Tomatoes are technically a fruit because they fit the botanical definition of one: they are the fleshy parts of a plant that surround its seeds. However, for nutritional and culinary purposes, tomatoes are considered a vegetable due to their taste, use in meals, and nutrient content.

Tomato Nutrition Facts

For ripe, red tomatoes, 100 grams have the following, according to the USDA:

Calories: 18 calories
Fat: <1 gram
Cholesterol: 0 milligrams
Sodium: 5 milligrams
Carbohydrates:3.89 grams
Fiber: 1.20 grams
Protein: <1 gram
Tomatoes are low in calories and provide important nutrients like vitamin C and potassium. They're also rich in antioxidants—one called lycopene, responsible for tomatoes' characteristic color, is linked to several benefits, such as a reduced risk of heart disease and certain cancers.

Benefits

Research shows that tomatoes in many forms—fresh, cooked and as juice—help protect against chronic diseases and support a physically active lifestyle.

May help protect brain health

In America, 10% of adults aged 65 years or older have Alzheimer's disease. The disease—which affects memory, thinking, and behavior—is a form of dementia that has no cure and that gets worse over time.
While more research on the connection between tomatoes and AD is needed, studies have suggested that the antioxidants in tomatoes, such as lycopene, may protect against neurodegenerative diseases like AD. One study showed that, over four years, there was a slower decline in cognitive function among participants aged 70 years or older who had a high lycopene intake.

More research on humans, specifically on adults aged 60 to 65, is needed to better understand the true connection between the potential protective benefits of tomatoes and AD and other neurodegenerative diseases like Parkinson's disease.

May help combat metabolic syndrome

Metabolic syndrome is a group of conditions that increase the risk of heart disease, diabetes, stroke, and other serious health problems. It involves having three or more of the following conditions:

A large waistline
High blood pressure
High blood sugar
High triglycerides or blood fats
Low "good" HDL cholesterol
About one in three US adults has metabolic syndrome.6 Researchers say that lycopene status—meaning the amount of lycopene in the blood—or lycopene consumption may be associated with favorable changes to the components of metabolic syndrome. And tomatoes are a major contributor of lycopene.

For one small study, 15 participants drank tomato juice once a day four times per week for two months with no specified amount. Despite the lack of a standardized portion of the juice, the group experienced significant decreases in "bad" LDL cholesterol, increases in "good" HDL cholesterol, and improvements in fasting insulin levels.

Helps protect heart health

A tomato-rich diet has been linked to a reduced risk of heart disease, the leading cause of death for adults in the US. One review of 25 previously published studies reported that a high intake of lycopene—as well as high blood levels of the antioxidant—reduced the risk of heart disease by 14%.

Another study of healthy people looked at the effect of a single dose of raw tomatoes, tomato sauce, or tomato sauce plus olive oil on measurements related to heart disease risk. All three doses reduced blood cholesterol and triglycerides—a type of fat in your blood—and raised HDL cholesterol and anti-inflammatory levels. The tomato sauce plus olive oil had the maximum effect, likely because the olive oil boosted the absorption of lycopene.

May help prevent constipation

Inadequate fluid and fiber can trigger constipation. Tomatoes provide both nutrients, with one whole tomato containing over four ounces of fluid and one and a half grams of fiber.

The water content and dietary fibers found in tomatoes are known to support hydration and healthy bowel movements. Tomatoes are an important source of both soluble and insoluble dietary fibers. Soluble fiber retains water to create a gel-like texture during digestion while insoluble fiber adds bulk to stool. Both of these changes form waste that is easier to pass. Specifically, the cellulose, hemicelluloses, and pectins fibers in tomatoes are resistant to digestion in the large intestine and help form healthy stool.

May help prevent type 2 diabetes

Among US adults, 14.7% have type 2 diabetes and 38% have prediabetes, when blood sugar levels are too high but not yet high enough to be diagnosed as type 2 diabetes. Some research shows that the antioxidant properties of lycopene contribute to the prevention of type 2 diabetes. This is due to its ability to protect cells from damage, reduce inflammation, and boost the body's defense mechanisms.16 Tomatoes' fiber can also help protect against diabetes.

May reduce cancer risk

Lycopene and beta-carotene, two antioxidants found in tomatoes, have been shown to possess anticancer properties. They do this in part by protecting against the kind of DNA damage in cells that can lead to the development of cancer and by causing cancer cells to die off.

Several studies have found that men with higher intakes of tomatoes—particularly cooked tomatoes—have a lower risk of prostate cancer. And, as a whole, eating non-starchy vegetables like tomatoes has been linked to a lower risk of estrogen receptor–negative breast tumors as well as cancer of the colon, rectum, lung, stomach, and upper aerodigestive tract (like the mouth, throat, and nasal sinuses).

Risks

As with any fresh produce, raw tomatoes can have germs like Listeria or Salmonella, resulting in foodborne illness. This is a greater concern for those who: are pregnant, over the age of 65, under the age of five, or have health problems or take medications that lower the body's ability to fight germs and sickness. This includes those living with diabetes, liver or kidney disease, HIV, or cancer. To reduce risk, you can cook your produce or, if you are using raw tomato, wash it.

In addition, tomatoes may worsen existing conditions like gastroesophageal reflux (GERD) or migraine. Talk with your healthcare provider to determine if you need to steer clear of tomatoes for any reason.

Tips for Consuming

Many of the benefits of consuming tomatoes are tied to their lycopene content. Research shows that tomatoes grown in fields contain higher levels of lycopene than those grown in greenhouses. In addition, cooking tomatoes increases their lycopene content. And eating them with fat, like avocado or extra virgin olive oil, boosts lycopene absorption from the digestive tract into the bloodstream.

That all being said, to take advantage of the full range of positive benefits, it's recommended to regularly consume tomato in various forms, including raw and cooked. Add raw tomatoes to anything from omelets to avocado toast to salads. Enjoy as fresh pico de gallo. Stuff fresh tomatoes with hummus, olive tapenade, or vinaigrette dressed greens. Grill or oven roast raw tomatoes, or enjoy cooked tomatoes in the form of paste, sauce, and salsa, incorporated into a variety of dishes like soup, pasta, chili, and tacos. Sip tomato juice as is or use it as the base for gazpacho.

Summary

Tomatoes offer several potential research-backed benefits, including protection for brain, heart, and gut health. The vegetable, which is also considered a fruit, is a solid source of nutrients like vitamin C, potassium, and antioxidants—namely, lycopene.

There might be some potential downsides to consuming them—especially depending on your health status—but most people can eat both raw and cooked tomatoes as part of a balanced diet. For guidance about whether tomatoes and the nutrients like lycopene they contain may help with a specific condition, talk with a healthcare provider.