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Teaming up with Tomatoes

Teaming up with Tomatoes

Tomatoes
Figure 1. Picture of tomatoes
(image: http://www.rattangardenfurniture.co.uk/blog/wp-content/
uploads/2013/04/tomatoes.jpg)

In pasta sauces, on sandwiches, on pizzas, and in soups, tomatoes are a staple of cuisines around the world. But did you know that this savory and juicy vegetable is not actually a vegetable? Scientifically known as Solanum lycopersicum, tomatoes are classified as fruits [1]. They are a part of the nightshade family, which also includes potatoes, peppers, and eggplants, as well as other common food plants. Originating from the mountainous Andes of South America, tomatoes have a long history of human cultivation and consumption. After they were introduced to Europe in the 1500's (not long after the Spanish "discovery" of the Americas), tomatoes became a global phenomenon. Today, over 159 million tons of tomatoes are produced worldwide per year [2]. It's hard to imagine what our cuisine would be like without them. Not only are tomatoes colourful and tasty, they are also incredibly good for you. Scientists have found tomatoes to be particularly rich in vitamins (A, C and K, biotin), and a host of bioactive phytonutrients (tomatine, lycopene, pregnane, naringenin chalcone, and fatty acid derivatives) that fight obesity, osteoporosis, cancer, and heart disease. Indeed there is far more in a juicy red tomato than meets the eye!

Vitamins

Vitamins are essential nutrients for homeostasis - the balancing act in that takes place in your body every day to keep you healthy. Vitamins can be found throughout the body, serving as enzyme or protein co-factors to help in blood clotting, vision, and bone health. Tomatoes are a great source of vitamin C, which is crucial in maintaining collagen - a protein found in skin, bones, tendons, ligaments and many other parts of your body. Without vitamin C, you would develop a disease called "scurvy", which is characterized by bleeding gums, spotty skin, jaundice and wounds that don't heal. Vitamin C is a critical cofactor that plays a role in fat and hormone metabolism [3]. Tomatoes are also rich in vitamin A. Vitamin A is important for vision - it is used in the eye's light absorbing protein (called rhodopsin). Children who are short on vitamin A can become blind. Indeed, vitamin A deficiency and childhood blindness is a major problem in the developing world [4]. Blood clotting is also aided by tomatoes, which are high in vitamin K. Vitamin K is also important in bone health and growth [5].
Bottom line: Tomatoes are plentiful in three essential vitamins (A, C and K) that keep your body functioning and healthy.

Biotin

Biotin
Figure 2. Structural diagram of biotin
Every living cell in your body contains biotin, an essential cofactor also known as vitamin B7, vitamin H, or coenzyme R. Biotin is not as well known as other vitamins but it is now considered an essential nutrient for humans [6]. Humans can fulfill this requirement, in part, through their diet. 1 cup of tomatoes has 24% of your daily requirement of biotin! If you become mildly deficient in biotin you can develop a number of neurological and psychological symptoms [6]. These include depression, hallucinations, and numbness in your extremities. If you continue to become severely deficient, the symptoms can include hair loss, conjunctivitis, and a red scaly rash on your face and genital areas. Pregnant women can sometimes become deficient in biotin. Having a deficiency during pregnancy is very problematic as this causes malformations like cleft palate in babies. Embryos and infants are more sensitive to the deficiency in biotin than the pregnant woman so even if the woman does not show any symptoms the baby can be affected.
Insulin resistance
Figure 3. Insulin resistance
(image: http://goodfoodeating.com/6758/insulin-
and-insulin-resistance/)
Getting enough biotin can prevent you from acquiring any of the previously mentioned symptoms but what can biotin do to benefit you? A study has shown that biotin supplements can help in the prevention of diabetes in people at risk for the disease [7]. Biotin leads to an increase in a special protein called the glucose transporter GLUT4. This insulin-regulated protein allows more movement of glucose into cells therefore decreasing the total amount of insulin you need. Decreasing your blood sugar level quicker lessens the amount of repetitive signaling by insulin that eventually leads to insulin resistance - which is also known as Type 2 diabetes.
Bottom Line: Tomatoes are a great source of biotin. Biotin is an essential nutrient that can help to prevent type 2 diabetes!

Tomatine

Tomatine
Figure 4. Structural diagram of tomatine
Who knew that deadly compounds could be good for you? Because tomatoes are part of the nightshade family, they contain glycoalkaloids such as alpha-tomatine and dehydrotomatine. In large amounts, these compounds can be deadly. Both are inhibitors of the enzyme acetylcholinesterase, which is critical for brain function and memory. However, you'd have to eat a lot of tomato stems and leaves (where the tomatines are most concentrated) to do any harm. But just eating a few tomatoes won't kill you! With ripening, the amount of tomatines within the tomato decreases, while the amount of carotenoids increases, making the fruit change colour from green to bright red.
Green tomato
Figure 5. Picture of a green tomato
(image: http://gardeningafterfive.wordpress.com/2010/
08/24/cracked-lazy-tomatoes/)
What this means is that green tomatoes will have a much higher level of tomatine compared to ripe red ones. But what are the positive effects of smaller amounts of these tomatine substances? Some studies have found that the administration of alpha-tomatines can inhibit growth of cancer cells, as tested on liver cancer, lung cancer, prostate cancer, and leukemia [8-10]. Tomatines stop the spread of cancer cells (metastasis), and can also induce the programmed cell death of cancer cells, otherwise known as apoptosis [11].
More positive health effects of tomatines include their ability to 1) help reduce cholesterol, and 2) boost the immune system to fight against pathogenic bacteria [8]. Cholesterol reduction is achieved when tomatine physically breaks down cholesterol in the cell membrane. One study found that cholesterol and tomatine bonded together pre-digestion and were excreted before absorption by the stomach, thereby reducing circulating cholesterol levels [12]. Other studies have shown that tomatine binds to and inhibits the ACAT enzyme (acyl-CoA-cholesterol acyl-transferase). This enzyme is important for cholesterol synthesis [13]. Tomatine has also been shown to be effective in fighting disease and infection. In one study, tomatine was shown to generate an antigen-specific cellular immunity, which means that there is great future capacity for fighting bacterial pathogens and viruses. Tomatine's ability as an immunostimulator means that it can be used as an effective vaccine adjuvant, inducing a response from T-killer cells (also known as a CTL response), improving the efficacy of vaccines [14].
Bottom Line: The tomatine from tomatoes in its various forms has lots of health benefits, including anti-cancer, cholesterol reduction, and improvement in immunity.

Lycopene

Lycopene structure
Figure 6. Structural diagram of lycopene
Lycopene is the main carotenoid found in tomatoes. Lycopene, along with other carotenoids such as alpha-, beta-, gamma- carotene, and lutein [15], give the tomatoes their bright red colour. Lycopene is also key to the many health benefits of the fruit. First, the lycopene contained in tomatoes has been shown to improve heart health by reducing not only total cholesterol, but also LDL cholesterol [16]. LDL cholesterol is often known as the "bad" cholesterol. High levels can lead to blocked arteries, atherosclerosis and heart attacks. Lycopene decreases cholesterol synthesis by reducing the activity and expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase (also known as HMG-CoA reductase). Lycopene also modulates low-density lipoprotein (LDL) receptor and acyl-coenzyme A:cholesterol acyltransferase activity [17].
Lycopene
Figure 7. Picture of a narrowed blood vessel
(image: http://www.hyderabaddiabetes.com/cholesterol-
control-clinic.html)
In one study, taking lycopene in doses (equal to approximately 500 mL of tomato juice a day) reduced LDL cholesterol by 10% [18]! This means that with each bite of that tasty red tomato, your risk of a heart attack will diminish [19].
The health benefits of lycopene don't end with cholesterol reduction. Lycopene is also an anti-inflammatory agent that prevents the production of inflammatory cytokines. A recent diet intervention trial [20] involving overweight and obese women showed that tomato juice consumption (1 glass/day) significantly reduced the levels of the inflammatory cytokines interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-a). These proteins can cause fever, swelling, redness, pain and muscle wasting. They can also exacerbate symptoms associated with obesity and metabolic syndrome. By reducing the levels of these noxious blood proteins, lycopene is able to protect overweight individuals from a state of chronic inflammation. Lycopene not only promotes heart health and cuts down inflammation, it also protects women against osteoporosis. Studies have found that women consuming larger amounts of carotenoids and lycopenes have a significantly reduced risk of hip fractures [21], while women who were on lycopene-restricted diets exhibited significant bone loss [22]. So eat more tomatoes if you want strong bones.
Bottom line: Lycopene makes tomatoes red and is excellent in promoting heart health, lowering cholesterol, reducing inflammation and preventing osteoporosis.

Exotic Phytochemicals

Nutrition facts
Figure 8. Tomato nutrition facts
More than 900 different chemicals have been identified in tomatoes. Some of these compounds are quite obscure but a few these "exotic phytochemicals" seem to pack quite a phytonutrient punch. One of the lesser-known but more important bioactive compounds in tomatoes is esculeoside A, a glycoalkaloid. This compound resembles certain human steroid hormones and when it is metabolized in the liver or in the intestine, it can be converted to a compound very similar to a human steroid hormone called pregnane. Pregnane and pregnane-like compounds are known to have useful anti-cancer, anti-osteoporosis, and anti-menopausal disorder activities [23]. Another relatively unknown, tomato-derived compound is a flavonoid called naringenin chalcone. This compound is found mostly in the tomato's peel. Flavanoids are a class of compounds found in many colored fruits and vegetables and they appear to have a number of beneficial health effects. A study tested this compound's effects on the body and found that it is a strong inhibitor of allergic reactions [24]. Allergy symptoms are caused by histamine. Mast cells in your body are responsible for releasing histamine in response to something foreign to your body. Mast cells are specially tuned to fight infections from parasites and other microorganisms invading your body. Nowadays, with most people living in "hyperclean" or near-sterile environments mast cells don't encounter those foreign objects and as a result they sometime overreact when you encounter dust, pollen or certain foods, causing unexpected allergic reactions. Naringenin chalcone appears to inhibit mast cells from releasing histamine and so it seems this tomato-derived substance may have some potential in limiting, preventing and even treating allergy symptoms. Another pair of exotic phytochemicals known as 9-oxo-octadecadienoic acid and 13-oxo-9,11-octadecadienoic acid are also found in tomatoes. These fatty acid derivatives are naturally occurring PPARα agonists - a group of ligands that promote gene transcription of fat-digesting enzymes and other fat combating proteins [25]. PPARα agonists are beneficial in combating high levels of fat in those suffering from obesity or metabolic syndrome-like symptoms [26,27]. Drug companies are spending millions trying to develop synthetic PPARα agonists to treat obesity and combat metabolic syndrome. The hope is to develop a "blockbuster" drug that would prevent obesity. It might be cheaper if we just ate more tomatoes.
Bottom line: A tomato a day can keep the doctor away


References