Can cats eat blueberries?

Why your cat sniffs a blueberry and walks away

Your cat cannot taste sweetness. The mammalian sweet receptor is built from two proteins, T1R2 and T1R3, each made by its own gene. In cats the gene for T1R2 carries a 247 base pair deletion that shifts the stop point and leaves it unable to produce a working protein. Without T1R2 the receptor never assembles, so the detector for sweet is simply not there. Researchers found the same defect in tigers and cheetahs, which puts it across the cat family rather than in one breed or one animal.

That is the whole reason blueberries land differently for your cat than they do for you. The sugar is the appeal, and the appeal is invisible. A cat who bats a frozen berry around the kitchen floor is far more likely to be enjoying the cold and the way it rolls than anything about the flavor.

Whether a blueberry does your cat any good

Blueberries are sold to people as an antioxidant food, and none of that reasoning transfers to a carnivore. Cats rely on nutrients found only in animal products, and they evolved eating prey that is high in protein, moderate in fat, and very low in carbohydrate. Merck is direct about the carbohydrate part: dietary carbohydrates are not considered essential nutrients for adult, non-reproducing dogs and cats.

The vitamin A point makes the gap concrete. Cats cannot convert beta-carotene from plants into vitamin A, because they lack the intestinal enzyme that splits it. They need a preformed source, which means animal tissue. Plant nutrition that works for you does not automatically work for your cat, and a blueberry is not filling a hole in a complete and balanced diet.

What is left is a small, watery, low-calorie snack. VCA lists berries served fresh or frozen among the low-calorie snacks worth offering an older cat, which is a fair description of the ceiling here: a treat some cats enjoy, not a supplement.

How many blueberries is too many

Treats are not complete and balanced, so they are capped to keep them from displacing the food that is. Merck puts the daily total of treats below 10% of calorie intake, and VCA gives the same 10% figure. Cornell’s Feline Health Center is a little more relaxed and says treats should not exceed 10 to 15 percent. The gap is not worth agonizing over at one berry, and 10% is the safer number to plan around.

Offer one new thing at a time. VCA’s advice for any new treat is to start with a small piece, especially if your cat has a delicate stomach, which is why half a berry is a sensible first serving rather than a handful.

Muffins, yogurt, dried berries, and other blueberry things

The berry is the easy case. Most of what people offer is not the berry.

Cats who should skip fruit treats altogether

• Diabetic cats. A diet low in carbohydrate has been shown to improve blood sugar regulation in diabetic cats, and casual sugary treats work against the plan your vet has set. Ask before offering fruit at all.
• Overweight cats. Obese cats are up to four times more likely to develop diabetes than cats at an ideal weight. Every treat calorie counts against the same allowance.
• Cats on an elimination diet trial. A strict dietary trial is the only reliable way to diagnose a food allergy, and food allergens turn up in treats and supplements as readily as in meals. One blueberry can waste weeks of work.

If your cat ate a pile of blueberries

Blueberries are not on the ASPCA’s list of people foods to avoid feeding your pets, and none of the veterinary sources below gives a toxic dose for cats. A cat who found the punnet and helped themselves has eaten a load of sugar and fiber that a carnivore’s diet would not normally contain, which is a stomach problem rather than a poisoning.

Watch for vomiting, loose stool, or a cat who goes off food. Call your vet if any of that keeps going, if your cat seems dull or uncomfortable, or if you are simply worried enough to want a professional opinion. A single berry is not a reason to call anyone.