Friday, September 30, 2005

Dietary Debate: Dogma, Opinion or Evidence

As difficult as it is to let go of old habits and engrained beliefs, it is something we must do if we are going to tackle the very real issue of obesity in the United States. For more than thirty years we have been entrenched in the belief that dietary fats are the enemy and that strict limitation is the key to health and weight management.

While it is easy to assume that the general population simply ignores the recommendations to their own detriment, it is much harder to ignore facts and hard data.

In recent months a number of scientific journals have published reviews, editorials and commentaries about carbohydrate restriction as a potential approach for the obese and those with Type II Diabetes. Each has a common thread - the dietary recommendations today lack sufficient scientific evidence to support them.

What? Could it be that the recommendations we have in place today are no more than a collection of misinterpreted data and opinions?

How about we look at one of the recent articles.

In the September issue of Endocrine Today, Samy McFarland, MD, MPH provides a guest editorial titled "Dietary recommendations for people with diabetes: Time to reduce the carbohydrate loads. Recommendations should take account of current evidence for carbohydrate restriction" (To read the article you will need to register. Registration is free.)

In it, he starts by building the case for alternative options based on cold hard data.

"According to the USDA Continuing Survey of Food Intakes by Individuals (CSFII), the absolute amount of fat as well as saturated fat consumed has significantly decreased during the obesity epidemic. From a public health perspective, this represents a failure of low-fat/high-carbohydrate strategies to curb the obesity epidemic or at least to negate the other contributing factors such as sedentary lifestyle."

He then continues to explore the impact of traditional low-fat recommendations in those with diabetes, examining reports by his own group and others, including national data.

" a national survey by our group across several health care delivery systems, 3,678 records of diabetic patients were examined with only one-third of the patients achieving HbA1c of less than 7%.

"These data, from 2002, are consistent with data from the Third National Health and Nutrition Examination Survey (NHANES III, conducted 1988-1994) and NHANES 1999-2000. Collectively, these data show a consistent pattern of overwhelming obesity and poor control of glycemia and dyslipidemia in the diabetic population despite decades of low-fat recommendations."

He believes this hard data points to the need explore alternative dietary approaches. High on the list of alternatives is carbohydrate restriction. His reasoning? "... the current evidence for its effectiveness."

First up in the current evidence - two large, long-term studies - the Nurses Health Study and the Health Professional Follow-Up Study. Both studies show that dietary carbohydrate intake (measured as glycemic load) is linked with the risk of type 2 diabetes and CVD. The use of glycemic load as a measure helps to determine the quality and quantity of the carbohydrate in the overall diet.

He continues with current prospective cohort studies which show worsening of glycemic control and dyslipidemia in diabetic patients with a high-carbohydrate diets, while showing how carbohydrate restriction may actually reverse these serious metabolic abnormalities.

He even brings to light the fact that these data were acknowledged during the development of the 2005 Dietary Guidelines for Americans, but were quickly dismissed on the basis of “concern that increased fat intake in ad libitum diets may promote weight gain.”

He continues with, "[t]his concern, however, has not been substantiated, and at least two studies show that low-carbohydrate diets are not associated with increase in dietary intake of proteins or fats presumably due to effect of these diets on satiety."

Throughout the rest of the editorial, he explores each of the benefits noted in various studies - glycemic control, reduction of postprandial hyperglycemia, improvements in dyslipidemia, increased insulin sensitivity, and reduction in antidiabetic medication in diabetics.

Sadly, he felt he needed to state within his editorial that "Because of the somewhat contentious atmosphere surrounding this subject, I feel obligated to point out that I am not supported or affiliated in any way with any individual or entity that promotes a particular diet."

Isn't this about science - the evidence and hard data? While I wish he didn't need to make such a statement, I understand his reasons. The current atmosphere around anyone advancing the scientific evidence that supports carbohydrate restriction today is indeed critical and filled with suspicion of influence from vested-interest parties; as if the science itself is not main driving force.

After his disclaimer, he states, "This editorial is intended to stimulate a scientific and scholarly debate that will lead to more effective dietary recommendations that take account of the current evidence for carbohydrate restriction. This will thereby provide more options to our patients and our society at large in the current struggle with the epidemic of obesity and diabetes, which is claiming thousands of lives daily and leaving many people disabled."

He wraps up the editorial quite nicely with "It is also important to establish guidelines for carbohydrate restriction, especially emphasizing the use of mono- and polyunsaturated fats as a way to achieve caloric balance, since these have been inversely linked with CVD risk. I also believe that clinical trials need to be conducted using graded levels of carbohydrate restriction and fat intake, with special emphasis on unsaturated fats, to examine their effects on weight loss, glycemic control, insulin resistance and CVD. An open-minded analysis of such experiments is needed to resolve the present controversy about optimal dietary recommendations for patients with diabetes."

Can you hear me saying "Yeah!"

For years I've been saying "we need to be strictly committed to the scientific evidence" to establish evidence-based recommendations.

When the 2005 Dietary Guidelines for Americans were released, I was highly critical of the lack of references to the data that was supposedly used to formulate the recommendations.

I've continued to advocate for more individualized approaches and options in the "toolbox" and will continue to do so in the future. We know there is no one dietary approach that works for everyone. It is high time the medical and scientific communities publically acknowledged such and started the process to develop clinical guidelines for the various approaches that are supported by evidence and hard data. Such guidelines would provide healthcare professionals with useful options and tools for their patients - each of whom is an individual in need of a "diet" that is best suited for their individual needs!

After you've had some time to read the above editorial, you might want to write to the Editor of Endocrine Today to express your appreciation for publishing what is, sadly, a highly contentious issue!

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