Tag Archives: glycemic index

High-Carbohydrate Eating Promotes Heart Disease in Women

Women double their risk of developing coronary heart disease if they have high consumption of carbohydrates, according to research recently published in the Archives of Internal Medicine

Men’s hearts, however, didn’t seem to be affected by carb consumption. I mention this crucial difference because I see a growing trend to believe that “replacing saturated fat with carbohydrates is a major cause of heart disease.”  If true, it seems to apply only to women.

We’ve known for a while that high-glycemic-index eating was linked to heart disease in women but not menGlycemic index is a measure of how much effect a carbohydrate-containing food has on blood glucose levels.  High-glycemic-index foods raise blood sugar higher and for longer duration in the bloodstream.

High-glycemic-index foods include potatoes, white bread, and pasta, for example.

The study at hand includes over 47,000 Italians who were interrogated via questionnaire as to their food intake, then onset of coronary heart disease—the cause of heart attacks—was measured over the next eight years. 

Among the 32,500 women, 158 new cases of coronary heart disease were found.

ResearchBlogging.orgResearchers doing this sort of study typically compare the people eating the least carbs with those eating the most.  The highest quartile of carb consumers and glycemic load had twice the rate of heart disease compared to the lowest quartile. 

The Cleave-Yudkin theory of the mid-20th century proposed that excessive amounts of refined carbohydrates cause heart disease and certain other chronic systemic diseases.  Gary Taubes has also written extensively about this.  Theresearch results at hand support that theory in women, but not in men. 

Practical Applications

Do these research results apply to non-Italian women and men?  Probably to some, but not all.  More research is needed.

Women with a family history coronary heart disease—or other CHD risk factors—might be well-advised to put a limit on total carbs, high-glycemic-index foods, and glycemic load.  I’d stay out of that “highest quartile.”  Don’t forget: heart disease is the No. 1 killer of women.

See NutritionData’s Glycemic Index page for information you can apply today.

Steve Parker, M.D.

Disclaimer:  All matters regarding your health require supervision by a personal physician or other appropriate health professional familiar with your current health status.  Always consult your personal physician before making any dietary or exercise changes.

References: Sieri, S., Krogh, V., Berrino, F., Evangelista, A., Agnoli, C., Brighenti, F., Pellegrini, N., Palli, D., Masala, G., Sacerdote, C., Veglia, F., Tumino, R., Frasca, G., Grioni, S., Pala, V., Mattiello, A., Chiodini, P., & Panico, S. (2010). Dietary Glycemic Load and Index and Risk of Coronary Heart Disease in a Large Italian Cohort: The EPICOR Study Archives of Internal Medicine, 170 (7), 640-647 DOI: 10.1001/archinternmed.2010.15

Barclay, Alan, et al.  Glycemic index, glycemic load, and chronic disease risk – a meta-analysis of observational studies [of mostly women].  American Journal of Clinical Nutrition, 87 (2008): 627-637.

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Filed under Carbohydrate, coronary heart disease, Glycemic Index and Load

Are Refined Carbs Worse for Your Heart Than Saturated Fat?

To reduce coronary heart disease, we need to focus on reducing consumption of refined carbohydrates rather than fat and cholesterol, according to Dr. Frank Hu.

Dr. Hu is not a wild-eyed, bomb-throwing radical. He’s a Harvard professor of nutrition and epidemiology with both M.D. and Ph.D. degrees.  High-glycemic-index carbs in particular are the bad boys, he writes in an editorial published in the American Journal of Clinical Nutrition earlier this year.

Additional details are at my April 26, 2010, post at the Self/NutritionData Heart Health Blog.

Steve Parker, M.D.

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Filed under Carbohydrate, coronary heart disease, Fat in Diet, Glycemic Index and Load

High Carbohydrate Eating Increases Risk of Diabetes

ResearchBlogging.orgThe American Journal of Clinical Nutrition reported earlier this month that high consumption of carbohydrates, high-glycemic-index eating, and high-glycemic-load eating increases the risk of developing diabetes.  High fiber consumption, on the other hand, seems to protect against diabetes. 

The article abstract doesn’t mention type 1 versus type 2 diabetes, but it’s probably type 2, the most common kind.

The observational reseach was done in the Netherlands, but I bet the findings apply to other populations as well.  Australian researchers had established years ago that high-glycemic-index and high-glycemic-load eating is associated with onset of diabetes, at least in women

Is high carbohydrate consumption putting too much strain on the pancreas, which produces the insulin needed to process the carbs?

Steve Parker, M.D.

Reference:  Sluijs I, van der Schouw YT, van der A DL, Spijkerman AM, Hu FB, Grobbee DE, & Beulens JW (2010). Carbohydrate quantity and quality and risk of type 2 diabetes in the European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) study. The American journal of clinical nutrition PMID: 20685945

1,2,3

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Filed under Carbohydrate, Causes of Diabetes

Grains and Legumes: Any Effect on Heart Disease and Stroke?

Several scientific studies published in the first five years of this century suggest that whole grain consumption protects agains coronary heart disease and possibly other types of cardiovascular disease, such as stroke. 

Note that researchers in this field, especially outside the U.S., use the term “cereal” to mean “a grass such as wheat, oats, or corn, the starchy grains of which are used as food.”  They also refer frequently to glycemic index and glycemic load, spelled “glycaemic” outside the U.S.  Most of the pertinent studies are observational (aka epidmiologic): groups of people were surveyed on food consumption, then rates of diseases were associated with various food types and amounts.  “Association” is not proof of causation. 

Here are highlights from a 2006 review article in the European Journal of Clinical Nutrition

The researchers concluded that a relationship between whole grain intake and coronary heart disease is seen with at least a 20% and perhaps a 40% reduction in risk for those who eat whole grain food habitually vs those who eat them rarely.

Whole grain products have strong antioxidant activity and contain phytoestrogens, but there is insufficient evidence to determine whether this is beneficial in coronary heart disease prevention.

Countering the positive evidence for whole grain and legume intake has been the Nurses Health Study in 2000 that showed women who were overweight or obese consuming a high glycaemic load (GL) diet doubled their relative risk of coronary heart disease compared with those consuming a low GL diet.

The intake of high GI carbohydrates (from both grain and non-grain sources) in large amounts is associatied with an increased risk of heart disease in overweight and obese women even when fiber intake is high but this requires further confirmation in normal-weight women.

Promotion of carbohydrate foods should befocused on whole grain cereals because these have proven to be associatied with health benefits.

Whether adding bran to refined carbohydrate foods can improve the situation is also not clear, and it was found that added bran lowered heart disease risk in men by 30%.

Recommendation:  Carbohydrate-rich foods should be whole grain and if theyare not, then the lowest GI product available should be consumed.

My Comments

This journal article focuses on whole grains rather than legumes, and promotes whole grains more than legumes.  For people with diabetes, this may be a bit of a problem since grains—whole or not—generally have a higher glycemic index than legumes, which may have adverse effects on blood sugar control.  Keep in mind that highly refined grain products, like white bread, have a higher glycemic index than whole grain versions.

Did you notice that the abstract doesn’t recommend a specific amount of whole grains for the general population?  My educated guess would be one or two servings a day. 

Grains are high in carbohydrate, so anyone on a low-carb diet may have to cut carbs elsewhere. 

Diabetes predisoses to development of coronary heart disease.  Whole grains seem to help prevent heart disease, yet may adversely affect glucose control, contributing to diabetic complications.  It’s a quandary.  “Caught between the horns of a dilemma,” you might say.  So, what should a diabetic do with this information in 2010, while we await additional research results?

Several options come to mind:

  1. Eat whatever you want and forget about it.
  2. Note whether coronary heart disease runs in your family.  If so, try to incorporate one or two servings of whole grains daily, noting and addressing effects on your blood sugar.
  3. Try to eat one or two servings of whole grains a day, noting and addressing effects on your blood sugar.  Then decide if it’s worth it.  Is there any effect?  Do you have to increase your diabetic drug dosages or add a new drug?  Are you tolerating the drugs?    
  4. Assess all your risk factors for developing heart disease: smoking, sedentary lifestyle, high blood pressure, age, high LDL cholesterol, family history, etc.  If you have multiple risk factors, see Option #3.  And modify the risk factors under your control.   
  5. Get your personal physician’s advice.    

Before you stress out over this, be aware that we don’t really know whether a diabetic who doesn’t eat grains will have a longer healthier life by starting a daily whole grain habit.  Maybe . . . maybe not.  The study hasn’t been done.    

Steve Parker, M.D.

References:

Flight, I. and Clifton, P.  Cereal grains and legumes in the prevention of coronary heart disease and stroke: a review of the literatureEuropean Journal of Clinical Nutrition, 60 (2006): 1,145-1,159.

Malik, V. and Hu, Frank.  Dietary prevention of atherosclerosis: go with whole grainsAmerican Journal of Clinical Nutrition, 85 (2007): 1,444-1,445.

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Filed under Carbohydrate, coronary heart disease, Diabetes Complications, Grains, legumes, Stroke

Eat the Right Carbs to Alleviate Diabetes and Heart Disease

Harvard’s Dr. Frank Hu in 2007 called for a paradigm shift in dietary prevention of heart disease, de-emphasizing the original diet-heart hypothesis and noting instead that “. . . reducing dietary GL [glycemic load] should be made a top public health priority.”  Jim Mann at the University of Otago (Dunedin, New Zealand) authored a 2007 review of carbohydrates and effects on heart disease and diabetes.  Here are highlights from the article summary in the European Journal of Clinical Nutrition:

The nature of carbohydrate is of considerable importance when recommending diets intended to reduce the risk of type II diabetes and cardiovascular disease and in the treatment of patients who already have established diseases. Intact fruits, vegetables, legumes and whole grains are the most appropriate sources of carbohydrate. Most are rich in [fiber] and other potentially cardioprotective components.  Many of these foods, especially those that are high in dietary fibre, will reduce total and low-density lipoprotein cholesterol and help to improve glycaemic control in those with diabetes.

Frequent consumption of low glycaemic index foods has been reported to confer similar benefits, but it is not clear whether such benefits are independent of the dietary fibre content of these foods or the fact that low glycaemic index foods tend to have intact plant cell walls.

A wide range of carbohydrate intake is acceptable, provided the nature of carbohydrate is appropriate. Failure to emphasize the need for carbohydrate to be derived principally from whole grain cereals, fruits, vegetables and legumes may result in increased lipoprotein-mediated risk of cardiovascular disease, especially in overweight and obese individuals who are insulin resistant.

Why does this matter to me and readers of this blog?  Dietary carbohydrates are a major determinant of blood sugar levels, tending to elevate them.  Chronically high blood sugar levels are associated with increased complication rates from diabetes.  People with diabetes are prone to develop heart disease, namely coronary artery disease, which causes heart attacks, weakness of the heart muscle, and premature death. 

Steve Parker, M.D.

References: 

Mann, J.  Dietary carbohydrate: relationship to cardiovascular disease and disorders of carbohydrate metabolismEuropean Journal of Clinical Nutrition, 61 (2007): Supplement 1: S100-11.

Hu, Frank.  Diet and cardiovascular disease prevention: The need for a paradigm shift.  Journal of the American College of Cardiology, 50 (2007): 22-24.

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Filed under Carbohydrate, coronary heart disease, Fiber, Fruits, Glycemic Index and Load, Grains, legumes, Vegetables

Low-Glycemic Index Eating Improves Control of Diabetes

Lowering glycemic index (GI) led to improved contol of blood sugar, better insulin sensitivity, and weight loss in people with type 2 diabetes given group education sessions, according to researchers at Pennsylvania State University.

As background, the scientists note that:

GI may play a role in preventing or treating type 2 diabetes by decreasing the risk for obesity or by altering metabolic endpoints.  Improvements in glycaemic control were observed in people with diabetes in a recent meta-analysis.  A lower-GI diet was shown to decrease postprandial glucose [blood sugar after meals] and insulin responses and improve serum lipid concentrations.  Lower-GL [glycemic load] diets were associated with decreased risk for type 2 diabetes, decreased levels of C-reactive protein and inflammation, and weight loss.

Ninety-nine test subjects completed the study that enrolled adults 40 to 70  years old who had diabetes at least one year but were not taking insulin shots.  Average body mass index was 33, so they were obese.  Average weights were 84.5 kg (186 lb) for women and 108.7 kg (239 lb) for men.  Average baseline hemoglobin A1c was estimated at 7%, so these folks were under good glucose control.  Baseline carbohydrate intake was 45% of total energy, a bit lower than the general population. 

The 9-week intervention involved nine weekly group education sessions—lasting 1.5 to 2 hours—focusing on selection of lower-GI (vs higher-GI) foods instead of restricting carbohydrates.  Also covered were monitoring of portion sizes to control carb consumption, carb counting to control carb distribution and intake, and self-monitoring of food intake. 

Results

Although weight loss was not a goal, weights fell by 1-2 kg (2-4 pounds).  Men lost more than women.  Overall diet glycemic index fell by 2-3 points (a modest amount).  Comparing values before and after intervention, fasting glucose and postprandial glucose fell significantly, and insulin sensitivity improved.  Although not measured, the authors estimate hemoglobin A1c levels would have fallen an absolute 0.3%, based on measured glucose levels.  Percentage of calories from carbohydrate did not change. 

Comments

This is one of the few studies to try low-glycemic index behavioral intervention in adults with type 2 diabetes.  Results are encouraging. 

The researchers and I wonder if results would have been even more dramatic if the test subjects hadn’t been so well controlled before intervention or if they had dropped their glycemic index even lower.  Probably so.  Many people with type 2 diabetes have hemoglobin A1c’s well over 7%.

The researchers attribute the weight loss to portion control and simple self-monitoring of consumption. 

For people with diabetes, this study supports selection of lower-glycemic index instead of higher-GI.  In fact, we’d see less diabetes, heart disease, breast cancer, and gallbladder disease if all women—diabetic or not—ate lower-GI

Steve Parker, M.D.

Reference:  Gutschall, Melissa, et al.  A randomized behavioural trial targeting glycaemic index improves dietary, weight and metabolic outcomes in patients with type 2 diabetes.  Public Health and Nutrition, 12(2009): 1,846-1,854.

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Filed under Carbohydrate, Glycemic Index and Load

Legumes and Whole Grains: Any Role in Diabetes?

Expert nutrition panels consistently recommend whole grains and legumes for people with diabetes.  Why?  And do these foods affect development of diabetes?  I found a pertinent scientific review article on the subject from 2004 in the European Journal of Clinical Nutrition.  Here are some pertinent quotes from the summary:

Epidemiological studies strongly support the suggestion that high intakes of whole grain foods protect against the development of type II diabetes mellitus (T2DM). People who consume approximately 3 servings per day of whole grain foods are less likely to develop T2DM than low consumers (<3 servings per week) with a risk reduction in the order of 20-30%.

The role of legumes in the prevention of diabetes is less clear, possibly because of the relatively low intake of leguminous foods in the populations studied. However, legumes share several qualities with whole grains of potential benefit to glycaemic control including slow release carbohydrate and a high fibre content. A substantial increase in dietary intake of legumes as replacement food for more rapidly digested carbohydrate might therefore be expected to improve glycaemic control and thus reduce incident diabetes. This is consistent with the results of dietary intervention studies that have found improvements in glycaemic control after increasing the dietary intake of whole grain foods, legumes, vegetables and fruit.

. . . it is cereal fibre that is largely insoluble [rather than soluble fiber] that is associated with a reduced risk of developing T2DM.

Thus, there is strong evidence to suggest that eating a variety of whole grain foods and legumes is beneficial in the prevention and management of diabetes. This is compatible with advice from around the world that recommends consumption of a wide range of carbohydrate foods from cereals, vegetables, legumes and fruits both for the general population and for people with diabetes.

Gluten Intolerance

A major protein in wheat is gluten.  The last few years have seen the popular emergence of gluten-free this and gluten-free that.  The idea is that gluten causes a variety of gastrointestinal, immunologic, and other problems, so wheat products should be avoided.  Certainly they should be avoided in people with celiac disease, a well-established medical condition.  I follow a few paleo blogs and know that grains and legumes are not part of that way of eating: the paleos say we are not evolved optimally to process them.    

If legumes or wheat or other grains cause problems for you, don’t eat them.  They have no essential nutrients that you can’t get elsewhere. 

Glycemic Index

In my quest to develop a healthy Diabetic Mediterranean Diet, I’m finding that grains—compared to nearly all other carbohydrate-containing food groups—tend to have a higher glycemic index (GI).   A low GI is 55 or less.  High GI is 70 or greater.  Grains in general raise blood sugar levels higher than many other sources of carbohydrates.  But this is highly variable and depends partially on preparation of the grain.  Whole grain products have a lower GI than highly processed counterparts.  For instance, white bread has a GI of 70; whole wheat bread 67.  Regular spaghetti is 38.  Table sugar’s GI must be sky high, right?  No, its just 61.  A baked potato is a whopping 85.   

Beans have a GI around 30 or 40.  And they pack a lot more fiber per serving.  For a diabetic struggling to keep blood sugars under control, which is a better choice: grains or legumes?  I’m leaning towards legumes and other components of a low-glycemic-index diet.   

Steve Parker, M.D.

PS:  [Before you correct my GI numbers, please note I’m  aware that various GI lists don’t agree with each other.]

Reference:  Venn, B.J. and Mann, J.I. Cereal grains, legumes and diabetes.  European Journal of Clinical Nutrition, 58 (2004): 1,443-1,461.

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Filed under Fiber, Fruits, Grains, legumes, Prevention of T2 Diabetes, Vegetables

Do Beans and Peas Affect Glucose Control in Diabetics?

Beans and peas improve control of blood sugar in diabetics and others, according to a recent report from Canadian researchers.  The effect is modest.

Dietary pulses are dried leguminous seeds, including beans, chickpeas, lentils, and peas.  Pulses fed to healthy volunteers have a very low glycemic index, meaning they don’t cause much of a rise in blood sugar compared to other carbohydrates.  They are loaded with fiber and are more slowly digested than foods such as cereals.   

Investigators examined 41 clinical trials (1,674 participants) on the effects of beans and peas on blood glucose control, whether used alone or as part of low-glycemic-index or high-fiber diets.  Eleven trials looked at the effect of beans and peas alone, with the experimental “dose” averging 1oo g per day (about half a cup).  The article doesn’t specify whether the weight of the pulse was the dry weight or the prepared weight.  I will assume prepared.

Pulse given alone or as part of a high-fiber or low-glycemic index diet improved markers of glucose control, such as fasting blood sugar and hemoglobin A1c.  The absolute improvement in HgbA1c was around 0.5%.  Effects in healthy non-diabetics were less dramatic or non-existent.

My Comments

This study was very difficult  for me to digest.  The researchers lumped together studies on diabetics  and non-diabetics, using various doses and types of pulses.  No wonder they found “significant interstudy heterogeneity.” 

Cardiovascular disease is common in diabetics.  I’m aware of at least one study linking legume consumption with lower rates of cardiovascular disease.  I was hoping this study would answer for me whether I should recommend legumes such as peas and beans for my type 2 diabetics.  Beans and peas do represent a low glycemic load, which is good.  But I think I’ll have to keep looking for better-designed studies.

Steve Parker, M.D. 

Reference:  Sievenpiper, J.L., et al.  Effect of non-oil-seed pulses on glycaemic control: a systematic review and meta-analysis of randomised controlled experimental trials in people with and without diabetesDiabetologia, 52 (2009): 1,479-1,495.  doi: 10.1007/s00125-009-1395-7

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Filed under Carbohydrate, Fiber, Prevention of T2 Diabetes

Glycemic Load Linked to Breast Cancer Risk

Who knew?

Who knew?

Swedish researchers report that  a high dietary glycemic load is tied to a woman’s risk of developing breast cancer.  This adds to a growing body of evidence that high glycemic index and load may be harmful.  Prior studies relate them to higher rates of diabetes and heart disease. 

Click here for my review of glycemic index and load.  NutritionData.com also has a good review of glycemic index.

Steve Parker, M.D.

References:

Reuters Health.  “Glycemic load” of diet tied to breast cancer risk.  MedlinePlus, July 10, 2009.

Parker, Steve.  Glycemic index and chronic disease risk (mostly in women).  Advanced Mediterranean Diet Blog, April 19, 2009.

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Filed under Glycemic Index and Load

Glycemic Index and Chronic Disease Risk (Mostly in Women)

"Would you like some high-glycemic index bread?"

"Would you like some high-glycemic index bread?"

I recently blogged about glycemic index (GI), glycemic load (GL), and glycemic diets in preparation for today’s post.

The concept of glycemic index was introduced by Jenkins et al in 1981 at the University of Toronto.

Studies investigating the association between disease risk and GI/GL have been inconsistent.  By “inconsistent,” I mean some studies have made an association in one direction or the other, and other studies have not.  Diseases possibly associated with high-glycemic diets have included diabetes, cardiovascular disease, cancer, gallbladder disease, and eye disease.

“Diet” in this post refers to a habitual way of eating, not a weight loss program.

Researchers with the University of Sydney (Sydney, Australia) identified the best-designed published research reports investigating the relationship between certain chronic diseases and glycemic index and load.  The studied diseases were type 2 diabetes, coronary heart disease, stroke, breast cancer, colorectal cancer, pancreatic cancer, endometrial cancer, ovarian cancer, gallbladder disease, and eye disease.

Methodology

Literature databases were searched for articles published between 1981 and March, 2007.  The researchers found 37 studies that enrolled 1,950,198 participants ranging in age from 24 to 76, with BMI’s averaging 23.5 to 29.  These were human prospective cohort studies with a final outcome being occurrence of a chronic disease (not its risk factors).  Twenty-five of the studies were conducted in the U.S., five in Canada, five Europe, and two in Australia.  Ninety percent of participants were women [for reasons not discussed].  Food frequency questionnaires were used in nearly all the studies.  Individual studies generated between 4 to 20 years of follow-up, and 40,129 new cases of target diseases were identified.

Associations between GI, GL, and risk of developing a chronic disease were measured as rate ratios comparing the highest with the lowest quantiles.  For example, GI and GL were measured in the study population.  The population was then divided into four groups (quartiles), reflecting lowest GI/GL to medium to highest GI/GL diets.  The lowest GI/GL quartile was compared with the highest quartile to see if disease occurrence was different between the groups.  Some studies broke the populations into tertiles, quintiles, deciles, etc.

Findings

Comparing the highest with the lowest quantiles, studies with a high GI or GL independently

  • increased the risk of type 2 diabetes by 27 (GL) or 40% (GI)
  • increased the risk of coronary heart disease by 25% (GI)
  • increased the risk of gallbladder disease by 26% (GI) or 41% (GL) [gallstones and biliary colic, I assume, but the authors don’t specify]
  • increased the risk of breast cancer by 8% (GI)
  • increased risk of all studied diseases (11) combined by 14% (GI) or 9% (GL)

Overall, high GI was more strongly associated with chronic disease than was high GL
So low-GI diets may offer greater protection against disease than low-GL diets.

Comments from the Researchers

They speculate that low-GI diets may be more protective than low-GL because the latter can include low-carb foods such as cheese and meat, and low-GI, high-carb foods.  Both eating styles will reduce glucose levels after meals while having very different effects in other areas such as pancreas beta cell function, free fatty acid levels, triglyceride levels, and effects on satiety.

High GI and high GL diets, independently of known confounders, modestly increase the risk of chronic lifestyle-related diseases, with more pronounced effects for type 2 diabetes, coronary heart disease, and gallbladder disease.

Direct quotes:

. . . 90% of participants were female; therefore, the findings may not be generalizable to men.

There are plausible mechanism linking the development of certain chronic diseases with high-GI diets.  Specifically, 2 major pathways have been proposed to explain the association with type 2 diabetes risk.  First the same amount of carbohydrate from high-GI food produces higher blood glucose concentrations and a greater demand for insulin.  The chronically increased insulin demand may eventually result in pancreatic beta cell failure, and, as a consequence, impaired glucose tolerance.  Second, there is evidence that high-GI diets may directly increase insulin resistance through their effect on glycemia, free fatty acids, and counter-regulatory hormone secretion.  High glucose and insulin concentrations are associated with increased risk profiles for cardiovascular disease, including decreased concentrations of HDL cholesterol, increased glycosylated protein, oxidative status, hemostatic variables, and poor endothelial function

Low-GI and/or low-GL diets are independently associated with a reduced risk of certain chronic diseases.  In diabetes and heart disease, the protection is comparable with that seen for whole grain and high fiber intakes.  The findings support the hypothesis that higher postprandial glycemia is a universal mechanism for disease progression.

My Comments

Studies like this tend to accentuate the differences in eating styles since they compare the highest with the lowest post-prandial (after meal) glucose levels.  Most people are closer to the middle of the pack, so a person there has potentially less to gain by moving to a low-GI diet.  But still some to gain, on average, particularly in regards to avoiding type 2 diabetes and coronary heart disease.

[To be fair, many population-based studies use this same quantile technique.  It increases the odds of finding a statistically significant difference.]

Only two of the 37 studies examined coronary heart disease, the cause of heart attacks.  One study was the massive Nurses’ Health Study database with 75,521 women.  The other was the Zutphen (Netherlands) Elderly Study which examined men 64 and older.  Here’s the primary conclusion of the Zutphen authors verbatim:

Our findings do not support the hypothesis that a high-glycemic index diet unfavorably affects metabolic risk factors or increases risk for CHD [coronary heart disease] in elderly men without a history of diabetes or CHD.

So there’s nothing in the meta-analysis at hand to suggest that high-GI/GL diets promote heart disease in males in the general population.

However, the recent Canadian study in Archives of Internal Medicine found strong evidence linking CHD with high-glycemic index diets.  Although not mentioned in the text of that article, Table 3 on page 664 shows that the association is much stonger in women than in men.  Relative risk for women on a high-glycemic index/load diet was 1.5 (95% confidence interval = 1.29-1.71), and for men the relative risk was 1.06 (95% confidence interval = 0.91-1.20).  See reference below.

Nine of the 37 studies examined the occurrence of type 2 diabetes.  Only one of these studied men only – 42,759 men: the abstract is not available online and the Sydney group does not mention if high-GI or high-GL was positively associated with onset of diabetes in this cohort.  Two of the diabetes studies included both men and women, but the abstracts don’t break down the findings by sex.  [I’m trying to deduce if the major overall findings of this meta-analysis apply to men or not.]

I don’t know anybody willing to change their diet just to avoid the risk of gallstones.  It’s only after they develop symptomatic gallstones that they ask me what they can do about them.  The usual answer is surgery.

The report is well-done and seems free of commercial bias, even though several of the researchers are authors or co-authors of popular books on low-GI eating.

Steve Parker, M.D.

References:

Barclay, Alan W.; Petocz, Peter; McMillan-Price, Joanna; Flood, Victoria M.; Prvan, Tania; Mitchell, Paul; and Brand-Miller, Jennie C.  Glycemic index, glycemic load, and chronic disease risk – a meta-analysis of observational studies [of mostly women].  American Journal of Clinical Nutrition, 87 (2008): 627-637.

Brand-Miller, Jennie, et al.  “The New Glucose Revolution: The Authoritative Guide to the Glycemic Index – The Dietary Solution for Lifelong Health.”  Da Capo Press, 2006.

Mente, Andrew, et al.  A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart DiseaseArchives of Internal Medicine, 169 (2009): 659-669.

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Filed under Causes of Diabetes, Glycemic Index and Load