There's no question that fruits and vegetables are an essential part of a healthy diet and provide benefits to body and mind that go far beyond conventional nutrition. Most are rich in phytochemicals, whose natural power to support health and combat disease is only now under serious study.
But industrial agriculture relies on hundreds of chemicals to target insects and diseases that can afflict crops. Unfortunately, many remain after the crops are harvested, even after produce is washed at home.
The U.S. Environmental Protection Agency tests the toxicity primarily of individual pesticide agents, but scientists are increasingly concerned about combined effects and the possible synergistic effects of consuming many chemicals, even in small amounts, at one time.
Using data from tests conducted by the U.S. Department of Agriculture, the Environmental Working Group has ranked 53 foods by amount and frequency of pesticide contamination. The shorter list below, adapted from their findings, is designed to help you limit your exposure by buying the organic versions of the ones most susceptible.
Foods best eaten organically grown (ranked from most to least contaminated)
Apples: Of every 10 apples, nine have traces of the fungicide thiabendazole, a carcinogen; eight also have diphenylamine (DPA), linked to bladder tumors; workers applying it are required to wear long sleeves and gloves. Apples carry 40 other pesticides: carcinogens, hormone disruptors, neurotoxins, developmental toxins. Pesticides aside, apples supply vitamin C and the soluble fiber pectin, which, with apple's many phytonutrients, curbs heart disease.
Celery: The USDA counts 64 pesticides on celery. Every celery stick you chew has traces of chlorantraniliprole, used to kill moths, caterpillars and beetles by overstimulating their muscles to contract. Spinosad, a similar insecticide, is also ever-present in celery. About 50 percent of celery samples carry methoxyfenozide, toxic if swallowed in large doses. But don't cut celery from your diet. It's mineral rich and an excellent source of fiber and vitamin K.
Strawberries: Of every two strawberries you enjoy, one probably contains the fungicide captan, a probable carcinogen. It is usually accompanied by fellow fungicide pyraclostrobin, a known skin and eye irritant. Still, strawberries are a great fruit to enjoy fresh. They're packed with vitamin C, antioxidants, folate and fiber. Recent research suggests they help regulate blood sugar levels.
Peaches: They carry residues of 62 pesticides. Almost every other peach has fludioxonil, which targets the liver and kidneys. Some 30 percent of samples contain traces of iprodione, a possible carcinogen, and phosmet, which targets the nervous system of insects and humans, along with our reproductive system. But peaches are rich in potassium and vitamins A and C.
Spinach: It harbors 48 pesticides. Close to every other leaf has permethrin and imidacloprid, which disrupt nerve signals. Spinach is still good for you though. It's rich in vitamins A and C, several B vitamins, many minerals, including potassium, as well as the antioxidant beta carotene. Spinach also protects against prostate cancer.
Nectarines: A clean-shaven variety of peach, the nectarine is a little cleaner pesticide-wise but contaminated with the same substances. The USDA counted 33 different residues. At the top of the list is formetanate, a neurotoxin found in every other nectarine you consume. But don't say no to nectarines; like peaches, they make for a low-calorie, succulent snack with a good dose of fiber and vitamins A and C.
Grapes: The USDA found traces of 34 pesticides on Chilean grapes. Of every 10 imported grapes, almost three have the fungicide cyprodinil, which can irritate eyes, nose and especially skin. One in 5 has the neurotoxin imidacloprid. But grapes are a great food, low in calories, rich in vitamin C and loaded with phytonutrients with beneficial effects on almost every body system, including compounds that promote weight control and longevity.
Foods safely eaten conventionally grown (ranked from least to most contaminated)
Onions: Onions make you cry, but they might be tears of joy, as onions carry the fewest pesticides — only 1 and on only 0.3 percent of samples tested. It's dicloran, a fungicide banned in most European countries. Aside from lending flavor to an array of dishes, onions have cardiovascular benefits, including cholesterol-lowering effects; they also boost immunity and combat inflammation. Onions contain many phytonutrients, too, including the antioxidant quercetin.
Sweet corn: Corn is virtually pesticide-free, harboring traces of just one pesticide (the neurotoxin dimethoate), and then on only 2.3 percent of samples. Apart from fiber-packed kernels, corn provides some B vitamins as well as vitamins C and E. It's also a good source of the carotenoid antioxidant lutein, which protects the retina.
Pineapples: Traces of six pesticides have been identified in this juicy fruit, most frequently the neurotoxin triadimefon, in 4.5 percent of samples. It's also a possible carcinogen. Another pesticide found in trace amounts is carbaryl, a neurotoxin and likely carcinogen which, like triadimefon, is banned in most European countries. Rich in vitamin C, pineapples also contain bromelain, a protein-digesting enzyme that can curb indigestion and reduce inflammation.
Avocado: The major pesticide used on avocados has as its active ingredient the neurotoxin abamectin, which can lead to loss of coordination and tremors in high doses. Avocados are a good source of fiber and folate, but increasingly research is focusing on avocado oil. Like olives, avocados are rich in oleic acid, known to protect the cardiovascular system. Among other beneficial fats in avocados are phytosterols, which fight inflammation.
Asparagus: The residue of nine pesticides has been found in asparagus, but in only 3.3 percent of samples. Methomyl, a neurotoxin, is the most frequent. Found in 3 percent of samples is chlorpyrifos, another neurotoxin. Asparagus is a nutritional powerhouse, with significant vitamins A and B, including folate, and many minerals. It's also antioxidant-rich, a protector of the nervous system, a promoter of heart health and a player in blood sugar regulation.
Sweet peas: The USDA found residues of 12 chemicals on sweet peas in frequencies ranging from 0.1 to 12.1 percent of samples. The only compound found in more than 10 percent of samples is dimethoate, a neurotoxin. These relatively unpolluted pearls contain omega-3 fats as well as vitamins A, B and C. Peas also boast a phytonutrient under investigation for its ability to fight stomach cancer and other phytonutrients linked to lowered risk of diabetes.
Mangoes: The two major pesticides used on mangoes are the neurotoxin imidacloprid and glyphosate, an herbicide that's relatively nontoxic to humans. One mango can supply all the vitamin C you need for a day. The antioxidant beta carotene gives the fruit its vibrant orange hue. Mangoes contain B vitamins, minerals such as potassium and proteolytic enzymes that aid and abet digestion.
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