Jim Mann on carbohydrate quality

“The problem is that many dietitians around the world are telling people to have wholegrain bread when most wholegrain bread is roughly comparable to eating a bag of glucose.”

Last month Professor Jim Mann** addressed the annual conference of the European Association for the Study of Diabetes (EASD) in Barcelona on the controversial topic of carbohydrate quality. Although he was mainly talking about carbohydrates in the diets of people with diabetes, what’s good for this group is good for most of us.


Given the current hysteria about sugar it was interesting that Professor Mann had little to say about it. He indicated that the current EASD recommendation for the general population i.e. that total free sugars be limited to 10% of energy, was appropriate and was likely to be retained when new EASD guidelines are released. He had a lot more to say about starch.

Image: source

Pity those seeking advice

Professor Mann highlighted some of the contradictory advice about starchy foods currently being offered to people with diabetes. In the United Kingdom, NHS Dietitians and Diabetes UK recommend eating plenty of starchy carbohydrate foods while the American Diabetes Association recommends the exact opposite – eating less.

Professor Mann suggested that the differing advice was the result of misinterpretations of current recommendations. Although these recommendations allow for a wide range of carbohydrate intakes (45-60% of energy) he stressed that when carbohydrate intake is at the upper end of this range it is particularly important to emphasise foods rich in dietary fibre and low in glycaemic index (GI). He cited a recent meta-analysis highlighting the benefits of fibre but also noted that many of the studies showing benefits of higher carbohydrate intakes employed legumes.

But typically most people in western countries don’t eat a lot of legumes and some frequently recommended ‘healthy’ alternatives don’t shape up as well.

Wholegrain bread: hero or villain?

Surprisingly, Professor Mann expressed concern about wholemeal bread and dietitians’ near-universal endorsement of it:

“The problem is that many dietitians around the world are telling people to have wholegrain bread when most wholegrain bread is roughly comparable to eating a bag of glucose.”

This was a reference to the high glycaemic response most people experience when they eat many wholemeal breads. Professor Mann argued that rather than actually containing whole grains, which he supported, many so-called wholegrain foods had had the structure of the grains disrupted.

He quoted “one of the most important papers that has ever been published in terms of the nature of carbohydrate” by Jarvi and colleagues. In this study the effects of two diets composed of the same foods and with identical macronutrient composition and fibre were compared, the only difference being that in one diet the structure of the starch had been disrupted, increasing the GI. Glycaemic control and blood lipids were significantly better on the diet with intact starch. Professor Mann encouraged the use of ‘genuine’ wholegrains rather than many of the products that currently pass for wholegrains.

Although he considered GI to be important, Professor Mann admitted to being a bit ‘nervous’ about it and suggested that it needed to be used ‘intelligently’. He argued that other nutritional attributes of foods had to be considered in combination with GI.

This is a common criticism of GI but it can be addressed by considering a food’s nutrient density and GI together, as Manny Noakes and I did in our carbohydrate quality model.

White rice: pure, white and deadly?

Professor Mann also took aim at white rice, citing a recent meta-analysis by Hu and colleagues showing that higher white rice consumption is associated with a significantly increased risk of type 2 diabetes, especially in Asian populations. He said it had been known for three decades that high carbohydrate, high refined starch diets were associated with a deterioration of glycaemic control.

So what was Diabetes UK thinking when they advised people with diabetes to eat plenty of starchy foods?

Image: source

Summing up

Professor Mann came to the following conclusions:

• A wide range of carbohydrate intakes is still acceptable, between 40-60% energy
• Legumes, pulses, fruits and ‘genuine’ wholegrains were optimal choices among carbohydrate-rich foods
• Dietary fibre was a good indicator of a healthy choice
• Rapidly digested starchy vegetables (such as potato), white rice and many breads should be limited, even some breads labelled wholegrain.


The thing I found interesting about Professor Mann’s talk was that he effectively put sugar and refined starch in the same category – both should be limited. This is an inescapable conclusion, yet the old starch-good, sugar-bad paradigm persists among many dietitians.

If sugar and refined starch are in the same category, it follows that the sugar content of a starchy food is a very poor way of assessing its nutritional quality. Other criteria (that have some relevance to health) are required to discriminate between such foods but none of them is perfect. It’s about shades of grey, rather than black or white. Carbohydrate quality is a complex, multi-faceted concept and efforts to simplify it inevitably give rise to misleading dietary advice.

A second thing that struck me is how little of the carbohydrate in the diets of many people is of high quality i.e. legumes, pulses, fruits and ‘genuine’ wholegrains. There are plenty more carbohydrate-rich foods that have at least some positive qualities, such as high fibre, low GI or nutrient-rich.

But there are lots more that have little going for them, including white rice which still features in many healthy eating guides. A traditional food isn’t necessarily a healthy food. Less of these foods would be better (Kodama and colleagues). Not surprisingly, in Professor Mann’s recommendations the lower boundary of the recommended carbohydrate range has edged down to 40% of energy.

Have a listen to Professor Mann’s presentation.

** Jim Mann is a Professor in Human Nutrition and Medicine from New Zealand and has a major interest in the role of nutrition in diabetes and cardiovascular disease. He is one of the leading nutritionists in the southern hemisphere and has worked on several European advisory groups including the EASD and the World Health Organisation.



9 thoughts on “Jim Mann on carbohydrate quality

  1. I have to agree, my biggest gripe is when patients are encouarged to consume an excessive amount of CHO typically after seeing local Gp’s or diabetes educators. Trying to influence a better perspective to eating less CHO for better BSL control is sometimes difficult after they have been advised other wise. I Also agree regarding the bread comments, some breads labeled “wholegrain” are almost as white as their white loaf neighbours and a huge difference to eating the real deal, or eating legumes (which is also a difficult food item to get clients eating!) . Keep up the great posts :)
    Gabrielle Maston
    Dietitian & Exercise physiologist

  2. Perhaps the existing authorities are working with/against the existing problematic diets, and this is why the advice would appear so bad compared to what is optimal.

    If someone’s regular breakfast is jam on toast, they’re getting 3 tablespoons worth of sugar and 4 peices of white bread and a tablespoon of butter.
    With advice of “eat wholegrain bread and avoid sugar”, you might convince them to have wholegrain toast with bananas (or nutella for some reason people think its healthy?) or a bowl of oats or something instead. Sub-optimal results, but you’re actually getting a step in the ‘right direction’?

    The same way that I have found “no carbs after 6pm” gets a positive result for weightloss, despite limited/no sound scientific basis, because people will just drop the habit of pastries or ice cream during TV time.

  3. Jim Mann and his research colleagues ( see http://www.otago.ac.nz/diabetes/research) have researched the diabetic diet extensively with a number of intervention studies, including publications on sugar. see Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. Lisa Te Morenga, Simonette Mallard, Jim Mann. BMJ 2013; 346

    In regard to carbohydrate I think Jim Mann’s conclusions are the take home message.
    Professor Mann came to the following conclusions:
    • A wide range of carbohydrate intakes is still acceptable, between 40-60% energy
    • Legumes, pulses, fruits and ‘genuine’ wholegrains were optimal choices among carbohydrate-rich foods
    • Dietary fibre was a good indicator of a healthy choice
    • Rapidly digested starchy vegetables (such as potato), white rice and many breads should be limited, even some breads labelled wholegrain.

    It is not just about % energy from CHO but the types of CHO foods chosen. Those less processed, more intact CHO foods are better and education on how to eat them in the right amount in a mixed meal can further lower GI with good clinical outcomes beyond weight. Their intervention study LOADD (Lifestyle Over and Above Drugs in Diabetes) support the acceptable range for CHO intake and this should be individualized for each person. Unfortunately the carbohydrate information given sometimes is only the GI information, without understanding how to apply this information. Very often people think it is a allowed/not allowed list of foods and those with a low GI can be eaten ad libitum. That is why good dietary advice is important.

  4. Bill as a GP I very much welcome your blog. I think it is quite common knowledge that we are not winning with the obesity epidemic. There are so many factors at play that are outside of even diet specifically sedentary behaviours and ‘screen time’ with evidence linking screen time in children as an independent cardiovascular risk factor. http://adc.bmj.com/content/97/11/935.extract?sid=ad65e98b-5c4a-4077-a6f8-d1706b381b4b

    What frustrates me as a doctor is people trying to find a ‘quick fix’ for their diet and vilify either carbohydrates or fats. As we health professionals know, low quality carbs (I.e refined rices/pastas/sugars) and low quality fats (trans/sats) are worse than their counterparts and there is benefit it ‘switching’ those aspects.

    Portion control is probably a major contributor. People seem to have warped concepts of what ‘one serve’ of carbohydrate is. Actually surprisingly small and often patients are shocked when I describe ‘servings sizes’

    However we seem to not be able to escape marketing. The florid marketing of fish oils in tablet form once omega 3/6′s were being studied is a prime example even though since then taking fish oil supplements has not shown to change CVD risk.
    Subsequently I am now seeing many more whole grain products on our shelves (welcomed).

    Something which is mostly ignored in he recent catalyst/fat vs sugar debates is the role of whole vegetables and fruits.
    The australian dietary guidelines (which also advocate true whole grains) suggest 5 serves of vegetables and 2 serves of fruit a day. The current Australian population eats 2-3 serves of vegetables a day.

    More and more we see ‘vitamins/mineral supplements’ when data suggests that these on their own can be harmful – that it is the whole composition of a food that seems to be more important.

    Try to increase the quantity and quality and range of vegetables in the diet and subsequently the proportion of food that comes from carbs/fats is diminished.

    We haven’t taught our population to cook and we haven’t taught our population to be active enough. We are bringing up our children in an environment of instant gratification which includes quick fixes for diet/food.

    Healthy eating and a healthy lifestyle takes effort. The first intervention for ANYONE presenting to me with a risk factor for heart disease is diet and exercise. People only here what they want to here. People prefer a quick fix pill than to change their diet and lifestyle.

    Link to pictorial of Aus diet guidelines: https://www.eatforhealth.gov.au/sites/default/files/files/the_guidelines/N55_A4_DG_AGTHE_HiRes.pdf

    • Thanks Ashlea. The principles of healthy eating are pretty simple – eat a variety of food groups; make healthy choices within those food groups; don’t eat too much. But people are seldom presented with this simple message for all the reasons that you mention. It makes our job a difficult one but if we don’t do it, who will? So we persevere! Regards, Bill

  5. Hi Bill,

    Could we get a definition of what a proper wholegrain product is? Are we talking food that literally has a WHOLE GRAIN visible in it?

    And could you also explain where fruit falls into this picture of diabetes and sugar vs starch?

    Thank you! Absolutely love reading your blog :)

    • Hi Katie. I think you have highlighted the problem. Some definitions of wholegrains include foods in which the starch has been disrupted, which is not the sort of wholegrains Prof Mann encourages.
      My approach to fruit may be different to other nutritionists. To me, most fruit has low GI (tick), contains fibre (tick), and other nutrients (tick). But whether a fruit is rich in sugar or starch is immaterial to me. How does a fruit’s sugar/starch make-up affect its nutrition/health effects? Regards, Bill

  6. This is a good discussion of Jim Mann’s presentation. I’m reminded of dietary advice for type 2 diabetes from the days before insulin, which was basically to take out all starchy food and replace it with fibrous vegetables, leaving protein and (usually) fat intakes as they were.
    If you have time, Bertha M. Wood’s “Foods of the Foreign-born in Relation to Health” from 1922 (link below) has fascinating instructions about how to adapt the diets of US immigrant communities so that they’re suitable for diabetics. A bit soft on sugar for some reason, but maybe there wasn’t much around.

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