What can cats not eat – 16 tips for proper cat nutrition

Most people are familiar with the image of a cat lapping up milk from a bowl. On farms, milk from the cows often still ends up in the cat’s bowl and nobody bats an eyelid. And yet this ingredient is often listed as a prohibited food. What is going on? Is milk actually toxic for cats? Absolutely not. But ... in the same way that many humans are lactose intolerant, most adult cats can no longer tolerate dairy products containing lactose. They won’t die and most will not get seriously ill as a result; however, most cats can only digest lactose with difficultyor not at all and this can result in diarrhoea.

This question will elicit a weary smile from proponents of the BARF (biologically appropriate raw food) diet – they offer their cats a daily meal that is as natural as possible, consisting of fresh meat and appropriate ingredients. BARF fans will even put raw chicken in their cat’s bowl (which many chefs fear as a potential source of salmonella). But not all cats tolerate raw meat equally well. Cats that are used to eating prepared food often do not get on with the natural microbial content in raw meat compared with cats that have followed a BARF diet and whose digestive tracts are accustomed to these bacterial demands. Immunocompromised animals are particularly at risk (irrespective of the type of food being offered) and can suffer serious illnesses including blood stream infections. But what meat are cats allowed to eat raw? In principle they can eat anything – the only exception is pork and wild boar meat. These varieties of meat should not be fed raw due to the risk of Aujeszky's disease (AD), which can be fatal for cats. This disease has been eradicated in domestic pigs, which act as hosts for the herpes virus (Germany has been AD-free since 2003), however cases of the Aujeszky virus do occasionally crop up in wild pigs. In addition, it is impossible to guarantee that pork has not been sourced from abroad.
Note: The risk of infection is always higher from raw meat than from prepared food. The possibility of transmitting germs to humans can also not be ruled out, which is a relevant consideration particularly for pregnant women, new-born babies, and older people. The same caution should be applied for preparing meat in general.

Eggs are healthy for cats because they contain lots of amino acids and vitamins. However, the egg white (unlike the yolk) should never be offered raw. Raw egg white contains high levels of avidin and ovomucin.
Avidin is a glycoprotein that can bind vitamin B7. If a cat is fed egg white too often, their body will become unable to absorb this important vitamin – also known as biotin – either from their food or from the substance produced by microorganisms in their intestinal flora. This can result in a biotin deficiency. When egg whites are cooked, the avidin is denatured and can no longer form an insoluble compound with the biotin found in food. The risk of a vitamin B7 deficiency is thus avoided.
The protein ovomucin, on the other hand, is a trypsin inhibitor, which is a vital enzyme in the digestive tract. If trypsin is inhibited, this can cause digestive problems.

Fruits that are literally forbidden include stone fruit such as plums, peaches and apricots. The stones contain hydrocyanic acid which, depending on the dose, can cause poisoning within a few seconds, potentially resulting in death a short time later due to asphyxiation. These fruit stones are even more dangerous for dogs because they tend to bite hard objects when playing.
Grapes and raisins should also be avoided on the feline menu plan. While most cats don’t like these fruits, if they do get carried away and eat them this can cause stomach pains and diarrhoea, or even kidney damage and death. It is still not known what the toxic substance in the grapes is and the dangerous dose has only been researched in dogs.

Unlike dogs, who eat all sorts of vegetables, cats are committed carnivores who are likely to turn their noses up at vegetables. In the wild, cats are predators whose only plant-based intake is whatever is found in the stomach of their prey.

Not all vegetables are suitable for cats. If humans can only eat something when it is cooked, cats will also generally tolerate these items in the same form. Caution is required with cabbage and pulses: many of these foods can cause unpleasant flatulence or stomach pain. Alliums like onions, chives and garlic are also dangerous for cats due to the sulphur compounds they contain in any form – raw, fried or boiled. Raw potatoes are another item that must not go into your cat’s food dish due to their high solanine content and starch levels.

Cats are natural predators and will hunt pretty much anything that moves, not just mice and birds. Flies are a little everyday treat in cat’s lives. They ensure species-appropriate activity, offer a physical challenge, and represent a small but nonetheless enjoyable delicacy. Cats fulfil their urge to play – before actually eating the fly, they usually just lick off the wings to stop the insect flying away. Once the fly has been physically disabled in this way, it is an easy victim, to be used by the cat as a living puck in a gruesome game of hockey. Flies and insects are a natural part of cats’ diet in the wild too, where they are a valuable source of high-quality protein.

Dog food is not toxic for cats, so you don’t need to panic if your cat occasionally helps himself to whatever is in the dog’s bowl. However, this shouldn’t become a regular habit because standard dog food does not have a suitable nutrient profile for cats. Cats need food that is very high in protein and taurine because they cannot synthesise amino sulfonic acid themselves. Semi-moist complete dog food can also contain propylene glycol as a preservative. This is not suitable for cats.

Most cats are not big bread fans – and that's for the best. Bread is not recommended for cats due to its imbalanced composition. Special caution required for mould: mouldy bread can cause vomiting, muscle tremors, rapid breathing, cardiac arrythmia and aggressivity. Sometimes cramps may also occur.

In the period shortly after the operation, you can offer your cat some fresh water, but no food. As long as the anaesthetic is in the cat’s bloodstream, there is a risk of vomiting if food is consumed. Food can be offered once the anaesthesia has worn off and your pet is coordinated and appears alert.

The following plants are poisonous for cats:

As hard as it might be to resist sharing your favourite treat with your cat, chocolate really is off limits for cats. Cocoa contains theobromine, a substance that is highly toxic for house cats. Even in small quantities, this alkaloid can trigger poisoning symptoms such as vomiting, diarrhoea, panting, elevated respiration, muscle tremors and cramps. Eating chocolate can even result in death – a third of a bar of dark chocolate can be fatal for a cat that weighs 5 kg. The higher the cocoa content in the chocolate, the higher its theobromine content.

Common sense tells us that crisps are not good for us – and they certainly are not healthy for little cat’s bodies either. Too many spices, too much saturated fat. You are not doing your cat any favours if you share your crisps or salty treats with them. And you really have to ask whether your cat should be sipping your morning coffee or partaking in a beer at the end of the day – hands off! Stimulants such as alcohol, tea or coffee are highly toxic! Alcohol, coffee and tea (including herbal teas) can be toxic and cause damage to the liver, kidneys and gastrointestinal tract.