High glycaemic load diets associated with insulin resistance

When carbohydrate is eaten, blood sugar (glucose) levels usually rise. The speed and extent to which blood sugar releases into the bloodstream has important implications for health. For example, the greater the level of blood sugar disruption, the more insulin will tend to be secreted by a functioning pancreas in response. High levels of this hormone predispose towards weight gain, as well as ‘insulin resistance’ ” a state where the body becomes somewhat ‘numb’ to the effects of insulin. In time, this may cause blood sugar levels to rise, which potentially can lead to the development of type 2 diabetes.

The speed and extent to which a food releases glucose into the bloodstream can be measured and expressed as its ‘glycaemic index’. The higher the glycaemic index, the more disruptive a food tends to be, and (all other things being equal), the worse it is for us. The thing is, though, other factors influence the effect a food will have on health, and one of the most important here is how much we eat of that food. For instance, it stands to reason that eating a lot of a high-GI food is doing to be generally more detrimental to the body than eating only a small amount of it.

This concept has spawned the development of another measure of the effect of food in the body known as the ‘glycaemic load’. The glycaemic load of a food is calculated by multiplying its GI by the amount of carbohydrate contained in a standard portion of food. This figure is then divided by 100. Basically, a food’s glycaemic load (GL) is thought to give a more realistic guide to the impact of that food on blood sugar and insulin balance.

High GL diets would be expected to lead to generally higher levels of insulin, which by rights should increase the risk of insulin resistance too. This idea got some support this week in the form of an article published on-line in the European Journal of Clinical Nutrition [1]. In this study, the relationship between dietary GL and risk of insulin resistance in women aged 42-81. Analysis revealed that women with insulin resistance ate diets of higher GL compared to women free of insulin resistance.

Also, a 15 unit increase in GL dietary value was associated with a more than doubling in risk of insulin resistance.

The authors of this study state that their results support the concept that diets with a higher GL are associated with an increased risk of insulin resistance adding Further studies are required to determine whether reducing the glycaemic intake, either by consuming lower GI foods or through smaller serves of carbohydrate, can contribute to a reduction in development of insulin resistance and long-term risk of type II diabetes.

I find it refreshing to see researchers suggest that limiting carbohydrate in the diet might be a worthy strategy for protection against insulin resistance and type 2 diabetes. All too often, the recommendation here is to eat a diet low in fat, mainly on the basis that ‘fat is fattening’, and excess weight increases the risk of insulin resistance and type 2 diabetes. I do think it’s worth bearing in mind that:

1. insulin resistance and type 2 diabetes are conditions principally of the handling of carbohydrate in the body (not fat)

2. low-carb diets generally out-perform low-fat ones regarding measures of blood sugar control and weight

Generally low GL foods to emphasise in the diet include meat, fish, eggs, nuts and green leafy vegetables.

References:

1. O’Sullivan TA, et al. Glycaemic load is associated with insulin resistance in older Australian women. EJCN 16th September 2009 [epub before print publication]

10 Responses to High glycaemic load diets associated with insulin resistance

  1. Steve Cooksey 22 September 2009 at 5:03 pm #

    Sincere thanks for your posts.

    I recently found your site from a link at Mark’s Daily Apple.

    You are helping to change lives!!!

    Steve

  2. Stephan 23 September 2009 at 12:06 am #

    The primary sources of high-glycemic carbohydrate in most Western nations are white flour and sugar. I think those are the problem, rather than carbohydrate itself. There are numerous heavily carb-based cultures in the world that remain quite insulin sensitive. But they all avoid flour and sugar.

  3. Helena Wojtczak 23 September 2009 at 8:45 am #

    I’m quite cross today because the UK government have created a healthy eating website to tackle the terrible epidemic of obesity we are experiencing in the UK.

    I’m annoyed that on the page about eatings fats, it begins:

    “We all know that fat is bad for us”.

    And that is as far as it goes on that!

    What kind of statement is that for the government to make? No facts, no explanation, just this “everybody knows” nonsense!

    Secondly, they advise getting more fruit and veg by adding pineapple and sweetcorn to pizza. As if eating pizza isn’t carby enough, they want to add another grain AND some sugary fruit to it.

    Furthermore, the site informs people that dried fruits, canned fruit (which is often in syrup) and fruit juices, are among the “Five-a-Day” requirement that is being currently being rammed down our throats from every direction (newspapers, blogs, magazines, doctors, nutritionists, dieticians, nurses, social workers, greengrocers, and every man and woman in the street).

    It has taken just a couple of years for people to parrot this phrase as though it is the Eleventh Commandment.

    Apparently you MUST eat five portions of fruit and veg every single day, or a terrible death will befall you. It is also supposed to guard against obesity, like some kind of talisman or rabbit’s foot, I suppose.

    Well, I guess eating five portions of broccoli and the like won’t do much harm, but corn, fruit juice, canned peaches and dried raisins? They’ll be saying that Pepsi and chocolate are two of “Our Five-a-Day” next, being as they originate from things that grow in the ground.

    The most tragic part of the Five-a-Day Religion is that it is going to lead, inevitably, to more children getting more obese. This is because as we all know, it is difficult to force children to eat green veggies. Busy parents will find that the easiest way to make sure their kids get their “Five-a-Day” is to give them cartons of fruit juice, packets of (probably chocolate) raisins and lots of grapes.

    On the British government’s health service website, one mother said she now sprinkles raisins on her children’s breakfast cereal to make sure they get one of their Five-a-Day! This is utter madness — she’s merely increasing their sugar consumption! A father gives his children banana pancakes for breakfast. White flour AND a heavy sugary load! I see sugar-addiction, tooth decay, obesity and diabetes in these children’s futures, yet the whole point of the darned campaign is to reverse the massive increase in diabetic and obese children!

    The editorial even states:

    “For extra sweetness, chop fruit onto your cereal or stir it into desserts”. Why should we be giving children EXTRA sweetness? This will make them develop a sweet tooth and expect breakfast and every meal to taste sweet.

    A survey recently done on the street in England showed that over 50% of people believed that potatoes and pasta were “vegetables” that could be included in Five-a-Day.

    I just checked the National Health Service website and it says that potatoes DO count as one of the Five a Day. How stupid. They are tubers. Oh, and parsnips are allowed event though they are one of the highest glycaemic foods there is, higher than even potatoes. Oh, and apparently tinned baked beans also count.

    http://www.5aday.nhs.uk/topTips/default.html

    This campaign started in California in 1991 when local politicians got together with local fruit and vegetable farmers to promote their products. It was a public/private partnership. Thus vegetable and fruit industry funded and directed the govt campaign.

    The Program aimed to increase the average consumption of vegetables and fruit in the United States to 5 or more servings every day, with the excuse of reducing the incidence of cancer and other chronic diseases.

    What proof is there that feeding children white flour pancakes with bananas, corn and dried raisins, and piling pineapple onto their pizzas to make them more sugary and sweet reduces ANY disease?

    Here were their reasons for five:

    “5 servings allowed for a daily mix of items high in [vitamins] … and therefore seemed likely to include choices associated with reduced cancer risk…”

    “Likely to include”.

    And why five? Because:

    “the number 5 was memorable”

    What a good reason! Just pick a number out of the hat. That’s good science – not!

    Another problem, “eat more fruit and veg”? Well certainly include fresh veg in your diet, but we must stop pressurising people to include more and more.

    The “Five a day” figure is a catchphrase, not set in stone as so many reporters and lobbyists seem to think: Professor Sir Charles George, medical director of the British Heart Foundation, was asked why, in view of this study, he advised people to eat 5 portions of fruit and veg a day. He stated that:

    “There is some argument about how much you need. I think five may be an arbitrary figure.”

    A Greek study showed two portions of fruit and veg a week were enough, so that is what the Greek government pushes people to eat.

  4. Ted Hutchinson 25 September 2009 at 12:09 pm #

    Just in case anyone new to this idea hasn’t yet read Taubes Good Calories Bad Calorie or as it is called in the UK The Diet Delusionhere is a link to Taubes Dartmouth lecture where he summarizes his book in about an hour.

    Why we gain weight: Adiposity 101 and the Alternative Hypothesis of Obesity
    I think the slides from number 44 (particularly slide 47) are the crux of the matter, using the Thumbs/slides tabs you can move through the talk to repeat those sections you may not grasp. (He’s a fast talker)

  5. Kristine 25 September 2009 at 2:21 pm #

    When I was a kid in New Zealand, we ate fruit off the trees at the end of summer, that was it, apart from a few apples from the cold store if we felt like it. We were all thin as rakes and very fit. This garbage of 5 a day involves importing fruit from other countries, not very planet friendly eh.

  6. Carol 26 September 2009 at 2:00 am #

    The recommendation to eat five portions of fruit and vegetables a day may have originated in a marketing campaign by fruit growers, but you are seriously misled if you think that is has no health benefit. The evidence on stroke, cancer, heart disease and a host of other chronic conditions is that a higher consumption of vegetables and fruit is associated with lower incidence of these typically Western diseases. The problem arises in the interpretation, hence the stupidity of advocating dried fruit or baked beans as meeting the requirement.
    But there is a more sinister side to the recommendations that the 5aday campaign is part of – that is the well-funded lobby by the producers of carb-rich processed cereals, baked goods and other processed foods. The British Nutrition Foundation, which feeds information to the Food Standards Agency, is funded by a whole list of food processing companies including Kellogs, British Sugar and Nestle. All those with a very large interest in promoting carbohydrate rich diets. If you want the whole list it appears in their Annual Report.
    http://www.nutrition.org.uk/upload/BNF%20Annual%20Report%2008_final.pdf.
    If you read the FSA recommendation on carbs it says it all – “eat plenty of carbohydrates, choosing wholegrain when you can”. This is clearly based on lobbying and not sound nutritional science. The British Dietetic Association have swallowed the same line and reiterate it ad nauseum.

    So don’t throw the veg and fruit out on the basis of risk of a high glycaemic load diet, choose your vegetables and fruit prudently, ie low GL. Other wise you really are jeopardising your long term health

    Qualified biochemist and nutritional therapist.

  7. Hilda Glickman 26 September 2009 at 11:05 pm #

    The point about eating fruit and vegetables is to do with their antioxidant capacity. Antioxidants protect us from just about every disease including cancer, heart disease, macular degeneration,etc. However some of the best are low GI such as blueberries, strawberries and other berries, oranges, , carrots, garlic, onions, broccoli etc. Potatoes are low in antioxs as are bananas. Adding raisins to processed cereals is silly. Why not just eat the fruit? It is the colour pigments in these foods that have the antioxidant capacities. Hilda Glickman BSc MA BPhil DipION Nutritionist

  8. Trinkwasser 29 September 2009 at 8:40 pm #

    The New Zealanders had a better slogan “Five COLOURS a Day” for that very reason.

    The horrible irony is that eating fat is often quoted as the “cause” for increased insulin resistance. Yet when you eat all those Healthy Whole Grains the excess carbs are converted into palmitic acid, which is one of those terribly dangerous saturated fats, which is implicated in causing insulin resistance!

    Stephan has a good take on this

    http://wholehealthsource.blogspot.com/2009/09/palmitic-acid-and-insulin-resistance.html

    which may explain the mechanism whereby the GL and carb consumption are actually responsible for the IR

  9. Hilda Glickman 30 September 2009 at 1:55 am #

    This is a hunch but I am of the opinion that the cell membrane which is mainly fat plays a part in insulin resistence as well as thyroid resistence. Eating processed fats goes into this membrane and prevents it from having proper docking sites for hormones which work on a lock and key basis. Hilda Glickman Nutritionist.

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