 Because they're such picky eaters, we sometimes think cats know what's best for them when it's time to eat. But the fact that they'll walk away from a piece of bad meat doesn't mean they'll bypass an open can of tuna. And that can of tuna can be just as dangerous. In fact, you may be surprised to learn some of the common foods your cats should never eat. TUNA Cats can be addicted to tuna, whether it's packed for cats or for humans. Some tuna now and then probably won't hurt. But a steady diet of tuna prepared for humans can lead to malnutrition because it won't have all the nutrients a cat needs. And, too much tuna can cause mercury poisoning. Remember the saying, honest as a cat when the meat's out of reach. Your cat will see an open can of tuna next to the sink as a dinner invitation. ONIONS, GARLIC, CHIVES Onion in all forms, powdered, raw, cooked, or dehydrated, can break down a cat's red blood cells, leading to anemia. That's true even for the onion powder that's found in some baby foods. Eating a large quantity once or eating smaller amounts regularly can cause onion poisoning. In addition to onions, garlic, which is 5 times as potent as onions, and chives can each cause major health and potentially life-threatening problems. MILK AND OTHER Dairy Products What could be wrong with offering your cat a saucer of milk or a piece of cheese? Most cats are lactose intolerant. Their digestive system cannot process dairy foods, and the result can be digestive upset with diarrhea. ALCOHOL Veer, liquor, wine, foods containing alcohol, none of it is good for your cat. That's because alcohol has the same effect on a cat's liver and brain that it has on humans. But it takes far less to do its damage. Just two teaspoons of whiskey can cause a coma in a 5 pound cat, and one more teaspoon could kill it. The higher the proof, the worse the symptoms. Grapes and raisins Grapes and raisins have often been used as treats for pets. But it's not a good idea. Although it isn't clear why grapes and raisins can cause kidney failure in cats. And, a small amount can make a cat ill. Repeated vomiting and hyperactivity are early signs. Although some cats show no ill effects, it's best not to give your cat any grapes and to keep grapes and raisins off countertops and other places accessible to your cat. Caffeine Caffeine in large enough quantities can be fatal for a cat. And there is no antidote. Symptoms of caffeine poisoning include restlessness, rapid breathing, heart palpitations, and muscle tremors. In addition to tea and coffee, including beans and grounds, caffeine can be found in cocoa, chocolate, colas, and stimulant drinks such as red bull. It's also in some cold medicines and painkillers. Hello. This video is sponsored by Beemix Pets. Are you looking for high quality cat collars at an affordable cost? Check out BeemixPets.com. Use coupon code KittenLife to get 20% off. Chocolate Chocolate can be lethal for cats. Although most cats won't eat it on their own, they can be coaxed to eat it by owners and others who think they are giving the cat a treat. The toxic agent in chocolate is theobromine. It's in all kinds of chocolate, even white chocolate. The most dangerous kinds, though, are dark chocolate and unsweetened baking chocolate. Eating chocolate can cause abnormal heart rhythm, tremors, seizures, and death. Fat trimmings and bones. Table scraps often contain fat trimmed off of meat and bones. Both fat and bones may be dangerous for cats. Fat, both cooked and uncooked, can cause intestinal upset, with vomiting and diarrhea. And a cat can choke on a bone. Bones can also splinter and cause an obstruction or cut the inside of your cat's digestive system. Raw eggs There are two problems with giving your cat raw eggs. The first is the possibility of food poisoning from bacteria like salmonella or E. coli. The second is a rare problem in which a protein in raw egg whites, called avitin, could interfere with the absorption of the B vitamin biotin. This can cause skin problems as well as problems with your cat's coat. Raw meat and fish Raw meat and raw fish, like raw eggs, can contain bacteria that cause food poisoning. In addition, an enzyme in raw fish destroys thiamine, which is an essential B vitamin for your cat. A lack of thiamine can cause serious neurological problems and lead to convulsions and coma. Dog food An occasional bite of dog food won't hurt your cat. But dog food is not a substitute for cat food. They do have many of the same ingredients. But cat food is specially formulated for a cat's needs, which include more protein as well as certain vitamins and fatty acids. A steady diet of dog food can cause your cat to be severely malnourished. Liver Small amounts of liver are okay, but eating too much liver can cause vitamin A toxicity. This is a serious condition that can affect your cat's bones. Symptoms include deformed bones, bone growths on the elbows and spine, and osteoporosis. Vitamin A toxicity can also cause death. Too many treats. Eating too much too often can do the same thing to cats that it does to humans. It can lead to obesity and even diabetes. Your medicine Ingesting a drug prescribed for humans is one of the most common causes of poisoning in cats. Just as you would do for your children, put all medicines where your cat can't get to them. And never give your cat any over-the-counter medicine unless advised to do so by your vet. Ingredients such as acetaminophen or ibuprofen are common in pain relievers and cold medicine. And they can be deadly for your cat.