Pet owners often feel guilty when they give in to their pets who beg to sample some of their human food. But it turns out a lot of the food on our plates is not only safe for our pets, it's good for them too.

"For the most part, the stuff that's healthy for us is healthy for them," Toronto veterinarian Dr. Ian Sandler told CTV's Canada AM this week.

That said, there are a number of people-foods that should never be fed to pets. That's because some people-foods contain toxins that don't affect humans but that can sicken or even kill pets.

Other foods are known to cause stomach upset among pets, who have trouble digesting some of the foods that we find delicious. And nothing ruins a pet and owner bonding moment faster than a treat gone bad.

"You don't want to be in the situation where you wanted to give them a nice healthy treat and suddenly they have vomiting and diarrhea," says Sandler.

So here are a few of the items Sandler recommends pet owners should avoid:

Fatty foods

These include such items as bacon, fat trimmings, anything deep-fried, cream sauces and gravies. Not only are these foods not healthy, they can upset pets' stomachs.

Lean meat, on the other hand, can be a great treat especially during training. It's rich in vitamins and protein. (Sandler's one exception to this rule is liver, which he says is too high-fat). Again, beware meat's high amount of calories and balance it with kibble or other starches and vegetables.

Chocolate, coffee-based products and soft drinks

These are well-known no-nos, especially to dogs. These products contain substances called methylxanthines, which are found in cacao seeds and well as in the fruit of coffee plants and the nuts of extracts used in some soft drinks. When ingested by pets, methylxanthines can cause vomiting and diarrhea, excessive thirst and urination, abnormal heart rhythm, tremors, and even death.

Raisins and grapes

These are also non-nos for dogs, though it's come to light only recently. Large amounts of grapes and raisins appear to cause kidney failure in dogs, but why they do is still not clear. Doctors are trying to narrow in on whether a toxin is present in grapes that affects pets, so until they know more it's best to just avoid grapes and raisins altogether.

Canned tuna

Although cats love fish, it's not a good idea to give them canned fish made for humans. That's because canned fish has been deboned, and cats actually need the minerals and other nutrients found in the bones. As well, vitamin E is not present in canned tuna, which could lead to a deficiency, resulting in a disease is called yellow fat disease, or steatitis.

Macadamia nuts

These nuts are toxic to dogs, though just like with grapes, no one has been able to figure out why. But even tiny amounts of the nuts should be avoided because they can cause toxicosis, which leads to weakness, vomiting, tremors and hyperthermia in dogs. Dogs generally recover within 48 hours.

Onions and garlic

Members of the onion family which includes garlic, contain compounds that can damage dogs' red blood cells if ingested in sufficient quantities. Although cats are more susceptible, dogs are also at risk if a large enough amount is consumed. Pets affected by onion toxicosis may seem weak or lethargic, and their urine may turn orange or red. An occasional low dose of onions likely will not cause a problem, pets should not given regular quantities.

Sandler says the trick with feeding pets people-food is to make sure that their animals are not taking in too many calories.

"We don't want treats or snacks to make up more than 15 or 20 per cent of what they're eating," advises Sandler.

So if you supplement your pet's regular diet with plenty of leftovers or even pet food you've cooked yourself, remember to cut back on your pet's kibble.

He also advises that if you are trying new foods on your pet, start with small amounts and wait to see if they have a reaction. Don't mix a number of food items at once in case since that will make it more difficult to figure out which food upset your pet.

Sandler says it's okay to give in to your pet's puppy dog eyes by feeding him or her treats, but never slip them to them under the table at dinnertime. Instead, put the food in his usual food dish and serve it to hem after your meal in an area separate from space from where you eat.

That way, mealtimes ca be peaceful times, free from hopeful, drooling pets whimpering for more.