Tomatoes

Tomatoes

There is nothing better than a tomato plucked straight from the vine right when it is ready to eat… what a sweet summer treat! Tomatoes come in a vast array of sizes, shapes and colours and enrich our diet with endless possibilities. This versatile fruit/vegetable is low in calories, packed with nutrients and delicious. They can be used fresh or canned; cooked, dried or raw; whole, diced, sliced or puréed; and in the form of paste to add colour, flavour, and texture to soups, stews and other savoury dishes in kitchens all over the world. Although not usual, tomatoes are also found in many desserts.

Curiosities about tomatoes:

From a botanical perspective, tomatoes are classified as a fruit since they result from the fertilization of flowers. From a horticultural standpoint, it is viewed as a vegetable due to its use and cultivation.

Tomatoes originated in the Andes where they grew wild. The plant was first cultivated by the Aztecs as early as 700 A.D. It was only around the 16th century that this plant of the nightshade family made its way to Europe, but for a long time was considered as poisonous thus unfit to human consumption. Only around the late 1880’s, thanks to Neapolitans and the creation of pizza, tomatoes became popular and garnered favor all over Europe. From there, tomatoes have traveled across oceans and today we have an abundance of varieties, and producers continue to create/select juicier and meatier fruits.

Nutrition:

Tomatoes are a nutrient dense food. One medium unit (about 125 g)  has approximately 22 calories, 1 gram of protein, 5 grams of carbohydrates and 1.5 g of fibre. Tomatoes are an excellent source of vitamin C, beta-carotene (a pro-vitamin A that is converted to vitamin A and retinol inside our bodies), and potassium.  In addition to beta-carotene, tomatoes also contain other carotenoids, among them lycopene, which is a potent antioxidant responsible for tomatoes’ red colour and also gives other fruits and vegetables their yellow, orange and red color. Carotenoids are fat-soluble compounds and for this reason they need fat from the diet to be absorbed by our bodies.

The redder and riper the tomato, the higher the levels of lycopene contained within it. Heirloom varieties have the most lycopene, followed by vine-ripened tomatoes and last those ripened after picking. The amount of lycopene in cultivated tomatoes is much lower than in wild species. The difference can account to 4 to 5 times more lycopene in wilder species.

Lycopene is better absorbed in cooked tomatoes than in raw tomatoes. Yet, we can still get lycopene from raw tomatoes, which have higher levels of vitamin C and folate than cooked tomatoes. To maximize the absorption of lycopene, tomatoes should be eaten with some sort of oil (as above mentioned, carotenoids are fat-soluble compounds), preferably healthy fats. Among numerous healthy options you can choose are: a simple but luscious tomato salad with basil leaves drenched in extra virgin olive oil (EVOO), sliced tomatoes and avocado in sandwiches or found in a traditional guacamole recipe,  hot or cold tomato soup, roasted tomatoes, spicy tomato juice (pay attention to sodium content of over-processed/industrialized products), or simply finalize a tomato sauce with some EVOO. The monounsaturated fat in EVOO and avocados make lycopene in tomatoes up to 4 times more bioavailable.

 

But why am I talking so much about lycopene? A number of studies have suggested that men who consume large quantities of tomatoes and tomato-based products have a lower risk of developing prostate cancer, especially men aged of 65 and over. The mechanism by which lycopene may reduce the development of prostate cancer is not yet well understood. Some researchers believe that lycopene’s antioxidant activity may impede prostate cancer development by interfering with sex hormones involved  in the excess growth of prostatic tissue and by disturbing the growth of tissue cells. Simply eating two meals a week with some tomato sauce can reduce the risk of developing prostate by 30 percent, not so difficult isn’t it?

Lycopene may also neutralize the action of free radicals produced by UV rays. Daily consumption of tomato based products may be associated with a higher degree of skin protection against the sun and lower the risk of melanoma, increased collagen levels and slowing down skin aging. Some researches extend the benefits of tomatoes on the prevention of kidney and breast cancers, while other studies show an association of dietary intake of tomatoes and its products with a decreased risk of cardiovascular diseases.

Besides tomatoes and tomato products, lycopene is also present in fruits such as guava, watermelon, papaya and pink grapefruit.

In addition to lycopene and beta-carotene, tomatoes are also a rich source of lutein. These powerful antioxidants that have been shown to protect the eyes against light-induced damage associated with age-related macular degeneration and the development of cataracts.

For maximum nutritional benefits avoid peeling and seeding tomatoes unless really necessary. The tomato peel is richer in nutrients than the flesh and the seed part in the center is high in salicylates.

Shopping for tomatoes:

• Choose ripe fruits with a smooth skin, which are firm but not hard.
• Locally grown tomatoes, especially heirloom varieties are the best choice for flavourful and lycopene rich tomatoes. If heirloom varieties are too expensive or not available look for tomatoes sold on the vine or those who claim to be naturally ripened.
• When buying canned tomatoes prefer products with no added salt or sugar, and cans which are not lined with Bisphenol A, i.e. BPA free cans.
• Cultivate tomatoes at the backyard or on your balcony. Most garden centers sell small plants that need to be re-potted to a larger container or start early in the spring if using seeds.
• If you don’t have a choice of buying ripe tomatoes, you can speed up the ripening process of under-ripe tomatoes by putting them within a brown paper bag along with a fruit that releases ethylene gas such as a banana or an apple.

How to store:

• Store ripe tomatoes at room temperature out of the direct sunlight. Cold temperatures damage enzymes found in the fruit that are responsible for flavour compounds and for proper the texture.
• Freeze tomatoes to use in cooked dishes and sauces.
• If the tomatoes are attached to its vine, leave it on. Otherwise, store them stem side down to prevent moisture loses.
• When buying canned tomatoes, check the “Use by” date to ensure the ingredient is at peak quality and avoid brands using BPA cans or that add sugar or salt.
• Storing unripe tomatoes in the fridge will prevent them from ripening but also affect their flavour and texture.
• Overripe tomatoes can be stored in the fridge to stop the ripening process without fully compromising the flavour.
• The best temperature to store tomatoes is 13°C or 55°F.

References:

– Age-Related Eye Disease Study Research Group, Arch Ophthalmol. (2007). The relationship of dietary carotenoid and vitamin A, E, and C intake with age-related macular degeneration in a case-control study.  Jama Network. http://jamanetwork.com/journals/jamaophthalmology/fullarticle/419811

– Béliveau, R. and Gingras, D. (2016). Foods that Fight Cancer, Preventing Cancer through Diet

– Canadian Nutrient File -Tomato, red, ripe, raw, year round average

– Heber, D. and Lu, Q.Y. (2002) Overview of mechanisms of action of lycopene. Exp. Biol. Med. 2002, 227, 920–923. [NCBI, PubMed]

– Mordente, A., Guantario, B. , Meucci, E. et al. (2011). Lycopene and cardiovascular diseases: an update. Curr Med Chem. 2011; 18(8): 1146–1163. [NCBI, PubMed]

– Cooking for Geeks, Jeff Potter, O’Reilly

– The Complete Vegetarian Cookbook, America’s Test Kitchen

– Vegetables the Essential Reference, Eating Well