Vegetables

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What is vegetable, how we can benefit from it?

 

Terminology

The exact definition of a “vegetable” may vary simply because of the many parts of a plant consumed as food worldwide – roots, tubers, bulbs, corms, stems, leaf stems, leaf sheaths, leaves, buds, flowers, fruits and seeds. The broadest definition is the word’s use adjectivally to mean “matter of plant origin” to distinguish it from “animal”, meaning “matter of animal origin”. More specifically, a vegetable may be defined as “any plant, part of which is used for food”,  a secondary meaning then being “the edible part of such a plant”. A more precise definition is “any plant part consumed for food that is not a fruit or seed, but including mature fruits that are eaten as part of a main meal”. Falling outside these definitions are mushrooms and other edible fungi, as well as edible seaweed which, although not parts of green plants, are often treated as vegetables.

In everyday language, the words “fruit” and “vegetable” are mutually exclusive. “Fruit” has a precise botanical meaning, being a part that developed from the ovary of a flowering plant. This is considerably different from the word’s culinary meaning. While peaches, plums, and oranges are “fruit” in both senses, many items commonly called “vegetables”, such as eggplants, bell peppers and tomatoes, are botanically fruits. The question of whether the tomato is a fruit or a vegetable found its way into the United States Supreme Court in 1893. The court ruled unanimously in Nix v. Hedden that a tomato is correctly identified as, and thus taxed as, a vegetable, for the purposes of the Tariff of 1883 on imported produce. The court did acknowledge, however, that, botanically speaking, a tomato is a fruit.

 

Nutrition and health

Vegetables play an important role in human nutrition. Most are low in fat and calories but are bulky and filling. They supply dietary fibre and are important sources of essential vitamins, minerals and trace elements. Particularly important are the antioxidant vitamins A, C and E. When vegetables are included in the diet, there is found to be a reduction in the incidence of cancer, stroke, cardiovascular disease and other chronic ailments. Research has shown that, compared with individuals who eat less than three servings of fruits and vegetables each day, those that eat more than five servings have an approximately twenty percent lower risk of developing coronary heart disease or stroke. The nutritional content of vegetables varies considerably; some contain useful amounts of protein though generally they contain little fat,and varying proportions of vitamins such as vitamin A, vitamin K and vitamin B6, provitamins, dietary minerals and carbohydrates. Vegetables contain a great variety of other phytochemicals (bioactive non-nutrient plant compounds), some of which have been claimed to have antioxidant, antibacterial, antifungal, antiviral and anticarcinogenic properties.

However, vegetables often also contain toxins and antinutrients which interfere with the absorption of nutrients. These include α-solanine, α-chaconine, enzyme inhibitors (of cholinesterase, protease, amylase, etc.),cyanide and cyanide precursors, oxalic acid and others. These toxins are natural defenses, used to ward off the insects, predators and fungi that might attack the plant. Some beans contain phytohaemagglutinin, and cassava roots contain cyanogenic glycoside as do bamboo shoots. These toxins can be deactivated by adequate cooking. Green potatoes contain glycoalkaloids and should be avoided.

Fruit and vegetables, particularly leafy vegetables, have been implicated in nearly half the gastrointestinal infections caused by norovirus in the United States. These foods are commonly eaten raw and may become contaminated during their preparation by an infected food handler. Hygiene is important when handling foods to be eaten raw, and such products need to be properly cleaned, handled and stored to limit contamination.

Dietary recommendations

The USDA Dietary Guidelines for Americans recommends consuming five to nine servings of fruit and vegetables daily. The total amount consumed will vary according to age and gender, and is determined based upon the standard portion sizes typically consumed, as well as general nutritional content. Potatoes are not included in the count as they are mainly providers of starch. For most vegetables and vegetable juices, one serving is half of a cup and can be eaten raw or cooked. For leafy greens, such as lettuce and spinach, a single serving is typically a full cup. A variety of products should be chosen as no single fruit or vegetable provides all the nutrients needed for health.

International dietary guidelines are similar to the ones established by the USDA. Japan, for example, recommends the consumption of five to six servings of vegetables daily.French recommendations provide similar guidelines and set the daily goal at five servings. In India, the daily recommendation for adults is 275 grams (9.7 oz) of vegetables per day.

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