Tomatoes
Tomatoes have long suffered an identity crisis: are they fruits or vegetables? Depending on who you think has the most authority, the U.S. Supreme Court, or the scientific community, they are vegetables or fruits. Does that tell you anything? I didn’t think it would. Actually, tomatoes are fruits. Specifically, they are berries–my favorite fruits! Unfortunately, the U.S. Supreme Court has ruled them as vegetables so the government can collect import taxes on them. The justices justified their decision by pointing out that
because tomatoes lacked the sweetness usually attributed to fruits they are used like vegetables in cooking. I guess justices can justify any way they want, but I’m sticking to the scientific facts and putting my tomatoes with the berries. Tomatoes are wonderfully good for you! Although tomatoes are most known for their high concentrations of lycopene, which is thought to have the highest antioxidant activity of all the carotenoids, they are the only fruit known to contain all four major carotenoids: alpha- and beta-carotene, lutein, and lycopene. Research has shown that the carotenoids in tomatoes work together to provide many health benefits.
Cancer
While the lycopene in tomatoes probably prompted early studies into this amazing fruit’s cancer-fighting properties, it turns out that a not-so-well-known phytonutrient, alpha-tomatine, may be the strongest anti-cancer chemical in tomatoes. Several studies have demonstrated that alpha-tomatine alters the metabolic activity of prostrate and non-small-cell lung cancer cells, slowing tumor growth and causing apoptosis.(1)
It’s important to note that one study, published in The Journal of Endocrinology and Metabolism, in December of 2013 (2) found a relationship between the body mass index of postmenopausal women and a higher risk of breast cancer. While a tomato-rich diet improved the risk factor for all women tested, those with a high body mass index didn’t receive as much cancer protection as the women with a healthier body mass index.
As I alluded to above, most cancer studies have tested the cancer fighting capability of lycopene, especially breast cancer studies. Lycopene has been repeatedly shown to slow the growth of breast cancer and pancreatic cancer cells. It has also been shown to reduce the risk of prostate cancer. However, a large study of 47,365 men started in 1986 and ending January 31, 1992 and reported in the journal, Pub Med compared the incidence of prostate cancer in men taking a lycopene supplement with those eating tomato-based foods. While both groups had a reduced incidence of prostate cancer, the men eating tomato-based food such as tomato sauce had fewer cancers than those taking just the lycopene supplement. (3)
Tomatoes and broccoli have synergy that may help reduce the risk of prostate cancer more than either can achieve individually. One study showed that prostate tumors grew much more slowly in rats that were fed both tomato and broccoli powder than in rats given lycopene as a supplement or fed just the broccoli or tomato powder alone. Lycopene has also been shown to have synergy with Vitamin E. When rats implanted with prostrate tumors were given doses of synthetic lycopene, their tumor growth rate slowed by 50 percent. When rats were given a combination of Vitamin E and lycopene the tumor growth rate slowed by 72 percent. (4)
There have been several other studies in recent years that report the cancer-fighting properties of tomatoes. In addition to pancreatic, breast and lung cancers, they have been shown to fight stomach, cervical, colorectal, oral and esophageal cancers.
Cardiovascular and Heart Benefits
There have also been many studies linking lycopene and tomatoes to the prevention or cure of heart and cardiovascular disease. One such study, published in the journal PLOS One found that lycopene improved the function of the endothelium (the thin layer of cells on the interior surface of the blood vessels) by 53 percent, thereby reducing the risk of heart attack and stroke. (5)
One of the most studied areas of tomato research involves the ability of the antioxidants in tomatoes to protect the fats in the bloodstream and in the cells lining the arteries from oxidation. This oxidation process is called peroxidation. Uncontrolled peroxidation causes inflammation and immune system responses that can lead to blocked blood vessels.
The phytonutrients in tomatoes have also been shown to help regulate the fats in our blood. They decrease LDL cholesterol and triglycerides. And they reduce platelet clumping.
Bone Health
Tomatoes belong to the nightshade family of plants, and nightshades are supposedly bad for your bones. Many doctors, including naturalists, will tell you to avoid tomatoes if you have or want to avoid getting osteoporosis. However, recent research has proven that tomatoes help prevent osteoporosis, and even increase bone density. In a recent study, postmenopausal women were asked to refrain from eating or drinking sources of lycopene for a four week period. At the end of the four weeks, the women showed a significant reduction in bone density. (7)
Another recent study at St. Michael’s Hospital in Toronto, Canada tested the role of lycopene and tomatoes in 33 postmenopausal women. They discovered that lycopene inhibits the formation and activity of osteoclasts (8), which are the cells that cause bone loss. Osteoblasts are the opposite, they build new bone. Lycopene stimulates osteoblasts and increases the production of new bone cells and bone density. These are both recent studies, and the researchers admit that they don’t tell the whole story concerning tomatoes, lycopene, and bone health. However, new, larger and more detailed studies are underway, and we should soon know more about the role tomatoes play in bone health and the prevention and treatment of osteoporosis.
Additional Health Benefits
As with other berry fruits, tomatoes are packed with phytonutrients and other antioxidants. While past research has mostly concentrated on the anti- cancer, cardiovascular, and heart disease benefits of lycopene and other known antioxidants, new research is beginning to tie little-known compounds in tomatoes to health benefits. Recent and preliminary results have shown that tomatoes help prevent dementia, diabetes, and even obesity. I look forward to future studies expanding on our knowledge of beneficial nutrients in tomatoes and the the many ways they help us heal and stay healthy.
Special note: Our bodies are more able to absorb the lycopene and other carotenoids in tomatoes after they are cooked. For that reason, tomato juice, tomato sauce, and even ketchup increase the amount of lycopene that reaches our blood serum. Also, most of the carotenoids is in the skin, and the seeds are full of antioxidants and other nutrients. Whenever possible, eat the whole tomato.
Eating tomatoes with a little olive, coconut, or avocado oil also helps us absorb the carotenoids. When eating a salad or other dish containing raw tomatoes, include a little of one of these oils to make sure you get all the nutrients possible. Just including an avocado in your recipe will do the job!
Finally, because of the acid in tomatoes, they leach more BPA from the can liner than many foods, so try to make sure the tomato products you buy have a “No BPA” disclaimer on the label.
References
(1) Lee S-T, Wong P-F, Cheah S-C, Mustafa MR (2011) Alpha-Tomatine Induces Apoptosis and Inhibits Nuclear Factor-Kappa B Activation on Human Prostatic Adenocarcinoma PC-3 Cells. PLoS ONE 6(4): e18915. doi:10.1371/journal.pone.0018915. (2)
Adana Llanos, et al., Effects of Tomato and Soy on Serum Adipokine Concentrations in Postmenopausal Women at Increased Breast Cancer Risk: A Cross-over Dietary Intervention Trial, published in The Journal of Endocrinology and Metabolism, December 2013.
(3) Giovannucci E, Rimm EB, Liu Y, Stampfer MJ, Willett WC. A prospective study of tomato products, lycopene, and prostate cancer risk. J Natl Cancer Inst. 2002 Mar 6;94(5):391-8.
(4) Canene-Adams K, Lindshield BL, Wang S, Jeffery EH, Clinton SK, Erdman JW Jr. Combinations of tomato and broccoli enhance antitumor activity in dunning r3327-h prostate adenocarcinomas. Cancer Res. 2007 Jan 15;67(2):836-43. Epub 2007 Jan 9.
(5) Parag R. Gajendragadkar, Annette Hubsch, Kaisa M. Mäki-Petäjä, Martin Serg, Ian B. Wilkinson, Joseph Cheriyan Effects of Oral Lycopene Supplementation on Vascular Function in Patients with Cardiovascular Disease and Healthy Volunteers: A Randomised Controlled Trial Published: June 9, 2014DOI: 10.1371/journal.pone.0099070.
(6) Iimura Y1, Agata U, Takeda S, Kobayashi Y, Yoshida S, Ezawa I, Omi N. Lycopene intake facilitates the increase of bone mineral density in growing female rats. J Nutr Sci Vitaminol (Tokyo), 2014;60(2):101-7.
(7) Mackinnon ES, Rao AV, and Rao LG. Dietary restriction of lycopene for a period of one month resulted in significantly increased biomarkers of oxidative stress and bone resorption in postmenopausal women. J Nutr Health Aging. 2011 Feb;15(2):133-8. 2011.
(8) Mackinnon, E S; Rao, A V; Josse, R G; Rao, L G. Supplementation with the antioxidant lycopene significantly decreases oxidative stress parameters and the bone resorption marker N-telopeptide of type I collagen in postmenopausal women. Osteoporosis International 22.4 (Apr 2011): 1091-101.