Major Studies Demonstrating Safety and Efficacy of Low Carb Diets
You may have been told that low carb diets are "dangerous" and can cause heart disease. This is because for many years it was a matter of religious belief that the Low Fat diet reduced heart disease and since people with diabetes are prone to get heart disease, the assumption was that anything but a low fat diet would be dangerous for them.
This turns out to be the single most damaging non-truth ever told to people with diabetes.
$415 Million Dollars and 49,000 Women Show No Benefits to the Low Fat Diet
In 2006, a $415 Million dollar, eight year study of almost 49,000 middle aged women, which had been run to prove the health benefits of the Low Fat diet, was forced to make these conclusions:
"Over a mean of 8.1 years, a dietary intervention that reduced total fat intake and increased intakes of vegetables, fruits, and grains did not significantly reduce the risk of CHD, stroke, or CVD in postmenopausal women."
Low-Fat Dietary Pattern and Risk of Cardiovascular Disease
In short, none of the heart health claims for the Low Fat diet held up. Though die hards immediately announced that maybe further study of the Low Carb fad diet would still show results in some OTHER group, no rational person can still believe that the very high carb, Low Fat diet has any health benefits.
The same study also found that "In this study, a low-fat dietary pattern intervention did not reduce the risk of colorectal cancer in postmenopausal women during 8.1 years of follow-up." And, "Among postmenopausal women, a low-fat dietary pattern did not result in a statistically significant reduction in invasive breast cancer risk over an 8.1-year average follow-up period."
Low-Fat Dietary Pattern and Risk of Colorectal Cancer
Low-Fat Dietary Pattern and Risk of Invasive Breast Cancer
Low-Fat Dietary Pattern and Risk of Cardiovascular Disease
The single "positive" finding for this entire study was that the Low Fat Diet did not appear to cause significant weight gain in post-menopausal women. This sounds like good news until you realize that it didn't cause weight loss, either!
Studies Show That Low Carb Dieting Works and Improves Cardiac Risk Factors
Just as the health benefits of the Low Fat diet were being revealed as fantasy, a wave of good, peer reviewed studies of the Low Carb diet found that it was more effective in causing weight loss than the Low Fat diet, that it improved Triglycerides and the Framingham Cardiac Risk Rations, and that contrary to previous belief, eating protein did not appear to damage kidneys in people who did not already have significant kidney damage.
Let's take a quick look at some of these studies.
A 2005 Comparison of Diets Shows Low Carb is Safer than Low Fat Ornish but None of the Diets Does Much for Weight
Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk Reduction. A Randomized Trial.Michael L. Dansinger, MD; Joi Augustin Gleason, MS, RD; John L. Griffith, PhD; Harry P. Selker, MD, MSPH; Ernst J. Schaefer, MD
JAMA. 2005;293:43-53.
http://jama.ama-assn.org/cgi/content/full/293/1/43
In this study, "A total of 160 participants were randomly assigned to either Atkins (carbohydrate restriction, n=40), Zone (macronutrient balance, n=40), Weight Watchers (calorie restriction, n=40), or Ornish (fat restriction, n=40) diet groups. After 2 months of maximum effort, participants selected their own levels of dietary adherence."
The group put on the Atkins, unfortunately, started out with significantly worse blood sugars than those put on the other diets, with twice as many people having abnormally high fasting glucose in this group as those in the low fat diet groups.
None of the groups of dieters stuck to their diets very well, and the weight loss results for all the diets were similar. The Low Carb diet, made modest improvements in the HDL, triglycerides, and Framingham ratios. The ultra Low fat Ornish diet worsened cardiovascular risk factors.
But Hold On If You Are Female, the Low Carb DOES Beat the Others for Weight Loss
Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women.The A TO Z Weight Loss Study: A Randomized Trial.Christopher D. Gardner, PhD; Alexandre Kiazand, MD; Sofiya Alhassan, PhD; Soowon Kim, PhD; Randall S. Stafford, MD, PhD; Raymond R. Balise, PhD; Helena C. Kraemer, PhD; Abby C. King, PhD.
JAMA. 2007;297:969-977.
http://jama.ama-assn.org/cgi/content/abstract/297/9/969
This was a "twelve-month randomized trial conducted in the United States from February 2003 to October 2005 among 311 free-living, overweight/obese (body mass index, 27-40) nondiabetic, premenopausal women."
The conclusion: In this study, premenopausal overweight and obese women assigned to follow the Atkins diet, which had the lowest carbohydrate intake, lost more weight and experienced more favorable overall metabolic effects at 12 months than women assigned to follow the Zone, Ornish, or LEARN diets. While questions remain about long-term effects and mechanisms, a low-carbohydrate, high-protein, high-fat diet may be considered a feasible alternative recommendation for weight loss.
What if You Have Diabetes?
Sadly, 99% of the money "researching" diabetes goes into studies run by drug companies to promote their drugs. The ADA is still violently against low carb diets, despite the research showing them safe and effective, which probably has a chilling effect on the choice researchers make of what to study.
One group of researchers, headed by Dr. Yancy from Duke University, has done some work on the effects of Low Carb dieting on diabetes.
William S Yancy, Jr, Marjorie Foy, Allison M Chalecki, Mary C Vernon, and Eric C Westman (2005). "A low-carbohydrate, ketogenic diet to treat type 2 diabetes". Nutrition & Metabolism 2005, 2:34doi:10.1186/1743-7075-2-34
http://www.nutritionandmetabolism.com/content/2/1/34
This as a small 16 week study of 28 participants who brought their mean A1c down from 7.5 ± 1.4% to 6.3 ± 1.0%.
The authors concluded, "LCKD [Low Carb Ketogenic Diet] improved glycemic control in patients with type 2 diabetes such that diabetes medications were discontinued or reduced in most participants. Because the LCKD can be very effective at lowering blood glucose, patients on diabetes medication who use this diet should be under close medical supervision or capable of adjusting their medication."
Other Studies of Very Small Groups Find the Low Carb Diet Dramatically Reduce Diabetic Blood Sugars
Here are some earlier studies that Dr. Yancy cited in his 2005 study. Most of these involve small samples, reflecting the difficulty of getting funding for studies that will enrich no drug company.
One study of 8 men with diabetes put on a low carb diet for five weeks found"A LoBAG [Low bioavailable Glucose--i.e. LOW CARB] diet ingested for 5 weeks dramatically reduced the circulating glucose concentration in people with untreated type 2 diabetes."
Effect of a High-Protein, Low-Carbohydrate Diet on Blood Glucose Control in People With Type 2 Diabetes.Mary C. Gannon, and Frank Q. Nuttall1, Diabetes 53:2375-2382, 2004
http://diabetes.diabetesjournals.org/cgi/content/full/53/9/2375
Another study of 10 obese men with diabetes put on a low carb diet for two weeks found "Mean 24-hour plasma profiles of glucose levels normalized, mean hemoglobin A1c decreased from 7.3% to 6.8%, and insulin sensitivity improved by approximately 75%. Mean plasma triglyceride and cholesterol levels decreased (change, -35% and -10%, respectively)."
http://www.annals.org/cgi/reprint/142/6/403.pdf
Effect of a Low-Carbohydrate Diet on Appetite, Blood Glucose Levels, and Insulin Resistance in Obese Patients with Type 2 Diabetes.Guenther Boden, MD; Karin Sargrad, MS, RD, CDE; Carol Homko, PhD, RN, CDE; Maria Mozzoli, BS; and T. Peter Stein, PhD.
Ann Intern Med. 2005 Mar 15;142(6):403-11
A Longer, Larger Study Still Finds Low Carb Diet Better for people with Diabetes Even Without Weight Loss
A longer larger study involved 132 obese adults 83% of whom had either diabetes or metabolic syndrome put half on a low carb diet and half on a "conventional weight loss diet."
The study found very slight differences in the weight loss provided by the two diets, which wasn't much, and as usual, people had difficulty staying on both diets for the year. However, the low carb diet was found to be much better for the people with diabetes.
To quote the published conclusions of this study: "As seen in the small group of persons with diabetes (n = 54) . . . hemoglobin A1c levels improved more for persons on the low-carbohydrate diet. These more favorable metabolic responses to a low-carbohydrate diet remained significant after adjustment for weight loss differences. Changes in other lipids or insulin sensitivity did not differ between groups.
In short, it didn't matter if the people with diabetes lost weight. Their blood sugars were better on the low carb diet and there was no worsening of cholesterol profiles.
The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomized trial.Stern L, Iqbal N, Seshadri P, Chicano KL, Daily DA, McGrory J, Williams M, Gracely EJ, Samaha FF. Ann Intern Med. 2004 May 18;140(10):778-85.
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=15148064
Finally, another small Swedish study of 16 obese people with diabetes found, "After 6 months a marked reduction in bodyweight of patients in the low-carbohydrate diet group was observed, and this remained one year later.... Large changes in blood glucose levels were seen immediately.
It concludes, "A low-carbohydrate diet is an effective tool in the treatment of obese patients with type 2 diabetes."
Lasting improvement of hyperglycaemia and bodyweight: low-carbohydrate diet in type 2 diabetes. A brief report.
Nielsen JV, Jönsson E, Nilsson AK. Ups J Med Sci. 2005;110(2):179-83.
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=16075898&dopt=AbstractPlus
Low Carbohydrate Diets and the Kidney
Many people believe that a Low Carb diet is a high protein diet, though in fact, it should be a High Fat diet. Now that we know that Low Fat diets fail to live up to their health claims, perhaps we can stop fearing the word "Fat" and tell the truth about what the Low Carb diet really is.
The Low Carb diet should have enough protein in it to fill your need to rebuild muscle tissue. If you are eating a very low carb diet, you need to eat enough protein to let the liver turn that protein into the carbohydrate you need to run your brain. How to calculate your actual need for protein on a low carb diet is discussed HERE.
However, if you are concerned about eating a moderate protein intake, you should know that a large study of 1624 women in the he Nurses Health Study has found that a high protein is not dangerous unless you already have kidney damage.
The authors of this study reported: "We observed no significant adverse renal effects of high protein consumption in women who had normal renal function at baseline. In addition, when we separately analyzed nondairy animal, dairy, and vegetable protein intake, we found no evidence of a detrimental effect of animal protein compared with vegetable protein."
However, they noet "We were also interested in the impact of dietary protein consumption in women with mild renal insufficiency. When we separately examined these women, we found that those who consumed the most protein had the greatest decline in estimated GFR."
This means that if you already have kidney damage you should replace dietary carbohydrates with fats, rather than protein. However, it is worth noting that this study was one where high protein was being eaten in the presence of high carbohydrate intake.
There is some anecdotal evidence that a very low carb diet with adequate protein is safe for people with early diabetic kidney disease. Dr. Bernstein discusses this topic at length in his book, Dr. Bernstein's Diabetes Solution.
There is no study that I can find looking at the impact of a moderate protein diet combined with very low carbohydrates on the kidney function of people with diabetes.
The Impact of Protein Intake on Renal Function Decline in Women with Normal Renal Function or Mild Renal Insufficiency
right arrow Eric L. Knight, MD, MPH; Meir J. Stampfer, MD, DrPH; Susan E. Hankinson, RN, ScD; Donna Spiegelman, ScD; and Gary C. Curhan, MD, ScD.Annals of Internal Medicine. 18 March 2003.Volume 138 Issue 6. Pages 460-467
http://www.annals.org/cgi/content/abstract/138/6/460
The Impact of Protein Intake on Renal Function Decline in Women with Normal Renal Function or Mild Renal Insufficiency
right arrow Eric L. Knight, MD, MPH; Meir J. Stampfer, MD, DrPH; Susan E. Hankinson, RN, ScD; Donna Spiegelman, ScD; and Gary C. Curhan, MD, ScD. Annals of Internal Medicine. 18 March 2003. Volume 138 Issue 6.Pages 460-467.
Low Carb Diet and the Brain
This study published in 2007 compared a Low Carb diet with a High Carb/Low fat diet. It studied 93 overweight or obese subjects (not diabetic) who ate a ketogenic diet for eight weeks.
The study concluded, "he LCHF diet resulted in significantly greater weight loss than did the HCLF diet (7.8 ± 0.4 and 6.4 ± 0.4 kg, respectively; P = 0.04). Both groups showed improvements in psychological well-being (P < 0.01 for time), with the greatest effect occurring during the first 2 wk, but there was no significant difference between groups. There were no significant between-group differences in working memory (P = 0.68), but there was a significant time x diet interaction for speed of processing (P = 0.04), so that this measure improved less in the LCHF than in the HCLF diet group."
In short, eating well below the 130 grams of carbs ignorant dietitians will tell you are essential for brain function works fine. Memory was not affected, and mood improved. Speed of processing "improved less" than it did on a low fat diet in this group. However, this may be because of the elevated blood sugar caused by the Low Fat diet. Over time, the damage caused by higher blood sugars to the brain, and the known association of high blood sugar with dementia would outweigh this very minor difference.
Note, also that the speed of processing did not decrease relative to baseline!
Low- and high-carbohydrate weight-loss diets have similar effects on mood but not cognitive performance. Angela K Halyburton, Grant D Brinkworth, Carlene J Wilson, Manny Noakes, Jonathan D Buckley, Jennifer B Keogh and Peter M Clifton.American Journal of Clinical Nutrition, Vol. 86, No. 3, 580-587, September 2007.
http://www.ajcn.org/cgi/content/abstract/86/3/580
The 10,000 Pound Gorilla of Nutritional Research: Gary Taubes' Book Good Calories, Bad Calories
If you are really interested in learning the whole ugly history of why modern nutritional "science" endorsed the low fat diet hypothesis in the absense of any rigorous research supporting its effectiveness either for fighting heart disease or causing weight loss, you must read Gary Taubes' book, published in October of 2007, Good Calories, Bad Calories . Taubes provides descriptions and analysis of hundreds of nutritiona studies performed since the 1940s, including many well-conducted studies whose results were suppressed because they didn't match what diet authorities thought the results should be. He also shows how many studies that were cited to support the low fat hypothesis actually did not prove what they were said to prove. While many reviewers have quibbled with a sentence here or there in Taubes' book, there is no way a thinking person can read it and not end up agreeing with is main point, which is that mainstream diet advice over the past fifty years has not been based on the findings of well conducted scientific research for reasons that have to do with power politics within science more than any other reason.
|
|
