If you thought you knew your fibres but haven’t heard of resistant starches, then it’s time to read up – this little fellow is an important part of your diet, as well as your children’s. Not only does it significantly aid in healthy digestion, it also plays a big role in maintaining good gut bacteria – which is important for a strong and healthy immune system.
What is resistant starch?
Resistant starch is the part of starchy food (approximately 10 percent) that resists normal digestion in the small intestine. It is found in many unprocessed cereals and grains, unripe bananas, potatoes and lentils, and is added to bread and breakfast cereals as Hi-Maize. It can also be formed by cooking and manufacturing processes such as snap freezing. Rather than being fully broken down, resistant starch is turned into short-chain fatty acids by intestinal bacteria, and provides food for friendly bugs, which in turn produce a substance called butyrate – something which does a lot of good things for the colon.
“Butyrate improves the acid balance of the colon and this helps healthy microbes to grow and deters the bad ones,” says Dr Trevor Lockett, Theme Leader of Colorectal Cancer and Gut Health at CSIRO. He adds that should cells in the colon lining start changing in a way that could lead to cancer, butyrate comes to the rescue and kills them, while helping feed the healthy cells.
Given that more than three-quarters of our immune system resides in our intestinal track, with more than 500 species of bacteria present, it makes sense that getting your recommended daily intake (RDI) of resistant starches is key in maintaining a healthy immune system.
Other health benefits of resistant starches
- Assisting in weight management by creating a feeling of fullness and by decreasing the number of kilojoules absorbed from carbohydrate.
- Fibre and resistant starch have a role to play in diabetes management. Eating a diet high in fibre slows glucose absorption from the small intestine into the blood, so for people with diabetes, this reduces the possibility of a surge of insulin, the hormone produced by the pancreas to stabilise blood glucose levels.
- Minimising tooth decay as it is resistant to fermentation by bacteria in the mouth, and is less likely to stick to the teeth.
If we don’t eat enough resistant starch our health will suffer. Without it, the good bacteria in our large bowel get hungry and feed on other things including protein, releasing potentially damaging products such as phenols (digestion products of aromatic amino acids) instead of beneficial short-chain fatty acids.
Where can I get resistant starch?
Consuming at least 20 grams a day of resistant starch is thought to promote optimal bowel health. This is almost four times more than a typical western diet provides – it’s the equivalent to eating three cups of cooked lentils (which I am sure few of us manage!)
Like other fibres, resistant starch is found in cereals, vegetables and fruits. Sometimes starches, which are usually well digested, become more resistant as they cool after cooking. Cooked, cold potato is one example. Some grains, such as high amylose maize starch, are naturally high in resistant starch; new bread products are available containing ‘high maize’ flours.
While breastfeeding will pass on your good gut bacteria, you can keep up the good work by making sure your baby consumes food sources of resistant starches as you move them on to solids. Be sure to take it slow though – too much too soon will wreak havoc with their digestion.
Here’s a quick cheat sheet for sources of resistant starch courtesy of accredited nutritionist and dietitian Catherine Saxelby:
Most starchy foods have 5 percent or less resistant starch, but certain foods carry much higher natural levels, and levels can be increased during cooking or processing (such as snap freezing.) Foods naturally high in it are unripe bananas (54 percent), legumes and high-amylose corn starch (50-85 percent)
| Food | % resistant starch |
| Beans, lentils, sweet corn | 2 – 5 |
| Crispbread, crackers | 2 – 4 |
| Banana, ripe | 2 |
| Cooked potato, hot | 1 – 1.5 |
| Cooked potato, cooled | 2 – 4 |
| Breakfast cereals | 0.5 – 3 |
| Breads & biscuits | 0.5 – 2 |
| Rice, pasta | 1 |
| Peas, baked beans | 1 |
A word of warning: start slow
If your, or your child’s, current diet is low in resistant starches and you’re keen to bump up your intake while avoiding the inevitable gastrointestinal discomforts that accompany it, the trick is to take it slow – increasing your fibre intake over weeks and drink adequate water. You might change to a high-fibre breakfast cereal one week, change to a wholegrain bread the next, and gradually introduce more legumes over several weeks.
