Leaves as Vegetables: Food Significance and Nutritional Information

By Roby Jose Ciju

Leafy vegetables or vegetable greens are considered to be richest source of dietary fiber, vitamins and minerals. Daily consumption of minimum 100 to 150 grams of leafy vegetables along with a main diet is recommended by many health experts for balanced nutrition of a human body. Apart from its health-providing properties many leafy vegetables are considered to have medicinal benefits also, especially those vegetable greens which are loaded with antioxidant vitamins and minerals. This eBook explains in detail the food significance and nutrition of about 48 leafy vegetables.

• Language: English
• Publisher: AGRIHORTICO
• Release date: Mar 18, 2021

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Ciju

Leaves As Vegetables: An Introduction

Feeling young and healthy is the most important preoccupation of people of all ages and types. Making conscious decisions about what to eat and how to eat has a great impact on our health and appearance. Eating a healthy, balanced diet is the only way to achieve health and youthful appearance for everyone. It is an indisputable fact that a balanced diet having a high nutritional value benefits you irrespective of who you are and what age you are. Now the question arises, what is a balanced diet?

What is a Balanced Diet? A balanced diet is nothing but the right diet that is balanced in its energy (calorie) value as well as in the composition of FIVE major food nutrients (proteins, carbohydrates, fats/fatty acids, minerals and vitamins, and sugars).

Why Leafy Greens are Important in Foods? It is an established fact, after decades of scientific researches that leafy greens are a major source of minerals and vitamins. A human body requires minerals and vitamins in minor quantities on a regular basis for performing major metabolic and physiological functions. However, intake of regular foods is not sufficient to meet our body’s daily requirement of vitamins and minerals. Here comes the significance of including leafy greens in a balanced diet.

Freshly harvested leafy greens may be consumed as such in its raw form only after washing them. They may also be consumed after minimal processing such as chopping and adding in salads and in other raw food preparations. Such leafy vegetables which may be consumed in its uncooked state such as salads are called leafy salad vegetables. Their leaves and leaf stalks are used for consumption and therefore they are termed as leafy greens or leafy vegetables. They are consumed as salads and therefore known as salad vegetables. Some popular leafy salad vegetables are lettuce, celery, chives, kale, and parsley. In addition to these vegetables, arugula, chicory, endive, garden cress, water cress and land cress, chervil etc may also be used as leafy salad vegetables.

Other leafy greens like amaranth, spinach, beet greens, mustard greens and fenugreek greens are used for various vegetable preparations. Leafy greens like garden cress and water cress are used as microgreens, especially sprouted seedlings of these vegetables.

As you see, including leafy greens in your diet is a healthy decision. You will never regret this choice, I promise.

Now let’s understand about different types of vegetables and their classification systems.

Classification of Vegetables: As we know, leafy greens or leafy vegetables are a part of vegetable kingdom. So, before moving on to the major topic of leafy greens, let us have a look at the classification of major vegetables.

All vegetables are part of plant kingdom. Plant kingdom is first divided into FOUR sub-communities: Thallophyta; Bryophyta; Pteridophyta; and Spermatophyta. All the vegetables are part of the sub-community Spermatophyta. Spermatophyta has two divisions: Gymnosperms and Angiosperms. All vegetable plants belong to the group Angiosperms. Group Angiosperms has two ‘Classes’: Moncotyledoneae and Dicotyledoneae. ‘Class’ are further divided into ‘Family’, ‘Genus’, ‘Species’, and ‘Subspecies’, ‘Cultivar’ or ‘Variety’.

Botanical Classification of Vegetables: Botanical classification of vegetables based on two basic classes Monocotyledoneae and Dicotyledonaeae is given below:

Monocotyledoneae: It includes families Amaryllidaceae, Liliaceae, Araceae and Dioscoreaceae

Dicotyledonaeae: It includes familiesAizoaceae, Chenopodiaceae, Compositae, Convolvulaceae, Cruciferae, Cucurbitaceae, Euphorbiaceae, Leguminosae, Malvaceae, Polygonaceae, Solanaceae and Umbelliferae

Family-wise Categorization of Vegetables: All vegetables can be grouped into 16 families. A list of these vegetables is given below:

Family Aizoaceae: e.g. New Zealand Spinach (Tetragonia expansa)

Family Chenopodiaceae: e.g. Beets (Beta vulgaris), Swisschard (Beta vulgaris var. cicla) and Spinach (Spinacia oleracea)

Family Compositae: e.g. Chicory (Cichorium intybus), Endive (Cichorium endivia, Lettuce (Lactuca sativa) and Globe Artichoke (Cynara scolymus)

Family Convolvulaceae: e.g. Sweet Potato (Ipomoea batatas)

Family Cruciferae (Brassica Vegetables or Crucifers): e.g. Kale (Brassica oleracea var.acephala), Brussels sprouts (Brassica oleracea var.gemmifera), Cabbage (Brassica oleracea var.capitata), Cauliflower (Brassica oleracea var.botrytis), Broccoli (Brassica oleracea var.italica), Kohlrabi or Knolkhol (Brassica caulorapa), Rutabaga (Brassica napus var.napobrassica), Turnip (Brassica campestris var. rapa), Mustard (Brassica juncea), Chinese cabbage (Brassica chinensis and Brassica pekinensis) and Radish (Raphanus sativus)

Family Cucurbitaceae (Cucurbits): e.g. Cucumber (Cucumis sativus), Bittergourd (Momordica charantia), Pumpkin (Cucurbita moschata), Sponge gourd or Towel gourd (Luffa cylindrica) and Bottle gourd or Calabash gourd (Lagenaria siceraria)

Family Euphorbiaceae: e.g. Tapioca or Cassava (Manihot esculenta)

Family Leguminosae (Legumes): e.g. Green Peas (Pisum sativum), Winged bean(Psophocarpus tetragonolobus), Cowpea (Vigna sinensis) and Broad beans or Fava beans (Vicia faba)

Family Malvaceae: e.g. Okra or Lady's finger (Abelmoschus esculentus)

Family Polygonaceae: Rhubarb (Rheum rhaponticum), Sorrels and Docks (Rumex vesicarius)

Family Solanaceae (Solanaceous Vegetables): e.g. Potato (Solanum tuberosum), Brinjal or Eggplant (Solanum melongena), Tomato (Lycopersicon esculentum) and Chilli Peppers (Capsicum annum)

Family Umbelliferae: e.g. Carrot (Daucus carota), Parsley (Petroselinum crispum), Celery (Apium graveolens) and Parsnip (Pastinaca sativa)

Family Amaryllidaceae: e.g. Onion (Allium cepa), Leek (Allium porrum), Garlic (Allium sativum), Shallots (Allium ascalonicum) and Chives (Allium schoenoprasum)

Family Liliaceae: e.g. Asparagus (Asparagus officinalis)

Family Araceae: e.g. Taro or Colocasia (Colocasia esculentum)

Family Dioscoreaceae: e.g. Yam (Dioscorea alata)

Classification of Vegetables Based on Their Temperature Requirements or Hardiness: Based on their temperature requirements, there are two types of vegetables: winter vegetables and summer vegetables. Winter vegetables are cool season vegetables or temperate-climate vegetables. Summer vegetables are warm season vegetables or tropical-climate vegetables. In winter-season vegetables, mostly vegetative parts are eaten as vegetables, though a few exceptions may be found. Immature fruits are eaten as vegetables in most of the warm season vegetables.

Classification of Vegetables Based on Seasons and Length of Growth Cycles: There are THREE major categories of vegetables based on their life cycles: Annuals; Biennials; and Perennials. Annual vegetables are also called seasonal vegetables as they complete their life cycle within a season or year. Biennial vegetables are those which complete their vegetative growth cycle in the first season or year and reproductive cycle in the next season or year. Perennial vegetables are those vegetables which grow beyond two or more years and have a long economic life. Most of the leafy vegetables are seasonal/annual vegetables. Cruciferous vegetables are biennials. Examples of perennial vegetables include rhubarb, asparagus, Jerusalem artichoke, and globe artichoke.

Classification of Vegetables Based on Their Soil Reaction: Based on their soil pH requirements vegetables are classified into three categories: slightly tolerant; moderately tolerant; and very tolerant.

Slightly tolerant (pH 6.8 to 6.0): Examples are Asparagus, Beets, Broccoli, Cabbage, Cauliflower, Celery, Chinese cabbage, Leek, Lettuce, Muskmelon, New Zealand Spinach, Okra/Lady’s finger, Onion, and Spinach.

Moderately tolerant (pH 6.8 to 5.5): Examples are Beans, Brussels sprouts, Carrot, Cucumber, Brinjal/Eggplant, Garlic, Kohlrabi, Parsley, Peas, Chilli Peppers, Pumpkin, Radish, Squash, Tomato and Turnip

Very tolerant (pH 6.8 to 5.0): Examples are Chicory, Endive, Potato, Rhubarb and Sweet potato

Classification of Vegetables Based on Plant Parts Used as Food: Leaves, shoots, stems, immature fruits, flower parts, and underground parts of the plants are generally consumed as vegetables. Based on plant parts used as food, vegetables are grouped into the following categories: Leafy Vegetables or Leafy Greens, Fruit Vegetables, Flower Vegetables, Bulb Vegetables, Tuber Vegetables and Root Vegetables.

Leafy Vegetables or Leafy Greens: Edible parts are leaves, shoots and/or tender stems. Examples are Cabbage, Chinese Cabbage, Kohlrabi, Spinach, New Zealand Spinach, Malabar spinach, Collard greens, Mustard greens, Coriander greens, Beet greens, Mint herbs, Fenugreek Leaves, Drumstick leaves, Curry leaves, Amaranth leaves, Kale and Lettuce.

Fruit Vegetables: Edible parts are immature fruits. Examples are Beans and Peas (Fava beans, Cluster beans, French beans), Gourds and Melons (Cucumber, Pumpkin, Wax gourd, Towel gourd, Bottle gourd), Tomato, Eggplant/Brinjal, Okra/Lady’s finger, Papaya, Jackfruit, Mango, Breadfruit, Plantains and Chilli Peppers.

Flower Vegetables: Edible parts are flowers, flower clusters and associated parts. Some examples are Broccoli flower clusters, Sesbania flowers, Pumpkin flowers, Calabash gourd flowers and Cauliflower.

Root Vegetables: Edible part is a modified root. Some examples are Carrot, Turnip, Radish, Cassava/Tapioca, Beetroots, Sweet potato and Colocasia/Taro.

Bulbous Vegetables: In these vegetables, edible part is a bulb. A bulb is a modified stem that grows under the soil surface. Some examples are onion, garlic, fennel bulb, and shallots.

There are tuber vegetables and rhizome vegetables also. Tuber vegetables are those vegetables in which tubers are used as vegetables. A tuber is a modified stem growing under the soil. Examples are potato and yam. Rhizome is a modified underground stem and examples of rhizome vegetables are ginger and turmeric.

Leafy Greens: Powerhouse of Nutrients

As mentioned earlier, regular intake of a balanced diet is essential for maintaining health and overall functioning of our body. A balanced diet provides right amount of energy and nutrients. In other words, a balanced diet contains right amounts of energy, dietary fiber, protein, carbohydrates, fats, vitamins and minerals, and sugars. Leafy greens are proved to be a powerhouse of almost all important nutrients including some vital minerals and vitamins.

Now let us have a detailed look at various food nutrients that are needed by our body.

Energy: A right diet is high in nutritional value and provides sufficient calories of energy for bodily functions. All foods, whether carbohydrates, fats or proteins, contain calories, i.e. provide energy. Calorie is a unit of measure of energy.  A successful diet program contains right measures of energy. It is all about balance: balance between the calories consumed and the calories required by the body to perform its functions. Surplus calorie consumption results in overweight and insufficient consumption of calorie results in underweight. Both the extremes need to be avoided while planning a balanced diet. Leafy greens are low-calorie foods and hence highly suitable for weight-reducing and health-promoting dietary programs.

Water: Skin needs to be well hydrated all the times to keep its healthy appearance. Our bodies are composed of up to 70% of water. Blood, brain, muscles, lungs etc all contain a lot of water. Body needs water to regulate the body temperature and for transporting nutrients, removing bodily toxins and waste, and for protecting body organs. A dehydrated body accelerates the ageing process. When body is dehydrated it results in energy loss, headaches and fatigue. We need to consume lots of water every day. Water also acts as appetite suppressant and hence helps in losing body weight. Water is the chief component of all leafy greens and hence regular intake of leafy greens is advised to keep body hydrated.

Protein: Protein is essential for body’s tissue building and muscle generation. Protein metabolism releases amino acids, basic building blocks of a cell. Leafy greens contain moderate amounts of protein.

Carbohydrates and Sugars: Carbohydrates are a vital component of a balanced diet and are a major source of energy. Starchy vegetables such as potatoes are rich source of carbohydrates. Too much of anything is too bad. While sufficient carbohydrates must be present in a right diet, its surplus must be avoided. Carbohydrate overload increases bodily stress and as a result occurrence of life style diseases such as type 2 diabetes and heart ailments may be enhanced. A right diet avoids foods high in unhealthy sugars. A human body is unable to break down large amounts of sugars and as a result additional sugars get deposited in the body tissues and body ages rapidly. It is always advisable to eat less sugar.

Isn’t it a pleasure to know that leafy greens are not loaded with carbohydrates and sugars?

Dietary Fiber: Dietary fiber is good for human body.