While it’s technically a fruit, most nutritionists still view tomatoes as a vegetable due to their lower fructose content and due to the fact that they’re most often used similarly to other veggies.
Our daily keto carb count shouldn’t be creeping over more than 30 grams per day, and luckily, from a macronutrient perspective, tomatoes contain between just 3-4 grams of net carbs per 100 grams.
However, a low carb count isn’t the only reason for including a food in your diet, and tomatoes themselves come in many varieties, so let’s take a closer look at them to see just how keto-friendly they are.
Types of Tomato
There are thousands of varieties of tomato grown around the world, so we’ll be sticking to the most common ones for now, but some of these do have different macros, so it’s worth knowing which are suitable for keto and which aren’t.
Roma tomatoes (also known as plum tomatoes) are the ones you’re most likely to see in your everyday grocery store and are popular around the globe.
A thick slice of Roma tomato will only contain 1 gram of carbs on average, which is fine if you’re eating it sparingly, however, it’s worth noting that these are the variety most commonly used in tomato pastes and sauces and a cup of diced Roma tomatoes can contain around 7 grams.
Paying attention to your quantities and the presence of tomato as an ingredient in other foods is key here.
Cherry tomatoes are ideal for keto. While they do have a similar carb content to your run-of-the-mill Roma tomato, their smaller size, crunchy skin, and juicy center make them perfect for using in keto-friendly meals, especially salads.
Beefsteak tomatoes are the most consumed variety in the world, mainly due to their presence in fast food and standard restaurant offerings, such as burgers and pizzas.
Their carb content is similar to that of Roma tomatoes at around 7 grams for a large one, but the fact that they usually come in a large serving means they’re not the best type for staying keto.
Additionally, unless you’re cooking with them yourself, they tend to be paired with foods that aren’t remotely keto friendly.
Grape tomatoes are a little smaller than cherry tomatoes and have a more oval shape to them, like Romas.
They have lower water content and a thicker skin which, as a result, means that they have one of the higher per-tomato carb counts and should be ditched for cherry tomatoes.
Although they can often be confused with cherry tomatoes due to their size and shape, Campari tomatoes have a unique texture and a distinct, sweet taste.
You can usually recognize them by the fact that most grocery stores tend to sell them on the vine, however, at nearly 4 grams of net carbs per tomato you should try and avoid them on keto.
Health Benefits of Tomatoes
Not only are most varieties of tomato suitable for keto from a macronutrient perspective, but they also come with a wide range of health benefits.
For most people, tomatoes are a primary dietary source of the antioxidant lycopene which, alongside the beta-carotene (that gives vegetables their red-orange hue), has been linked to a decreased risk of heart attack  or stroke .
Lycopene has also shown potential for lowering bad cholesterol and tomatoes may be responsible for protecting our blood vessels  and reducing the risk of clotting.
While studies are still being conducted, some research has led nutritionists and scientists to believe that tomatoes and tomato-based foods that have a high lycopene content may protect us from sunburn . Their high vitamin content is also thought to contribute to skin health.
Prevention Against Cancer
There have been numerous observational links between the consumption of tomatoes and a lower rate of certain cancers , and lycopene is again believed to be the antioxidant behind this increased protection.
Additionally, there have been studies that indicated that high levels of carotenoids6 could also protect against cancer; however, in both cases, there must be more research conducted.
How to Use Tomatoes in Your Keto Diet
Like with almost every other keto-friendly food, you still need to pay attention to how you incorporate it into your diet to avoid going over your carb limit. Fortunately, there are plenty of delicious low-carb, high-fat recipes for you to try.
Low-carb Roasted Tomato Soup
A perfect lunchtime meal that’s easy to prep and batch in advance, this warm treat is excellent on keto. To thin out the tomato and cut down on the carbs, you can add broth and cream to boost both the flavor and the fat content.
You can even add some fresh feta for some extra tang and a fat boost.
Cheesy Baked Tomato
This recipe is straightforward but moreish, and takes no time to whip up. Slice yourself four pieces of tomato, then de-case one Italian sausage and cook it through.
Place the tomato slices in a baking tray, divide the sausage evenly between the tops of each one, and sprinkle a tablespoon of gouda cheese on each afterward.
Baking only takes around four minutes or until the cheese is golden, and all four slices will just set you back around 6 grams of net carbs while giving you a whopping 26 grams of fat and 20 grams of protein.
Salads and Sides
We may have mentioned it before, but tomatoes are an excellent addition to most salads and can easily be added to most dishes as a simple side. Cherry tomatoes are our favorites here, but as long as you check the variety, you’ve got a lot of freedom to go with your personal taste.
In summary, most varieties of tomatoes are keto-friendly in the right quantities, and as long as you pay attention, there’s no reason not to include them in your diet.
They’re delicious on their own or as an ingredient in a number of great low-carb recipes, so you should definitely add fresh tomatoes to your next shopping list.
 https://www.ncbi.nlm.nih.gov/pubmed/22158914 Karppi J, Laukkanen JA, Mäkikallio TH, Kurl S. Low serum lycopene and β-carotene increase risk of acute myocardial infarction in men. Eur J Public Health. 2012 Dec;22(6):835-40. doi: 10.1093/eurpub/ckr174. Epub 2011 Dec 7.
 https://www.ncbi.nlm.nih.gov/pubmed/23045517 Karppi J, Laukkanen JA, Sivenius J, Ronkainen K, Kurl S. Serum lycopene decreases the risk of stroke in men: a population-based follow-up study. Neurology. 2012 Oct 9;79(15):1540-7. doi: 10.1212/WNL.0b013e31826e26a6.
 https://www.ncbi.nlm.nih.gov/pubmed/22969932 Palomo I, Fuentes E, Padró T, Badimon L. Platelets and atherogenesis: Platelet anti-aggregation activity and endothelial protection from tomatoes (Solanum lycopersicum L.). Exp Ther Med. 2012 Apr;3(4):577-584. Epub 2012 Feb 9.
 https://www.ncbi.nlm.nih.gov/pubmed/15830922 Aust O, Stahl W, Sies H, Tronnier H, Heinrich U. Int J Vitam Nutr Res. Supplementation with tomato-based products increases lycopene, phytofluene, and phytoene levels in human serum and protects against UV-light-induced erythema. 2005 Jan;75(1):54-60.
 https://www.ncbi.nlm.nih.gov/pubmed/10050865 Giovannucci E. Tomatoes, tomato-based products, lycopene, and cancer: review of the epidemiologic literature. J Natl Cancer Inst. 1999 Feb 17;91(4):317-31.
 https://www.ncbi.nlm.nih.gov/pubmed/12010859 Sato R, Helzlsouer KJ, Alberg AJ, Hoffman SC, Norkus EP, Comstock GW. Prospective study of carotenoids, tocopherols, and retinoid concentrations and the risk of breast cancer. Cancer Epidemiol Biomarkers Prev. 2002 May;11(5):451-7.