Whether you're a strict vegan or more meat-and-potatoes, anyone can enjoy a meat-free meal now and then; they're affordable, nutritious, low-calorie and environmentally-friendly.

Plant-based meals often raise concerns about protein; do they offer the "complete" protein our bodies need? A complete protein source has all 9 essential amino acids in roughly equal amounts. Essential amino acids are not produced by the body, and must be obtained through food.

While it's true we need all 9 essential amino acids, we don't have to get them from one place. Vegan meals contain a broad range of amino acids from a wide variety of foods, so it's not hard to gather what you need next Meatless Monday.

12 Easy Sources of Plant-Based, Complete Protein:

1. Hemp Seeds

Protein: 10 grams per 2 tablespoon serving

Creamy little hemp seeds (hearts) can be sprinkled on salads, soups, desserts...and anything else your heart desires. They contain significant amounts of all nine essential amino acids, as well as plenty of magnesium, zinc, iron, and calcium. And it gets better! They're also a rare vegan source of essential fatty acids, like omega-3s, which can help fight depression.

2. Quorn

Protein: 13 grams per ½ cup serving

Orignally developed to combat global food shortages, Quorn, or mycoprotein, is a meat substitute made by growing a certain type of fungus and binding it with free-range egg whites. (OK, so not technically 'vegan' but definitely 'vegetarian'). Full of protein, it's a tasty meat-free option that comes in sausages, burgers, "chicken" tenders, and more.

3. Chia Seeds

Protein: 4 grams per 2 tablespoon serving

Protein-packed chia seeds are the highest plant source of omega-3 fats, and contain more fiber than flax seeds or nuts. Full of iron, calcium, zinc, and antioxidants, they gel in liquid for a fantastic vegan pudding - the perfect breakfast or midnight snack.

4. Rice & Beans

Protein: 7 grams per 1 cup serving

Budget-friendly and delicious, rice and beans is a great protein source; in fact, its protein content is on par with that of meat. Load up on carbs and protein after an intense workout with this filling duo.

5. Spirulina with Grains or Nuts

Protein: 4 grams per 1 tablespoon

Spirulina is a protein-packed algae that's only missing two essential amino acids: methionine and cysteine. This is easily remedied by adding in some grains, oats, nuts or seeds; think spirulina energy bars or a nutty spirulina smoothie.

6. Hummus and Pita

Protein: 7 grams per 1 whole-wheat pita and 2 tablespoons of hummus

Similar to rice, the protein in wheat is only missing the amino acid lysine. Chickpeas (a legume) make up for it in spades, however, in this creamy, protein-rich snack.

7. Peanut Butter Sandwich

Protein: 15 grams per 2-slice sandwich with 2 tablespoons of peanut butter

Just like hummus & pita, peanuts (a legume)+bread results in a complete protein. Who doesn't love a PB sandwich?

8. Quinoa

Protein: 8 grams per 1 cup serving, cooked

Similar in texture to couscous, quinoa is a super-versatile and nutritious seed. It's packed with protein, fiber, iron, magnesium, and manganese, makes a great substitute for rice and can be used in muffins, fritters, cookies or breakfast dishes.

9. Buckwheat

Protein: 6 grams per 1 cup serving, cooked

Disregard the misleading name; buckwheat is not wheat at all, but a grain-like seed related to rhubarb. Used by the Japanese to make soba noodles, most cultures grind it into flour or cook the hulled kernels (groats) to make a comforting breakfast similar to oatmeal.

10. Soy

Protein: 10 grams per ½ cup serving (firm tofu), 15 grams per ½ cup serving (tempeh), 15 grams per ½ cup serving (natto)

This protein is an easy swap for meat; try tempeh or natto (fermented soybeans), or tofu (bean curd) in tacos or stir frys. If using tofu - the firmer it is, the more protein it has.

11. Ezekiel Bread

Protein: 8 grams per 2 slice serving

This ultra-nutritious bread offers complete protein thanks to wheat, barley, beans, lentils, millet, and spelt. Typically made from sprouted ingredients, it's easy to digest and fiber-rich to boot.

12. Seitan

Protein: 21 grams per 1/3 cup serving

Created over a thousand years ago by Chinese Buddhist monks, this meat substitute is made by mixing gluten (wheat protein) with herbs and spices and simmering it until a meat-like texture emerges. In order to be a complete protein, it must be cooked in soy-sauce rich broth to add in lysine. Try seitan fajitas, stir-fry or sliders.

Adapted from greatist.com, here.