Tomatoes protect against heart attack and stroke
Carotenoids are a family of over six hundred phytochemicals, including alpha-carotene, beta-carotene, lycopene, lutein and zeaxanthin. Carotenoids are abundant in green and yellow-orange vegetables and fruits and help to defend the body’s tissues against oxidative damage, which is a natural byproduct of our metabolic processes; oxidative damage from free radicals contributes to chronic diseases and aging.1
The levels of carotenoids in your skin are a good indicator of your overall health because the levels parallel the levels of plant-derived phytochemicals in general. In fact, I use a carotenoid skin testing method to non-invasively track my patients’ progress as they adopt a nutritarian diet. In a study of over 13,000 American adults, low blood levels of carotenoids were found to be a predictor of earlier death. Lower total carotenoids, alpha-carotene, and lycopene in the blood were all linked to increased risk of death from all causes; of all the carotenoids, very low blood lycopene was the strongest predictor of mortality.2
Lycopene is the signature carotenoid of the tomato. The lycopene in the American diet is 85 percent derived from tomatoes.3 Lycopene is found circulating in the blood and also concentrates in the male reproductive system, hence its protective effects against prostate cancer.4 In the skin, lycopene helps to prevent UV damage from the sun, protecting against skin cancer.5 Lycopene is known for its anti-cancer properties, but did you know that lycopene has also been intensively studied for its beneficial cardiovascular effects?
Links between blood lycopene and cardiovascular diseases
Many observational studies have made a connection between higher blood lycopene and lower risk of heart attack. For example, a study in men found that low serum lycopene was associated with increased plaque in the carotid artery and triple the risk of cardiovascular events compared to higher levels. Triple!6-8 In a separate study, women were split into four groups (quartiles) according to their blood lycopene levels; women in the top three quartiles were 50% less likely to have cardiovascular disease compared to the lowest quartile.9
A 2004 analysis from the Physicians’ Health Study data found a 39% decrease in stroke risk in men with the highest blood levels of lycopene.10 Newer data from an ongoing study in Finland has strengthened these findings with similar results. One-thousand men had their blood carotenoid levels tested and were followed for 12 years. Those with the highest lycopene levels had the lowest risk of stroke – they were 55% less likely to have a stroke than those with the lowest lycopene levels.11 Previous data from this same group of men found that higher lycopene levels were associated with lower risk of heart attack as well.12
How does lycopene work?
Lycopene is an extremely potent antioxidant; several studies that gave supplemental tomato products to volunteers found that their LDL particles were more resistant to oxidation – LDL oxidation is an early event in atherosclerotic plaque formation, and lycopene helps to prevent this.13-15 Another study found improved endothelial function after just two weeks of a tomato-rich diet; endothelial function refers to the ability of the endothelium (the inner lining of blood vessels) to properly regulate blood pressure, and oxidative damage can impair endothelial function.16
Lycopene also has non-antioxidant actions that may protect against cardiovascular disease. First, there is evidence that lycopene may inhibit HMG-CoA reductase, the enzyme responsible for making cholesterol (also the enzyme that is inhibited by cholesterol-lowering statin drugs).17 So as you might expect, trials that added extra tomato products to subjects’ diets reduced their blood cholesterol levels. A meta-analysis of 12 trials found that daily supplemental tomato products (approximately 1 cup of tomato juice or 3-4 tbsp. of tomato paste) reduced LDL cholesterol by 10% - this effect is comparable to low doses of statin drugs (with no risk of side effects, of course).18 Lycopene also has several anti-inflammatory actions and may prevent excessive proliferation of vascular smooth muscle cells, which is a contributor to atherosclerotic plaque development.19,20
Enjoy your tomatoes!
Of course, lycopene is not the only nutrient in tomatoes – tomatoes are also rich in vitamins C and E, beta-carotene, and flavonol antioxidants just to name a few.3 Single antioxidants usually don’t exert their protective effects alone; we learned this lesson from clinical trials of beta-carotene, vitamin C, and vitamin E supplements, which did not reduce cardiovascular disease risk.21 It is the interactions between phytochemicals in the complex synergistic network contained in plant foods that is responsible for their health effects, and this is something that we cannot replicate in a pill. Out of all the common dietary carotenoids, lycopene has the most potent antioxidant power, but combinations of carotenoids are even more effective than any single carotenoid – they work synergistically.22 Blood lycopene, as used in many of these studies, is simply a marker for high tomato product intake; similarly high alpha-carotene and beta-carotene levels are markers of high green and yellow-orange fruit and vegetable intake. Colorful fruits and vegetables provide significant protection.
In a given year, a typical American will eat about 92 pounds of tomatoes.23 Enjoy those 92 pounds and even add some more! Add fresh, juicy raw tomatoes to your salad, diced or unsulphured sun-dried tomatoes to soups, and enjoy homemade tomato sauces and soups. Be mindful of the sodium content of ketchup and other tomato products – choose the low sodium or no salt added versions. No salt added, unsulphured dried tomatoes are also great. Also keep in mind that carotenoids are absorbed best when accompanied by healthy fats – for example, in a salad with a seed or nut-based dressing.24,25 Lycopene is also more absorbable when tomatoes are cooked, so enjoy a variety of both raw and cooked tomatoes in your daily diet.26
Image credit: Flickr - MaplessInSeattle
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