Supplementation with antioxidants can help support the vision and overall health of hypertensive cats.
Oxidative stress is essential for normal cellular and body functions, but unbalanced oxidative stress can be harmful. Many conditions may benefit from antioxidant supplementation, including cognitive dysfunction, retinal disease, glaucoma, cataracts, diabetes mellitus, and systemic hypertension. Hypertensive cats often develop vision loss from hypertensive retinopathy.
Cats can benefit from antioxidant supplements, but because cats are not small dogs the supplement types and/or doses given to dogs of comparable weight might not be safe for cats. Cats evolved to eat mice and other prey. They are hypercarnivores and are a uniquely nutritional dead-end species requiring a high-protein diet containing low-to-moderate fat and almost no carbohydrates. Cats are a desert animal that obtain water from eating their prey and therefore have highly concentrated urine.
Where commercial cat food is lacking
Commercial cat food often contains excessive carbohydrates and inadequate protein and moisture, which can contribute to chronic conditions such as kidney and liver disease, obesity, and diabetes. Correcting dietary issues can be complicated: for example, cats must obtain taurine from their diets (meat protein is high in taurine), and low taurine levels can cause dilated cardiomyopathy and/or vision loss from feline central retinal degeneration. However, it is not a simple matter for feline diets to contain an adequate amount of taurine: the daily requirement for taurine in cats is very food-specific and related to how foods can alter intestinal microflora.
Choosing the right supplements
Cat physiology, biochemistry, and behavior are uniquely different, which matters when choosing supplements. Cats have different abilities to metabolize substances compared to dogs, including liver glucuronidation and transport function.
Transport function of the drug-transporter ABCG2 is defective in cats compared to dogs and humans, with the most important clinical consequence being fluoroquinolone-induced retinal degeneration. Most fluoroquinolone antibiotics generate reactive oxygen species (ROS) when exposed to light. Because of defective ABCG2 function in cats, fluoroquinolones can accumulate in retinal tissue. When exposed to light, the drug generates ROS that can attack cell membranes of rod and cone photoreceptors, causing phototoxic vision loss. Therapy for affected cats includes specific antioxidant vision supplementation (including lutein, omega-3 fatty acids, and grapeseed extract) and limiting light exposure; affected cats should be kept in darkness for at least two weeks.
Cats also differ from dogs in how cats metabolize the powerful antioxidant alpha lipoic acid (ALA). Normal healthy cats do not require dietary ALA, as muscle meats are rich in ALA. However, due to disease, aging, diminished absorption of nutrients, and diets with poor quality protein or meal instead of meat, the amount of dietary ALA may be suboptimal. Conversely, ALA is ten times more hepatotoxic in cats than in dogs. The recommended ALA dose for cats is 1 to 5 mg/kg body weight, with a maximum dose of 25 mg/day.
Because cats are so dependent on the type of food they eat, they are driven by the smell and taste of food and they struggle with change. The goals of supplementation in cats are to balance their quality of life, improve their health, and deepen their relationships with their human family.