Category Archives: Carbohydrate

November 18, 2009 · 9:58 PM

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 diabetes.  Diabetologia, 52 (2009): 1,479-1,495.  doi: 10.1007/s00125-009-1395-7

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November 15, 2009 · 2:00 AM

Low-Carb Diet Helps Obese Swedes With Diabetes

Swedish boyObese people with type 2 diabetes following a 20% carbohydrate diet demonstrated sustained improvement in weight and blood glucose control, according to two Swedish physicians.  These doctors also have research experience with traditional low-fat diets in overweight diabetics, having demonstrated that a 20% carbohydrate diet was superior to a low-fat/55–60% carb diet in obese diabetes patients over six months.

What Was the Intervention?

Proportions of carbohydrates, fat, and protein were 20%, 50%, and 30% respectively.  Total daily carbs were 80–90 g. 

Recommended carbs were vegetables and salads. 

Rather than ordinary bread, crisp/hard bread was recommended (3.5 to 8 g carb per slice).  Starchy breads, pasta, potatoes, rice, and breakfast cereals were excluded. 

They were instructed to walk 30 minutes daily, take a multivitamin with extra calcium daily, and to not eat between meals. 

At the outset, diabetic medications were reduced by 25–30% to avoid low blood sugars.   

Results

The doctors followed 23 patients over the course of  44 months.  Average initial body weight was 101 kg (222 pounds).  After 44 months, average body weight fell to 93 kg (205 pounds).  Hemoglobin A1c, a measure of diabetes control,  fell from 8% to 6.8%. 

My Comments

In these pages over the last few months, we’ve seen the effectiveness of low-carb diets in people with type 2 diabetes in widespread populations: Japanese, U.S. blacks and caucasions, and, now, Swedes. 

The standard Western diet derives 55–60% of its energy from carbohydrates.  If you’ve been following this blog, we’ve looked at diets containing 40%, 30%, 20%, and 10% carbs.  Have you noticed the trend? 

Reducing the percentage of carbohydrates in the diet improves diabetic control and loss of excess weight.  And the more you reduce carbs, the greater the degree of diabetic control and weight loss.   

Steve Parker, M.D.

Reference:  Nielsen, Jörgen and Joensson, Eva.  Low-carbohydrate diet in type 2 diabetes: stable improvement of body weight and glycemic control during 44 months follow-up.  Nutrition & Metabolism, 5:14   doi:10.1186/1743-7075-5-14

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November 13, 2009 · 2:00 AM

Moderate Low-Carb Diet Just as Effective as Insulin Shots in Type 2 Diabetes

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Mount Fuji

A low-carbohydrate diet is just as effective as insulin shots for people with severe type 2 diabetes, according to research recently announced by Japanese investigators.

Thirty-three uncontrolled Japanese type 2 diabetics, similar numbers of men and women, were placed on a low-carbohydrate diet for six months.  The diet provided 30% of energy from carbs, 44% fat, and 20% protein.  [By point of reference, the average American derives 55–60% of energy from carbs.]  Average caloric intake was 1,852/day.  [I’m not sure what provided the other 6% of calories – I suspect distilled liquor.]  Average body mass index was 24  and did not change during the six months.  The only adverse effect was mild constipation.  Two people dropped out of the study before completion.  Seven participants were on sulfonylurea drug therapy.

Protein and fat intake were unlimited.  They were given a list of high-carbohydrate foods to avoid (see reference).

Results

Hemoglobin A1c, a standard test of diabetes control, fell from10.9% to 7.8% at three months and 7.4% at six months.  Five of the seven patients on sulfonylurea were able to stop the drug.  No patient required insulin therapy or hospitalization. 

Comments

The low drop-out rate may be a testament to the palatability of this low-carb way of eating.

Japanese diabetes may not be exactly the same disease as American or European diabetes.  For instance, Japanese diabetics are not as overweight.  Only 3% of the Japanese population is obese (body mass index over 30), compared to 30% of the U.S. population. 

The degree of carbohydrate restriction in this study is not nearly as severe as with the Ketogenic Mediterranean Diet.  Yet the improvement in hemoglobin A1c was dramatic after just three months.

Being aware of genetic and other influences on disease, I’m always wary about generalizing research results from one race or ethnic group to others.  When it comes to the efficacy of low-carb eating in people with type 2 diabetes, however, we’ve seen similar results already in white and black Americans. 

Steve Parker, M.D. 

Reference:  Haimoto, Hajime, et al.  Effects of a low-carbohydrate diet on glycemic control in outpatients with severe type 2 diabetes.  Nutrition and Metabolism, 6:21   doi:10.1186/1743-7075-6-21

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November 10, 2009 · 2:00 AM

Low-Carb Ketogenic Diet Beats Low-Glycemic Index Diet in Overweight Type 2 Diabetes

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Avoid the needle with a low-carb ketogenic diet

Duke University (U.S.) researchers demonstrated better improvement and reversal of type 2 diabetes with an Atkins-style diet, compared to a low-glycemic index reduced-calorie diet.

Methodology

Ninety-seven overweight and obese adults, 78% women and 40% black, were randomly assigned to either:

  • a very low-carb ketogenic diet (Atkins induction phase, as in Atkins Diabetes Revolution) or
  • a low glycemic-index index calorie-restricted diet (The GI Diet by Rick Gallop). 

Thirty-eight were in the Atkins group; 46 in the low-glycemic index (low-GI) group.  Seventeen dropped out of each group before the end of the 24-week study.  Average weight was 234.3 pounds (106.5 kg); average body mass index was 37.  The Atkins group averaged 13% of total calories from carbohydrate; the low-GI cohort averaged 44%. 

Results

Both groups lost weight and had improvements in hemoglobin A1c, fasting insulin, and fasting glucose. 

The Atkins group lowered their hemoglobin A1c by 1.5% (absolute drop, not relative) versus 0.5% in the other group. 

The Atkins group lost 11.1 kg versus 6.9 kg in the other group. 

The Atkins group increased HDL cholesterol by5.6 mg/dl versus no change in the other group. 

All the aforementioned comparisons were statistically significant. 

Diabetes medications were stopped or reduced in 95% of the Atkins group versus 62% of the low-GI group.

Total and LDL cholesterol levels were unchanged in both groups. 

Triglycerides fell significantly only in the Atkins group.

My Comments

You may be interested to know that this study was funded by the Robert C. Atkins Foundation.

One strength of this study is that it lasted for 24 months.  Many similar studies last only eight to 12 weeks.  A drawback is that, with all the drop-outs,  the number of participants is low. 

The GI Diet performed pretty well, too, all things considered.  Sixty-two percent reduction or elimination of diabetes drugs—not bad.  For a six-year-old book, it’s still selling fairly well at Amazon.com.  That may be why they chose it as the comparison diet.

The diet with fewer carbohydrates—Atkins induction—was most effective for  improving control of blood sugars.  So effective, in fact, that the researchers sound a note of warning:

For example, participants taking from 40 to 90 units of insulin before the study were able to eliminate their insulin use, while also improving glycemic control.  Because this effect occurs immediately upon implementing the dietary changes, individuals with type 2 diabetes who are unable to adjust their own medication or self-monitor their blood glucose should not make these dietary changes unless under close medical supervision.  

[Not all insulin users were able to stop it.]

Overall, lipids were improved or unchanged in the Atkins group, despite the lack of limits on saturated fat intake.  A common criticism of the Atkins diet is that it has too much saturated fat, leading to higher total and LDL cholesterol levels, which might raise long-term cardiovascular risks.  Not so, here. 

When you reduce carbohydrate intake, the percentages of fat and protein in the diet also change.  In this Atkins diet, protein provided 28% of daily calories, and fat 59%.  In the low-GI diet, protein provided 20% of daily calories, fat 36%.  The beneficial effects of the Atkins diet probably reflect the low carbohydrate consumption rather than high protein and fat. 

The Atkins induction-phase diet was clearly superior to the low-glycemic index diet in this overweight diabetic sample, without restricting calories.

Steve Parker, M.D.

Reference:  Westman, Eric, et al.  The effect of a low-carbohydrate, ketogenic diet versus a low-glycemic index diet on glycemic control in type 2 diabetes mellitus.  Nutrition & Metabolism 2008, 5:36   doi:10.1186/1743-7075-5-36

Additional Reading

Samaha, F., et al.  A low-carbohydrate as compared with a low-fat diet in severe obesity.  New England Journal of Medicine, 348 (2003): 2,074-2,081.

Boden, G., et al.  Effect of a low-carbohydrate diet on appetite, blood glucose levels, and insulin resistance in obese patients with type 2 diabetes.  Annals of Internal Medicine, 142 (2005): 403-411.

Vernon, M., et al.  Clinical experience of a  carbohydrate-restricted diet: Effect on diabetes mellitus.  Metabolic Syndrome and Related Disorders, 1 (2003): 233-238.

Yancy, W., et al.  A pilot trial of a low-carbohydrate ketogenic diet in patients with type 2 diabetes.  Metabolic Syndrome and Related Disorders, 1 (2003): 239-244.

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September 17, 2009 · 12:20 PM

Low-Carb Diet Lowers Glucose Levels More Than Standard-Carb Diet

Stephan Guyenet, Ph.D., (neurobiology) posted a graph at his blog (Whole Health Source) showing dramatically better glucose levels in people with diabetes eating a low-carb diet (20% of energy from carbs) compared to those on a 55% carb diet. 

No great surprise, but it has more impact when you see it graphed out.

Steve Parker, M.D.

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September 13, 2009 · 3:41 AM

Low-Carb Mediterranean Diet Beats Low-Fat For Recent-Onset Type 2 Diabetes

MPj03417870000[1]A low-carbohydrate Mediterranean diet dramatically reduced the need for diabetic drug therapy, compared to a low-fat American Heart Association diet.  The Italian researchers also report that the Mediterranean dieters also lost  more weight over the first two years of the study.

Investigators suggest that the benefit of the Mediterranean-style diet is due to greater weight loss, olive oil (monunsaturated fats increase insulin sensitivity), and increased adiponectin levels.

The American Diabetes Association recommends both low-carbohydrate and low-fat diets for overweight diabetics.  The investigators wondered which of the two might be better, as judged by the need to institute drug therapy in newly diagnosed people with diabetes.

Methodology

Newly diagnosed type 2 diabetics who had never been treated with diabetes drugs were recruited into the study, which was done in Naples, Italy.  At the outset, the 215 study participants were 30 to 75 years of age, had body mass index over 25 (average 29.5), had average hemoglobin A1c levels of 7.73, and average glucose levels of 170 mg/dl.

Participants were randomly assigned to one of two diets:

  1. Low-carb Mediterranean diet (“MED diet”, hereafter):  rich in vegetables and whole grains, low in red meat (replaced with poultry and fish), no more than 50% of calories from complex carbohydrates, no less than 30% of calories from fat (main source of added fat was 30 to 50 g of olive oil daily).  [No mention of fruits or wine.  BTW, the traditional Mediterranean diet derives 50-60% of energy from carbohydrates.]
  2. Low-fat diet based on American Heart Association guidelines:  rich in whole grains, restricted additional fats/sweets/high-fat snacks, no more than 30% of calories from fat, no more than 10% of calories from saturated fats.

Both diet groups were instructed to limit daily energy intake to 1500 (women) or 1800 (men) calories.

All participants were advised to increase physical activity, mainly walking for at least 30 minutes a day.

Drug therapy was initiated when hemoglobin A1c levels persisted above 7% despite diet and exercise.

The study lasted four years.

Results

By the end of 18 months, twice as many low-fat dieters required diabetes drug therapy compared to the MED dieters—24% versus 12%.

By the end of four years, seven of every 10 low-fat dieters were on drug therapy compared to four of every 10 MED dieters. 

The MED dieters lost 2 kg (4.4 lb) more weight by the end of one year, compared to the low-fat group.  The groups were no different in net weight loss when measured at four years: down 3–4 kg (7–9 lb).

Compared to the low-fat group, the MED diet cohort achieved significantly lower levels of fasting glucose and hemoglobin A1c throughout the four years.

The MED diet group saw greater increases in insulin sensitivity, i.e., they had less insulin resistance.

The MED group had significantly greater increases in HDL cholesterol and decreases in trigylcerides throughout the study.  Total cholesterol decreased more in the MED dieters, but after the first two years the difference from the low-fat group was not significantly different. 

The Mediterranean group’s intake of carbohydrates was 8-9% lower than baseline, monounsaturated fat was 5.5% higher than baseline, and polyunsaturated fat was 2.5% higher than baseline.  Compared with their baseline, the low-fat group didn’t make much change in these nutrient groups.  These numbers hold up for all four years of the study. 

Comments

The MED diet here includes “no more than 50% of calories from complex carbohydrates.”  The authors don’t define complex carbs.  Simple carbohydrates are monosaccharides and disaccharides.  Complex carbs are oligosaccharides and polysaccharides.  Another definition of complex carbs is “fruits, vegetables, and whole grains,” which I think is definition of complex carbs applicable to this study. 

The editors of the Annals of Internal Medicine conclude that:

A low-carbohydrate, Mediterranean-style diet seems to be preferable to a low-fat diet for glycemic control in patients with newly diagnosed type 2 diabetes.

I’m sure the American Diabetes Association will take heed of this study when they next revise their diet guidelines.  If I were newly diagnosed with type 2 diabetes, I wouldn’t wait until then.

This study dovetails nicely with others that show prevention of type 2 diabetes with the Mediterranean diet, reversal of metabolic syndrome—a risk factor for diabetes—with the Mediterranean diet (supplemented with nuts), and prevention of type 2 diabetes and pre-diabetes in people who have had a heart attack.

For instruction on how to lose weight with a Mediterranean-style diet, click here (it’s not the low-carb diet used in the study at hand).

For general information on Mediterranean eating, visit Oldways.

Steve Parker, M.D.

Reference:  Esposito, Katherine, et al.  Effects of a Mediterranean-style diet on the need for antihyperglycemic drug therapy in patients with newly diagnosed type 2 diabetes.  Annals of Internal Medicine, 151 (2009): 306-314.

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August 15, 2009 · 10:33 AM

Atkins Diet Beats Low-Fat Diet Over Three Months in Overweight Diabetic Black Women

MPj04384250000[1]A recent study compared effects of a low-carb versus low-fat diet in overweight diabetics (mostly blacks).  After one year, the only major difference they found was  lower HDL cholesterol in the low-carb eaters.  The low-carb diet was more effective measured at three months into the study.  Study participants were overwhelmingly black women, so the findings may not apply to you.

Background

The authors note at the outset that:

Optimal weight loss strategies in patients with type 2 diabetes continue to be debated, and the best dietary strategy to achieve both weight loss and glycemic control . . . is unclear.

They also note that in short-term randomized studies, low-carb diets help improve glucose control in type 2 diabetics.

Methodology

Participants (105) were randomized to either:

  • a low-fat diet in the fashion of the Diabetes Prevention Program, with a fat gram goal of 25% of energy needs, or . . .
  • the Atkins diet, including the 2-week induction phase and gradually increasing carb grams weekly, etc.

The adult partipants were black (64%), Hispanic (16%), white (15%), or other.  Women were 80% of the group.  Average age 54.  Average weight 215 pounds (98 kg).  Average BMI 36.  Most of them were taking metformin, half were taking a sulfonylurea, 30% were on insulin.  Thiazolidinedione drugs were discontinued since they cause weight gain as a side effect.  Short-acting insulins were changed to glargine (Lantus) to help avoid hypoglycemia.  For the low-carb group initially, insulin dosages  were reduce by half and sulfonylureas were stopped (again, to minimize hypoglycemia).  For the low-fat group, insulin was reduced by 25% and sulfonylurea by 50%.  Metformin was not adjusted.  Subjects were instructed to keep daily food diaries.  Goal rate of weight loss was one pound per week.   

Results

The drop-out rate by the end of 12 months was the same in both groups – 20%.  The low-carbers lost weight faster (3.7 lb/month) in the first three months, but by month twelve each group had the same 3.4% reduction of weight (6.8 lb or 3 kg).  As measured at 3 months, low-carbers were down 11.4 lb (5.2 kg) and low-fat dieters were down 7 lb (3.2 kg).  Maximum weight loss was at 3 months, then they started gaining it back.  At 12 months, low-carb subjects using insulin were on 10 less units, while low-fat dieters were using 4 more units (not statistically significant).  Hemoglobin A1c measured at 3 months was down 0.64 in the low-carb group and down0.26 in the low-fat.  By 12 months, HgbA1c’s were back up to baseline levels for both groups.  Blood lipids were the same for both groups at 12 months except HDL was about 12% higher in the low-carb dieters.

At baseline, subjects derived 43% of calories from carbohydrates, 36% from fats, 23% from proteins.  At three months, the low-carb group ate 24% of calories as carbohydrates (estimated at 77 grams of carb daily) and 49% from fat.  The low-fat group at 3 months derived 53% of calories from carbohydrate (199 grams/day) and 25% from fat. Diet compliance deteriorated as time passed thereafter. 

Study Author Conclusions

After one year, the low-carb and low-fat groups had similar weight reductions.  The low-carb dieters raised their HDL cholesterol levels significantly [which may protect against heart disease].

My Comments

Lasting weight loss is difficult!  Down only 6.8 pounds for a year of  effort. 

These study participants needed to lose a lot more than 6.8 pounds.  They needed to lose 50.  Both groups were woefully noncompliant with diet recommendations by the end of the study year.  They were eating more carbs or other calories than they were assigned.  But their results weren’t much different than other groups studied for an entire year. 

How do we keep people fired up about maintaining their weight-loss efforts?  The solution to that problem will win someone a Nobel Prize.

The Atkins diet was superior – for weight loss and glycemic control – when measured at three months, when compliance by both groups was still probably fairly good.

Results of this study may apply only to black women.  There weren’t enough men and other ethnic groups to make meaningful comparisons.    

Steve Parker, M.D.        

Reference:  Davis, Nichola, et al.  Comparative study of the effects of a 1-year dietary intervention of a low-carbohydrate diet versus a low-fat diet on weight and glycemic control in type 2 diabetes.  Diabetes Care, 32 (2009): 1,147-1,152.

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August 5, 2009 · 4:45 AM

Dental Problems and Systemic Chronic Disease: A Carbohydrate Connection?

Perfect health on a carnivorous, low-carb diet

Perfect health on a carnivorous, low-carb diet

Dentists are considering a return to an old theory that dietary carbohydrates first cause dental diseases, then certain systemic chronic diseases, according to a review in the June 1, 2009, Journal of Dental Research. 

We’ve known for years that some dental and systemic diseases are associated with each other, both for individuals and populations.  For example, gingivitis and periodontal disease are associated with type 2 diabetes and coronary heart disease.  The exact nature of that association is not clear.  In the 1990s it seemed that infections – chlamydia, for example – might be the unifying link, but this has not been supported by subsequent research.     

The article is written by Dr. Philippe P. Hujoel, who has been active in dental research for decades and is affiliated with the University of Washington (Seattle).  He is no bomb-throwing, crazed, radical. 

The “old theory” to which I referred is the Cleave-Yudkin idea from the 1960s and ’70s that excessive intake of fermentable carbohydrates, in the absence of good dental care, leads both to certain dental diseases – caries (cavities), periodontal disease, certain oral cancers, and leukoplakia – and to some common systemic chronic non-communicable diseases such as coronary heart disease, type 2 diabetes, some cancers, and dementia.  In other words, dietary carbohydrates cause both dental and systemic diseases – not all cases of those diseases, of course, but some.   

Dr. Hujoel does not define “fermentable” carbohydrates in the article.  My American Heritage Dictionary defines fermentation as:

  1. the anaerobic conversion of sugar to carbon dioxide and alcohol by yeast
  2. any of a group of chemical reactions induced by living or nonliving ferments that split complex organic compunds into relatively simple substances

As reported in David Mendosa’s blog at MyDiabetesCentral.com, Dr. Hujoel said, “Non-fermentable carbohydrates are fibers.”  Dr. Hujoel also shared some personal tidbits there. 

In the context of excessive carbohydrate intake, the article frequently mentions sugar, refined carbs, and high-glycemic-index carbs.  Dental effects of excessive carb intake can appear within weeks or months, whereas the sysemtic effects may take decades. 

Hujoel compares and contrasts Ancel Keys’ Diet-Heart/Lipid Hypothesis with the Cleave-Yudkin Carbohydrate Theory.  In Dr. Hujoel’s view, the latest research data favor the Carbohydrate Theory as an explanation of many cases of the aforementioned dental and systemic chronic diseases.  If correct, the theory has important implications for prevention of dental and systemic diseases: namely, dietary carbohydrate restriction.

Adherents of the paleo diet and low-carb diets will love this article; it supports their choices.

I agree with Dr. Hujoel that we need a long-term prospective trial of serious low-carb eating versus the standard American high-carb diet.  Take 20,000 people, randomize them to one of the two diets, follow their dental and systemic health over 15-30 years, then compare the two groups.  Problem is, I’m not sure it can be done.  It’s hard enough for most people to follow a low-carb diet for four months.  And I’m asking for 30 years?!   

Dr. Hujoel writes:

Possibly, when it comes to fermentable carbohydrates, teeth would then become to the medical and dental professionals what they have always been for paleoanthropologists: “extremely informative about age, sex, diet, health.”

Dr. Hujoel mentioned a review of six studies that showed a 30% reduction in gingivitis score by following a diet moderately reduced in carbs.  He mentions the aphorism: “no carbohydrates, no caries.”  Anyone prone to dental caries or ongoing periodontal disease should do further research to see if switching to low-carb eating might improve the situation. 

Don’t be surprised if your dentist isn’t very familiar with the concept.  Has he ever mentioned it to you?

Steve Parker, M.D.,

Author of The Advanced Mediterranean Diet

Reference:  Hujoel, P.  Dietary carbohydrates and dental-systemic diseases.  Journal of Dental Research, 88 (2009): 490-502.

Mendosa, David.  Our dental alarm bell.  MyDiabetesCentral.com, July 12, 2009.

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July 10, 2009 · 4:11 AM

Low-Glycemic-Index Eating Had No Effect on Control of Mild Type 2 Diabetes

Caprese salad

Caprese salad

A Canadian study last year found no overall effect on type 2 diabetes control by using a low-glycemic-index diet and lower-carbohydrate diet, although the low-glycemic-index diet did reduce post-meal glucose levels and C-reactive protein.

Background

For many years, a high-fat, low-carbohydrate diet was recommended for type 2 diabetics.  Then in 1979 the American Diabetes Association recommended a high-carb, low-fat diet.  Later, the ADA allowed more fat, mostly monounsaturated. 

The experts are still debating how much and what kind of carbohydrate people with diabetes should eat.  Recent years have seen a trend towards lower carbohydrate intake and lower-glycemic-index eating.  Much of the supportive evidence we have is based on short-term studies – six to 12 weeks. 

A Cochrane review in 2004 concluded that there was no high-quality data on the effectiveness of dietary treatment of diabetes.

The authors of the Canadian study at hand wrote:

Although almost everyone would agree that diet is the cornerstone of diabetes therapy, there is marked disagreement about what kind of dietary advice is best, particularly with respect to dietary carbohydrate.

We can put a man on the moon, but still aren’t sure what’s the best diet for people with diabetes despite years of experience and experimentation.

The Canadian researchers aimed to compare the effects of altered glycemic index and amount of carbohydrate on hemoglobin A1c, blood glucose, lipids, and C-reactive protein in men and women with type 2 diabetes.

Methodology

162 subjects with mild diabetes, 35-75 years old, managed by diet alone, were randomly assigned to one of three diet groups:

  1. high-carb, high-glycemic-index (“high-GI“): 47% of calories from carb, 31% of cals from fat, glycemic index 63
  2. high-carb, low-glycemic-index (“low-GI“): 52% of cals from carb, 27% of cals from fat, glycemic index 55
  3. low-carb, high-monounsaturated fat (“low-CHO“): 39% of cals from carb, 40% of cals from fat, glycemic index 59

Average body mass index was 31 (mildly obese); average weight 83 kg (183 lb).  The study lasted one year, a major strength of the study.

Results One Year Later

Hemoglobin A1c rose from 6.1% to 6.3%, with no difference between the various diet groups.  There were no differences in insulin levels, whether fasting or two hours after an oral glucose tolerance test.  Blood sugar levels after a glucose tolerance test were 7% lower with the low-GI diet compared to the other diet groups.  No difference in LDL cholesterol levels.  Little effect on triglycerides and HDL cholesterol.  No differences in weight.  C-reactive protein in the high-GI group fell from3.34 mg/L to 2.75.  C-reactive protein in the low-GI group fell from 2.64 to 1.95.  [All these C-reactive protein readings are in the normal range.]        

Comments

Nearly all the people with diabetes I encounter are very different from this study cohort: they are on drug therapy for diabetes.  So the results here don’t  necessarily apply to the more typical cases of moderate or severe diabetes that require one or more glucose-control drugs. 

Low-carb diet advocates can justifiably argue that the carb intake was still too high, and that’s why their numbers weren’t better.  Vernon and Eberstein in their book, Atkins Diabetes Revolution, note that many people with type 2 diabetes will have to limit carboydrates (“net carbs”) to 40-60 grams a day.  In the study at hand, the low-carb diet aimed for 39% of calories from carbohydrates.  On a 2000-calorie diet, that’s 195 grams – a far cry from 60 grams.      

Low-Gi advocates also can justifiably argue that the glycemic index was not low enough to make a difference.  The researchers admit that the test diet reductions in carb intake and glycemic index were “modest.”  Perhaps they thought that more drastic reductions were unsustainable.

Attempts to control diabetes with low-carb or low-glycemic-index eating should make more dramatic changes.

The low-glycemic-index diet lowered two-hour glucose levels on the glucose tolerance tests.  The authors state that this parameter is a better indicator of heart disease risk – lower in this case – than are fasting glucose levels.  Findings suggests improvements in insulin resistance and/or pancreas beta cell function.  This finding may have no real-world clinical significance: remember that hemoglobin A1c levels were the same across all groups. 

The changes in C-reactive protein just don’t seem clinically significant to me (nor to an editorialist in the same journal issue).

The aforementioned editorialist, Dr. Xavier Pi-Sunyer, had an interesting comment:

This finding suggests that we must be careful about disrupting subjects’ or patients’ diets with radical , doctrinaire changes that may actually be counterproductive.  Furthermore, the diets had carbohydrate contents that varied from 39% to 52% of energy intake, and yet this variability had no effect on the subjects’ HbA1c.  This finding confirms previous reports that the proportion of carbohydrate in the diet is not very important in determining the concentration of fasting blood glucose and that variations of 10% to 15% of total calories make little difference to overall control in patients with early type 2 diabetes.

I would emphasize “. . . in patients with early type 2 diabetes.”

A Mediterranean-style diet, then, could be just as effective as, if not better than, all the other “diabetic diets” out there.

Steve Parker, M.D.

References:  Wolever, Thomas, et al.  The Canadian Trial of Carbohydrates in Diabetes (CCD), a 1-y controlled trial of low-glycemic-index dietary carbohydrate in type 2 diabetes: no effect on glycated hemoglobin but reduction in C-reactive protein.  American Journal of Clinical Nutrition, 87 (2008); 114-125.

Additional Resource:  Michael R. Eades, M.D.  Making worthless data confess.  The Blog of Michael R. Eades, December 13, 2008.  Accessed July 10, 2009.  [Highly critical analysis from a leading low-carb, high-protein advocate.]

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July 5, 2009 · 2:00 AM

ADA Now Says Low-Carb Diets OK for Overweight Type 2 Diabetics

CB037166Eighty-five percent of type 2 diabetics are overweight or obese.  Overweight either causes or aggravates many cases of diabetes.

For the last quarter-century, many U.S. government agencies and healthcare organizations have advocated a low-fat diet for overweight people, including type 2 diabetics.  Recent studies have documented that low-carbohydrate diets can also be effective in weight loss.  Low-carb diets replace carbohydrates with either fats or proteins, or both.  The A to Z Weight Loss Study compared the Atkins, Ornish, LEARN, and Zone diets in 311 overweight pre-menopausal women.  The Atkins group tended to lose a bit more weight. Changes in lipid profiles, waist-hip ratios, fasting insulin and glucose levels, blood pressure, and percentage of body fat were comparable or better with Atkins versus the other diets.

The Amerian Diabetes Association now gives the go-ahead for use of low-carb diets as a weight-control method for type 2 diabetics.  Previously, the organization had recommended against diets that restrict carbohydrates to less than 130 grams daily.  (A baked potatoe without the skin has 30 grams.)  Understand that the ADA does not endorse low-carb diets for weight loss or diabetes management.  They simply say that either low-carb or low-fat calorie-restricted diets might be effective for up to one year.

I caution you that low-carb diets may be deficient in fiber, minerals, vitamins, and phytonutrients that may be very beneficial in terms of long-term health and longevity.

The tide has been turning against low-fat diets for the last six years.

Steve Parker, M.D.

Reference: American Diabetes Association.  Clinical Practice Recommendations 2008.  Diabetes Care, 31 (2008): S61-S78.

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