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Resistant Starch
What is Resistant Starch?
Resistant starch is a type of starch that acts like dietary fibre. When we eat food it is broken down or digested in the stomach and absorbed from the small intestine (small bowel). Indigestible fibre and resistant starch pass into the large intestine (large bowel) where it has health benefits due to its ability to absorb water, lower pH and increase good bacteria growth. Like fibre, resistant starch probably helps protect against diverticular disease, irritable bowel syndrome, diarrhoea, constipation and cancer of the large bowel.
What does resistant starch do?
- It lowers the pH of the bowel making it more acidic where as fat increases the pH.
- It produces large quantities of short chain fatty acids (SCFA), especially Butyrate. SCFA are thought to reduce the risk of bowel cancer by keeping the bowel lining healthy and reducing the growth of tumour cells.
- It has a mild laxative effect which will helps prevent constipation.
- It encourages the growth of healthy bacteria in the bowel.
- It increases the bulk of the stools through good bacterial growth and discourages the growth of pathogenic bacteria.
How much Resistant Starch do Australians eat?
According to a recent CSIRO report, we only eat about 5 grams of resistant starch per day. We require 20 grams in order to get bowel related benefits. We should try to eat four times the resistant starch that we currently do. At the same time, we should continue to try and include more fibre from breads, cereals, bran, fruit and vegetables.
Where is Resistant Starch found?
Resistant starch is found in small amounts in lentils and some cereals but also found in cold potato, rice, corn, green banana and pasta. The richest source of resistant starch comes from a special Australian maize (corn). This is called 'Hi-maize' which is undetectable when added to cooked food and some drinks. Hi-maize is now added to some popular food brands. Look for the logo on bread and cereal products in the supermarkets. There are also now two Hi- maize powders available. One is for adding to drinks and the other for adding to food in cooking. These will be available from health food stores.
Starch Australasia, a member of the Goodman Fielder Group have published a chart showing some of the total fibre and resistant starch content of some foods. The chart is is reproduced below. Note the resistance starch is much higher in chilled potato, rice, pasta, and lentils. This is because the body finds cold starch from these foods difficult to break down in the small bowel. Hi maize is just about pure resistant starch so total fibre is low. The total fibre does not include resistant starch.
FOOD | RESISTANT STARCH % |
TOTAL DIETARY FIBRE % |
---|---|---|
White bread | 0.8 | 2.8 |
Wholemeal bread | 0.8 | 6.5 |
Buttercup Wonder White™ | 2.8 | 5.6 |
Shredded Wheat | 1.0 | 11.0 |
Rice Krispies | 0.1 | 1.1 |
Cornflakes (extruded) | 0.2 | 1.4 |
Porridge Oats | 1.8 | 6.9 |
Uncle Toby’s Grinners | 2.4 | 10.6 |
Whole Rye Crispbread | 1.2 | 13.4 |
Boiled Potato (hot) | 1.1 | 1.9 |
Boiled Potato (cold) | 2.4 | not available |
Hi-maize™, in cooking | 63.1 | 25.0 minimum |
Lentils (boiled 20 minutes, cold) | 2.5 | 3.7 |
Apple Granny Smith (raw) | 0 | 1.9 |
High fibre diets including resistant starch improve health by:
- Increasing the bulk of the stools.
- Reducing the transit time. (the time from eating to elimination).
- Decrease the production of harmful substances that increase the risk of cancer.
- Produce beneficial substances in the bowel to protect against cancer.
What else can we do to reduce the risk of cancer?
- Eat more fruit and vegetables and high fibre cereals.
- Eat less fat, alcohol and avoid over cooked or charred meats.
- Eat foods rich in calcium.
- Maintain a healthy body weight with sensible food intake and regular exercise.
Only 15% of bowel cancer cases are genetic in origin or passed on by parents. Diet and life style are associated with 50% of cases.