Nutrients are essential for the survival and proper functioning of all living organisms. These chemical compounds, mainly vitamins and minerals, serve as the building blocks and catalysts for various physiological processes within the body. To ensure that the body receives an adequate supply of these nutrients, maintaining a well-balanced diet is crucial. Balanced diets, encompassing a range of food groups, offer a unique set of nutrients necessary for optimal health and bodily function. Green onions are an important source of many essential nutrients, offering a rich array of vitamins, minerals, dietary fiber, proteins, carbohydrates and phytochemicals in various culinary dishes. Whereas macronutrients, encompassing proteins, carbohydrates and fats, represent the foremost sources of energy in the human body and are involved in various metabolism processes, micronutrients (minerals and vitamins) play critical cellular functions, serving as important antioxidants and participating in diverse enzymatic reactions. These nutrients contribute to the overall well-being of individuals, aiding in the maintenance of proper bodily functions and the prevention of nutritional deficiencies.
1. Vitamins
Vitamins are indispensable for building a healthy human body, but the human body cannot synthesize them
[1]. So, the consumption of diets rich in vitamins is the main source of the body’s vitamin requirement
[2]. Despite being required in smaller quantities in the body
[3], vitamins are pivotal in various metabolic pathways in living organisms, contributing to essential physiological functions
[4]. Green onions contain a range of vitamins that are essential for various metabolic processes in the body
[5] (
Figure 1). More importantly, most of these vitamins are associated with important biological activities; for instance, they serve as antioxidants and anticancer, antimicrobial and antiobesity agents
[6]. The major vitamins reported in green onions include vitamin A (in the form of pro-vitamin A-beta carotene), a range of vitamin B derivatives, including thiamine (B1), riboflavin (B2), niacin (B3), pyridoxine (B6) and folate (B9), and vitamin C
[7]. These vitamins are vital for energy metabolism, nervous system function, DNA synthesis and overall human well-being
[4].
Figure 1. Solubility, nutritional composition and biological function of key vitamins in A. fistulosum.
Vitamin A in green onions is primarily present in the form of beta-carotene, a precursor to active vitamin A
[8], which, as a component of the light-absorbing molecule in the eye’s retina, plays a critical role in maintaining healthy vision
[4]. Vitamin A is also essential for cellular differentiation, gene expression, growth, healthy skin, healthy immune system function, bone development and reproduction
[9]. Thiamine aids in converting food into energy and plays an essential role in maintaining a healthy nervous system
[10]; riboflavin supports tissue growth
[11]; niacin is crucial for skin health, metabolic processes, the central nervous system and energy production
[12]; pyridoxine plays a role in brain development and the synthesis of neurotransmitters
[10]; and folate is essential during pregnancy for fetal development.
The diverse array of B vitamins in green onions underscores their nutritional value and their potential to contribute to overall health and vitality. A comparative analysis indicates that the leaves of green onions contain higher amounts of vitamins B1, B2, B3 and C, carotenoids and minerals relative to the pseudostem
[13]. In a study that investigated the nutritional composition and antiobesity effects of mixed
Allium fistulosum and
Viola mandshurica extracts (AFE + VME) in high-fat-diet-induced obese mice, Sung et al.
[7] detected the presence of higher amounts of several nutrient elements, including vitamin B (B1, B2, B3 and B9). The presence of these nutritional elements, along with various bioactive compounds, was found to control obesity and various metabolic disorders.
Vitamin C, also known as ascorbic acid or ascorbate, is a crucial water-soluble vitamin that plays a multifaceted role in the body. It acts as a reducing agent in various enzymatic reactions, helping to facilitate critical physiological processes
[14]. Additionally, vitamin C serves as a soluble antioxidant, protecting cells and tissues from damage caused by free radicals
[15]. While vitamin C is found primarily in fruits and vegetables, it is interesting to note that animal organs like the liver and kidneys also contain this vitamin, highlighting its importance in both plant- and animal-based diets and its essential role in maintaining overall health
[16].
The vitamin C (ascorbic acid) content in green onions is very high
[17] and plays many important roles in boosting the body’s immune defenses, aiding in collagen production, and having antioxidant properties that protect cells from damage
[18]. A study by
[19] indicates that a delay in harvesting green onions may cause a substantial yield increment but a concurrent reduction in the content of important nutrient elements such as vitamin C, carotenoids, chlorophyll-a, chlorophyll b, sugars, volatile oils, nitrates and total N, K and Ca. Vitamin K, a vital fat-soluble nutrient, acts as a coenzyme in the carboxylation of specific amino acids, transforming glutamic acid into γ-carboxyglutamic acid
[20]. This conversion is crucial for the activation of proteins involved in blood coagulation, making vitamin K essential for the body’s ability to form blood clots and control bleeding
[21]. Rich dietary sources of vitamin K include green leafy vegetables like green onions as well as certain plant oils such as canola oil and soybean oil; ensuring an adequate intake of this nutrient can support proper blood clotting and overall health
[22]. Vitamin K in green onions is involved in blood clotting and bone health
[23].
2. Dietary Fiber
Dietary fiber constitutes a diverse combination of compounds, primarily consisting of non-starch polysaccharides like cellulose, hemicelluloses, pectins and lignin, along with substances such as gums, resistant dextrins and resistant starches, all of which resist digestion in the small intestine
[24]. These indigestible components of fiber provide numerous health benefits, including promoting digestive regularity, reducing cholesterol levels and helping to control blood sugar, making them an essential part of a healthy diet
[25]. Fiber-rich foods have the unique ability to create a sense of satiety and fullness while providing minimal calories, making them a valuable tool in weight management by curbing overeating and promoting weight loss, as well as helping to maintain healthy blood pressure levels
[26]. Green onions are a source of dietary fiber (non-digestible carbohydrates), which is important for a healthy digestive system
[22]. Fiber aids in maintaining regular bowel movements, preventing constipation by adding bulk to the stool for easier passage and promoting a feeling of fullness, which can be helpful for weight management
[22]. A diet rich in fiber supports heart health by lowering cholesterol levels and by regulating blood sugar, making green onions a favorable choice for people who are at risk of developing diabetic and cardiovascular disease conditions
[25].
3. Calories and Fat
Green onions are low in calories (energy intake) and fat content, making the crop one of the most suitable vegetable commodities for maintaining a healthy weight
[27]. Typically, green onions contain approximately 32 kcal calories per 100 g of fresh weight
[23]. Their low calorie content implies that a substantial amount of green onions may be consumed without significantly impacting the daily caloric intake required by the body. By incorporating more vegetables, such as green onions into one’s diet, individuals can effectively lower their consumption of saturated fats and high-calorie foods. The low calorie content implies that a substantial amount of green onions may be consumed without significantly impacting the daily caloric intake required by the body, potentially contributing to the development of a healthier and more balanced eating pattern
[28]. This dietary shift towards vegetables not only promotes better nutrition but also aligns with a broader strategy for overall health by reducing the intake of less nutritious options, thereby supporting a more wholesome and well-rounded diet. This property makes green onions an excellent addition to any meal plan for individuals seeking to control their energy intake and is thus essential for weight management. Generally, green onions are virtually fat-free, containing just about 0.2 g of fat per 100 g
[23], which is appreciated for maintaining a healthy weight. When fewer calories are consumed than expended, the body starts to utilize its stored fat for energy, leading to weight loss or weight maintenance. Dietary fat is more calorie-dense than protein and carbohydrates, making the consumption of low-fat vegetables like green onions more convenient.
4. Minerals
Plants play a crucial role in providing essential minerals necessary for maintaining a healthy human body
[29]. A variety of vegetables and fruits serve as abundant sources of major minerals like potassium and calcium, both of which are integral to various physiological functions
[8]. Green onions, like many other fresh vegetables, are noted for their rich source of these vital minerals, including potassium, magnesium, phosphorus and calcium, making them a valuable addition to a balanced diet
[30]. Potassium is essential for maintaining proper nerve function, muscle contractions and regulating blood pressure. Calcium, on the other hand, is crucial for bone health, blood clotting and muscle function. Both of these minerals are integral to maintaining overall health, and green onions contribute to meeting the body’s requirements for these minerals
[8]. Incorporating green onions into one’s diet not only adds flavor and nutrition but also helps ensure an adequate intake of essential minerals, further emphasizing the importance of including a variety of plant-based foods to support human health and well-being. Micronutrients, also known as trace minerals, have enormous health benefits. Manganese in green onions contributes to bone formation, blood clotting and a healthy metabolism in the human body
[31]. A nutritional component analysis of green onions based on powder extract reveals that green onions are a source of iron and zinc
[32]. In the human body, iron forms complexes with molecular oxygen in hemoglobin and myoglobin
[33]. Along with iron, zinc is crucial for bodily functions, such as oxygen transport, immune system support and overall human health. Zinc is an indispensable trace mineral with diverse roles in the body. Structurally, it is an integral component of numerous proteins, contributing to their stability and function.