Protein-rich fruits and vegetables are healthy alternatives to meat and dairy products because they don't have as much fat and cholesterol, which can reduce the risks of cardiovascular diseases. However, protein from fruits and vegetables are not complete, as they do not contain all the amino acids the body requires for building blocks. Thus, you need to combine a variety of fruits and vegetables to match the protein quality of meats and dairy products. Additionally, you need to consume a greater volume to match the protein quantity of animal sources.
Proteins
Proteins are chains made of amino acids connected by peptide bonds. Twenty amino acids are used by human beings to build a variety of structures in the body including muscle tissue. Of the 20 amino acids, nine are considered essential because they can't be synthesized and must be obtained from food sources. These essential amino acids are leucine, isoleucine, valine, lysine, threonine, tryptophan, methionine, phenylalanine and histidine. Most animal sources of protein contain the complete complement of amino acids in adequate proportions. With the exception of soybeans and quinoa, which are complete, vegetable and fruit protein sources are incomplete, but can be combined with one another to provide all of the essential amino acids.
Protein-Rich Fruits
Fruit is often not thought of as a source of protein, but some varieties are surprisingly good sources. For example, a cup of dried apricots contains 5 g of protein, whereas the equal measure of dried prunes contains 4.5 g. One cup of cherries contain 3 g, a banana has 2.5 g, a papaya, 2.3 g and a kiwi has 2.1 g. Avocado is often misclassified as a vegetable, but it is a very protein-rich fruit containing about 4.5 g of protein per cup. Coconut is also a fruit and the average sized fruit contains about 2 g. Other fruits considered decent sources of protein include dates, watermelon, peaches and tomatoes.
Protein-Rich Vegetables
The protein content of vegetables often pales in comparison to that of beef, fish or eggs, but many vegetables contain some protein and a few are considered very good sources. For example, a cup of packed spinach contains 5 g of protein, whereas the same size serving of asparagus contains 4.2 g, broccoli has 4 g, cauliflower has 3.8 g, a potato with skin has 3.8 g and a cup of celery has 1.5 g. Other decent sources of vegetable protein include kale, celery and carrots. An advantage of plant protein over animal protein is that it is low in fat content and high in dietary fiber, which can reduce the risks of heart attacks and atherosclerosis.
Legumes
Legumes can be considered plants, vegetable matter and even dried fruits of specific plants. They are often generically called peas, nuts and beans. In general, legumes are the best source of non-animal based protein. Legumes contain relatively low amounts of the essential amino acid methionine, but are rich in lysine. So some vegetarians compensate by mixing legumes with grains, which are high in methionine and low in lysine. A good example of this is native Indians eating beans with corn tortillas, or the Japanese eating tofu with rice. Protein-rich legumes include soybeans, which contain 29 g of protein per cup, while lentils contain 18 g, black beans 15 g, chickpeas 12 g and green peas 9 g. Other good sources of protein include quinoa, alfalfa, clover, carob, Brazil nuts, almonds and peanuts.
References
- "Biochemical, Physiological and Molecular Aspects of Human Nutrition"; Martha Stipanuk; 2006
- "American Dietetic Association Complete Food and Nutrition Guide"; American Dietetic Association; 2006
- "Contemporary Nutrition"; Gordon M. Wardlaw; 2010
- "Biochemistry of Human Nutrition"; George Gropper; 2000
- Ohio State University Extension; Chow Line: 'Mother grain' quinoa a complete protein; Martha Filipic; September 26, 2008
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