Glycaemic Surprises

June 19th, 2017 | Posted in Uncategorized

Whilst we like to believe that food has a consistent and measurable effect on us it is becoming increasingly apparent that this is not the case. Often, the actual effects of foods on measurable health parametres are different from what would be expected based on the macronutrient content of the foods. For example, although almonds are high in calories they do not lead to weight gain due to the inefficiency in the absorption of energy from almonds and the fat content not being 100% bioavailable (1).
Usually the carbohydrate content determines the effect of food on blood sugar but it may not be as simple as was once thought. Let’s take a look at some surprising findings about the glycaemic effects of foods.

Glycaemic Index Variability

The Glycaemic Index (GI) and Glycaemic Load (GL) of foods aim to indicate their effects on blood sugar after ingestion. However, research has found that the GI can vary by 20% within an individual and 25% between individuals. This means that not only do people have different metabolic responses to food but the same food can trigger a different response in the same individual at different times. A food that triggers a low glycaemic response in you at one time could trigger a high glycaemic response at another time.

For example, research into the glycaemic response to white bread found that even within the same individual the glycaemic value could differ by more than 60 points between tests. The researchers took into account gender, BMI, blood pressure, physical activity levels and other characteristics. Most factors only had a minor effect on GI variability.

This means that the Glycaemic Index has limited use as an indicator of an effect of food on blood sugar levels, even under highly standardised conditions. In real life, because foods are not eaten in isolation, the variability is likely to be even greater. It seems that using the glycaemic index or glycaemic load as indicators of the effect of food on health needs to be reconsidered (2).

Blood Sugar Support

So if the Glycaemic Index and Glycaemic Load of foods are unreliable indicators of their effect on blood sugar what can we do to support blood sugar control? Here are some ideas:

  • Vinegar – add a vinegar based dressing to your foods. Vinegar is anti-glycaemic and has a beneficial effect on blood sugar levels. Vinegar is found to lower blood sugar levels by preventing the complete digestion of carbohydrates, possibly by inactivating some of the enzymes that break down carbohydrates into sugar (3). Vinegar may also improve insulin sensitivity, enhance blood flow to the peripheries and increase satiety, thus reducing overall food intake (4).
  • Protein – have some protein with your carbs. This slows down the release of glucose from carbohydrates (5)
  • Oil – adding olive oil or coconut oil to carbohydrate rich foods reduces the glycaemic response. (5,6,7). The omega 3 essential fats are also beneficial for aiding blood sugar stability.
  • Fibre – fibre slows down the release of glucose from carbohydrates which is why complex carbs tend to be better than simple carbs – they contain more indigestible fibre. Good sources of fibre include oats, barley, buckwheat, quinoa, millet, brown rice, vegetables and pulses.
  • Cool it – leaving starchy foods such as rice, pasta or potatoes to cool down after cooking increases their resistant starch levels. This means they have a reduced glycaemic response (8)
  • Up the Polyphenols – polyphenol rich foods inhibit glucose absorption and increase insulin sensitivity. Good sources of polyphenols include tea, cacao, cinnamon, grapes, pomegranates, red wine, berries and olive oil (9). 
  • Spice it up – cinnamon, fenugreek, rosemary, turmeric, nigella (black seed) and ginger can all help with blood sugar control and metabolic function.
  • Avoid Artificial Sweeteners – for more info as to why these are worth avoiding see the previous blog post at:
  • Exercise – exercise improves insulin sensitivity and blood sugar control. Even a few minutes of exercise before a meal can improve glycaemic control in people with insulin resistance (10).
  • Get Outside – vitamin D helps with blood sugar control and the insulin response. It is formed by the action of sunlight on the skin. In the winter it may be advisable to take vitamin D supplements. For more info about the benefits of vitamin D see the previous blog post at:
  • Breathe – breathing exercises designed for relaxation before and after meals improve the glycaemic response of healthy people (11).
  • Nutrients to support blood sugar control include chromium, magnesium, manganese, zinc, vitamin C, vitamin D and B vitamins. There are many combination supplements designed to aid blood sugar control.
  • The herbs gymnema sylvestre, rhodiola and ginseng may all help to support blood sugar control.



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  2. 2. Matthan NR, Ausman LM, Meng H et al.  Estimating the reliability of glycemic index values and potential sources of methodological and biological variability. Am J Clin Nutr, 2016
  3. 3. Budak NH, Aykin E, Seydim AC et al. Functional properties of vinegar. J Food Sci. 2014 May;79(5):R757-64
  4. 4. Lim J, Henry CJ, Haldar S. Vinegar as a functional ingredient to improve postprandial glycemic control-human intervention findings and molecular mechanisms. Mol Nutr Food Res. 2016 Aug;60(8):1837-49.
  5. 5. Hatonen KA, Virtamo J, Eriksson JG. Protein and fat modify the glycaemic and insulinaemic responses to a mashed potato-based meal. Br J Nutr. 2011 Jul;106(2):248-53.
  6. 6. Gatti E, Noe D, Pazzucconi F.  Differential effect of unsaturated oils and butter on blood glucose and insulin response to carbohydrate in normal volunteers. Eur J Clin Nutr. 1992 Mar;46(3):161-6.
  7. 7. Lau E, Zhou W, Henry CJ. Effect of fat type in baked bread on amylose-lipid complex formation and glycaemic response. Br J Nutr. 2016 Jun;115(12):2122-9. 
  8. 8. Sonia S, Witjaksono F, Ridwan R. Effect of cooling of cooked white rice on resistant starch content and glycemic response. Asia Pac J Clin Nutr. 2015;24(4):620-5.
  9. 9. Kim Y, Keogh JB, Clifton PM. Polyphenols and Glycemic Control. Nutrients. 2016 Jan 5;8(1). pii: E17.
  10. 10. Francois ME, Baldi JC, Manning PJ et al. ‘Exercise snacks’ before meals: a novel strategy to improve glycaemic control in individuals with insulin resistance. Diabetologia. 2014 Jul;57(7):1437-45.
  11. 11. Wilson T, Baker SE, Freeman MR et al. Relaxation breathing improves human glycemic response. J Altern Comp. Med. 2013 Jul;19(7):633-6.