Protein is made up of amino acids, which unlike carbohydrates and fats, contain nitrogen. The liver produces most of the amino acids needed by the body, but some, including histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine, must be obtained from food sources. Foods containing all of these essential amino acids are called complete proteins. Most beans, nuts, grains and vegetables contain only some essential amino acids; eating a variety of plant-based foods can provide adequate dietary proteins. A few vegetarian superfoods qualify as complete proteins.
Chlorella
A single-celled green algae, chlorella, grows in fresh water under sunlight, which gives it a high chlorophyll content. Chlorella is a complete protein, rich in iron, omega-3 fatty acids, carotenoids, vitamin C and B-12. The algae must be carefully cultivated, harvested and processed to retain nutrients, and it is considered a traditional remedy for a wide variety of health conditions. The American Cancer Society states that chlorella drew the attention of scientists after World War II as a possible major food source, because of its high protein content and rapid growth rate. The impracticality of large-scale production and the public's dislike of chlorella's earthy taste helped to discourage commercial development. Chlorella powder can be added to dips and baked goods. Look for it in health food stores.
Hempseeds
A review of emerging research on the effects of dietary hempseed was published in the April 2010 "Nutrition and Metabolism." Researchers Delfin Rodriguez-Leyva and Grant N. Pierce of the University of Manitoba wrote that hempseed is a complete protein similar to soybean, a very rich source of omega-3 fats, vitamin E and the minerals phosphorus, potassium, magnesium, sulfur, calcium, iron and zinc. Additionally, hempseeds are high in arginine, an amino acid important to cardiovascular health. The seeds are hulled, packaged and sold in health food stores for use on salads or blending into a nutritious drink.
Quinoa
This cereal grain has been cultivated as an important food in the Andes for thousands of years. In a review conducted by A. Vega-Galvez and colleagues of Universidad de La Serena in Chile, quinoa's nutritional value is attributed to its balanced composition of oil and complete protein. The grain is also a rich source of minerals, vitamins, fatty acids and antioxidants found to be protective of nerve cells and brain functions. The findings were published in the September 2010 "Science of Food and Agriculture."
Soy
Perhaps the most versatile of the complete plant proteins, soy foods are a good alternative to meat. Soy contains isoflavones, substances that have estrogen-like effects. They may protect against hormone-dependent cancers. High doses, however, may increase the risk of estrogen-responsive cancers. The American Cancer Society advises women with breast cancer to limit intake to a few servings per week of soy foods, and to avoid concentrated sources, such as protein bars, powders or supplements containing high amounts of isoflavones.
References
- ACS: Chlorella
- "Nutrition & Metabolism": The Cardiac and Haeomstatic Effects of Dietary Hempseed
- "Journal of the Science of Food and Agriculture": Nutrition Facts and Functional Potential of Quinoa (Chenopodium quinoa wild), an Ancient Andean Grain: A Review
- American Cancer Society: Common Questions About Diet
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