Diets, Nutrition | January 8, 2018 | Author: Naturopath
Carbohydrates - “carbs” – have been receiving a lot of attention in recent years following the popularity of low carbohydrate/high protein diets for weight loss. Yet, while low-carb diets can be highly effective for rapid weight loss, they are not suitable for everyone.
The quality of the carbohydrates you eat is more important than the quantity. Before we look at healthy carbohydrate choices, we need to understand what carbohydrates are and how they affect our blood sugar.
Carbohydrates are one of the three food groups called macronutrients. Together with protein and fats, carbohydrates provide the body with energy and are needed in large quantities for everyday function. When digested, carbs break down to glucose (sugar).
Sugars (also known as simple carbohydrates) – sugar can be naturally occurring as in fruit or milk, or added to many processed foods such as cakes and biscuits, ice cream, sugar-sweetened drinks, flavoured yoghurts, breakfast cereals, etc.
Starch (also known as complex carbohydrates) – starchy foods include peas, corn, dried beans, potatoes, oats, barley and rice.
Fibre – dietary fibre is a non-digestible carbohydrate in plant food, meaning the body cannot break it down.
Fibre helps stabilise blood sugar levels, reduce cholesterol, and improve the sensation of feeling full and satisfied after eating.
Good fibre sources include whole grains (such as brown rice, buckwheat, oats, barley and quinoa), green leafy vegetables and other vegetables (such as broccoli, carrots, beetroot, potatoes and sweet potatoes), fruit (apples, berries), legumes (beans, lentils, chickpeas), and flaxseeds.
Animal food sources contain no fibre.
Another way of categorising carbohydrates is according to how they affect blood sugar. Glycaemic index (GI) was first introduced in the early 1980’s by researchers at the University of Toronto as a way to measure the ability of carbohydrate foods to raise blood sugar after a meal, compared with the rise after eating the same amount of pure glucose (sugar).
Foods are ranked on a scale of 0 to 100, with pure glucose given a value of 100.
The higher a food’s glycaemic index, the quicker and higher blood sugar rises after eating it.
Foods with a high glycaemic index signal the body to produce large amounts of insulin, the hormone that transports sugar into the cells after a meal. After eating high GI foods, large amounts of insulin may be released into the bloodstream in order to transport the blood glucose into the cells. As a result, you may experience a rapid drop in blood sugar that can lead to shakiness or fatigue several hours after eating, as well as an increase in appetite.
Excess blood sugar over long periods of time may eventually lead to insulin resistance, where after a while the body's cells become resistant to the effects of insulin. That is, the normal response to a given amount of insulin is reduced. As a result both insulin and sugar are at high levels in the blood.
Continual high spikes in blood sugar and insulin can damage metabolism and cause weight gain. The excess sugar in the blood is converted into fats, and causes inflammation in the lining of the blood vessels.
For GI of specific foods, go to GI database
GI values have their limitations. For example, the way a carbohydrate food is cooked or prepared may raise or lower its glycaemic index, so it is not always easy to predict its GI value. Also, the presence of fat or acid in the meal may have an effect on GI values. It also appears that blood sugar response after meals greatly vary across individuals even when they consume identical meals.
One ground-breaking study that monitored blood sugar response in 800 people found that the type of gut bacteria of the participants as associated with their blood sugar levels following the same meal.
Additionally, glycaemic index does not reflect the amount of carbohydrate consumed. For example, carrots have a high GI. However, GI values are calculated for 50 grams of carbohydrates in a particular food. A small carrot contains only about 5 grams of carbohydrates, which means you would need to eat 10 small carrots at one serving to get the high GI effect.
A more accurate way of taking into account how much carbohydrate a serving of a food contains is using what is called “glycemic load” (GL).
The glycaemic Load concept was developed in 1997. It involves multiplying the grams of carbohydrate in a serving by the glycaemic index and dividing by 100. A glycaemic load of 10 or below is considered low; 20 or above is considered high. Carrot, for example, has a high glycaemic index of 71, but a glycemic load of out 6.
Weight loss. Consuming low GI foods is a useful way for some people to lose weight and maintain weight loss, as long as they make healthy food choices.
Diabetes. When someone has diabetes, their body cannot maintain healthy levels of glucose in the blood.
Consuming low GI foods has been shown to help people with diabetes reduce their average blood glucose levels.
Diabetes Australia recommends that people with diabetes have moderate amounts of carbohydrate and include high fibre foods that also have a low GI (not all high fibre foods have a low GI).
The recommendation is to eat more low and intermediate GI foods, not to exclude high GI foods.
Augustin, L.S.A. et al., 2015. Glycemic index, glycemic load and glycemic response: An International Scientific Consensus Summit from the International Carbohydrate Quality Consortium (ICQC). Nutrition, Metabolism and Cardiovascular Diseases, 25(9), pp.795–815. Available at: http://linkinghub.elsevier.com/retrieve/pii/S0939475315001271
Diabetes Australia, 2015. Glycaemic Index. Available at: https://www.diabetesaustralia.com.au/glycemic-index
Harvard Health, 2017. A good guide to good carbs: The glycemic index -. Available at: https://www.health.harvard.edu/healthbeat/a-good-guide-to-good-carbs-the-glycemic-index
Linus Pauling Institute, Oregon State University, 2016. Glycemic Index and Glycemic Load. Available at: http://lpi.oregonstate.edu/mic/food-beverages/glycemic-index-glycemic-load
The University of Sydney, 2017. GI Database. Available at: http://www.glycemicindex.com/foodSearch.php
Zeevi, D. et al., 2015. Personalized Nutrition by Prediction of Glycemic Responses. Cell, 163(5), pp.1079–1094. Available at: http://www.ncbi.nlm.nih.gov/pubmed/26590418