Diet Detective Investigates Two Red Fruits: Tomatoes and Strawberries

by Charles Platkin, PhD


Why: Have you tasted a delicious, sweet strawberry lately? I know, I sound like some health nut pushing fresh fruit, but seriously, strawberries taste as good or better than any piece of candy. They’re also loaded with fiber, potassium, vitamin C and folate. And one large strawberry has only six calories. Also, one interesting fact: There are about 200 little seeds right on the surface of a strawberry.

Nutritional Information (1 cup): 46 calories; 0.45 g fat; 11 g carbs; 3 g fiber; 1.5 g protein.

Health Perks: Research conducted by the UCLA Center for Human Nutrition at the David Geffen School of Medicine and others has shown that the phenolic compounds in strawberries have potent antioxidant, anti-cancer, anti-atherosclerotic (prevents hardening of the arteries, which leads to heart disease and stroke) and anti-neurodegenerative (leads to Alzheimer’s) properties.

Anthocyanins and ellagitannins are the major antioxidant phytochemicals present in strawberries. Ellagitannins are tannins not commonly found in foods that react with water to become ellagic acid, which may slow the growth of some cancer cells. Anthocyanin, the pigment responsible for the red color in strawberries, helps reduce the risk of blood coagulation, preventing the development of the blood clots involved in strokes, pulmonary embolisms and heart attacks.

Additionally, researchers at the Salk Institute for Biological Studies found that fisetin, a naturally occurring flavonoid commonly found in strawberries, stimulates signaling pathways that enhance long-term memory. And research from Harvard Medical School found that strawberries may offer cardiovascular disease protection. Specifically, the study reported that those who ate two or more servings of strawberries per week were 14 percent less likely to have elevated blood levels of C-reactive protein, an indicator of inflammation in the blood vessels, than those who reported eating none in the past month.

Strawberries are also relatively high in magnesium (19 milligrams, 5 percent of daily recommended amount) and potassium (220 milligrams, 6 percent of daily recommended amount), which are minerals that help in lowering blood pressure.

Purchase and Storage Tips: Pick bright, firm strawberries with vivid red color. The tops should be fresh, green and intact. Avoid withered or squishy berries. They will keep in the refrigerator for two to three days. Wash them only when ready to eat.


Why: They’re really a very beautiful fruit (yes, fruit, not a vegetable): bright red, crisp, a symbol for freshness. They’re tasty, low in calories and great in salads or on pizzas. They come in many varieties, including cherry, plum and slicing tomatoes, and they seem easy to grow. In fact, when I was just 8 years old I grew several tomato plants and harvested them over the course of the summer. Tomatoes are a rich source of lycopene, beta carotene, folate, potassium, vitamin C, flavonoids and vitamin E. They reduce oxidative stress, inflammation and the risk of osteoporosis.

Nutritional Information (1 large whole, 3″ diameter): 33 calories; 0.36 g fat; 7.13 g carbs; 2.2 g fiber; 1.6 g protein.

Health Perks: According to research reported in the Canadian Medical Association Journal, lycopene, a carotenoid that is present in tomatoes, is one of the most potent antioxidants of all dietary carotenoids. The researchers also reported that dietary intake of tomatoes has been shown to be associated with a decreased risk of chronic diseases, such as cancer and cardiovascular disease. While lycopene has been praised as the main reason for the reduced risk of disease, evidence is mounting that other mechanisms in tomatoes may also be involved.

According to the European Journal of Clinical Nutrition, “Most of the clinical trials with tomato products suggest a synergistic action of lycopene with other nutrients in lowering biomarkers of oxidative stress and carcinogenesis.”

And while there has been a significant amount of research linking tomatoes, and more specifically lycopene, to a reduction in prostate cancer, a 2007 study done at the National Cancer Institute and the Fred Hutchinson Cancer Research Center reported that lycopene does not effectively prevent prostate cancer. The researchers followed more than 28,000 men between the ages of 55 and 74 and found no significant difference between those who had prostate cancer and those who did not in relation to the concentration of lycopene in their bloodstream.

When the H. J. Heinz Co. applied to the United States Food and Drug Administration (FDA) to be able to have a health claim for tomatoes, the FDA allowed a claim for reduced risk of prostate cancer, although it was limited. The claim is as follows: “Very limited and preliminary scientific research suggests that eating one-half to one cup of tomatoes and/or tomato sauce a week may reduce the risk of prostate cancer. FDA concludes that there is little scientific evidence supporting this claim.” The bottom line, more than likely, is something in tomatoes is associated with a reduction in risk of prostate cancer, and it can’t hurt for men to have a few fresh, low-calorie tomatoes in their regular diet. Keep in mind that research has shown that cooking tomatoes with a bit of oil leads to increased bioavailability of lycopene.

In addition to lycopene, tomatoes have other health benefits. One large tomato has 431 milligrams of potassium (12 percent of daily recommended amount). Potassium is necessary for muscle contractions (including your heartbeat), transmission of nerve impulses, and the regulation of fluids and electrolytes. Diets rich in potassium blunt the adverse effects of salt on blood pressure, may reduce the risk of kidney stones and may decrease bone loss. The Institute of Medicine recommends 4,700 milligrams of potassium for adults, but more than 90 percent of Americans are not meeting this recommendation.

Tomatoes are also high in vitamin A (30 percent of the daily recommended amount), which is important for proper vision, gene expression, cellular differentiation, and the growth and maintenance of healthy bones, teeth and hair. Vitamin A also promotes improved immune function, possibly by increasing the effectiveness of white blood cells, which fight infections.

Lastly, tomatoes are loaded with vitamin C (39 percent of the daily recommended amount). Vitamin C is an antioxidant that counteracts damage to cells from smoking and pollution and helps protect against cancer. It helps the body absorb iron, strengthens blood vessels and maintains healthy gums. Vitamin C is required for synthesizing important body compounds and chemicals such as collagen (an important structural component of blood vessels, tendons, ligaments and bone), norepinephrine (a brain chemical) and carnitine (assists in transporting fat).

Purchase and Storage Tips: Pick tomatoes that are red or red/orange, depending on variety. They should be plump (feel heavy) and free of bruises and blemishes. Store tomatoes at room temperature; cold temperatures can ruin the flavor.

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