NEW YORK (TheStreet) -- All right, everyone. It's time to challenge the notion that eating healthy is just too expensive.

Healthy food helps you control weight, prevent disease, regulate digestion, and even boost your mood. There's nothing more important than taking care of your own body, and not wanting to pay for healthy food is no longer an excuse to choose junk food.

When you eat fast foods, such as cheeseburgers and milkshakes, you're consuming highly processed foods full of fat, sugar, and salt. The harm junk food does to your overall health typically outweighs any nutritional value, which could cost you later in life.

If you think healthy eating on a budget is too hard, then think again. You don't need to snack on $20 bags of goji berries or go on those $360 juice cleanses to be healthy. There are plenty of affordable and healthy foods you can get.

We organized the top 13 based on cost per serving of each food, calculated by using the most recent data from the Bureau of Labor Statistics, U.S. Department of Agriculture, Centers for Disease Control and Prevention and WebMD.

Read on to see the top 13 cheapest healthy foods to help you stretch your dollar, and not your waistband.

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#13 - Beets

Cost per serving: 51 cents

This root vegetable cleanses the body and works as a purifier for the blood. It also boosts your mental health and acts as a source of energy. Beets are high in many vitamins and minerals including potassium, manganese, vitamin-B folate, fiber, and folic acid, just to name a few. 

A half-cup serving contains just 37 calories, and may also improve the health of your colon.

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#12 - Canned Tuna

Cost per serving: 46 cents

A can of tuna is packed with protein! Each serving of canned tuna contains 30 grams of protein, which is about 50% of the recommended daily protein intake per day. It also has 0.3 grams of omega-3 fatty acids, or 19% of your daily recommended intake.

Tuna is also low in both fat and calorie, and can help boost brain power and fight off heart disease.

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#11 - Garlic

Cost per serving: 30 cents

Garlic does a lot more than just stink up our breath. It's high in a sulfur compound called allicin, which has many health benefits (and is also responsible for that distinct smell).

A 28-gram serving of garlic contains 23% of our daily intake of manganese, 17% of Vitamin B6, 15% of Vitamin C, and 6% of selenium. It also has 1 gram of fiber, 1.8 grams of protein, and 9 grams of carbs, all combining for a total of 46 calories a serving.

Garlic can also boost the immune system, reduce blood pressure, lower cholesterol, improve bone health, and help enhance memory. 

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#10 - Onions

Cost per serving: 28 cents

Onions are high in polyphenols and flavonoids, both linked to lower stress and reduced cancer risk. An onion's sulfur compounds can help control diabetes and protect you from heart disease. Chromium, which regulates blood sugar, is also found in onions.

The flavonoids in onion are more concentrated in its outermost layers. There are 41 to 46 calories in one serving with only 2% of the calories from fat. Although onions are made up of mostly carbohydrates, they are considered "low-carb" vegetables and are healthy additions to a diet over more starchy vegetable like carrots, potatoes, and corn.

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#9 - Cabbage

Cost per serving: 27 cents

This underrated vegetable is powerful. Cabbage contains high sulfur and vitamin C content, which helps boost your immune system and remove toxins. It's also full of vitamin K and anthocyanins that help fuel your brain and help with concentration. The high potassium content in cabbages opens up blood vessels and helps maintain healthy blood pressure.

One cup of cooked cabbage is only 33 calories. It's low in fat and high in fiber, so it keeps you full longer and makes for an ideal diet food.

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#8 - Bananas

Cost per serving: 21 cents

At under a quarter per serving, this nutritious fruit is good for your heart and is especially high in potassium, magnesium, fiber, vitamin C and vitamin B6. Eating bananas can help regulate bowel movements, improve heartburn, battle depression, and lower risks of kidney cancers, diabetes, and osteoporosis. They are also rich in pectin, which helps get rid of toxins and heavy metals from the body.

Bananas have 110 nutrient-dense calories per serving. But they are a sugary fruit, so eat them in moderation.

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#7 - Popcorn

Cost per serving: 20 cents

Popcorn kernels are packed with inflammation fighting antioxidants that help prevent heart disease and depression. Popcorn is also the only 100% unprocessed whole grain, which makes it one of the best snacks to eat. It has zero cholesterol and is a low-calorie, low-fat, high-fiber food.

A three-cup serving of popcorn contains 93 calories. Be sure to go with the plain, natural popcorn kernels and not the already popped kind or the microwaveable packages that have unhealthy oils and other additives.

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#6 - Brown Rice

Cost per serving: 18 cents

Brown rice, with its mild and nutty flavor, is a rich source of selenium, which is essential for healthy thyroid metabolism, DNA, and immune system. It's low in fat and high in fiber, which makes it a more nutritious alternative to white rice because of the way it is processed. Brown rice is also a good source of manganese and niacin, which are both important for brain and heart health.

One cooked cup contains more than 27% of your daily selenium needs, and has approximately 216 calories.

#5 - Watermelon

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Cost per serving: 17 cents

This quintessential summer snack is high in lycopene, a carotenoid nutrient important for cardiovascular health as well as bone health. Watermelon also contains high amounts of vitamin A, vitamin C, pantothenic acid, copper, and potassium. This fruit can also sooth sore muscles.

Watermelon has an extremely high water content of 92% and is rich in electrolytes. It has approximately 46 calories per cup.

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#4 - Eggs

Cost per serving: 16 cents

Eggs are a dietary mainstay for every meal and are an ingredient in all kinds of sweet and savory recipes. Eggs are high in cholesterol, but one egg a day won't hurt you. In fact, the yolk is loaded with vitamins, minerals, and good fats. The egg whites contain protein.

The egg is full of disease fighting nutrients like lutein and zeaxanthin that reduce risk of blindness in older adults. It also contains choline, which helps with brain development and memory enhancement.

One whole egg contains 77 calories. With so many ways to cook an egg, we bet you can find a way to add it to your diet.

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#3 - Dried Beans

Cost per serving: 14 cents

Beans are one of the best foods for good health. One cooked cup has as much as 17 grams of fiber and is loaded with protein. They are low-fat and also contain dozens of key nutrients like calcium, potassium and magnesium. Beans help reduce risk of heart disease, type 2 diabetes, high blood pressure, and breast and colon cancers.

Get your hands on all kinds of beans: pinto, black, garbanzo, etc. On average, one serving of beans have around 100 calories.

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#2 - Oats

Cost per serving: 13 cents

This high-fiber cereal grain is a satisfying and enriching way to start your day. It is known as a "superfood" that's packed with soluble fiber and healthy carbohydrates. It helps curb appetite, reduce cholesterol, regulate bowel functions, and fight cancer. Oats are rich in antioxidants and specifically reduce risk of colon cancer.

Oats have approximately 124 calories per serving and plenty of health benefits.

So, what's our top pick for the cheapest healthy food?

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#1 - Flaxseed

Cost per serving: 10 cents

Flaxseed is the seed from the plant Linum usitatissimum. These little shiny brown seeds are low in carbs and high in B vitamins. They are an excellent source of omega-3 fatty acids and a good source of omega-6, as well as dietary fiber. The seeds also contain a phytonutrient called lignans, which has been found to lower risks of heart disease and possibly some cancers.

One serving is just 2 tablespoons. At just 10 cents per serving, flaxseed is number one in this list of top 13 cheapest healthy foods.

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