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FoodInfo Online Features 28 October 2009 http://www.foodsciencecentral.com/fsc/ixid15792 © IFIS Publishing 2010 - All Rights Reserved Focus on food myths
Stephen Buckley  Despite impressive advances in food science in recent decades, and notably in identifying the role certain foods play in improving health, myths about foods still persist. Most of us will be familiar with one of the following - "oysters are aphrodisiacs", "food colorants make children hyperactive" and "spicy foods cause ulcers". But how many of us believe these statements to be true? This article looks at three popular food 'myths' in more detail and attempts to unravel whether they are based on science fiction or science fact.
"Eating carrots will help you see in the dark" This claim has its 'roots' in World War II. To prevent Germany from finding out the real reason their aircraft were suddenly being shot down in large numbers by the RAF (Airborne Interception Radar), Britain's Air Ministry spread the word that RAF pilots were being fed a diet of carrots which helped them see enemy bombers at night! It was already known at that time that carrots contained vitamin A, which is essential for healthy eyesight, and the humble carrot was one vegetable in plentiful supply. The slogan "Carrots keep you healthy and help you see in the blackout" was also used extensively, and carrots were promoted heavily in the Dig for Victory campaign. This claim became so persuasive to the British public during World War II that carrots were consumed in large amounts, even becoming the main ingredient in mouth-watering recipes such as carrot fudge, mock apricot tarts and carrot jam. There was also a homemade beverage called carrolade made from swede juice and carrot juice. Is there any scientific evidence to suggest that carrots make you see better in the dark? The answer is no for people with otherwise healthy eyesight. However, nyctalopia (night blindness), a disorder of cells in the retina responsible for vision in dim light, can be caused by vitamin A deficiency. The condition is improved by eating more vitamin A rich foods, including eggs, meat and fish, and not just carrots! "Fresh fruits and vegetables are more nutritious and healthier than frozen or canned fruits and vegetables" Fruits and vegetables are important for health, but are fresh better than the rest? At the moment they are picked this is undoubtedly true but not everyone can benefit from growing their own produce, and most of us buy fruits and vegetables from a grocery or supermarket. When purchased from a grocery or supermarket, fruits and vegetables have usually travelled some distance to get there, especially if they're out of season. Harvesting, packing and transportation can take days, and during this time valuable minerals and nutrients may be lost. For some vegetables this loss can be large, e.g. spinach and green beans can lose up to 70% of their vitamin C content within 7 days of harvest, even under recommended storage conditions. Contrast this situation with frozen fruits and vegetables, which are often packed and frozen within hours of being harvested and before being transported. Freezing ensures that valuable minerals and nutrients are not lost prior to sale. Not all fruits and vegetables can be frozen after harvest, but those that are, e.g. peas, are highly nutritious after cooking. It is also believed that canned fruits and vegetables are less nutritious than fresh or frozen. Although the levels of some vitamins and minerals are reduced by canning, others remain unaffected or may be increased. E.g. research has shown that canned apricots contain as much vitamin A as fresh or frozen apricots, and the vitamin C content of canned asparagus is higher than that of freshly cooked asparagus. Canned tomatoes have higher contents of absorbable lycopene (a dietary antioxidant) than fresh tomatoes. Evidence would suggest, therefore, that fresh, frozen or canned fruits and vegetables are all healthy and nutritious, and that this particular myth can be misleading. "Drink at least eight glasses (or 2 L) of fresh water each day" Under normal circumstances the human body can lose up to 2.5 L of water each day, and that water needs replacing if we are to stay healthy - but is there any medical justification for drinking eight glasses of water each day? Where did this guideline come from? Although its exact origin is unknown, it may have started in 1945 when dieticians at the US Food and Nutrition Board suggested a person should consume 1 ml of water for each calorie consumed. A daily diet containing approximately 1900 calories, therefore, equals nearly 2 L of water, 64 fluid oz or eight 8 oz glasses which became the well-known "8 × 8" rule. However, what dieticians at that time failed to realise was that water in fresh foods can contribute substantially to a person's daily intake. For example strawberries and watermelons are 92% water and radishes are 95% water. Although consuming 2 L of water daily is a good guideline, it does not have to be in the form of eight glasses of fresh water, and there is no medical evidence to support consuming this amount. Drinking cups of tea, coffee or other beverages (such as fruit juices) also contributes to the daily intake of water. Although some beverages contain caffeine (a diuretic), at least 50% of the water consumed is retained by the body. It would seem, therefore, that provided a person's diet is healthy and balanced this claim is not exactly water tight. So, is it a case of mythinformation? Only three myths have been discussed in this article but they appear to have one thing in common which may be true of all food myths - they all make a scientific statement which is not entirely in agreement with scientific fact. Despite this, food myths appear to have a powerful effect on the food choices of some people. This could be because they convey a very simple, short and memorable message about how a particular food may or may not be beneficial to health. However, it's also because of this that they should be treated with caution. An apple a day will keep the doctor away - but only when it's included in a balanced diet. |
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