Tomatoes nutrition

While tomatoes are often used as a salad vegetable or as a vegetable ingredient, they are actually a fruit (Heuvelink, 2018). They can be used either fresh or processed, and 35 % of raw tomatoes are processed into sauces (Canene-Andrews, Campbell, Zaripheh, Jeffrey, & Erdman, 2005). They are the second most important vegetable crop in the world, after potatoes (Heuvelink, 2018). Tomatoes are part of the nightshade family, which also includes chilli, bell peppers, potatoes, and aubergines (Heuvelink, 2018). They are a good source of vitamins A, C, E (second only to carrots for their amount of vitamin A), potassium, folate, and phytochemicals such as carotenoids and flavonoids.

Vitamins A, C, and E

Vitamin C is important for the growth, development, and repair of all bodily tissues. Most other animals are able to metabolize their own vitamin C, so humans are unusual in needing to obtain from dietary intake (Linster & Schaftingen, 2007). A deficiency in vitamin C can lead to scurvy. (Hirschmann & Raugi, 1999). Scurvy was first noticed in sailors (the first to be away from dietary sources for prolonged periods) and includes symptoms such as tiredness and weakness, irritability and sadness, joint or leg pain, swollen and bleeding gums, tooth loss, red or blue spots on the shins, and bruising easily (Hirschmann & Raugi, 1999). Since tomatoes are a good source of vitamin C, they can lower your risk of developing scurvy, although scurvy is extremely rare.

Vitamin A is involved in immune system functioning, reproduction, cellular communication, and is also an essential component for the protein responsible for absorbing light in the retinas. The latter makes it important for the improvement of night vision. (Olsen, 2001). Vitamin E is primarily an antioxidant. Antioxidants have wide-ranging health benefits because they are able to reduce oxidative stress by scavenging free radicals that can lead to cell damage (Azzi & Stocker, 2000). This can reduce the risk of several chronic diseases and some cancers.

Potassium

Potassium helps with the absorption of other minerals (Camire, Kubow, & Donnelly, 2009), but it can also lower blood pressure, reducing the risk of stroke and heart failure, reduce age-related bone loss, and reduce the risk of kidney stones (Weaver, 2013).

Folate

Folate has several important health benefits. First, it is protective against anemia. In fact, vitamin B12 deficiency anemia is actually caused by vitamin B12’s influence on folate absorption (Bailey, 2009). It is the subsequent lack of folate that causes the anemia, not the lack of B12. This is because folate is important for iron absorption. Second, folate deficiency in pregnancy can cause neural tube defects in the fetus, such as spina bifida. Women who can conceive are advised to take folic acid supplements from before they become pregnant until they are 12 weeks pregnant because these deficiencies occur so early on in pregnancy (https://www.nhs.uk/common-health-questions/pregnancy/why-do-i-need-folic-acid-in-pregnancy/).

Carotenoids

Tomatoes contain phytochemicals called carotenoids, the most prevalent of which is lycopene (Canene-Andrews et al., 2005). These carotenoids are what gives tomatoes their red colour (they do the same for other vegetables such as carrots). Carotenoids can confer several important health benefits (Story, Kopec, Schwartz, & Harris, 2010). First, they can lower the risk of cancer. Giovannucci, Rimm, Liu, Stampfer, & Willett (2002) looked at the data from a longitudinal study that followed 47, 365 men, with follow-ups in 1986, 1990, and 1994. Those men that had at least two servings of tomato sauce per week had a reduced risk of developing prostate cancer. Interestingly, this effect was greater than for men who took lycopene supplements, suggesting that there may be other protective elements against prostate cancer present in tomatoes.

Second, they can lower the risk of cardiovascular disease. Cardiovascular disease is the leading cause of death in the U.S. (Story et al., 2010). Lycopene can protect against cardiovascular disease because it reduces the production, and increases the degradation, of “bad” low-density lipid (LDL) cholesterol (Arab & Steck, 2000). LDL can cause fatty build-up in the arteries, which is a major cause of cardiovascular disease (Hirayama & Milda, 2012). When 24 people were given a diet including fresh tomato, tomato juice, or a lycopene drink for six weeks, it was found that there was a large effect on the risk factors for cardiovascular disease. Specifically, triglyceride levels decreased, LDL levels also decreased, and “good” high-density lipid (HDL) cholesterol increased. Again, this was only true for the people who had tomatoes and tomato juice, but not for the people who had the lycopene drink alone (Arab & Steck, 2000).

Third, lycopene can lower the risk of UV-induced sunburn. Nine people were given 40g of tomato paste and olive oil (versus the control group who had olive oil alone) for ten weeks. They were then irradiated with a solar simulator. There was a 32% reduction in biological sunburn markers (Stahl, Heinrich, Wiseman, Eichler, Sies, & Tronnier, 2001). Lycopene is, therefore, an important antioxidant for improving health, and 85% of the consumption of lycopene in the population comes from tomato sauces (Canene-Andrews et al., 2005).

Carotenoids are antioxidants (Stort et al., 2010). They work in a similar way to vitamin E by scavenging the free radicals responsible for causing oxidative damage. Oxidative damage is a risk factor for prostate cancer (Paschos, Pandya, Duivenvoorden, et al., 2013), cardiovascular disease (Singh, Singh, Kumar Singh, Kumar Singh, Kafle, & Agrawal, 2012), and sunburn (Kim, Yim, Eom, Yeoun Lee, & Kim, 2017). Tomatoes also contain flavonoids, which are another antioxidant that has a similar effect. All told, the nutritional makeup of tomatoes confers a large amount of antioxidant protection. It is worth noting, however, that these protections against disease seem to be at least mediated by other elements present in tomato since the effects are weaker with the antioxidant compound alone. It is also important to note that, unlike many other vegetables, the nutritional content of tomatoes actually increases when it is cooked and processed (Story et al., 2013).

Conclusion

Tomatoes are a popular and versatile fruit. They are used extensively and are an important dietary source of vitamins A, C, and E, as well as potassium and folate. Carotenoids, an antioxidant, give tomatoes their red colour and also provide protection against prostate cancer, cardiovascular disease, and sunburn.

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