Low GI diet outperforms high fibre one in diabetics

Diabetes is condition characterised by higher-than-normal levels of sugar in the bloodstream. It’s a problem caused by either not enough insulin and/or insulin not doing its job. Either way, the result is generally raised levels of sugar. One effect of this is a greater tendency to combine with protein in tissues (called ‘glycation’) which can damage them and predispose to problems such as eye disease and blindness, nerve damage and kidney damage.

Because diabetes is essentially a condition where the body has difficulty moderating sugar levels in the body, it makes sense for diabetics to avoid eating much in the way of foods that tend to be disruptive for blood sugar levels. This thinking has led to at least some popularity for low glycaemic index (GI) diets among diabetics.

In a study published today, a low GI diet was tried in half a group of 210 type 2 diabetics over a 6-month period. Individuals had levels of HbA1c (also known as glycosylated haemoglobin) measuring at the start and finish of the study. HbA1c levels give a guide to the general level of blood sugar control over the preceding 3 months. Over the course of the study, HbA1c levels dropped significantly. HbA1c levels are measured as a percentage, where healthy percentages are generally less than 5 per cent. Diabetics tend to have higher levels. Overall, HbA1c levels dropped 0.5 per cent.

Another blood parameter monitored in this study was levels of high-density lipoprotein (HDL) cholesterol. This is the forming of cholesterol associated with a reduced risk of cardiovascular disease. On average, in individuals eating a low GI diet, HDL levels went up by a statistically significant amount: 1.7 mg/dL (0.04 mmol/L).

While half of the 210 people in this study were assigned to eat a low GI diet, the other half were assigned to eat a diet rich in cereal fibre. Testing such a diet makes good sense, because diabetics are often recommended to eat a diet rich in cereal (starch), with the some time proviso that should be wholegrain in form and therefore rich in fibre. The problem with this sort of diet, as I see it, is that with a diet rich in cereal fibre the diet may also be rich in cereal, and some cereal products are actually quite disruptive for blood sugar levels, particularly when eaten in quantity.

As it happens, individuals on the fibre-rich diet didn’t fair as well as those onf the low GI diet: HbA1c levels dropped by only 0.18 per cent, and HDL levels actually dropped by 0.2 mg/dL, though this was not statistically significant. What this study shows is that a low GI diet outperforms a diet rich in cereal fibre in type 2 diabetics. And it’s another example of why we need to be wary regarding the conventional dietary advice given to diabetics.


Jenkins DJA, et al. Effect of a Low”Glycemic Index or a High”Cereal Fiber Diet on Type 2 Diabetes: A Randomized Trial JAMA. 2008;300(23):2742-2753.

8 Responses to Low GI diet outperforms high fibre one in diabetics

  1. Chris 17 December 2008 at 11:16 pm #

    You’ll like this one too: http://tinyurl.com/ysesd7

  2. Anne 18 December 2008 at 10:52 pm #

    Hi Dr Briffa,

    For more about that study you might like to read Jenny Ruhl’s (author of ‘Bood sugar 101, what they don’t tell you about diabetes’) latest blog:

    “Despite the media spin, what this study actually did was attempt to answer a stupid question: Is a high carb diet/low fat made up predominantly of pasta, beans, carrots, pears, oranges and skim milk better for people with diabetes than a high carb/low fat diet made up of Wheetabix, potatoes, mangoes, skim milk and toast.

    The answer turns out to be “yes,” very slightly.”

    For the rest of it: ‘More Bad Science: The “Low Glycemic” Diet in the JAMA Study is the ADA Low Fat Diet’ http://diabetesupdate.blogspot.com/2008/12/more-bad-science-low-glycemic-diet-in.html


  3. Dr John Briffa 19 December 2008 at 12:01 pm #

    Agreed: the low GI diet in this study was quite a long way off what I would regard as a good diet for diabetics (or people in general). If someone is really serious about their glycaemic control then a diet much more restricted in carb would be better, I think.

  4. Neil Fiertel 19 December 2008 at 9:05 pm #

    As I take meds that require increased levels of Potassium in one’s diet, I have found that I naturally have replaced breads and general carb intake with one of more fruits and nuts. Because I live in a northern climate, it is a lot more likely that dried fruits as well as canned or jars of such products as well as juices are a daily part of one’s diet. I have found that to keep the sugar levels down in such a diet one must consider eating apricots for example over having a sweeter dried fruit for this Potassium gain or drinking the low salt type of V-8 vegetable cocktail type beverages which has a huge Potassium concentration and is low in carbs. In other words, reading the label, considering the downside to one’s eating as well as the advantages of this food over another can maintain both one’s need for certain nutrients as well as avoidance of large intakes of sugars even if naturally associated with a certain food group. People must really consider as I have done, finding a chart on line of various foods and food types and post in on the fridge. I can for example eat an avocado and get a huge Potassium intake, no carbs and a lovely portion of good oils all at one sitting. I would never have considered avocado in this light without this charting of foods. Given choices of good foods, it becomes a lot easier to eat proportionately lower carbs but at the same time really improve nutrition and along with the many choices of protein rich foods one can eat with pleasure and have good choices for health. I think that one needs to compromise however and for me, it is not avoiding meats that I like to eat. It is not about NOT eating certain things but rather eating them sometimes but not daily. Having a weakness for beef and pork and lamb I simply consider that some days I will not eat them or even for days and then, I have a nice steak…why not? It is all about moderation and not about eating like a chemist. For those that do not like fish ( not I ..for I love it) there are very handly omega fish oils in capsules and even better, in a sort of fudge form which easily replaces a chunk of fish each day with a couple of these supplements. Cutting down on pasta, cereals, breads and so forth was a no brainer for me and I lost a small amount of weight in so doing. As well, my appetite is better controlled without breads for certain. I suggest..go for the apricots, dried and then rehydrated in a microwave with a bit of water..tastes great that way and a near perfect low sugar fruit. In essence, the primitive diet seems to work for me with a few adjustments for my particular needs.

  5. Lee 21 December 2008 at 11:25 am #

    I have been reading about a raw food diet that acts as a reset for diabetes. Whilst I take all claims with a pinch of salt I would love to hear about anyone elses opinions about this matter. I tend to only carbs early on in the day and I try and eat a green smoothie packed with at least 6 portions of fruit and veg every day. That way any other veg I manage to eat through the day is an added bonus.
    I am a new diabetic type 2 so I am still trying to find my way. At the moment I am medication free but I suspect that I teeter on the edge of being medicated.
    I have also heard that even 1 cup f coffee a day can increase insulin resistance by up to 33%.
    I have also been told that as a dibetic I should only eat 1 piece of fruit aday and substitute the rest with veg, also that this fruit should be low GI.
    The chimp diet lots of green veg, fruit and smaller portions of meat and grains. I will give it a go as I would love to control my diabetes and not have it control me.

  6. helen 22 December 2008 at 2:40 am #

    hey Neil, why not just take a potassium supplement or use a salt substite that is potassium based then you don’t have to worry about the added sugar as dried fruit is extremely high in this not so great for diabetics food.

  7. Hilda Glickman 25 December 2008 at 1:20 am #

    I cannot see how dried fruit could be eaten by diabetics. It is concentrated sugar. Most vegetables are high in potassium but I expect that V8 has added sodium too so better to make your own vegetable juice.

  8. On anon. 28 April 2009 at 9:24 pm #

    “I cannot see how dried fruit could be eaten by diabetics. It is concentrated sugar.”

    Certain dried fruits, such as cranberries, have added sugar but, so far as I know, most dried fruits differ from fresh fruit only by virtue of being dehydrated. All fruits contain sugar which is what makes them appealing to our palette.
    Either fresh or dried the sugars are intrinsic to the fruit and are supplied and eaten with the fibre that is also intrinsic to the fruit. Ingested fibre slows the release of sugars from the gut and reduces GL. I cannot see why a diabetic cannot snack on a dried apricot or two at an appropriate time and as part of a satisfactorily diverse nutrient rich and low GL diet.
    I concede the drawback with dried fruits is the temptation to gorge.

    Dentists acknowledge that sugar and acidity in fresh orange juice is unhelpful where a whole orange is less so; because the sugar is intrinsic to the fruit.

    Orange juice from the chiller is trumpeted as counting to your ‘five a day’. What a nonsense. Sure, helpful vitamins and phyto-nutrients are present and available in th juice but the juiced orange contributes to higher GL – problems lie with high aggregate GL.
    Eating the whole orange for its’ nutrient value and drinking water to satisfy ones thirst contitutes a lower GL.

    Modern humans have become very picky over what constitutes palettable food; we have developed very sweet tooths and are unaccustomed to the bitter flavours that our evolutionary ancestors must have tolerated.

    Take the orange example further; most people are inclined to be very picky when peeling away the white pith because most find it too bitter for their palette. Likewise the zest (skin) is discarded.
    Many would regard it as odd to observe somebody eat a whole orange with pith and skin – how uncivilised! Yet the pith would provide considerable pectin (fibre) to counter the disastrous decline in consupmtion of soluble fibre to good effect, and the zest would provide limonene with acknowledged anti-oxidant and anti-cancer properties.

Leave a Reply