Glycemic Index and Youth

The glycemic index was brought to us by the pioneering work of Dr. David Wolever and Dr. David Jenkins in the early 1980s, finally giving a reliable and accurate measurement of blood glucose. The GI is simply a ranking of carbohydrate foods, according to their immediate influence on blood glucose levels after eating. Although its original conception was as a tool for helping type 2 diabetics control their blood sugar levels, the GI has become credible in achieving optimal health for both adults and children.

The “obesity epidemic” among children has been described as a “public health time bomb” by the Chief Medical Officer in the UK. Worldwide, there are reportedly 20 million children under the age of five who are overweight, and in the UK alone, 10 percent of six year olds and 17 percent of 15 year olds are classed as clinically obese (1). This is worrying for many reasons: it’s one thing when an adult is overweight and later develops type 2 diabetes and implicated CV disease, but when children as young as age 10 are showing signs of atherosclerosis and type 2 diabetes, it is another thing entirely. Clearly, being obese or overweight is a major issue, not least because there is a knock on effect into adulthood (i,e,. obese children are more likely to become obese adults). But it’s not just the effect on children’s physical appearance that is causing concern among health professionals. Children’s mental and emotional health also seems to be adversely affected by poor nutrition, with ADHD, dyspraxia and mental health issues becoming more evident among children.

So what’s changed in the last 20 to 30 years to adversely affect the physical, emotional and mental well being of children? Dietary fat has taken a bad rap over the last few decades. At one time, it was a taboo word, with many health professionals advocating removing it from the diet entirely. It seems, though, that fat and carbohydrate have a reciprocal relationship in the diet. That is, if you remove one, you tend to eat more of the other. So by removing fat, people started to eat more carbohydrates, the kind of carbohydrates like chips, fries, processed cereals and white breads that became more abundant in the supermarkets. It was around this time that the obesity epidemic really took off. Many schools had vending machines offering fizzy drinks and canteens serving up chicken nuggets and fries. It appears that the kind of carbohydrate your child eats affects health rather than all carbohydrates, per se.

Each time your child eats a high GI carbohydrate, he will almost instantly experience soaring blood sugar levels, which, if done habitually, can damage nerves and blood vessels as well as increasing the likelihood of type 2 diabetes. To cope with the rise in blood sugar, the pancreas excretes insulin, a powerful hormone that regulates blood sugar levels by aiding transport into working muscles for use as energy or to the liver where it is stored as glycogen or converted to fat. You may be surprised at some of the high GI foods that cause such a rise in blood sugar: bagels, white bread, frosted cereals and instant porridge: all interestingly often heralded as low fat healthy choices!

The problem is that many of these refined, simple carbohydrates have been stripped of their wholesome goodness in their processing, making them act in a similar fashion to pure sugar from the throat downwards. Insulin acts fast and deals with the rapid rise in blood sugar, though the peaks known as hyperglycemia are often accompanied by a subsequent rebound hypoglycaemia whereby blood sugars crash to low levels.

This is a concern for numerous reasons, including the potential impact on a child’s behavior. It has long been considered that a constant, even supply of blood sugar ensures optimum functioning of the brain. The brain is a hugely sugar-dependent organ and relies on a stable supply to function correctly. Research conducted at Swansea University found that these peaks and troughs experienced by consuming high GI carbohydrates are associated with poor memory, attention and concentration (2). A study conducted by Northumbria University showed the importance of feeding your child a low GI breakfast (3). They had two groups of children between six and 11 years old and fed them either chocolate rice cereal, which rapidly elevated blood sugar levels after consumption, or a starchy all-bran breakfast cereal that released the energy much more slowly. Hourly memory and attention tests were then administered thereafter, and researchers found that although both groups, as expected, declined in performance, the group that consumed the starchy breakfast fared much better in the subsequent tests than their counterparts.

Secondly, consuming a diet rich in high GI carbohydrates can also affect a child’s overall eating habits and weight. Research conducted by David Ludwig and colleagues looked at a group of 12 obese boys (4). On three separate days, the boys were given three breakfasts with identical calorie densities. On the first day, it was instant porridge, the second it was steel-cut oat porridge, and on the final day, it was a vegetable omelette and fruit. After each breakfast, the boys were allowed to freely graze on a snack platter. Shockingly, researchers found that the boys consumed an average of 600 to 700 calories more during the immediate hours following the high GI instant porridge compared to the other two lower GI breakfasts, suggesting that low GI foods are more satiating and keep your child fuller for longer. As expected, after the boys consumed the high GI instant porridge, there was a subsequent rise and fall in blood sugar.

Interestingly, from a behavioral standpoint, the rebound crash in blood sugar coincided with a surge in the hormone adrenaline, usually associated with times of stress. Adrenaline implicated in the “fight or flight” state may well cause children to appear hyperactive, anxious or aggressive. Further research conducted on children found that administering a low fat, calorie restricted diet was less successful (to the tune of seven pounds in four months) compared to the low GI, no restriction diet (5). The take home message here is, due to the satiating effects of low GI foods, children will naturally eat less and feel hungry less often when consuming low GI foods whenever they want. This also has implications for avoiding any eating disorders as children can freely consume healthy foods with no limitations, unlike many popular diets seen in the media.

By consuming a diet rich in low GI foods such as pulses wholegrains, fruits and vegetables, children are more able to control their appetite and ultimately bodyweight. It appears that cognitive performance in children is also associated with the type of carbohydrate they habitually consume. So not all carbohydrates are the same, and as such, the right kind of carbohydrates (low GI) should form the foundations for a healthy, balanced and nutritious diet for mental, emotional and physical well being.