Do not feed onions, onions can cause haemolytic anaemia (bursting of red blood cells)
Small amounts of onion in small amounts of table scraps is unlikely to ever cause your dog a problem, but larger amounts can. So just use common sense
Do not feed vegetables from the cabbage family regularly in large quantities. These can interfere with thyroid function. Do not feed raw potato, these are toxic to your dog.
Fruit should be approx 5-10 % of your dogs diet, feed it separately, as a treat, fruits contain different types of proteins to meat and by feeding them separately, you ensure your dog can get the maximum benefit from both. In our experience most dogs will leave fruit, if fed with a meat meal.
Some dogs will not eat fruit in any shape or form, --- including our own dog ---
Just accept that and concentrate on the rest of their diet and you could of course feed our excellent supplementHerb Hound, produced from whole herb and fruit powders, this way you can supplement their diet with the multitude of vitamins and mineral naturally occurring in the fruit and herbs it contains.
If your dog is asking for more fruit, give it, it will do her/him good, again if you have a dog with no stop tap, you will have to hold back, otherwise just be guided by them.
Nuts, feed small quantities as treats, not salted of course, do not feed Macadamia nuts, they are toxic to dogs.
Good additions to add in moderation to the above basic diet would be: eggs either raw or cooked, tinned tuna, sardines in oil. Cooked beans and chickpeas are also a great addition and can, some days replace some of the meat, a good idea if say the previous day you fed quite large quantities of meat. If using tinned beans, rinse to remove excess salt.
If you add some table scraps to your dogs food, avoid pasta, rice, couscous etc. Include only small amounts of cooked potato, they are a high carbohydrate rich food from which they derive little benefit.
Dairy products, adult dogs do not need dairy, if you feed it occasionally as a treat, in small amounts no harm done and much joy had!
Why not to feed grains, quite simply they have no or very little benefit to your dog. Although they are omnivores their digestive system are in no way adapted to consume the large quantities, which has now become the norm, secondly grains contain naturally occurring phytic acid, phytic acid partly prevents uptake of minerals in food phytic acid can also interfere with the action of digestive enzymes. The result is a chronic lack of essential nutrients, needed for good and long term health. Grains and in particular wheat can damage the lining of the intestines, causing leaky gut/ inflammation, this allows particles/molecules from the digestive process to enter the blood stream in a form that would otherwise not be possible, this in turn, can cause the immune system to try to clear these substances as quickly as possible, one route would be the skin, this can be the start of a compromised immune system and will most likely show up as, itching, rashes, boils and or digestive problems.