GI Profile

Prof Tom Wolever
Tom Wolever is a name you’ll see on many research papers involving the glycemic index. In fact his name is on the first paper ever published about slow-release carbs. GI News asked Prof. Wolever how he became involved in research in this area.


Tom Wolever

‘Research on the GI is very exciting – the more we explore, the more we discover. The health benefits are far-reaching: from diabetes risk reduction and management to long-term cardiovascular health. The power to improve health through informed nutritional choices is very rewarding.’

Before completing medical school, I was involved in the development of the concept of slow-release carbohydrate and the glycemic index with Dr David Jenkins and his research team, including his wife, Alexandra, playing a major role in the data analysis for the first paper on GI published in 1981. (Jenkins DJA, Wolever TMS, Taylor RH, Barker HM, Fielden H, Baldwin JM, Bowling AC, Newman HC, Jenkins AL, Goff DV. ‘Glycemic index of foods: a physiological basis for carbohydrate exchange.’ Am J Clin Nutr 1981;34:362-366)

Throughout my career I’ve had a special interest in diabetes. My research has been focused on the role of dietary carbohydrates in human nutrition and metabolism, with particular interests in insulin resistance and diabetes. It probably all started after grade 12, when I went to the UK as an exchange student, and to Oxford University to study medicine where I discovered that many of my friends helped to make ends meet by being ‘research subjects’. I joined them, at first doing breathing experiments, then donating blood for Dr David Jenkins.

I took a year off from medical studies to do an MSc on the effects of dietary fibre on blood glucose responses under the supervision of Dr Jenkins. As part of my research, I was involved in designing the first study that showed the ability of fiber to reduce blood glucose and insulin responses is related to its viscosity. We also conducted the first successful study using purified fiber supplements (guar) to treat diabetes mellitus. After completing medical school (and continuing to perform research in my spare time), I joined Dr. Jenkins at the University of Toronto to complete my PhD – on the glycemic index.

In 1995, my wife Judy and I founded an independent company to facilitate commercial food testing and research. Just to show how life goes in a full circle – Dr Alexandra Jenkins, along with Dr Vlad Vuksan, is now our partner in the expanded Glycemic Index Laboratories, and we continue to work closely with David Jenkins and his team at the University of Toronto. It is my continued pleasure to collaborate with the University of Sydney’s Jennie Brand-Miller both on research papers and in the advocacy and promotion of the benefits of GI.

I love the research with which I am involved. But just as we must all strive for balanced diet, I also think it’s important to have a balanced life. I enjoy spending time with my wife, Judy, and our three children. In fact, I have just returned from a two-week bike trip around Wales with my 15-year-old son. I also make time for involvement in church activities, fitness, and competing in my favourite sport, orienteering.

Tom Wolever is full Professor in the Department of Nutritional Sciences, Faculty of Medicine at the University of Toronto, a member of the medical staff at St. Michael’s Hospital in the Division of Endocrinology and Metabolism, President of Glycemic Index Laboratories, and is an active volunteer for the Canadian Diabetes Association.

Feedback—Your FAQs Answered

I have been low carbing (not excluding carbs all together, just switching to healthier ones) for over 3 years and have dropped my weight, cholesterol, triglycerides, blood pressure, etc. I appreciate that you don’t advocate a low carb diet – but where do you draw the line? How much carb is high, medium and low?

We believe that the type or source of the carbohydrate and fat are more important than the amount. In the end the choice of how much carbohydrate is up to the individual. A moderate carb diet would be around 40–50% of energy intake as carbs; and high over 50% of energy intake as carbs. Here’s what Prof Jennie Brand-Miller and her co-authors say in The Low GI Diet.

In 2002, the National Institute of Health (NIH) in the USA advised that a range of carbohydrate intakes could adequately meet the body’s needs while minimising the risk of disease. Specifically, they advised the following ranges:

CARBOHYDRATES:
45–65% OF ENERGY

FAT:
25–35% OF ENERGY

PROTEIN:
15–35% OF ENERGY

We like these figures because they allow for individual tailoring. The American Heart Association even ruled that as little as 40% of energy intake as carbs could be eaten and still be good for the heart. Chances are your diet already falls within these flexible ranges and, if so we encourage you to stick with what you have. If your preference is for more protein and more fat than you are currently eating, then go ahead—just be choosy about quality. We believe that you are the best judge of what you can live with for the rest of your life and, anyway, there is plenty of room for flexibility. We recommend you consume at least 130 grams of carbohydrate a day, even during active weight loss. Whatever the number, the type of carbohydrate is important. And that’s where the GI comes to the fore.’
– The Low GI Diet is published by Marlowe & Company in the US; Hachette Livre in Australia and New Zealand and Hodder Mobius in the UK.

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GI News—April 2006

In This Issue:

• Food for Thought
  —Potato Lovers Look Back to a Healthy Future
  
• GI News Briefs
  —Memorable Meals
  —Men are Different
  —A Heart-healthy Diet
  —Devaluing the Value of GI
  
• GI Values Updates
  —How do you know if it’s low, medium or high GI?
  
• Low GI Food of the Month
  —Wild About Blueberries
  
• Low GI Recipe of the Month
  —Lemon Semolina Pudding with Berry Coulis
  
• Success Stories
  —Jeanne: ‘I lost over 100 pounds using a combination of good eating habits and low GI foods.’
  —Anne’s Story: Battling hypoglycemia
  
• Books, DVDs, Websites: What’s New?
  —The Spanish language edition of The New Glucose Revolution
  —The Korean language edition of The New Glucose Revolution
  —Translate GI News and www.glycemicindex.com to another language
  
• Feedback—Your FAQs Answered
  —How relevant is the GI for athletes in terms of carbohydrate metabolism?
  —I have recently been diagnosed with celiac disease (gluten sensitivity) on top of diabetes. It's extremely hard to find both low GI and wheat-free foods. Any suggestions?
  —I am a type 1 diabetic and enjoy an occasional beer or dry wine. What’s the real deal on the GI of alcoholic beverages?
  

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Food for Thought

Potato Lovers Look Back to a Healthy Future
There’s a ‘modest positive association between the consumption of potatoes and the risk of type 2 diabetes in women’ write the authors in a prospective study reported in the February 2006 issue of the American Journal of Clinical Nutrition. ‘This association was more pronounced when potatoes were substituted for whole grains.’ The Harvard investigators conducted a prospective study of 84,555 women, aged 34 to 59 years with no history of chronic disease, who were enrolled in the Nurses' Health Study. The women completed a validated food frequency questionnaire and they were followed up for 20 years with repeated dietary assessments. During the study, 4,496 participants were diagnosed as having type 2 diabetes. After adjustment for age and dietary and non-dietary factors the researchers found that those with the highest potato intake (around one serving a day) had a modestly elevated risk of developing type 2 diabetes (about 20% higher). The link was strongest among obese women, who are already at increased risk of the disease, suggesting that heavy potato consumption may pose a particular problem for them, the researchers point out. ‘These data support a potential benefit from limiting the consumption of these foods in reducing the risk of type 2 diabetes,’ conclude the authors. ‘Substitution of these sources of carbohydrate with lower glycemic, high-fibre forms of carbohydrates such as whole grains should be encouraged.’



Cutting back on potatoes is something many people on a low GI diet find hard to do. So what’s the answer?
First of all, there’s no need to say ‘no’ to potatoes altogether just because they may have a high GI. They are fat free (when you don’t fry them), nutrient rich and filling. Not every food you eat has to have a low GI. So enjoy them but in moderation.

Secondly, look for the lower GI varieties of potato or serve them in a way that reduces the glycemic response. University of Toronto researchers found that the GI of potatoes ranged from 56 to 89 depending on variety and cooking method (Journal of the American Dietetic Association). Precooking and reheating potatoes or consuming cold cooked potatoes (such as potato salad) reduced the glycemic response. The highest GI values were found in potatoes that were freshly cooked and in instant mashed potatoes. Margareta Leeman and her colleagues at the University of Lund in Sweden found that preparing potatoes the day before and serving them cold as potato salad with a vinegary vinaigrette dressing can lower the GI (European Journal of Clinical Nutrition). In Low GI Eating Made Easy, dietitian Kaye Foster-Powell suggests steaming small new potatoes (with their skin for added nutrients), or bake a jacket potato and add a tasty topping based on low GI beans, chickpeas or corn kernels.

Third, remember that potatoes are a relative newcomer to the Western dinner plate. Athough the Spanish brought them back to Europe from South America in the mid-sixteenth century, people tended to regard them with suspicion and fit only for animals. They didn’t become a regular part of the European diet until the late eighteenth century. And it wasn’t until the nineteenth century that we really developed a taste for them replacing traditional wholegrain staples such as wheat, barley, rye and oats, which have much lower GI. So look back to a healthy future and add variety to your meals by enjoying wholegrains, legumes, pasta, noodles, basmati rice on a regular basis and potatoes occasionally. You’ll reduce the overall GI and GL of your diet and your risk of chronic disease.

GI News Briefs

Memorable Meals
In recent years, a number of studies have shown that older people with type 2 diabetes have significantly greater risk of performing poorly in cognitive function tests such as recalling word lists. University of Toronto researchers say that a low-GI meal generally results in better verbal memory in the post-meal period, particularly in those who experience the greatest food-induced elevations in blood glucose levels, compared with a high-GI meal.



They reported their findings of a study involving 21 older adults (10 males, 11 females) with type 2 diabetes in the March 2006 issue of Diabetologia. Both the GI of the carbohydrate meal and individual differences in response to the meal contributed to the variation in consequent memory recall, they write. The scientists had set up the study to determine whether minimising the increase in blood glucose by eating a low GI meal (50 g pasta) rather than a high GI meal (50 g bread) would affect cognitive performance in the post-meal period. They found that:

• Bread consumption, relative to pasta, resulted in both a higher area under the curve and worse delayed verbal memory (paragraph and word list recall) performance;
• Performance following bread consumption was poorer than that following pasta on measures of working memory, executive function and auditory selective attention;
• Sustained attention showed no sensitivity to type of carbohydrate food consumed.

– Diabetologia, March 2006 (email: carol.greenwood@utoronto.ca)

Men Are Different
Men with cardiovascular disease may be at considerably increased risk for death even when their blood sugar level remains in the ‘normal’ range, suggests a new study by a team of scientists at UCLA and Cedars-Sinai Medical Centre in Los Angeles published in the American Journal of Epidemiology. Using extensive data from the Framingham study collected between 1948 and 1978, the scientists statistically analysed the connection between glucose (blood sugar) levels and death in patients with cardiovascular disease. ‘While our results show that glucose is a strong independent predictor of mortality,’ writes lead author Dr Sidney Port, ‘they also unequivocally show that the mortality/glucose relations are quantitatively different for men and women. Indeed for men risk rises very rapidly through the normal range and is flat thereafter. For women, risk is unrelated to glucose in the normal range, then rises quickly through the impaired range and at a much slower rate thereafter.’ The findings suggest that: ‘although 5.55 mmol/liter (= 100 mg/liter, normal) may be a useful mortality risk division (albeit with different implications for men and women), 6.99 mmol/litre (= 126 mg/litre, diabetic) is not, especially for men.
– American Journal of Epidemiology, vol 163, No. 4

A Heart-healthy Diet
Foods based on soybeans have a beneficial role in our defence against heart disease.


photo: New England Journal of Medicine

There are three attributes of soybeans with the potential to reduce heart disease risk:

1. soy protein
2. anti-oxidant substances called isoflavones
3. low GI carbohydrate

In a new study published in Nutrition, lead author Dan Lukaczer reports that postmenopausal women on a low GI diet (incorporating 30 grams of soy protein and 4 grams of phytosterols a day) showed a ‘significantly greater improvement’ in CVD risk factors compared with women on the AHA Step 1 diet. Scientists from the Functional Medicine Research Center of Mutagenics Inc., the company that manufactures the fortified soy beverage used in the study, carried out the 12-week study. The average age of the women in the study was 55, and all were clinically obese and at higher risk of CVD. Both groups started with high levels of total cholesterol, low-density lipoprotein (bad) cholesterol and triacylglycerols. The scientists collected 3-day diet records from the women at weeks 2, 4, 8 and 12. At the end of the program the low GI group showed statistically significant decreases in total cholesterol, low-density lipoprotein cholesterol and triglycerols say the authors. In addition, high-density lipoprotein (good) cholesterol rose significantly in the low GI group group, but not the AHA Step 1 diet group.
– Nutrition (Vol 22, pp104–113)

Evaluating the value of GI …
‘The present results call into question the utility of GI and GL to reflect glycemic response to food adequately, when used in the context of usual diet’ write Elizabeth Mayer-Davis and her co-authors reporting their study in the British Journal of Nutrition. Using the glucose tolerance and insulin sensitivity data for 813 adults who participated in the Insulin Resistance Atherosclerosis Study, the researchers set out to evaluate the correlation of GI and GL with measures of glycaemia based on the responses the participants had given to that study’s food frequency questionnaire. They assigned mean GI values based on published data. Despite acknowledging the limitations of their study, their major finding was that ‘no statistically significant association was observed for GI in relation to fasting glucose, postprandial glucose, incremental postprandial glucose or A1c either at baseline [the start date] or at the follow-up examination.’
– British Journal of Nutrition (2006), 95, 397-405

GI Group: This study has attracted an amazing amount of headline-making media mileage and we have received a number of inquiries from GI News readers. Here is a brief summary of our key concerns with the design of this study and its findings.

1. The food frequency questionnaire used for Insulin Resistance Atherosclerosis Study has a poor correlation (just 0.37) with other measures of carbohydrate intake. What this simply means is that it doesn’t provide truly reliable data on how much carbohydrate the volunteers ate. Without accurate information on an individual’s carb intake it is unlikely they can confidently assess its GI or to calculate GL. Assessing food intake from food frequency questionnaires (FFQ) is subject to error and bias (it’s human nature for people to under-report some foods and overestimate others). This is why researchers always compare the estimates of nutrient intake from FFQs with an independent method such as a dietary record. A good study will have a correlation value above 0.5.
   
   
2. No FFQ has been validated as truly reflecting the GI of a diet. For example, one question reads: ‘How often do you eat dark bread (including whole wheat, rye, pumpernickel, other high-fiber bread)’. Obviously the GI values of these various breads can vary greatly, yet a single GI value was assigned to all responses to this question.
   
   
3. The cross-sectional, rather than prospective, nature of the Insulin Resistance Atherosclerosis Study. A better study would take either normal individuals or people with impaired glucose tolerance (IGT) and track changes in glucose metabolism over time and try to relate those changes to differences in food quality (such as the Harvard Nurses' Studies).
   

GI Values Update

How do you know if it’s low, medium or high GI?
Living in the USA, where would you suggest I look for GI information on our food? Or are foodstuffs pretty comparable? Any US sites you would recommend?’



Low GI eating often means making a move back to staple foods – fruit, vegetables, legumes (home-cooked or canned beans, chickpeas and lentils), wholegrains (pearl barley, bulghur), pasta, noodles, dairy foods (milk, yoghurt) – which naturally have a low GI, so it doesn’t matter which brand you buy. The top 100 low GI foods are listed in Low GI Eating Made Easy (US edition: Marlowe & Company) along with ideas for including them in your meals. When it comes to carb-rich processed foods such as breakfast cereals, bread, bakery items (cookies, cakes, muffins etc), you do need to know the GI of different brands as it can range from low to high and there’s no easy way to make an educated guess. To find the GI of your favourite brands you can:

• Look for an independently accredited GI symbol on the product
• Check the nutritional label – some manufacturers now include GI (but you need to be sure that an accredited lab tested the food. (See our note below on when to be wary.)
• Visit www.glycemicindex.com to search the database
• Contact the manufacturer and ask (hound) them to have the food tested by an accredited lab.

GI testing – make sure an accredited lab tested the product
Not all claims are reliable. Why? Well, The GI rating of a food must be tested physiologically and only a few centres around the world currently provide such a testing service (see our list below). In fact the GI is defined by its internationally standardised method of testing in human subjects (we call this in vivo testing). You may hear about in vitro (test tube) methods, but these are simple short cuts, which may be useful for food manufacturers developing new products, but may not reflect the true GI of a food. Here’s a list of the accredited labs we know (in no particular order) that carry out GI testing following the internationally standardised method. Apologies to any we have left out – please send us your details so we can publish them in future editions of GI News.

• Sydney University s Glycemic Index Research Service (SUGIRS), Sydney, Australia (www.glycemicindex.com)
• International Diabetes Institute, Melbourne, Australia (www.idi.org.au)
• Glycemic Index Laboratories, Inc., Toronto, Canada (www.gilabs.com)
• Reading Scientific Services Limited (RSSL), Reading, UK (www.rssl.com)
• Leatherhead Food International, Surrey, UK (www.lfra.co.uk)
• Oxford Brookes University, Oxford, UK (www.brookes.ac.uk/bms/research/nfsg/index.html)
• Hammersmith Food Research Unit, Hammersmith Hospital, London, UK (www.foodresearch.co.uk)
• Glycaemic Index Otago, University of Otago, New Zealand (www.glycemicindex.otago.ac.nz)

Symbols to look for
When you see one of these symbols you will know that the food has been tested by an accredited lab.

The GI Symbol Program
This international symbol is a guarantee that the product meets strict nutritional criteria. Glycemic Index Limited is a non-profit company established to run the GI Symbol Program. Its members are: the University of Sydney, Diabetes Australia and the Juvenile Diabetes Research Foundation. For more information, visit www.gisymbol.com.


International GI Symbol

Sainsbury's and Tesco
In the UK, Sainsburys and Tesco are testing and labelling foods low and medium Gi across a range of products.

Sainsbury's

Tesco

When you need to be wary
Sometimes a GI value may be too low to be true. If a manufacturer is promoting a carb-rich processed food with an ultra low GI, be wary before you buy. Processed foods such as breakfast cereals and breads and bakery products are very unlikely to have a very low GI. In fact, if the GI is less than say 50, we suggest that you ask the manufacturer for the name of the lab that tested it and the method that was used.

Low GI Food of the Month

Wild About Wild Blueberries
Make blueberries an everyday health habit. As one of today’s superfoods, they are bursting with nutrition and flavour while being very low in kilojoules/calories. They are popular for eating fresh or using in pancakes and smoothies, muffins, jams, as a snack and in many other dishes and desserts.



But like us, you probably didn’t know that not all blueberries are the same. Most blueberries you buy in the supermarket or fresh produce store will be cultivated highbush blueberries (Vaccinium corymbosum L). In the US, it’s also possible to buy frozen wild blueberries (V. angustifolium), all year long (GI 53 tested by Glycemic Index Laboratories, Inc). Wild blueberries are smaller, about one-third the size of cultivated and have a more intense blueberry flavor and they retain their shape well in cooking. Wild blueberries are also significantly higher in anti-oxidant activity than their cultivated cousins. In fact, they are richer in anti-oxidants compared with more than 20 other fruits (Journal of Agricultural and Food Chemistry, 2004, 52: 4026-4037) including cranberries, strawberries, plums, and raspberries. The blue pigment in blueberries called anthocyanins is responsible for most of the antioxidant activity. Blue is good for you!

Wild blueberries are one of three berries native to North America – the others are cranberry and Concord grapes. They thrive in the northern climate of Maine, Atlantic Canada and Quebec where the growers manage the traditional fields and ‘barrens’ to encourage the crop to grow in a sustainable fashion. Although they are may be harvested in a traditional way (with hand-held berry rakes), they are sorted, cleaned and processed using state-of-the-art-technology to preserve their flavor, quality and anti-oxidant qualities. Frozen wild blueberries are shipped world wide Japan, Europe, Korea, Middle East, and Australia. Fresh wild blueberries are only available during the short season locally in Maine and Canada. (Wild blueberries have never been hybridized so don’t ship well in the fresh state or hold up in stores for any length of time.)

Try these quick and easy serving suggestions for fresh and frozen wild blueberries:

• Combine blueberries with a little caster sugar and a tablespoon or two of balsamic vinegar or a little white wine or orange juice. Let the flavours develop for 30 minutes or so at room temperature then serve on their own or with low-fat ice-cream
• Make blueberry smoothies with low fat milk, soy milk or yoghurt for breakfast or a meal in a glass when you are on the run.) If you use frozen fruit you don’t need ice cubes.
• Add 1/2 cup to your morning cereal or yoghurt or yogurt
• Toss them into pancake or waffle batter
• Sprinkle them into your garden salad or fruit salad

For a selection of tasty wild blueberry recipes go to www.wildblueberries.com