By: Judy Davie - The Food Coach (adapted from an article by Dietitian Glenn cardwell)
It was interesting to read the other week that doctors at Westmead Hospital in Sydney have discovered some patients with Type 2 Diabetes who also have scurvy. Scurvy as you may well know is a Vitamin C deficiency and the clue for doctors was that these patients' wounds would not heal: Without Vitamin C, nothing heals. Type 2 diabetes is associated with poor diet, however according to the article these patients were eating vegetables, however they were overcooking them.
It's true, heat, storage and light diminishes some nutrients but not all
Vitamin C is a particularly unstable water soluble nutrient which can be lost with excess light and heat. Fresh fruit is probably the best source of vitamin C, however people who suffer from Type 2 Diabetes are often cautious to eat fruit for fear it will raise their blood sugar levels. It should be said that one kiwi fruit, or some fresh strawberries would be an excellent addition to their daily diet as both are relatively low in natural sugar and loaded in vitamin C. Those who prefer not to eat fruit would do well to eat raw salad with sliced red capsicum.
Another unstable nutrient which diminishes when subjected to light, heat and too much time in storage is folate. Folate is required in larger amounts than Vitamin C but provided you eat plenty of raw salad greens, asparagus, avocadoes and bananas, all of which require no cooking, you should get enough. Pregnant women need more folate, to avoid neural tube defects and may like to consider taking a supplement.
The stable nutrients
Minerals are generally unfazed by heat. Iron stays the same regardless of temperature and the calcium, iron, magnesium and zinc content of food will remain steady independent of the quality or cooking time of the food. Nuts will provide almost the same amount of minerals whether fresh or roasted.
Beyond vitamins and minerals, most fresh produce is also rich in bioactive compounds including antioxidants which help to protect body cells from oxidation and free radical damage which can lead to premature aging and disease. Until fresh produce starts to perish - by then no one will want to eat it - the antioxidant level in stored fruit and vegetables remains fairly constant.
How cooking in some instances improves bioavailability
In some instances cooking actually makes these bioactive compounds more available. Tomato sauce for example has more of the antioxidant lycopene than raw tomatoes and cooked carrots provide more beta-carotene than raw. The heat breaks down plant cell walls and helps release more of the nutritional goodness.
While it's true that cooking does diminish some nutrients, it's not the case for all, in some instances cooking maximizes the power of the nutrients. Commonsense would therefore suggest that a diet with both raw and cooked food is the best option for good health and, in my opinion it's the most interesting and delicious diet anyway.
This article was modified from an original written by Dietitian Glenn Cardwell Glenn is an Accredited Practising Dietitian with 30 years in clinical and public health nutrition, including 10 years as consultant dietitian to the National Heart Foundation, five years at the Children's Hospital in Sydney and was a major player in establishing the WA School Canteen Association in 1994. He began his nutrition consultancy company, Nutrition Impact, in 1996. Go to www.glenncardwell.com
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