Can Cats Eat Tomatoes?
Small quantities of ripe tomato are safe for curious cats to eat. However, cats are obligate carnivores, so they won’t gain any nutritional benefit by eating tomatoes.
Unripe tomatoes, and the leaves and stems of tomato plant contain a substance called tomatine, which is toxic to cats – so don’t let your cat eat these.
Where Do Tomatoes Come From?
Tomatoes were cultivated as long ago as 700 AD by early the Aztecs. In the 16th century, Spanish explorers brought tomatoes to Europe from Mexico.
Although popular in Southern Europe, for almost two centuries, many people were suspicious of tomatoes, believing them to be poisonous.
Tomatoes were known to be members of the nightshade family.
People feared nightshades not only for their potential to cause physical harm but for their reputed use as tools to summon werewolves!
In addition, it’s likely tomatoes developed a bad reputation due to the type of crockery common to the period. Many plates and bowls of the time were made of pewter, which has a high lead content.
When pewter comes into contact with acidic foods, lead can leach out into the food. Lead ingestion causes serious health problems.
Thus, many mistakenly assumed tomatoes were to blame. Tomatoes finally began to shed their bad reputation in the early 1800s.
A Good Day for Tomatoes
Famously, in the 1820s, Robert Gibbon Johnson stood on the steps of the courthouse in New Jersey and ate a tomato to demonstrate it was safe to eat!
By the mid 19th century, the tomato was a kitchen staple.
Today, tomatoes are one of the world’s most popular foods. In 2014, 170 million tonnes of tomatoes were produced worldwide.
Tomatoes are also one of the most popular plants grown by amateur gardeners.
Tomatoes can be grown at home from seed or seedlings, and can be planted directly into soil beds, or grown in containers or greenhouses.
Why Do Tomatoes Have A Reputation For Being Poisonous To Cats?
Tomatoes are part of the nightshade (Solanaceae) family, made up of over 3000 plant species including potatoes, peppers, and eggplant.
To understand why nightshades can be poisonous, we need to understand some of the chemistry of these plants.
Nightshades contain glycoalkaloids.
Glycoalkaloids are chemical compounds made up of alkaloids (nitrogenous compounds known for causing significant physiological effects) and sugars.
Many nightshades- including potatoes- contain the glycoalkaloid solanine.
It is often claimed that it is solanine in tomato plants which makes them dangerous for cats.
The Plot Thickens
However, research suggests it is a different glycoalkaloid, tomatine, which can be problematic.
Tomatine is present in the stem, leaves and fruit of the tomato plant. The good news is that tomatine appears to be less toxic than other types of glycoalkaloid.
Evidence suggests that once ingested tomatine forms a complex with cholesterol. This complex is insoluble, and is excreted with very little tomatine actually absorbed.
Moreover, research has shown that tomatine levels in tomatoes decrease with ripening.
Not a major concern
This would suggest that ripe red tomatoes pose little threat to our feline friends.
However, it is important to remember tomatine is present in higher concentrations in unripe tomatoes, green tomatoes, and the stem and leaves of the tomato plant.
While ingestion of low levels of tomatine is unlikely to prove fatal, it can lead to physical effects.
These include diarrhea, vomiting, loss of appetite, increased heart rate, confusion, dilated pupils and changes in behavior.
What Is A Natural Cat Diet?
Cats are obligate carnivores. This means that they rely on nutrients from animal tissues to meet their body’s requirements.
In the wild, cats eat a high protein diet with some fat and few carbohydrates.
As such, their bodies have adapted to primarily use protein and fat, rather than carbohydrates, as their main energy source.
Unlike omnivorous species such as the dog, cats bodies cannot adapt enzyme activity levels in response to diet composition- for example, increased levels of carbohydrates.
This means that cats gain little nutritional benefit from carbohydrates.
Why Might Owners Want To Feed Their Cat Tomatoes?
Given that cats are obligate carnivores, why would we give them tomatoes?
Cats can be picky eaters. Often, they will show more interest in the food their human is eating than cat food! Thus, some owners allow their cats occasional, safe, ‘people food’ treats.
For more information on human foods considered safe for cats, check out our guides here.
Many commercial cat foods actually contain tomatoes already.
You may have experienced your cat taking an interest in tomatoes, as well as other vegetables or plants. But are tomatoes safe?
Can Cats Eat Ripe Tomatoes?
Despite their reputation for being poisonous, research suggests that ripe, red tomatoes can be safe for cats in small quantities.
As we know, tomatoes contain the glycoalkaloid tomatine, which is less potent than other glycoalkaloids.
Tomatine can cause gastrointestinal distress among other symptoms if ingested in sufficient quantities.
However, levels of tomatine decrease as tomatoes ripen. In ripe red tomatoes, levels are usually very low. That being said, tomatine is present in all parts of the tomato plant.
Keep the green bits out of reach
While a ripe red tomato is unlikely to do your kitty any harm, they should be prevented from nibbling on the stems or leaves of tomato plants, or unripe tomatoes. These elements can contain higher levels of tomatine which could potentially trigger a reaction.
Cat owners who grow tomatoes should take care to fence off the plants, or to position them in places curious kitties cannot access.
Also, it’s important to remember that, like humans, cats can have individual sensitivities and allergies.
While one cat may be fine eating ripe red tomatoes occasionally, another could have an allergic reaction.
With this in mind, it’s vital that if you do allow your cat to taste ripe tomatoes, you monitor them carefully for any signs of a negative reaction to the food.
If your cat displays unusual behavior or symptoms, you should consult your veterinarian immediately.
Can Cats Eat Cooked Tomatoes?
Tomatine is a very stable compound. This means that heating will not break it down.
Hence, cooked tomatoes still contain tomatine.
However, as long as you are cooking ripe red tomatoes, the level of tomatine is likely to be very low.
Thus, cooked tomatoes in small quantities can be safe for cats.
Can Cats Eat Tinned Tomatoes?
Tinned tomatoes can be considered relatively safe for cats, depending on whether or not they have added ingredients.
Tinned tomatoes generally contain salt, but research suggests that in healthy cats, this does not pose major concerns.
If tinned tomatoes have other ingredients- like seasonings- while they are unlikely to do harm, your cat may find them too spicy or unappealing.
If tinned tomatoes contain onion or garlic, they should not be given to cats, as they can be poisonous.
Can Cats Eat Tomato Soup?
Tomato soup is not comprised purely of tomatoes. Garlic and onion are common soup ingredients. Both have been identified as potentially poisonous to cats.
Hence, you should not give soup containing garlic or onion to cats.
Soups without onion or garlic usually have other types of seasoning, and may have preservatives or added sugar.
Whilst not necessarily harmful, these ingredients may be unappealing to your cat. Moreover, sugar can increase their risk of obesity and so is best avoided.
Can Cats Eat Tomato Ketchup?
Tomato ketchup contains a significant amount of sugar.
Research shows cats are largely indifferent to sugary foods, and indicates they may even be ‘sugar blind’ and unable to taste sweet things.
Sugar is not poisonous to cats. But if they ingest too much, they can be at risk of obesity or even diabetes.
Hence, it’s probably best to keep this condiment out of your kitty’s reach!
Are Tomatoes Good For Cats?
As we’ve learned, cats are obligate carnivores.
They have evolved to obtain most of their energy from fats and proteins, rather than carbohydrates.
While they are a source of water and fiber (potentially useful if your kitty gets constipated) tomatoes offer little nutritional value.
Are Tomatoes Bad For Cats?
Generally speaking, ripe, red tomatoes are unlikely to do any harm to your cat.
However, the stems and leaves of tomato plants, green tomatoes, or large quantities of tomatoes, do have the potential to cause gastrointestinal distress and other unpleasant symptoms.
While unlikely to prove fatal, tomato toxicity of this kind is distressing for your kitty and will require veterinary intervention.
Do Cats Like Tomatoes?
Cats, like humans, are all unique.
Obligate carnivores like cats do not need tomatoes in their diet, but many cats may show interest in eating tomatoes or other plant-based foods.
This is because their tastes, like ours, differ!
Some cats may be attracted to tomatoes. Others may show no interest at all.
Can Cats Eat Tomatoes?
Yes, as long as they are ripe and red!
Ripe, red tomatoes have low levels of tomatine, the glycoalkaloid responsible for physical symptoms. Thus, they are considered safe for cats to consume in small quantities.
Ensure tomatoes are diced to reduce choking risk, and monitor your pet for signs of any adverse effects.
Caution is Key
Remember that cats, like people, can have allergies. Be mindful of this when you introduce them to any new food.
Unripe tomatoes and the stems and leaves of tomato plants, however, have higher levels of tomatine and hence are potentially more likely to cause ill-effects.
You should take care and keep these well out of your pet’s reach.
If you are concerned that your cat has ingested any of the above, contact your veterinarian immediately.
References & Resources
- Bushway R.J. et. al, High-Performance Liquid Chromatographic Determination of the Tomato Glycoalkaloid, Tomatine, in Green and Red Tomatoes, Journal of Agricultural and Food Chemistry, 1994
- Beresford, M. The White Devil: The Werewolf in European Culture, 2013
- British Tomato Growers’ Association
- Cope, R.B., Allium species poisoning in dogs and cats, Veterinary Medicine, 2005
- Dalvi, R. R. & Bowie, W.C., Toxicology of solanine: an overview. Veterinary and human toxicology 1983
- Friedman, M. et. al., Lowering of plasma LDL cholesterol in hamsters by the tomato glycoalkaloid tomatine, Food and Chemical Toxicology, 2000
- Gray, C. et. al., Nutritional adequacy of two Vegan diets for cats, Journal of the American Veterinary Medical Association, 2004
- Guan, Z. et. al., The US Tomato Industry: An Overview of Production and Trade, The UF/IFAS Extension Publication, 2017
- Kozukue, N. & Friedman, M., Tomatine, chlorophyll, β‐carotene and lycopene content in tomatoes during growth and maturation, Journal of the Science of Food and Agriculture, 2003
- Li, Xia, et al. Pseudogenization of a sweet-receptor gene accounts for cats’ indifference toward sugar. PLoS genetics, 2005
- Luckschander, N. et. al., Dietary NaCl Does Not Affect Blood Pressure in Healthy Cats, Journal of Veterinary Internal Medicine, 2008
- Stimekova, E. & Horcin, V., Determination of Solanine in Tomato Cultivars, Food Science, 1980
- Yamashoji, S. & Onoda, E., Detoxification and function of immature tomato, Food Chemistry, 2016
- Zoran, D., The carnivore connection to nutrition in cats, Journal of the American Veterinary Medical Association, 2002
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