Blog Summary
We know that most indoor cats miss out on one of Australia’s greatest treasures — sunshine. While cats don’t make vitamin D from sunlight like humans, natural light still benefits them by supporting sleep-wake cycles, boosting serotonin for better mood, and promoting healthy skin and coats.
We also focus on diet to meet their vitamin D needs, mainly through animal-based sources like egg yolks, oily fish, or liver in safe amounts. Most complete cat foods already include vitamin D3, but if you’re home-cooking or supplementing, it’s important to check with your vet.
We recommend creating sunny napping spots indoors or a safe outdoor catio so your cat can enjoy natural light alongside a balanced diet. A patch of sunshine plus proper nutrition helps keep indoor cats happy, healthy, and calm.
Most cats live happily indoors, safe from cars, predators, and neighbourhood scuffles. But one thing many indoor cats miss out on is something wonderfully abundant here in Australia - our glorious sunshine.
Unlike humans, cats don’t make vitamin D from sunlight; they get it from their diet instead. But Aussie rays still play a big role in their health:
Better sleep and mood – Sunlight helps regulate circadian rhythms. Cats exposed to natural light have healthier sleep-wake cycles, which supports calmer behaviour and better rest.
Serotonin boost – Just like in people, light influences serotonin - the “feel-good” chemical. More natural light may reduce stress and anxiety in indoor cats.
Shinier coats and healthier skin – Regular daylight exposure can support skin health and natural shedding cycles.
Diet Tips for Indoor Kitties
Because cats can’t make their own vitamin D from sunshine, diet matters:
How much do they need?
According to AAFCO feline nutrition standards, cats require around 5–10 IU of vitamin D per day (for an average 4–5 kg cat). Too little can cause bone and immune problems, while too much can be toxic - so balance is key.
Animal sources
Cats absorb vitamin D3 most efficiently from animal-based foods such as cooked free-range egg yolk (~20 IU per yolk), oily fish such as salmon or sardines (200–400 IU per 100 g - but only a teaspoon or two as an occasional treat), or liver (sparingly, as excess can be harmful).
Sun-exposed mushrooms?
These are rich in vitamin D2. While helpful for humans, cats use vitamin D3 far more effectively. A sprinkle of mushrooms won’t hurt, but it’s not a reliable source of this nutrient.
A balanced diet is key
Most complete, balanced cat foods already include added vitamin D3 in safe amounts. If you’re home-cooking or supplementing, it’s best to check with your vet to avoid deficiency or overdose.
💡 Practical Tip
Create sunny napping spots by opening blinds, adding a cat perch near a window, or even setting up a safe outdoor catio. Pairing natural light exposure with a balanced diet rich in safe vitamin D sources helps support mood, coat, and overall wellbeing.
Because sometimes, the best medicine for your cat really is a patch of warm sunshine… plus a healthy dinner.
References
AAFCO (2021). Official Publication: Feline Nutrition Standards.
Backus, R. C., & Shor-Line, M. (2011). Vitamin D metabolism in cats: peculiarities and clinical importance. Journal of Feline Medicine and Surgery, 13(9), 698–704.
Morris, J. G. (2002). Cats discriminate between cholecalciferol and ergocalciferol. Journal of Animal Physiology and Animal Nutrition.
Norman, A. W. (2008). From vitamin D to hormone D: fundamentals of the vitamin D endocrine system. American Journal of Clinical Nutrition, 88(2), 491S–499S.
Disclaimer
This blog is for educational purposes only and is not a substitute for professional veterinary advice. Always consult your vet before making changes to your cat’s diet, supplements, or routine.