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I am curious why cereals like Bran Flakes and Sultana Bran that look so healthy, and everyone assumes are healthy, actually have a high GI?


Bran Flakes and Sultana Bran (Raisin Bran in the US) are fibre-rich breakfast cereals designed to keep you ‘healthy on the inside’ as the ads say. But sadly they are high GI and digested in a flash because the long cooking times, the presence of lots of water, the flaking process and finally the toasting all conspire to make the starch very accessible. Here’s how Prof Jennie Brand-Miller describes what happens in The New Glucose Revolution.

‘Grinding, milling, flaking, popping and puffing grains radically changes nature’s architecture and makes it easier for water to be absorbed and digestive enzymes to attack the food. This is why many foods made from fine flours tend to have a high GI value. The larger the particle size, the lower the GI value, as the diagram below shows. One of the most significant alterations to our food supply came with the introduction, in the mid-19th century, of steel-roller mills. Not only did they make it easier to remove the fibre from cereal grains, but also the particle size of the flour became smaller than ever before. Prior to the 19th century, stone grinding produced quite coarse flours that resulted in slower rates of digestion and absorption. When starch is consumed in ‘nature’s packaging’ – whole intact grains that have been softened by soaking and cooking – the food will have a low GI. For example, cooked pearl barley’s GI value is 25 and most cooked legumes have a GI of between 30 and 40 whether home cooked or canned.


I was diagnosed with PCOS about 20 years ago with most of the standard symptoms. My doctor did a glucose tolerance test, which came out to be normal. Why I am not showing any signs of insulin resistance, if PCOS is supposed to be caused by it?
Insulin resistance is the most common cause and 70–80% of women with PCOS have insulin resistance. But a glucose tolerance test doesn’t pick up insulin resistance. It picks up the inability of the pancreas to deal with insulin resistance. If your pancreas has lots of ‘puff’, your glucose tolerance will remain normal, perhaps all your life. Only a fraction of people with insulin resistance go on to develop impaired glucose tolerance. Nonetheless, high insulin levels can cause other problems downstream, and the ovaries are particularly sensitive. Any woman with diagnosed PCOS also needs to have the actual cause of the problem pinpointed so she gets the right treatment for her and thus the best outcomes. Some of the other causes are anorexia, bulimia, stress, excessive exercise, high blood levels of prolactin and tumors of the adrenal glands, ovaries or pituitary gland. And for some women the cause is unknown. There’s a really excellent paper by Dr Warren Kidson on PCOS called ‘The Polycystic Ovary Syndrome – A Starting Point Not a Diagnosis’ which you can download here.