Contents
Abstract
Plant Based Foods: Discover Sustaining Protein Nutrition Options proteins are essential components of the human diet. Dietary proteins could be derived from animals and plants. Animal protein, although higher in demand, is generally considered less environmentally sustainable. Therefore, a gradual transition from animal- to plant-based protein food may be desirable to maintain environmental stability, ethical reasons, food affordability, greater food safety, fulfilling higher consumer demand, and combating of protein-energy malnutrition. Due to these reasons, plant-based proteins are steadily gaining popularity, and this upward trend is expected to continue for the next few decades. Plant proteins are a good source of many essential amino acids, vital macronutrients, and are sufficient to achieve complete protein nutrition. The main goal of this review is to provide an overview of plant-based protein that helps sustain a better life for humans and the nutritional quality of plant proteins. Therefore, the present review comprehensively explores the nutritional quality of the plant proteins, their cost-effective extraction and processing technologies, impacts on nutrition, different food wastes as an alternative source of plant protein, and their environmental impact. Furthermore, it focuses on the emerging technologies for improving plant proteins’ bioavailability, digestibility, and organoleptic properties, and highlights the aforementioned technological challenges for future research work.
Plant-Based Foods Introduction
Since the beginning of life, plants have been utilized for human benefits, providing food, therapeutics, wood, fibers, and many others. Moreover, plants were considered the bioproduction system for valuable substances and provide many primary and secondary metabolites having therapeutic effects. Primary metabolites (protein, carbohydrates, fats, and nucleic acid) are the building blocks of life. Besides these, the secondary metabolites are produced by plants to protect them from predators and pathogens, cope with environmental stress, attract pollinators, and work as their defense system . Proteins are molecules with great complexity and diversity that play an important role in maintaining the structure and function of the living form . Therefore, it is being used for many applications such as medicine, food, and feed.
By 2050, the world’s total population is expected to grow or might exceed 9 billion, and, hence, the demand for food, feed, and fiber around the globe is expected to increase by 70% . To meet this increasing demand, new sources must be explored. Nowadays, food derived from plants plays a vital role in the human diet as an important source of bioactive components, such as vitamins, phenolic compounds, or bioactive peptides. Hence, these components benefit human health and protect against various disease conditions .For meeting protein requirements, generally, animals are considered perfect. However, due to many diseases in animals, their consumption is not safer for human health. Also, it replaces animal-based proteins with plant-based proteins due to various limitations, such as increased cost, limited supply of nutrients, hazard for human health, freshwater depletion, and susceptibility to climate change . Plant-based proteins are considered vegan food, provide an ample number of amino acids, are directly absorbed by the body, and help in treating various disease ailments. Moreover, the proteins derived from plant-based foods are rich in fiber, polyunsaturated fatty acids, oligosaccharides, and carbohydrates. Hence, they are mainly associated with a reduction in cardiovascular diseases, low-density lipoprotein (LDL) cholesterol, obesity, and type II diabetes mellitus . Different sources of plant-based protein that include cereals (wheat, rice, millet, maize, barley, and sorghum), legumes (pea, soybean, bean, fava bean, lupin, chickpea, and cowpea), pseudo cereals (buckwheat, quinoa, and amaranth), nuts, almonds, and seeds (flaxseed, chia, pumpkin, sesame, and sunflower) were well-explored . However, the demand for the supply of protein is continuously increasing with the rise of the global population hence the need to search for new sources.
Definitions of Plant-Based Diets
The presented case is a dramatic example of the effect a plant-based diet can have on biometric outcomes like blood pressure, diabetes, and lipid profile. The reduction in HbA1C from 11.1% to 6.3% in 3 months is much better than would be expected with monotherapy with metformin or daily exercise.7 The improvement in blood pressure observed over a 4-month period with few medications is also rarely encountered in clinical practice and is likely related to a low-sodium diet and the avoidance of red meat. Because the patient was not obese and did not have significant weight loss with the diet, the dramatic improvements appear to be related to the quality of his new diet.
A healthy, plant-based diet aims to maximize consumption of nutrient-dense plant foods while minimizing processed foods, oils, and animal foods (including dairy products and eggs). It encourages lots of vegetables (cooked or raw), fruits, beans, peas, lentils, soybeans, seeds, and nuts (in smaller amounts) and is generally low fat.8,9 Leading proponents in the field have varying opinions as to what comprises the optimal plant-based diet. Ornish et al recommends allowing animal products such as egg whites and skim milk in small amounts for reversal of disease.10,11
Esselstyn, who directs the cardiovascular prevention and reversal program at the Cleveland Clinic Wellness Institute, recommends completely avoiding all animal-based products as well as soybeans and nuts, particularly if severe coronary artery disease is present.
Despite these smaller differences, there is evidence that a broadly defined plant-based diet has significant health benefits. It should be noted that the term plant-based is sometimes used interchangeably with vegetarian or vegan. Vegetarian or vegan diets adopted for ethical or religious reasons may or may not be healthy. It is thus important to know the specific definitions of related diets and to ascertain the details of a patient’s diet rather than making assumptions about how healthy it is. The following is a brief summary of typical diets that restrict animal products. A key distinction is that although most of these diets are defined by what they exclude, the plant-based diet is defined by what it includes.
Benefits of Plant-Based Diets
The goal of our diet should be to improve our health. In this section, we will review the literature for key articles that demonstrate the benefits of plant-based diets. Our review consists of existing studies that include vegan, vegetarian, and Mediterranean diets.
Obesity
In 2006, after reviewing data from 87 published studies, authors Bercow and Barnard13 reported in Nutrition Reviews that a vegan or vegetarian diet is highly effective for weight loss. They also found that vegetarian populations have lower rates of heart disease, high blood pressure, diabetes, and obesity. In addition, their review suggests that weight loss in vegetarians is not dependent on exercise and occurs at a rate of approximately 1 pound per week. The authors further stated that a vegan diet caused more calories to be burned after meals, in contrast to nonvegan diets which may cause fewer calories to be burned because food is being stored as fat.
Farmer et al14 suggest that vegetarian diets may be better for weight management and may be more nutritious than diets that include meat. In their study, they showed that vegetarians were slimmer than their meat-eating counterparts. Vegetarians were also found to consume more magnesium, potassium, iron, thiamin, riboflavin, folate, and vitamins and less total fat. The authors conclude that vegetarian diets are nutrient dense and can be recommended for weight management without compromising diet quality.
In 2009, Wang and Beysoun15 analyzed the nationally representative data collected in the 1999–2004 National Health and Nutrition Examination Survey. The aim of their study was to analyze the associations between meat consumption and obesity. Using linear and logistic regression analyses, they showed that there was a positive association between meat consumption and obesity.
Plant-Based Sources and Demand of Dietary Protein
Plant-Based Protein Sources
Among all the existing sources of dietary proteins, plant-based sources dominate the supply of proteins (57%), with the remaining 43% consisting of dairy products (10%), shellfish and fish (6%), meat (18%), and other products from animals (9%) .
To provide dietary protein supply and overcome the challenges of feeding the population, several sources of proteins from plants have been searched recently . Based on sources, proteins from plant origin might lack some essential amino acids. For instance, cereals generally contain less lysine, whereas legumes are deficient in sulfur-containing amino acids like cysteine and methionine . However, a good amount of lysine is present in pseudo cereals (e.g., quinoa and amaranth). Sometimes, the same plants have different nutrients due to differences in soil diversity, climatic conditions, precipitation levels, geographic latitude and altitude, agricultural practices, and different varieties/cultivars . Some traditional plants have been utilized by human beings as protein sources, including beans, pea, and soybean. Also, new sources (such as proteins from insects and algae) and unconventional and alternative protein sources (like agro-industry by-products from the extraction of edible oil and those discarded by fruit processing) have been discovered . In addition, different meat, milk, and egg analogs from plant-based protein sources have also been identified .
Legumes A diet rich in legumes provides various health beneficial effects for humans . Legumes are considered the best dietary options due to their abundant carbohydrates, protein, energy, vitamins, minerals, and fibers. Various commonly known legume crops for protein and other nutritional sources include soybean, common beans, peas, and chickpea. The protein obtained from soybean has been widely studied . Common beans are considered the primary source of vegetable protein in developing countries . Highly nutritious legumes such as peas can be utilized for different food product formulations to improve the human intake of protein. Food products from chickpea are the major dietary protein source of high-quality protein. The protein isolates and defatted flour from lupin fulfill the requirements of essential amino acids . Moreover, pigeon pea and its derived isolates of protein are the potential sources rich in sulfur-containing amino acids suitable for the consumption of human beings.
Demand of Dietary Protein
Proteins are molecules with great complexity and diversity that have played an important role in maintaining the structure and function of living cells. It is being applied in a number of applications, such as medicine, nutraceuticals, industries, food, feed, etc., and the demand for protein is continuously increasing with the rise of the global population . Globally, protein requirements are fulfilled by both plants (80%) (such as cereal grains, beans, soy, pulses, nuts, vegetables, and fruits) and animals (~20%) (such as meats, milk, eggs, fish, yogurt, and cheese) . Along with the increasing nutritious food demand, the protein demand is continuously increasing globally by changing socioeconomic status. Increased urbanization, as well as economic development, has led to various transitions in dietary patterns in the population of low- and middle-income countries, especially the demand for foods derived from animals, which is noticed in developing countries . Protein from animal origin causes emissions of greenhouse gases from livestock as well as loss of terrestrial biodiversity by human interventions . Therefore, plant-based protein requirements are continuously increasing.
Plant-based proteins play a major role in the human diet as they are rich in a large number of other nutrients, vitamins, and minerals . Foods obtained from plants enhance the content of protein that contains various essential amino acids and may also improve the nutritional status of human diets. From the last few decades, interest has been drawn for the search of protein sources with high nutritional quality and functionality and industrial applications (like emulsification, solubility, gelation, foaming, viscosity, oil holding, and water-holding capacities). Furthermore, the development and utilization of novel techniques of food processing enhance the nutritional quality of traditional sources of plant protein. According to the overall status of health, human nutrition is considered an important issue that provides the methods for prevention or development of a number of diseases resulting from excessive, unbalanced, or insufficient nutrient intake . Generally, the daily intake of protein is provided by animal-based foods. However, changes in the consumers’ requirement led to adoption of alternative sources of proteins for human consumption. And, also, the protein produced from animal sources is costly and environmentally non-sustainable and requires more water (about 100 times) during production than plant protein. Emerging factors in animal proteins, like the growth of world population, climate change, and occurrence of animal diseases, more research is now dedicated to finding various new sources and technologies to produce proteins from plants with high content and resilient to changing climate and thus provide balanced nutrition in humans’ diet .
Factors Affecting the Nutritional Value of Plant Proteins
The protein’s nutritional quality can be identified in different ways, but, in a simple way, it is the balance and relative amounts of essential amino acids, as well as digestibility, bioavailability, and bioactivity, which mainly identify its nutritional value. Compared with animal-based protein, the proteins derived from plants are easier to produce; however, when utilized as dietary sources for human consumption, most of the plant proteins are deficient in essential amino acids and are, therefore, nutritionally incomplete. For example, some cereal proteins are low in tryptophan, lysine, and threonine content, while vegetable proteins and legumes have a lower amount of sulfur-containing amino acids, such as methionine and cysteine . Due to this deficiency, these essential amino acids become the limiting factor in legumes and cereals. Practically, neither legumes nor cereals can compensate for the deficiency of amino acids for other crops, and, hence, diet feeding regularly provides supplementary amino acids. There are also other factors that affect the nutritional quality of crops, including soil condition, crop maturity, postharvest handling, storage, use of fertilizers and pesticides, crop variety, and climatic conditions.
Conclusion
A healthy, plant-based diet requires planning, reading labels, and discipline. The recommendations for patients who want to follow a plant-based diet may include eating a variety of fruits and vegetables that may include beans, legumes, seeds, nuts, and whole grains and avoiding or limiting animal products, added fats, oils, and refined, processed carbohydrates. The major benefits for patients who decide to start a plant-based diet are the possibility of reducing the number of medications they take to treat a variety of chronic conditions, lower body weight, decreased risk of cancer, and a reduction in their risk of death from ischemic heart disease.
A plant-based diet is not an all-or-nothing program, but a way of life that is tailored to each individual. It may be especially beneficial for those with obesity, Type 2 diabetes, high blood pressure, lipid disorders, or cardiovascular disease. The benefits realized will be relative to the level of adherence and the amount of animal products consumed. Strict forms of plant-based diets with little or no animal products may be needed for individuals with inoperable or severe coronary artery disease. Low-sodium, plant-based diets may be prescribed for individuals with high blood pressure or a family history of coronary artery disease or stroke. A patient with obesity and diabetes will benefit from a plant-based diet that includes a moderate amount of fruits and vegetables and minimal low-fat animal products. Severe obesity may require counseling and initial management with a low-calorie diet or very-low-calorie diet and the supervision of a physician’s team. Patients with kidney disease may need a plant-based diet with special restrictions, for example fruits and vegetables that are high in potassium and phosphorus. Finally, patients with thyroid disease will need to be careful when consuming plants that are mild goitrogens, like soy, raw cruciferous vegetables, sweet potatoes, and corn. These patients should be informed that cooking these vegetables inactivates the goitrogens.
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