Key 4 - Carb Sources
CARB SOURCES should mostly consist of SLOW DIGESTING CARBS and WHOLE GRAINS (low GI carbs, depending on your activity level and the timing of the meal).
Whole grains have pre-biotic effects, selectively increasing the beneficial friendly microbes in your gut and as a consequence your immune response. This beneficial effect is much higher in the whole grain, compared to only bran consumption because whole grains work synergistically together. Friendly microbes and their by-products produce a myriad of beneficial effects like decreasing inflammation and oxidative stress. They also have a detoxifying effect and improve the digestion, absorption and filtering of the foodstuffs that journey through your gut.
It is important to incorporate whole grain foods into your diet and lifestyle program. By the way, all the Blue Zone communities that are the healthiest people on earth have lots of whole grain foods. “Whole grains” include grounded, cracked or flaked fruit of the whole grain, whose principal components; bran, endosperm and germ, are present in the same relative proportions as they exist in the intact grain, although they are higher glycemic index (GI) than most intact whole grains. So you won’t necessary see or bite an intact grain in a “whole grain” food product.
Whole grain foods that undergo processing and reconstitution have the same proportion of bran (fibre part), endosperm (starchy part) and germ (protein part) as that of the original intact whole grain, unless some of this is sifted out or otherwise removed. Whole grains would include barley, brown rice, maize/mealies/corn, oats, rye, sorghum and wheat and also include rolled oats, whole grain breakfast cereals like Bran flakes/sticks, some mueslis, etc. Unfortunately with refining, the outer bran and inner germ layers are removed with substantial losses in of fibre, essential vitamins, minerals and phyto-nutrients and an increase in the GI. Millet is the only whole grain that is high GI, even when intact and ground millet/ flour is even higher GI.
Whole grains, apart from being rich sources of a variety of different fibres, vitamins and minerals are also rich in plant-sterols, anti-oxidants and phyto-chemicals. The latter fights off all kinds of cancer, and more specifically colorectal cancer.
Whole grains have beneficial effects on heart disease due to anti-inflammatory and anti-oxidant properties, improved cholesterol levels, reduced blood pressure and improved insulin sensitivity. Improved insulin sensitivity together with improved blood sugar levels very directly reduces the risk for type II diabetes.
Many dietary components in the whole grain positively affect gut health and they are also associated with a lower body-mass-index, less abdominal fat and trends toward lower weight gain over time. Read More on Fibre.
Not all carbohydrate sources are equal though – meaning they are digested and absorbed by the Gastro Intestinal Tract at different rates. As a matter of fact - not even all breads are equal in their digestive qualities. Common white and brown bread are digested and absorbed quite fast. At the other end you will have bread baked with rye, oat, barley and/or soya flour, with seeds and/or fruit like raisins or cranberries, which would be quite filling and will be digested much slower. Often breads are fortified with fibre-like stretching ingredients e.g. gums, carrageenan, CMC (carboxy methyl cellulose), inulin, etc. which would also cause a slower digestion and absorption rate. Even regular ingredients like vinegar, organic salts and even sugar can slow down the digestion of bread.
This is good as fast absorption usually causes a blood glucose spike and this triggers a significant insulin excretion, which stresses the beta cells of the pancreas in the body. In addition, a huge blood glucose drop follows after approximately 100 minutes. The blood glucose drop makes the body feel unfocused and lazy, and often the tendency to look for another meal to get pepped up.
In the 1980’s Wolever and Jenkins, two scientists in Canada, developed a scientific tool to measure the digestion rate of carbohydrates and named it the Glycemic Index (GI). Over the past 35 years, the GI of thousands of variants of foods has been determined, in actual human subjects. More on the factors that influence the GI of foods. Over the years it was determined that there are some general factors that have a direct influence on the GI of a foodstuff. To name a few:
Smaller particle sizes of the ingredients included in the foodstuff will cause a faster absorption. As in the case of breads mentioned above, the lower GI breads generally include less refined flour and/or lower GI flours like legume flours and more granular like ingredients, e.g. low GI intact whole grains (see above), seeds or legumes like lentils.
The inclusion of fibre generally hinders fast digestion which will cause a slower digestion and absorption and thus a lower GI. Soluble fibre found in oats, barley and legumes are especially GI lowering, as it delays emptying of the stomach, slowing down absorption. Insoluble fibre (as found in most whole grains and bran) can also slow down digestion, but only if double the amount present in intact whole grains are used.
When fat and protein are in the product naturally, as in the case of beans (all kinds) and lentils, it also slows down digestion and absorption. But the fat and proteins, even if added to a mixed breakfast cereal, also results in a lower GI, as fat delays emptying of the stomach and protein increases insulin secretion.
Because of their molecular structure some sugars, like lactose, are digested slowly, others like sucrose are digested medium fast and others, like glucose, dextrose, maltose and maltodextrine, are digested even faster still. Sugars are not unhealthy or evil, but they are a very dense and concentrated form of kilojoules. Many overweight people consume far too much, either out of ignorance or out of habit, especially through drinks.
All kinds of cakes and confectionaries generally have a high GI, because of the refined flour used, unless some of the high GI flours (wheat, rice, potato, sorghum, millet, tapioca, sago, etc.) are replaced with low GI flours (mostly legume) flours (soya, chickpea, [split] pea, mesquite) or at least intermediate GI flours (rye, quinoa, buckwheat or brown rice).
Not all pastas have the same GI and neither have all types of rice. Pasta made from durum wheat is digested slower than past made from high GI flour. Rice that contains more amylose type of starch are usually more “loose” and low GI, whereas those that contain more amylopectin type of starch are usually more “sticky” and high GI. There are comprehensive lists freely available . Detailed information is very affordable and easy to come by. Subscribe on the Home page, then we can keep you up to date with new tools as they are developed.
Higher GI foodstuffs are very handy to keep your energy levels up during extended endurance exercise, after you have been at it for an hour or more in your session. It is also excellent to have immediately after exercise, when your insulin is still “switched off” for a while. This is due to the action of the enzyme, glycogen synthase that is active immediately after exercise to replenish the glycogen lost from your muscles during exercise. There is comprehensive information at hand for the sportsperson who strives for optimum sports performance by improving his/her nutrition (See Eat Smart for Sport by Liesbet Delport and Dr Paula Volscheck, Tafelberg, 2015).
Very often it is your blood glucose levels that determine how energetic, alert, and focused you feel. When it is too low (less than 4mmol/l) you will feel lethargic and struggle to focus. When it is too high (above 8mmol/l) you will still feel OK but there will be an energy crash waiting for you as what goes up must come down - meaning your blood glucose will spiral down in a couple of hours. Sustained energy comes from managing your blood glucose levels between a lower level of about 4.5 and upper level of about 7.5mmol/l. We coined this way of eating; “GI Smart”, as your blood glucose will be in this optimum range if you eat low GI when inactive and before exercise and keep higher GI products for during endurance exercise and after all exercise.
To have sustained energy levels it is important to eat at the right time. My apologies for stating the obvious but: the morning, before 9am, is a good time to have breakfast with lunch around 1pm, but not later than 2pm and dinner around 7pm. Regular balanced meals is the basis for healthy eating and sustained energy. Going without a meal for more than 5 hours during the day is not an option if you want to have energy and feel alert. And you need to supplement this with a light in between snack before 12pm and at about 5pm. It is all designed to keep your blood glucose level in the sustained energy zone.
For most of us a balanced lower GI breakfast, as can be found on the complimentary meal plan, is the ideal breakfast to keep your energy levels optimum for 3 to 4 hours. Here is a 3 minute video explaining the importance of having a low GI breakfast, and having low GI carbs in general. Early morning exercisers need extra vuma in the form of higher GI foods like bread/toast and jam, together with some low fat protein and a bit of good fat. After exercise blood glucose levels are usually depleted and a low GI meal will not do it for you. Serious exercise warrants an extra slice of bread or glass of fruit juice.
We encounter people weekly who think they will lose weight faster if they skip breakfast or lunch. They are trying to be good and brave by denying themselves a proper meal, but this leaves them with a lower than usual blood glucose level later in the day. Come late afternoon or early evening they feel starved, because their blood glucose is so low, and they have an uncontrollable appetite that leaves them consuming just about anything and everything the rest of the evening. Tomorrow morning they feel guilty and they don’t feel particularly hungry as the body is still working off the overload from the previous evening, and the whole cycle repeats itself.
The secret is to eat regularly and keep your blood glucose levels between the upper and lower limit. OK we don’t have a “dashboard” to give us a glucose reading all the time, but with a little experience you can feel when your blood glucose level is dropping. Then it is probably time for a balanced meal or a fruit, or other healthy snack, to give you blood sugar level a lift into the well feeling zone. The GI is a fantastic dietary tool to help you remain energetic all day.
Glycaemic Load (GL)
This concept fine-tunes the GI and was developed by scientists from Harvard University. It addresses the concern of rating carbohydrate foods as either “good” or “bad”, based only on their GI values. There is no such thing as a good or bad carbohydrate food; all foods can fit! It all depends on when you eat it, how much of it you eat, and what you combine it with. For example, although low GI, slowly digestible carbohydrate rich products are usually the preferred choice, a higher GI product, such as a sports drink is perfect during and after a marathon, as a low GI drink during endurance and/or after intense exercise could in fact result in hypoglycemia, seeing that the carbohydrate from low GI products is released into the blood stream too slowly at this stage.
The GL of a specific food portion is an expression of how big a glucose load the body has to deal with, to keep blood glucose levels within the normal range. It is calculated by taking the carbohydrate content in a specific portion of food and multiplying it by its GI value, but as the GI is an index, the value obtained should be divided by 100. (GL = carbohydrate content of a portion of food x GI/100.) It is thus a measure that incorporates both the quantity (amount) and quality (GI) of the dietary carbohydrates consumed. Some fruits and vegetables, for example, have higher GI values and might be perceived as “bad”. However, considering the amount of carbohydrate per portion, the GL is low. This means that their effect on blood glucose levels would be minimal.
Let us consider some examples: The GI of watermelon is high (GI = 72), but the GL of one serving or portion is small (GL= 7), because the amount of carbohydrate in a serving/portion of watermelon (150g or 1 cup watermelon cubes) is little (about 10g), as it contains a lot of water. However, this does not hold true for watermelon juice, as the amount of carbohydrate in a small glass of watermelon juice (250ml) is much more (about 30g), as fruit juice is a more concentrated source of carbohydrate. Should you, however, indulge in watermelon and eat 4 cups of it, it will have an even greater effect on blood glucose levels, as the GI is high and you will consume a lot of carbohydrate!
Considering an average apple, which is low GI, the GL of a medium apple is 7. This means that eating 1 apple will have little effect on blood glucose levels. However, if you eat a whole 500g packet of dried apples, its GL would be 50, which means that it will have a huge effect on your blood glucose levels, despite the fact that it is low GI and thus absorbed into the blood stream slowly, as it contains a lot of carbohydrate. The GL therefore shows us how important it is to control portion sizes!
The GI value of SA brown bread is high (GI over 70) and the GL of two slices is about 30, because the amount of carbohydrate therein is substantial. This means that a sandwich made with two slices of brown bread will have a marked effect on blood glucose levels. However, should you use a thin slice of brown bread as part of a mixed meal containing about ½ cup low GI baked beans, 1 – 2 slices ham and other salad vegetables, the GL of the meal will be lower and more acceptable (GL = 22). Note that the two slices of bread on their own have a higher GL than a whole meal, in which only one thin slice of bread is used in combination with other low GI foods. You can, however, also lower the GL of this meal from 30 to about 20, by eating 2 slices of lower GI bread, instead of brown bread.
From this we can see that it is quite acceptable to include small amounts of high GI foods in a meal, as long as the bulk of the meal contains lower GI carbohydrate foods (vegetables, fruit, low GI starches and/or dairy).
There is new evidence associating high GL meals with increased risk for heart disease, diabetes and cancer, especially in overweight and insulin resistant individuals. We therefore have the following GL recommendation for meals and snacks:
• Keep the GL per serving of breakfasts and light meals below 20, as far as possible, but definitely below 25.
• Keep the GL per serving of main meals below 25, as far as possible, but definitely below 30.
• Keep the GL per serving of a typical snack below 10, as far as possible, but definitely below 15.
• Keep your total daily GL below 100.
The above minimum recommendations are mostly applicable to the average sized woman, 165cm in height, who is overweight. The maximum recommendations above apply to the average sized woman of normal weight, who is moderately active, as well as to overweight men. Active and taller women, as well as the average sized man (about 170cm in height) of normal weight and who is moderately active, should aim at keeping total daily GL below 120. Sportsmen and women who do 2 or more hours of sport per day should aim for a total daily GL of > 120.
It is important to remember that you need not necessarily be adding up GL values all the time, unless you like arithmetic. It is more important to focus on lower GI lower (mainly beneficial) fat choices and to control portion sizes; then the GL will take care of itself.
Aller, EEJG, Abete, I, Astrup, A, Martinez, JA and van Baak, MA (2011): Starches, Sugars and Obesity. Nutrients 3: 341 – 369.
Augustin LS, Dal Maso L, La Vecchia C, Parpinel M, Negri E, Vaccarella S, et al (2001): Dietary glycemic index and glycemic load and breast cancer risk: as case-control study. Ann. of Onc. 12, 1533–1538.
Augustin LS, Kendall CW, Jenkins DJ, Willett WC, Astrup A, Barclay AW, Björck I, Brand-Miller JC, Brighenti F, Buyken AE and Ceriello A (2015): Glycemic Index (GI), Glycemic Load (GL) and Glycemic Response (GR): an International Scientific Consensus Summit. Nutrition, Metabolism and Cardiovascular Diseases.
Brand Miller J, Hayne S, Petocz P and Colagiuri S (2003): Low Glycemic Index diets in the management of diabetes. Diab Care 26(8): 2261 - 2267.
Buettner D 2008): The Blue Zones: lessons for living longer from the people who’ve lived the longest. The National Geographic Society.
Crapo PA, Reaven MD, Olefsky J. (1977): Postprandial plasma-glucose and -insulin responses to different complex carbohydrates. Diab, 26(12):1178- 83.
Higgins, JA (2011): Whole grains, legumes and the subsequent meal effect: implications for blood glucose control and the role of fermentation. Jnl Nutri and Met, 2012: 1 – 7.
ILSI Europe Concise monograph series (2011): Food, glycemic response and health.
Jacobsen MU and Dethlefsen C, et al. (2010): Intake of carbohydrates compared with intake of saturated fatty acids and risk of myocardial infarction: importance of the glycemic index. Am J Clin Nutr, 91:1764 - 8.
Jenkins DJA, Wolever TMS, Taylor RH, Barker H, Fielden H, Baldwin JM, et al. (1981): Glycemic index of foods: a physiological basis for carbohydrate exchange. Am J Clin Nutr, 34:362-6.
Jonalagadda SS, Harnack L, Liu RH, McKeown N, Seal C, Liu S and Fahey GC (2011): Putting the whole grain puzzle together: Health Benefits Associated with whole grains – Summary of American Society of Nutrition 2010 Satellite Symposium. Journal of Nutrition, 141: 1011S – 1022S.
Kaushik M, Mozaffarian D and Spiegelmann et al (2009): Long-chain omega-3 fatty acids, fish intake and the risk of type 2 diabetes mellitus. Am J Clin Nutr, 90:613 - 20.
Liu S, Willett WC, Stampfer MJ, Hu FB, Franz M, et al (2000): A prospective study of dietary glycemic load, carbohydrate intake and risk of coronary heart diease in US women. Am J Clin Nutr, 71(6), 1455-1461.
Maughan RJ and Burke LM (2011): Practical nutritional recommendations for the athlete.
Nestlé Nutrition Institute Workshop Series, 69:131–149.
McMillan-Price and J Petoca P, et al (2006): Comparison of 4 Diets of varying Glycemic Load on weight loss and cardiovascular risk reduction in overweight & obese young adults. Arch Intern Med, 166:1466 - 1475.
Mondazzi L and Arcelli E (2009): Glycemic index in sport nutrition. Journal of the American College of Nutrition, 28(4):455S–463S.
Opperman AM, Venter CS, Oosthuizen W, Thompson RL and Vorster HH (2004): Meta-analysis of the health effects of using the Glycemic Index in meal planning. B Jnl Nutr, 367 - 381.
Pawlak DB, Kushner JA and Ludwig DS (2004): Effects of dietary glycaemic index on adiposity, glucose homeostasis and plasma lipids in animals. Lancet, 364:778-85.
Rossouw JE. The diet-heart hypothesis, obesity and diabetes. S Afr J Clin Nutr. 2015;28(1):38-43.
Salmeron J, Ascherio A, Rimm EB, Colditz GA, Spiegelman D, Jenkins DJ, et al (1997a): Dietary fibre, glycemic load and risk of non-insulin-dependent diabetes mellitus in men. Diab Care, 20(4), 545-550. & Salmeron J, Manson JE, Stampfer MJ, Colditz GA, Wing AL & Willett WC (1997b): Dietary fibre, glycemic load and risk of non-insulin-dependent diabetes mellitus in women. J Am Med Ass, 277(6), 472-477.
Thomas EE, Brotherhood JR, Brand JC (1991): Carbohydrate feeding before exercise: Effect of glycemic index. International Journal of Sports Medicine, 12(2):180–6.