some amino acids. Thiamine requirements can vary depending on the amount of carbohydrates in the diet.
Deficiency Symptoms: It can affect central nervous system function, as the brain is heavily reliant on glucose for energy. Deficiency is rare.
Symptoms of Excess: None reported.
Sources: Beef and heart, liver, and wheat germ. Thiamine deficiency can occur in homemade diets prepared without considering nutritional requirements.
Important note: Those preparing homemade baby food should be cautious about foods containing the thiaminase enzyme.Functions: It is a component of two important coenzymes involved in oxidative enzyme systems that produce energy from carbohydrates, fats, and proteins. It also plays a role in the functioning of various biosynthetic metabolic pathways.
Deficiency Symptoms: Impaired central nervous system function and dermatitis.
Symptoms of Excess: None reported.
Sources: Organ meats, some vegetables, and milk. Microbial synthesis can occur in the large intestine, but the amount synthesized varies depending on the species and the carbohydrate levels in the diet.
Functions: It plays a role in cellular oxidation-reduction enzyme systems. As part of the NADH and NADP coenzymes, it is critical for cellular respiration and ATP production (energy metabolism).
Deficiency Symptoms: Pellagra*.
Symptoms of Excess: None reported.
Sources: Liver, some fish products, chicken, turkey, and animal-based foods in general. Bioavailability is low in plant-based sources.
* Pellagra (or 3D) is a disease caused by niacin (vitamin B3) deficiency. Due to the deficiency of NAD and NADP coenzymes, which are involved in energy metabolism, it primarily affects the skin, digestive system, and nervous system. 3D stands for diarrhea, dermatitis, and dementia.Functions: It is found in all tissues of the body and plays an important role in energy metabolism and the metabolism of macronutrients (protein, fat, carbohydrates).
Deficiency symptoms: Loss of appetite and weight loss.
Symptoms of Excess: None reported.
Sources: Offal, fish, and wheat germ.
Vitamin B6 consists of three different compounds: pyridoxine, pyridoxal, and pyridoxamine.
Functions: Energy metabolism, DNA and RNA synthesis, formation of red and white blood cells, antibody and neurotransmitter synthesis. It also plays a role in glucose and fatty acid metabolism. It is essential for the conversion of tryptophan to niacin, therefore the need for vitamin B6 is affected by the amount of protein in the diet.
Deficiency Symptoms: Microcytic hypochromic anemia, convulsions, and muscle twitching.
Symptoms of Excess : None reported.
Sources: Offal, fish, and wheat germ.
Functions: It is a coenzyme involved in various carboxylation reactions. It acts as a carbon dioxide carrier in reactions where carbon chains are elongated. Therefore, it plays a role in fatty acid metabolism, certain steps in the synthesis of some non-essential amino acids and purines. It is also important for energy metabolism, skin, coat, and nervous system health.
Deficiency Symptoms: Dermatitis.
Symptoms of Excess: None reported.
Sources: Eggs.
Important note: Healthy animals can synthesize most of their biotin needs through gut microorganisms, but antibiotic use can reduce gut bacteria, thereby decreasing biotin synthesis and increasing the need for dietary biotin.Functions: It plays a role in the synthesis of thymidine, a component of DNA. Therefore, it is important for cellular DNA production, cell growth, and cell maturation.
Deficiency symptoms include anemia, leukopenia, and weakened immune function.
Symptoms of Excess: None reported.
Sources: Liver, offal, kidneys, and lean meats.
Vitamin B12 (Cobalamin) contains the trace element cobalt and is synthesized only by microorganisms. It is the only B vitamin that can be stored in the liver.
Functions: It plays a role in fat and carbohydrate metabolism and is essential for the synthesis of the myelin sheath surrounding nerves. Its absorption requires glycoproteins called intrinsic factor. This factor is mainly produced in the pancreas, and in dogs also in the gastric mucosa. Intrinsic factor deficiency can lead to B12 deficiency, which may require high-dose supplementation or injections.
Deficiency Symptoms: Anemia and impaired neurological function.
Symptoms of Excess: None reported.
Sources: Meat, fish, and poultry such as turkey and chicken.
Functions: It acts as a methyl group donor in metabolic reactions. It is a precursor to the neurotransmitter acetylcholine and is essential for the transport of fatty acids in cells. It is an important component of cell membranes and is involved in the structure of two phospholipids, lecithin and sphingomyelin. It is important for liver health, and low folate intake may increase choline requirements.
Deficiency Symptoms: Neurological dysfunction.
Symptoms of excess: Diarrhea.Sources: Eggs and liver.
Functions: It plays a role in the hydroxylation of proline and lysine amino acids, which are essential for collagen and elastin formation. It is also important for acetylcholinesterase synthesis, bone formation, and connective tissue health. Furthermore, it is part of the antioxidant defense system.
Deficiency Symptoms: Vitamin C is not an essential component of the diet for dogs and cats.
Symptoms of excess: Digestive discomfort and diarrhea. May have adverse effects in some cats and dogs prone to stone formation.
Sources: Vitamin C is synthesized in the liver of dogs and cats from galactose or glucose.
This doesn't mean that supplementing it through diet is useless. Dogs with high activity levels, such as working dogs, or those exposed to environmental toxins, may benefit from additional vitamin C in their diet.