Known scientifically as Solanum lycopersicum, the tomato is the berry of a plant from the nightshade family, native to South America.
Despite technically being a fruit, the tomato is generally categorized as 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.
They are usually red when mature, but can come in a variety of colors, including yellow, orange, green and purple.
Then there are many subspecies of tomatoes, with different shapes and flavor.
One medium sized tomato (123 grams) contains only 22 calories.
The table below contains detailed information on the nutrients found in tomatoes ().
Carbohydrates make up 4% of raw tomatoes, which amounts to less than 5 grams of carbs for an average sized tomato (123 grams).
Simple sugars, such as glucose and fructose, make up almost 70% of the carbohydrate content.
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 ().
Bottom line: Fresh tomatoes are low in carbs (4%). The carb content consists mainly of simple sugars and insoluble fibers.
Tomatoes are a good source of several vitamins and minerals.
- Vitamin C: An essential nutrient and antioxidant. One medium sized tomato can provide about 28% of the recommended daily intake.
- Potassium: An essential mineral, beneficial for blood pressure control and cardiovascular disease prevention ().
- Vitamin K1: Also known as phylloquinone, vitamin K is important for blood coagulation and bone health (, ).
- Folate (B9): One of the B-vitamins, important for normal tissue growth and cell function (). It is particularly important for pregnant women ().
Bottom line: 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 can vary greatly between different tomato varieties and sampling periods (, , ).
Here is a list of the main plant compounds in tomatoes.
- Lycopene: A red pigment and antioxidant, which has been extensively studied for its beneficial health effects ().
- Beta-Carotene: A yellow antioxidant, which is converted into vitamin A in the body.
- Naringenin: Found in tomato skin, this flavonoid has been shown to decrease inflammation and protect against various diseases in mice ().
- Chlorogenic acid: A powerful antioxidant compound, which may lower blood pressure in patients with high blood pressure (, ).
Chlorophylls and carotenoids are responsible for the color of tomatoes.
When the ripening process starts, the chlorophyll (green) is degraded and carotenoids (red) are synthesized (, ).
Bottom line: The main plant compound in tomatoes is lycopene. They also contain beta-carotene, naringenin and chlorogenic acid.
Of all the plant compounds found in tomatoes, lycopene is particularly noteworthy.
Lycopene is the most abundant carotenoid in the ripened tomato and is found in the highest amount in the tomato peel (, ).
The rule of thumb is, the redder the tomato, the more lycopene it contains ().
Tomato products, such as ketchup, tomato juice, and tomato-based sauces, are the richest dietary sources of lycopene and provide more than 80% of the dietary lycopene in the US (, ).
The amount of lycopene in processed tomato products is often much higher than in fresh tomatoes (, ).
Ketchup for example, contains 10-14 mg/100 g but fresh tomatoes contain only 1-8 mg/100 g of lycopene ().
Other foods in the diet may have a strong effect on the absorption of lycopene from the digestive system. Consuming it with fat can increase absorption up to 4-fold ().
However, there is some individual variability here, and not everyone absorbs lycopene at the same rate ().
Even though processed tomato products are higher in lycopene, it is still recommended to consume fresh, whole tomatoes whenever possible.
Bottom line: Lycopene is the most abundant plant compound in tomatoes. It is found in the highest amounts in tomato products, such as ketchup, tomato juice, and tomato-based sauces.
Consumption of tomatoes and tomato-based products has been linked to many benefits regarding heart disease, cancer prevention and skin health.
Cardiovascular disease, including heart attacks and strokes, is the world's most common cause of death.
A study in middle-aged men showed that low blood levels of lycopene and beta-carotene are linked to increased risk of heart attacks and strokes (, ).
Increasing evidence from clinical trials shows that lycopene supplementation is effective at lowering LDL cholesterol ().
Clinical trials of tomato products have also shown benefit against inflammation and markers of oxidative stress (, ).
They also show a protective effect on the inner layer of our blood vessels and may decrease the risk of blood clotting (, ).
Cancer is a generic term for the uncontrolled growth of abnormal cells that spread beyond their normal boundaries, often invading other parts of the body.
Observational studies have found links between tomatoes, tomato products, and fewer incidences of prostate-, lung- and stomach cancers (, ).
The high lycopene content is believed to be the main reason for these protective effects, but high quality human trials are needed to confirm this (, , ).
A study in women shows that high concentrations of carotenoids, found in high amounts in tomatoes, may protect against the development of breast cancer (, ).
Tomatoes are considered beneficial for skin health.
Tomato-based foods rich in lycopene and other plant compounds may protect against sunburn (, ).
According to one study, there were 40% fewer sunburns after ingesting 40 grams of tomato paste (providing 16 mg of lycopene) with olive oil, every day for 10 weeks ().
Bottom line: Studies show that tomatoes and tomato products may reduce the risk of heart disease and several cancers. They are also considered to be beneficial for skin health, and may protect against sunburns.
When tomatoes start to ripen, they begin producing a gaseous hormone called ethylene (, ).
Tomatoes produced by traditional methods are harvested and transported while still green and immature. To make them red before selling, artificial ethylene gas is used.
The disadvantage of this, is that it does not lead to the development of natural flavor, and may result in tasteless tomatoes ().
Local tomatoes may therefore taste better, because they are allowed to ripen naturally.
Bottom line: Tomatoes are often harvested and transported while still green and immature, and are then ripened with artificial ethylene gas. This may lead to less flavor development, resulting in tasteless tomatoes.
Tomatoes are generally well tolerated and tomato allergy is very rare (, ).
Although tomato allergy is rare, they more frequently cause allergic reactions in individuals allergic to grass pollen.
This condition is called pollen-food allergy syndrome or oral-allergy syndrome ().
In oral-allergy syndrome, the 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 ().
People with latex allergy can also experience cross-reactivity to tomatoes (, ).
Tomatoes may contain higher levels of fluoride if they are exposed to fluoride gas or fluoride in the soil ().
Bottom line: Tomatoes are generally well tolerated, but they may cause allergic reactions in people allergic to grass pollen. Tomatoes grown in contaminated soils may contain higher levels of fluoride.
Tomatoes are juicy and sweet, full of antioxidants and may help fight several diseases.
They are especially high in lycopene, a plant compound that has been linked to improved heart health, cancer prevention and protection against sunburns.
Tomatoes can be a valuable part of a healthy diet.