There are more and more reports on the fact that the nutrients in our food are decreasing (1), (2), (3). The food problem as I call it is an increasing issue which needs to be addressed. A number of studies of fruits, vegetables and grains have shown a decline in nutritional value over time. The reason for this are plenty, soil depletion, change in farming methods, extensive use of chemical fertilizers and food processing and preparation.
Soil depletion occurs when the components which creates fertility are removed and not replaced, and the conditions which helps soil fertility are not maintained. This leads to poor crop yields. Depletion can be a cause of intense cultivation and inadequate soil management. Humans have been depleting the soil of the earth at an alarming rate, faster than the nutrients can be replenished. If this trend cannot be reversed, soil erosion in combination with the effects of climate change, will be an increasing threat to our global food security in the coming century. “Ever since humans developed agriculture, we’ve been transforming the planet and throwing the soil’s nutrient cycle out of balance,” says Ronald Amundson, a UC Berkeley professor of environmental science. Soil erosion has increased since the industrial revolution and today the ability of our soil to support the growth of our food supply is declining. Fertile soil is being lost at the rate of 24bn tonnes per year according to a report from the UN.
Change in farming methods
The farming methods have changed in a dramatic fashion since world war II. Productivity of food and fibers has soared due to new technologies, mechanization, increased chemical use, specialization, and government policies that favored maximizing production and reducing food prices. These changes have allowed fewer farmers to produce more food and fiber at lower prices. Although these developments have had many positive effects and reduced many risks in farming, they also have significant costs. Prominent among these are topsoil depletion, groundwater contamination, air pollution, greenhouse gas emissions, the decline of family farms, neglect of the living and working conditions of farm laborers, new threats to human health and safety due to the spread of new pathogens, economic concentration in food and agricultural industries, and disintegration of rural communities. When the production of food and fiber degrades the natural resource base, the ability of future generations to produce and flourish decreases. The decline of ancient civilizations in Mesopotamia, the Mediterranean region, Pre-Columbian southwest U.S. and Central America is believed to have been strongly influenced by natural resource degradation from non-sustainable farming and forestry practices.
Extensive use of chemical fertilizers
Chemical fertilizers have aided farmers in increasing crop production since the 1930s. While chemical fertilizers have their place increasing plant nutrients in adverse weather conditions or during times when plants need additional nutrients, there are also several harmful effects of chemical fertilizers. Some harm chemical fertilizers may cause include waterway pollution, chemical burn to crops, increased air pollution, acidification of the soil and mineral depletion of the soil. The over-use of chemical fertilizers can lead to soil acidification because of a decrease in organic matter in the soil. Nitrogen applied to fields in large amounts over time damages topsoil, resulting in reduced crop yields. Sandy soils are much more prone to soil acidification than are clay soils. Clay soils have an ability to buffer the effects of excess chemical fertilization.
There is an increasing concern that continuous use of chemical fertilizers on soil depletes the soil of essential nutrients. As a result, the food produced in these soils have less vitamin and mineral content. Chemical fertilizers are high in nutrient content such as nitrogen. Over-application of chemical fertilizer to plants may cause the leaves to turn yellow or brown, damaging the plant and reducing crop yield. This condition is known as chemical leaf scorch. Leaf scorch can cause the leaves of the plant to wither and may cause the plant to die. According to data produced by the U.S. Department of Agriculture Nutrient Data Laboratory, foods grown in soils that were chemically fertilized were found to have less magnesium, potassium and calcium content. The use of chemical fertilizers on crops can have adverse effects on waterways caused by chemical run off of the excess fertilizer. The over-abundance of nutrients in the water reduces the amount of oxygen. The existing organisms living in the water use up the oxygen that is left. The result is oxygen depletion causing the fish to die.
Food processing and preparation
variety of things can happen during the growing, harvesting, storage and preparing of food that can affect its nutritional content. Processes that expose foods to high levels of heat, light or oxygen cause the greatest nutrient loss. Almost all food is processed in some way before it is eaten. Commercially, the main reasons to process food are to eliminate micro-organisms (which may cause disease) and to extend shelf life. Simply cooking or combining food with other foodstuffs to create a recipe is also considered a form of food processing. Whatever the case, the nutrient value of any food is often altered by the processing. The following are some food processes:
- Milling – Cereals such as wheat can be ground to remove the fibrous husks. The husks contain most of the plant’s dietary fibre, B-group vitamins, phytochemicals and some minerals. That is why products such as white bread are less nutritious than wholemeal varieties, even if they have been artificially fortified with some nutrients that were lost after milling. It is impossible to add back everything that is taken out, especially the phytochemicals. The ‘fibre’ that is added back to some products is often in the form of resistant starch, which may not be as beneficial as the fibre removed.
- Blanching – Before food is canned or frozen, it is usually heated very quickly with steam or water. The water-soluble vitamins, including vitamin C and B-complex, are sensitive and easily destroyed by blanching.
- Canning – Food is heated inside the can to kill any dangerous micro-organisms and extend the food’s shelf life. Some types of micro-organisms require severe heat treatment and this may affect the taste and texture of the food, making it less appealing. Preservatives are generally not needed or used in canned foods. Water-soluble vitamins are particularly sensitive to high temperatures. Many people believe that canned foods are not as nutritious as their fresh counterparts, but this is not always the case, as fresh food often deteriorates more rapidly than canned foods.
- Freezing – The nutrient value of food is retained when it is frozen. Any nutrient losses are due to the processing prior to freezing and the cooking once the frozen food is thawed.
- Pasteurization – Pasteurization involves heating liquid foods such as milk and fruit juices to specific temperatures to destroy micro-organisms. The nutrient value of milk is generally unaffected. In the case of pasteurized fruit juices, some losses of vitamin C can occur.
- High pressure processing– This alternative preservation method subjects food to elevated pressures, with or without the use of heat to kill micro-organisms. This method has been used in foods such as fruit juices. As heat is not required, this process impacts less on the vitamin content, flavour and colour of foods.
- Dehydrating – Drying out foods such as fruits can reduce the amount of vitamin C they retain, but it can also concentrate other nutrients, particularly fibre in plant foods. Dehydrating food also makes food products more energy dense, which may contribute to weight gain. If a dehydrated food is reconstituted and cooked with water, further nutrients are leached out of the food and lost in the cooking water.
- Preparation of vegetables – Most vegetables are peeled or trimmed before cooking to remove the tough skin or outer leaves. But most nutrients, such as vitamins, tend to lie close to the skin surface, so excessive trimming can mean a huge reduction in a vegetable’s nutrient value.
- Loosing nutrients through cooking – Some vitamins dissolve in water, so you lose your vitamins to the cooking water if you prefer to boil your vegetables. For example, boiling a potato can cause much of the potato’s B and C vitamins to migrate into the boiling water. It is still possible to benefit from these nutrients if you consume the liquid, for example, by turning the potato and the liquid into a soup. Alternative cooking methods such as grilling, roasting, steaming, stir-frying or microwaving generally preserve a greater amount of vitamins and other nutrients.
There are some who claim that the nutrients in our food are not declining and some who claim that the “solution” to the decline is just to eat more fruit and vegetables which sounds more of a quick fix “solution” from the food industry to just buy more of their products. However, there are in fact more reports who support the fact that the nutrients in our food are declining than their our reports which say they don’t. In the long run we need a sustainable agriculture which can only be maintained by creating policies that integrate social, environmental, and economic interests to preserve our food security for the future so we get nutritious and healthy food. Last but not least find better ways to process our food in order to preserve a good nutritional value.
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