You may have heard that buying organic is best, but what exactly does it mean for a food to be organic? According to the Organic Foods Production Act (OFPA), in order for a food to be legally labeled as "organic," it must "have been produced and handled without the use of synthetic chemicals."

Buying organic food reduces the amount of pesticides, or chemicals full of hormones, that your body is exposed to. Some pesticides can contain carcinogens, neurotoxins, and developmental toxins, which can adversely affect your health if eaten in large amounts. Below are the foods that contain the highest amount of pesticides in their non-organic form (aka "the Dirty Dozen"), making them the best organic foods you should be buying.

Peaches

Peaches are a summertime favorite for many, with the added benefits of being a great source of vitamin A and C. However, non-organic peaches can contain levels of dangerous pesticides such as fludioxonil, which has been shown to disrupt endocrine levels and lead to liver tumor growth in mice.

Apples

whole apple, Fruit, Fuji apple, apples
Jocelyn Hsu

Apples are high on the list of contaminated foods, with a whopping 47 different pesticides found on several varieties. The most common pesticide found on apples is diphenylamine, which has been shown to be toxic in large amounts. Make sure you get your apple a day, but preferably organically! 

Bell Peppers

pepper, vegetable, chili, sweet pepper
Torey Walsh

Bell peppers are made of 92% water and are an excellent source of vitamin C, and they also happen to be my favorite veggie. They can go in salads, on top of pizza, be stuffed, or just eaten plain. Try to buy organic peppers, as one sample of a non-organic bell pepper contained 15 different pesticides

Celery

meat, celery, chicken, sauce, vegetable
Maxwell Faucher

Celery is very low in calories due to it being 95% water, and its mild taste makes it a versatile vegetable for cooking. You can cook it in a soup, or simply use it as a side for some Super Bowl wings. More than 60 different pesticides have been found on celery, including insecticides chlorantraniliprole and spinosad.

Nectarines

apple, peach, nectarine, pasture
Dea Uy

Fun fact: peaches and nectarines are practically genetically identical. This means that like peaches, nectarines are also high in vitamin C. The main difference between the two is that peaches have a fuzzy outer skin while nectarines are smooth. One similarity both fruits share is the prevalence of the fungicide fludioxonil, which can potentially adversely affect the endocrine system in the body with chronic exposure. 

Strawberries

Fruit, red berry, red fruit, sweet, berry, strawberry
Amelia Hitchens

Strawberries are at the top of the Dirty Dozen list as the most contaminated non-organic produce. With an average of 7.7 different pesticides per sample, and the most contaminated sample having 21 different pesticides on it, make a point to buy organic berries as much as possible. Malathion, a popular pesticide used on strawberries, damages the nervous system, while carbindazim damages the male reproductive system. 

Cherries

juice, sweet cherry, berry, sweet, cherry
Jocelyn Hsu

Cherries are full of healthy antioxidants that can help protect your body against chronic diseases. Not only do they do good inside your body, but they also look good on top of ice cream sundaes and other desserts. Be wary of non-organic cherries, as there have been a total of 42 different pesticides found on them.

Pears

sweet, juice, quince, apple, pasture, pear
Amber Holte

Pears are relatively new to the Dirty Dozen list, due to the doubling of the amount of pesticude residue found on non-organic varieties. Pesticides can have adverse affects on not only humans, but important insects as well. For instance, contaminated pears contain the insecticides acetamiprid and imidacloprid, which kill bees. Bees are needed to pollinate crops, and without them life would be very different!

Grapes

grape, pasture, berry, wine
Lila Seeley

Grapes, enjoyed plain, frozen, or in wine, are full of antioxidants and have been said to prevent heart disease. In addition, while they are sweet, they do not elevate blood sugar levels as much, so they're safe to eat if you have diabetes. Unfortunately, through studies done to wine vineyards, it has been found that there has been about a 20% increase in pesticide use on grapes.

Spinach

spinach, vegetable, salad, lettuce, basil, relish, herb
Kristine Mahan

Spinach is a nutrient-dense food, which means it has a lot of vitamin and nutrients in each serving for a small amount of calories. Unfortunately, non-organic spinach can contain number of carcinogens and neurotoxins such as permethrin, a neurotoxic insecticide.

Lettuce

farmer's market, produce, fresh vegetables, local vegetables, lettuce, vegetable, herb
Sam Jesner

The great thing about lettuce is that you can pair it with virtually any meal, because there are so many different varieties and flavors. It can be used as a simple and healthy base for a salad, wrap, sandwich, or even soup in some cases. In addition to being low in calories, lettuce packs a punch by providing many vitamins and minerals. The many varieties of lettuce also come with many varieties of pesticides—52 to be exact.

Potatoes

potato, vegetable, tuber, carbohydrate, pasture, spuds
Katherine Baker

Potatoes: a comfort food classic. When they aren't deep fried, potatoes can help build brain cells thanks to Vitamin B6. Sweet potatoes are also packed full of potassium and Vitamin A, which help promote healthy vision are are a good source of healthy carbohydrates. Steer clear of non-organic varities, as many have been treated with the insecticide chlorprpham, which is toxic to bees and could be harmful to humans with chronic exposure. 

The best organic foods to buy are the foods with the most pesticides found on their non-organic varieties. It's better to buy organic foods due to their lack of harmful pesticides, however non-organic food is often less expensive because they require less labor to produce.

That being said, just like there is a "Dirty Dozen," there is also a "Clean 15," which are foods that have the least amount of pesticide residue. These foods (such as avocados and mangos) are better to buy non-organic than the other foods explained above. Regardless if it's non-organic or organic, make sure to thoroughly wash your foods before eating in order to clean off dirt and bacteria. After all, clean eating is good eating.