Dietary carbohydrate restriction as the first approach in diabetes management

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Dietary carbohydrate restriction as the first approach in diabetes management: Critical review and evidence base

Richard D. Feinman Ph.D., Wendy K. Pogozelski Ph.D., Arne Astrup M.D., Richard K. Bernstein M.D., Eugene J. Fine M.S., M.D., Eric C. Westman M.D., M.H.S., Anthony Accurso M.D., Lynda Frassetto M.D., Barbara A. Gower Ph.D., Samy I. McFarlane M.D., Jörgen Vesti Nielsen M.D.,Thure Krarup M.D., Laura Saslow Ph.D., Karl S. Roth M.D., Mary C. Vernon M.D., Jeff S. Volek R.D., Ph.D., Gilbert B. Wilshire M.D., Annika Dahlqvist M.D., Ralf Sundberg M.D., Ph.D., Ann Childers M.D., Katharine Morrison M.R.C.G.P., Anssi H. Manninen M.H.S., Hussain M. Dashti M.D., Ph.D., F.A.C.S., F.I.C.S.,
Richard J. Wood Ph.D., Jay Wortman M.D., Nicolai Worm Ph.D.

A b s t r a c t

The inability of current recommendations to control the epidemic of diabetes, the specific failure of the prevailing low-fat diets to improve obesity, cardiovascular risk, or general health and the persistent reports of some serious side effects of commonly prescribed diabetic medications, in combination with the continued success of low-carbohydrate diets in the treatment of diabetes and metabolic syndrome without significant side effects, point to the need for a reappraisal of dietary guidelines. The benefits of carbohydrate restriction in diabetes are immediate and well documented. Concerns about the efficacy and safety are long term and conjectural rather than data driven. Dietary carbohydrate restriction reliably reduces high blood glucose, does not require weight loss (although is still best for weight loss), and leads to the reduction or elimination of medication. It has never shown side effects comparable with those seen in many drugs. Here we present 12 points of evidence supporting the use of low-carbohydrate diets as the first approach to treating type 2 diabetes and as the most effective adjunct to pharmacology in type 1. They
represent the best-documented, least controversial results. The insistence on long-term randomized controlled trials as the only kind of data that will be accepted is without precedent in science. The seriousness of diabetes requires that we evaluate all of the evidence that is available. The 12 points are sufficiently compelling that we feel that the burden of proof rests with those who are opposed.
 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND

“At the end of our clinic day, we go home thinking, “The clinical improvements are so large and obvious, why don’t other doctors understand?” Carbohydrate restriction is easily grasped by patients: Because carbohydrates in the diet raise the blood glucose, and as diabetes is defined by high blood glucose, it makes sense to lower the carbohydrate in the diet.

By reducing the carbohydrate in the diet, we have been able
to taper patients off as much as 150 units of insulin per day in
8 days, with marked improvement in glycemic control and even
normalization of glycemic parameters.”
dEric Westman, MD, MHS [1].

Introduction
Reduction in dietary carbohydrate as a therapy for diabetes has a checkered history. Before and, to a large extent, after the discovery
of insulin, it was the preferred therapeutic approach [2]. Only total reduction in energy intake was comparable as an effective dietary intervention. The rationale was that both type 1 and type 2 diabetes represent disruptions in carbohydrate metabolism. The most salient feature of both diseases is hyperglycemia and the intuitive idea that reducing carbohydrate would ameliorate this symptom is borne out by experiment with no significant exceptions.

Two factors probably contributed to changes in the standard approach. The ascendancy of the low-fat paradigm meant that the fat that would replace the carbohydrate that was removed was now perceived as a greater threat, admittedly long term, than the immediate benefit from improvement in glycemia.

The discovery of insulin may have also cast diabetes (at least type 1) as a hormone-deficiency disease where insulin (or more recent drugs) were assumed to be a given and dietary considerations were secondary. For these and other reasons, dietary carbohydrate holds an ambiguous position as a therapy.

Although low-carbohydrate diets are still controversial, they have continued to demonstrate effectiveness with little risk and good compliance. At the same time, the general failure of the low-fat paradigm to meet expectations, coupled with continuing reports of side effects of different drugs, indicates a need for reevaluation of the role for reduction in carbohydrate. The current issue seems to be whether we must wait for a long-term randomized controlled trial (RCT) or whether we should evaluate all the relevant information. Practical considerations make it virtually impossible to fund a large study of nontraditional approaches. In any case, the idea that there is one kind of evidence to evaluate every scientific question is unknown in any science. Here we present 12 points of evidence supporting the
use of low-carbohydrate diets as the first approach to treating type 2 diabetes and as the most effective adjunct to pharmacology in type 1. They are proposed as the most well-established, least controversial results. It is not known who decides what constitutes evidence-based medicine but we feel that these points are sufficiently strong that the burden of proof rests on critics. The points are, in any case, intended to serve as the basis for improved communication on this topic among researchers in the field, the medical community, and the organizations creating dietary guidelines. The severity of the diabetes epidemic warrants careful and renewed consideration of our assumptions about the diet for diabetes.

12 Points of evidence

Point 1. Hyperglycemia is the most salient feature of diabetes.
Dietary carbohydrate restriction has the greatest effect on
decreasing blood glucose levels

Point 2. During the epidemics of obesity and type 2 diabetes, caloric increases have been due almost entirely to increased carbohydrates

Point 3. Benefits of dietary carbohydrate restriction do not require weight loss

Point 4. Although weight loss is not required for benefit, no dietary intervention is better than carbohydrate restriction for weight loss

Point 5. Adherence to low-carbohydrate diets in people with type 2 diabetes is at least as good as adherence to any other dietary interventions and is frequently better.

Point 6. Replacement of carbohydrate with protein is generally beneficial.

Point 7. Dietary total and saturated fat do not correlate with risk for cardiovascular disease.

Point 8. Plasma saturated fatty acids are controlled by dietary carbohydrate more than by dietary lipids.

Point 9. The best predictor of microvascular and, to a lesser extent, macrovascular complications in patients with type 2 diabetes, is glycemic control (HbA1c).

Point 10. Dietary carbohydrate restriction is the most effective method (other than starvation) of reducing serum TGs and increasing high-density lipoprotein.

Point 11. Patients with type 2 diabetes on carbohydrate-restricted diets reduce and frequently eliminate medication. People with type 1 usually require lower insulin.

Point 12. Intensive glucose lowering by dietary carbohydrate restriction has no side effects comparable to the effects of intensive pharmacologic treatment.

Discussion

The need for a reappraisal of dietary recommendations stems from the following:

1. General failure to halt the epidemic of diabetes under current guidelines.
2. The specific failure of low-fat diets to improve obesity, cardiovascular risk, or general health (points 1 and 4).
3. Constant reports of side effects of commonly prescribed diabetic medications, some quite serious (points 12).
4. Most importantly, the continued success of low carbohydrate diets to meet the challenges of improvement in the features of diabetes and metabolic syndrome in the absence of side effects.

The benefits of carbohydrate restriction are immediate and well documented. Concerns about the efficacy and safety of carbohydrate restriction are long term and conjectural rather than data driven. Most objections stem from the proposed dangers of total or saturated fat embodied in the so-called diet-heart hypothesis. At this point, the diet-heart hypothesis has had a  record of very limited clinical or experimental success to support its position. The issue has become the subject of strong reaction in both the scientificliterature and the popular press (point 8)

It is well established that weight loss, by any method, is beneficial for individuals with diabetes. The advantages of a low carbohydrate approach are that, because of greater satiety  explicit calorie reduction on the part of the patient may not be required. There may be de facto reduction in calories without the need for replacement. The extent to which there is replacement, either fat or protein may be beneficial (points 4 and 6) although in practice, fat is recommended unless there is already lower protein. Concerns about high protein in carbohydrate restriction have been raised but, except for those people with existing kidney disease, none has ever been demonstrated. Protein also tends to a stable self-limiting part of the diet. Perhaps most important, if carbohydrate is low, glycemic control and other physiologic parameters are improved even if weight loss is not accomplished (point 3).

Finally, it should be recognized that the use of low carbohydrate diets is not a recent experiment and may well approximate the diet used by much of humanity for tens of thousands of years before the rise of agriculture. Current knowledge dictates that carbohydrate restriction should be a default treatment for type 2 diabetes and a default adjunct therapy for type 1. Given the superior outcomes of carbohydrate restricted diets, patients should not be discouraged from adhering to them as is frequently observed. They should, in fact, be encouraged to follow this approach.

The 12 points of evidence represent the best investigated and least conjectural ideas on diabetes. It is unlikely that one dietary strategy, any more than one kind of pharmacologic treatment will be best for all individuals. Patients can refuse medication or opt out of surgery, but they cannot not be on a diet and low carbohydrate is the reasonable place to start.

We recognize that there are many complications and issues that are still not understood, however, we have tried to isolate the factors that have the fewest contradictions. This review emphasized the most obvious principles.

Conclusion and recommendations

What evidence would be required to change the current recommendations for dietary treatment in diabetes? Evidence basedmedicine tends to emphasize RCTs as a gold standard. Such absolute requirements, however, are unknown in any scientific discipline. As in a court of law, science admits whatever evidence is relevant. Following the legal analogy, one has to ask: Who decides on the admissibility of the evidence? The parody by Smith and Pell has been described as both funny and profound in illustrating how there is not a single type of experiment that fits every scientific question. Given the current state of research funding and the palpable bias against low carbohydrate approaches, it is unlikely that an RCT can be performed that will satisfy everybody.

The seriousness of diabetes suggests that we have enough evidence of different types to reevaluate our current recommendations for treatment. This review has described 12 points of evidence based on published clinical and experimental studies and the experience of the authors. The points are supported by established principles in biochemistry and physiology and emphasize that the benefits are immediate and documented while the concerns about risk are conjectural and long term.

We would recommend that government or private health agencies hold open hearings on these issues in which researchers in carbohydrate restriction can make their case. We think that traditional features of the analysis of evidence such as vigorous cross-examination should be part of the process. We suggest that open discussion with all sides contributing will be valuable. The seriousness of diabetes suggests that a bench decree will be inappropriate.

 

 

 

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