Food Nutritional Value
When it comes to choosing healthy food nutritional value is a priority.
So how do you create healthy meals with high nutritional value?
And what are superfoods?
What is a food's nutritional value?
The nutritional value of food simply means the quantity, range and quality energy (calories), vitamins, minerals and phytochemicals that are found in a food (1):
• Minerals: inorganic micronutrients (meaning they come from soil, air or water)
• Phytochemicals: only found in plants. They are known for their antioxidant activity and include anthocyanins (e.g. red pigments in fruits) and flavonols (like compounds found in cranberries.
Already, you can see that with plant-based food nutritional value is probably higher than other foods, because plants contain special nutrients not found anywhere else.
They are superfoods!
For any soil-grown food nutritional value is only as good as the soil and water used to grow it.
Soil with lowered nutrient content means lower nutritional value of food crops grown in that soil. Things that deplete soil nutrients include: years of intensive agriculture (soil nutrient depletion), poor irrigation practices, erosion, the use of pesticides and herbicides.
Just like humans, low levels of nutrients in plants means that the plants have trouble fighting off predators and diseases.
The growing conditions for our stock animals also have a huge impact on the quality of meat. There are many instances where animals have been fed poor quality feeds which reduce the health of the animal….and who wants to eat something unhealthy? It’s lower quality meat and has lower nutritional value. Know your farmer.
Shiny, large, luscious fruits look great, but usually come from plants which make a lot of large fruit.
In comparison, plants that make fewer smaller, brightly coloured fruits and vegetables usually have higher nutritional value, but they are less popular at the market so growers tend to avoid them (1). When choosing fresh food nutritional value could be higher in smaller, brighter fruits and vegetables.
Livestock (farmed cattle, sheep) tends to have lower nutritional value than its wild counterpart. The animal with a healthy natural diet, good dietary variety and lots of exercise is healthier and more nutritious to eat.
Once you've picked a fresh food nutritional value declines quickly. Fruit or vegetables start decaying and losing vitamins, even at low temperatures. For example, the nutritional value of green beans is highest in the first five days after picking. Pick and eat immediately!
Sometimes this is difficult, especially when food has to be shipped long distances and kept on display for several days.
Cold storage (below five degrees Celcius) slows the rate of decay of all foods. But with each passing day, the content of some vitamins can decrease significantly. One study shows that the nutritional value of kale, cold stored at 1 degree C for 6 weeks, had six times lower vitamin C than freshly-picked kale plants(2).
Dried food lasts longer than fresh food because without water, there’s less chance of decay. But any drying method causes chemical reactions in that cause a loss of vitamins, proteins and/or fats. Depending on the food nutritional value can be noticeably depleted (3, 4, 5, 6).
Food additives like sulphur dioxide are often used to prevent spoilage of foods that aren’t completely dried, like dried apricots. Some food additives can trigger health problems, like sulphur dioxide which can trigger asthma or respiratory problems (7).
The canning process involves heat, pressure and/or food additives. The initial heating reduces the nutritional value of fruit and vegetables (water soluble vitamins).
But once canned, the lack of oxygen in the can prevents further vitamin loss (8).
However, opening the can and heating the contents may cause further loss of vitamins (10).
The removal of the skins of fruit and vegetables prior to canning or freezing reduces their nutritional value (fibre and vitamins) (9).
Frozen vegetables and fruits lose fewer nutrients in the initial stages of the freezing process due to a shorter heating time (blanching).
But once frozen, the nutritional values gradually decrease because oxygen is present (8). Once opened, cooking the frozen food may cause additional loss of vitamins (10).
The nutritional value of frozen and canned food varies according to the water content of the food, which differs between methods of preservation (8).
Foods are often also processed to reduce spoilage and increase shelf life. But processing can really reduce the nutritional value of foods and make the food downright unhealthy. Do you want to know how to identify and start eliminating processed foods from your diet?
Many ‘experts’ claim that by mainly eating raw food and little or no cooked food, you’re getting greater health benefits. But is this really true? Click here to find out the surprising truth about raw food health benefits and hazards.
5. Cooking methods affect nutritional value too.
Choose the right healthy cooking method!
Cooking certainly plays a role in our modern society.
This comes from the practices of our ancestors who discovered fire and food cooking, thousands of years ago.
Despite what you might think, cooking plays an important role in food's nutritional value and in keeping you safe and healthy.
Click here to find out why.
(2) Hagen, SF, Borge GIA, Solhaug KA and Bengtsson GB. (2007). Effect of cold storage and harvest date on bioactive compounds in curly kale (Brassica oleracea L. var. acephala). Postharvest Biology and Technology 51 (1), 36 – 42.
(3) Lyimo, MH, Nyagwegwe, S and Mnkeni, AP (1991). Investigations on the effect of traditional food processing, preservation and storage methods on vegetable nutrients: a case study in Tanzania. Plant Foods for Human Nutrition 41 (1): 53 – 57.
(4) Maeda, EE, Salunnkhe, DK (2006). Retention of Ascorbic Acid and Total Carotene in Solar Dried Vegetables. Journal of Food Science 46 (4): 1288 – 1290.
(5) Rasmujssel Al (1978). Nutrient comparison of fresh and field-dried green-seeded soybeans. Journal of American Dieticians Association 72 (6); 604 – 608.
(6) Shilton, N (2003). Drying. Chemical Changes. Encyclopedia of Food Sciences and Nutrition (2) 1947 – 1950.
(7) Freedman, BJ (2004). Sulphur dioxide in foods and beverages: its use as a preservative and its effect on asthma. British Journal of Diseases of the Chest 74: 128 – 134.
(8) Rickman, JC, Bruhn, C, and Barrett, DM (2007). Nutritional comparison of fresh, frozen and canned fruits and vegetables Part 1. Vitamin A and carotenoids, vitamin E, minerals and fibre. Journal of the Science of Food and Agriculture 87 (6): 930 - 944.
(9) Rickman, JC, Bruhn, C, and Barrett, DM (2007). Nutritional comparison of fresh, frozen and canned fruits and vegetables Part 2. Vitamin A and carotenoids, vitamin E, minerals and fibre. Journal of the Science of Food and Agriculture 87 (7): 1185 – 1196.
(10) Worlds Healthiest Foods www.whfoods.org