Extensive Reading

1.     Why are our foods decreasing in the nutrient content?

In recent decades, modern agriculture has been evolving towards monoculture in order to increase crop yields. This boost in food production has been mainly due to the use of pesticides, herbicides and fertilizers, development of large-scale agricultural machinery, tillage and GMOs. Although modern agriculture successfully meets the growing demand for food by the worlds’ population for now, it has been destroying soil and plant health in the long run, which also results in declining nutrient content of crops. There are two main causes why modern agriculture decreases the nutrient content of our food.

1. “Genetic Dilution Effect”. Commercial plant breeders keen on developing “improved” species which grow bigger crops and give higher yields so that farmers can increase their profits. Since 80-90% of the dry weight yield of vegetables and fruits is usually carbohydrates, “improved” species are actually selecting crops with high carbohydrates with no assurance that other nutrients will also increase in proportion to yield ^[1]. Hence, commercial farm practices genetically dilute nutrient content of bigger vegetables and fruits.

2. “Environmental Dilution Effect”. Commercial agriculture uses a high rate of fertilizer to increase crop yields. However, if the crops are fertilized (e.g. phosphorus) beyond a certain level, the crops would contain more phosphorus, but the other minerals and vitamins absorption would be inhibited due to antagonism (i.e. decreased availability of other nutrients to plants due to the chemical reaction of certain nutrient.)^[2].

Although vegetables and fruits are getting bigger and heavier nowadays due to selective plant breeding and fertilization techniques, their nutrient content does not increase proportionally, or even decline because of dilution effects. Not only do these effects apply to vegetables and fruits, but also to meats, eggs and dairy products. Compared with industrial products, foods from animals raised on pasture are richer in vitamins A, D and E, beta-carotene and other beneficial fatty acids ^[3].

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2.     Why are antioxidant and chlorophyll content used as indicators for nutrition and plant health check?

Antioxidants are plant-based nutrients that are generally used for plant defence. Each antioxidant serves different functions to plants. Some act as pigment, giving fruits and vegetables vibrant colors to threaten their predators^[1]. Others act as plant defence against ultraviolet radiation (UV) and aggression by pathogens and insects. Common types of antioxidants include carotenoids, anthocyanin and curcumin.

Now that the general public is more concerned about a healthy and nutritious diet, while consuming antioxidants can neutralize potentially dangerous molecules in our body, which exert a protective effect to control chronic diseases. Therefore, the rise of antioxidants drew attention in recent years and has become one of the nutritional indicators for plant-based foods.

Chlorophyll is a green pigment found in plant leaves. It is essential in photosynthesis, which allows plants to generate sugars (i.e. food for plants). Therefore, chlorophyll indicates plants’ ability to make food which also implies plant health.

Moreover, as leaf chlorophyll will be degraded gradually along with postharvest senescence, chlorophyll content can estimate the harvest time of green leafy vegetables^[2]. Thus, high leaf chlorophyll content may imply that the vegetables are harvested recently and the freshness is also high. As a result, chlorophyll content of green leafy vegetables can be used as visible parameters for health and freshness of vegetables.

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