The tomato (Solanum lycopersicum) is a fruit from the nightshade family native to South America.

Despite botanically being a fruit, it’s generally eaten and prepared like a vegetable.

Tomatoes are the major dietary source of the antioxidant lycopene, which has been linked to many health benefits, including reduced risk of heart disease and cancer.

They are also a great source of vitamin C, potassium, folate, and vitamin K.

Usually red when mature, tomatoes can also come in a variety of colors, including yellow, orange, green, and purple. What’s more, many subspecies of tomatoes exist with different shapes and flavor.

This article tells you everything you need to know about tomatoes.

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The water content of tomatoes is around 95%. The other 5% consists mainly of carbohydrates and fiber.

Here are the nutrients in a small (100-gram) raw tomato (1):

  • Calories: 18
  • Water: 95%
  • Protein: 0.9 grams
  • Carbs: 3.9 grams
  • Sugar: 2.6 grams
  • Fiber: 1.2 grams
  • Fat: 0.2 grams

Carbs

Carbs comprise 4% of raw tomatoes, which amounts to fewer than 5 grams of carbs for a medium specimen (123 grams).

Simple sugars, such as glucose and fructose, make up almost 70% of the carb content.

Fiber

Tomatoes are a good source of fiber, providing about 1.5 grams per average-sized tomato.

Most of the fibers (87%) in tomatoes are insoluble, in the form of hemicellulose, cellulose, and lignin (2).

SUMMARY Fresh tomatoes are low in carbs. The carb content consists mainly of simple sugars and insoluble fibers. These fruits are mostly made up of water.

Tomatoes are a good source of several vitamins and minerals:

  • Vitamin C. This vitamin is an essential nutrient and antioxidant. One medium-sized tomato can provide about 28% of the Reference Daily Intake (RDI).
  • Potassium. An essential mineral, potassium is beneficial for blood pressure control and heart disease prevention (3).
  • Vitamin K1. Also known as phylloquinone, vitamin K is important for blood clotting and bone health (4, 5).
  • Folate (vitamin B9). One of the B vitamins, folate is important for normal tissue growth and cell function. It’s particularly important for pregnant women (6, 7).
SUMMARY Tomatoes are a good source of several vitamins and minerals, such as vitamin C, potassium, vitamin K, and folate.

The content of vitamins and plant compounds in tomatoes can vary greatly between varieties and sampling periods (8, 9, 10).

The main plant compounds in tomatoes are:

  • Lycopene. A red pigment and antioxidant, lycopene has been extensively studied for its beneficial health effects (11).
  • Beta carotene. An antioxidant that often gives foods a yellow or orange hue, beta carotene is converted into vitamin A in your body.
  • Naringenin. Found in tomato skin, this flavonoid has been shown to decrease inflammation and protect against various diseases in mice (12).
  • Chlorogenic acid. A powerful antioxidant compound, chlorogenic acid may lower blood pressure in people with elevated levels (13, 14).

Chlorophylls and carotenoids like lycopene are responsible for the rich color of tomatoes.

When the ripening process starts, the chlorophyll (green) is degraded and carotenoids (red) are synthesized (15, 16).

Lycopene

Lycopene — the most abundant carotenoid in ripened tomatoes — is particularly noteworthy when it comes to the fruit's plant compounds.

It's found in the highest concentrations in the skin (17, 18).

Generally, the redder the tomato, the more lycopene it has (19).

Tomato products — such as ketchup, tomato juice, tomato paste, and tomato sauces — are the richest dietary sources of lycopene in the Western diet, providing over 80% of dietary lycopene in the United States (20, 21).

Gram for gram, the amount of lycopene in processed tomato products is often much higher than in fresh tomatoes (22, 23).

For example, ketchup boasts 10–14 mg of lycopene per 3.5 ounces (100 grams), while one small, fresh tomato (100 grams) holds only 1–8 mg (24).

However, keep in mind that ketchup is often consumed in very small amounts. Thus, it may be easier to bump up your lycopene intake by eating unprocessed tomatoes — which also have far less sugar than ketchup.

Other foods in your diet may have a strong effect on lycopene absorption. Consuming this plant compound with a source of fat can increase absorption by up to four times (25).

However, not everyone absorbs lycopene at the same rate (26).

Even though processed tomato products are higher in lycopene, it’s still recommended to consume fresh, whole tomatoes whenever possible.

SUMMARY Lycopene is one of the most abundant plant compounds in tomatoes. It’s found in the highest concentrations in tomato products, such as ketchup, juice, paste, and sauce.

Consumption of tomatoes and tomato-based products has been linked to improved skin health and a lower risk of heart disease and cancer.

Heart health

Heart disease — including heart attacks and strokes — is the world's most common cause of death.

A study in middle-aged men linked low blood levels of lycopene and beta-carotene to increased risk of heart attacks and strokes (27, 28).

Increasing evidence from clinical trials suggests that supplementing with lycopene may help lower LDL (bad) cholesterol (29).

Clinical studies of tomato products indicate benefits against inflammation and markers of oxidative stress (30, 31).

They also show a protective effect on the inner layer of blood vessels and may decrease your risk of blood clotting (32, 33).

Cancer prevention

Cancer is the uncontrolled growth of abnormal cells that spread beyond their normal boundaries, often invading other parts of the body.

Observational studies have noted links between tomatoes — and tomato products — and fewer incidences of prostate, lung, and stomach cancers (34, 35).

While the high lycopene content is believed responsible, high-quality human research needed to confirm the cause of these benefits (36, 37, 38).

A study in women shows that high concentrations of carotenoids — found in high amounts in tomatoes — may protect against breast cancer (39, 40).

Skin health

Tomatoes are considered beneficial for skin health.

Tomato-based foods rich in lycopene and other plant compounds may protect against sunburn (41, 42).

According to one study, people who ingested 1.3 ounces (40 grams) of tomato paste — providing 16 mg of lycopene — with olive oil every day for 10 weeks experienced 40% fewer sunburns (43).

SUMMARY Studies show that tomatoes and tomato products may reduce your risk of heart disease and several cancers. This fruit is also beneficial for skin health, as it may protect against sunburns.

When tomatoes start to ripen, they produce a gaseous hormone called ethylene (44, 45).

Commercially grown tomatoes are harvested and transported while still green and immature. To make them red before selling, food companies spray them with artificial ethylene gas.

This process inhibits the development of natural flavor and may result in tasteless tomatoes (46).

Therefore, locally grown tomatoes may taste better because they’re allowed to ripen naturally.

If you buy unripened tomatoes, you can speed up the ripening process by wrapping them in a sheet of newspaper and keeping them on the kitchen counter for a few days. Just make sure to check them daily for ripeness.

SUMMARY Tomatoes are often harvested while still green and immature, then ripened artificially with ethylene gas. This may lead to less flavor development, resulting in bland tomatoes.

Tomatoes are generally well tolerated and tomato allergy is very rare (47, 48).

Allergy

Although tomato allergy is rare, individuals allergic to grass pollen are more likely to be allergic to tomatoes.

This condition is called pollen-food allergy syndrome or oral-allergy syndrome (49).

In oral-allergy syndrome, your immune system attacks fruit and vegetable proteins that are similar to pollen, which leads to allergic reactions like itching in the mouth, scratchy throat, or swelling of the mouth or throat (50).

People with latex allergy can also experience cross-reactivity to tomatoes (51, 52).

SUMMARY Tomatoes are generally well tolerated but may cause allergic reactions in people allergic to grass pollen.

Tomatoes are juicy and sweet, full of antioxidants, and may help fight several diseases.

They are especially high in lycopene, a plant compound linked to improved heart health, cancer prevention, and protection against sunburns.

Tomatoes can be a valuable part of a healthy diet.