This is a summary of a series of recent articles and letters in the journal Nutrition.
In short: the current guidelines to eat a low-fat (and therefore high-carb) diet and take drugs to treat diabetes was never based on solid science. The weight of the science actually supports a low-carb diet. In fact, the controversy over low-carb can be characterized as evidence on one side and dogma on the other.
Feinman’s review article
We’ll start off with a big review by a lot of experts. The title is “Dietary carbohydrate restriction as the first approach in diabetes management: Critical review and evidence base.” The lead author is Richard D. Feinman Ph.D and there are 26 others signed on. 1 The article itself is licensed CC BY-NC-ND.
The article is kicks off by reminding us that historically the preferred approach to diabetes therapy was low-carb eating and/or fasting, even after the discovery of insulin. The biggest factor in diabetes is excess blood sugar and eating less food, particularly less food rich in sugar (carbohydrates), immediately reduces blood sugar.
The introduction goes on to explain that low-carb has become controversial not because it became less effective, or because new or long-term side effects emerged, but rather because common thinking changed. A shift in focus from diet to drugs and the assumption that eating fat leads to heart disease has erected a barrier to acceptance of low-carb.
What follows are 12 points of evidence which are well established and non-controversial. It’s important to note that carbohydrate tolerance varies between individuals and what people mean by “low-carb” is inconsistent. 2
- High blood sugar is the most salient feature of diabetes. Eating less carbohydrates (which turn into blood sugar) has the greatest effect on decreasing blood sugar.
- During the epidemics of obesity and type 2 diabetes, the average number of calories people eat has increased. The increase has been almost entirely carbohydrates.
- Benefits of eating less carbs show up even if you don’t lose weight.
- Although weight loss is not required for benefit, nothing eaten is better than low-carb for weight loss.
- Adherence to low-carb diets in people with type 2 diabetes is at least as good as adherence to any other diet and is frequently significantly better.
- Replacement of carbohydrate with protein is generally beneficial.
- The amount of total and saturated fat eaten do not correlate with risk for cardiovascular disease.
- In fact, the amount of fat in blood is actually more strongly controlled by the carbs you eat.
- The best predictor of cardiovascular complications in patients with type 2 diabetes, is blood sugar control.
- Eating low-carb is the most effective method (other than fasting) of reducing triclycerides and increasing high-density lipoprotein.
- Patients with type 2 diabetes on low-carb diets reduce and frequently eliminate medication. People with type 1 usually require lower insulin.
- Intensively lowering blood sugar by eating low-carb has no side effects comparable to the effects of intensive drug treatment.
Additional statements from the paper:
- 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.
- 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.
- 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.
- It is unlikely that one dietary strategy, any more than one kind of pharmacologic treatment will be best for all individuals.
- Given the current state of research funding and the palpable bias against low-carb approaches, it is unlikely that a large, randomly controlled trial can be performed that will satisfy everybody.
Response by Nystrom & Quon
The copyright on Man Shall Not Live By Bread Alone doesn’t allow sharing beyond quotations.
- With the massive and rising epidemic of obesity driving type 2 diabetes and its cardiovascular complications in the United States and the developed world, it is abundantly clear that conventional treatments with acceptable adverse events are simply insufficient to treat and improve, let alone cure, diabetes.
- …low-fat diets have the unintended consequence of increasing intake of refined carbohydrates to replace calories contained in fat. This is harmful for patients with insulin resistance (IR) and impaired beta-cell function (i.e., insulin secretion), the sine qua non of type 2 diabetes.
- Interestingly, the concept of dietary carbohydrate restriction is not new but has been in existence for millennia.
The authors go on to respond to each of the 12 points, which I’ve paraphrased here:
- They say that some interventions “including insulin and hydration, among others” have larger effects on blood glucose than low-carb “in certain clinical contexts.”
- They say that “fat-phobic reasoning has likely contributed to, rather than opposed, abdominal obesity, dyslipidemia, and IR.”
- They say it is “absolutely true” that the benefits of low-carb do not require weight loss, but the same can be said for other interventions such as low-impact exercise, caloric restriction, and gastric bypass surgery.
- See 6
- See 6
- They make the general point that the real problem with dieting is short-term success followed by long-term failure due to the body’s physiological feedback systems returning to a set-point. They do agree that “the Atkins diet (high protein and fat, low carbohydrate) is more effective than a low-fat diet for initial weight loss and for maintaining weight loss up to 2 y with concomitant improvement of blood lipid levels.”
- See 8
- They agree that “low-fat diets have indeed been tested in large American outcome trials” with “no effect on the reduction of cardiovascular risk” and in fact “patients with established CVD experienced a significant increase in cardiovascular events.”
- They agree “there is certainly evidence to support this point.” I think they also point out that it’s not as simple as just looking at blood sugar in isolation.
- They say “this point may be true with respect to lifestyle interventions” but to not forget that drugs can help too.
- See 12
- They say “although points 11 and 12 are unequivocally true, the real question is whether dietary or lifestyle modification is appropriate as first-line therapy in patients with frank diabetes.” They say it “seems unwise” given issues with compliance.
Fenton’s etter to the Editor
A letter by Carol J. Fenton B.H.Sc. M.D. and Tanis R. Fenton Ph.D. R.D. F.D.C, in response to the original article, titled Dietary carbohydrate restriction: compelling theory for further research refers to the original article as “a novel approach.” They recommend “caution and exercising due diligence before recommending changes to treatment guidelines.” They agree that “dietary fat, except for trans-fat, is not as dangerous to health as was once thought.” Ultimately, they seem to be saying that only a randomized controlled trial (RCT) or two would be enough to justify making low-carb the default treatment for diabetes.
Dr. Feinman responded with a letter titled Carbohydrates for people with diabetes is not cautious. He clarifies that restricting carbohydrates is (emphasis his) the cautious approach to diabetes treatment given that diabetes is “a disease of carbohydrate intolerance”. Additionally, he points out that “most of the authors of our review have extensive experience treating patients with low-carb diets with clinical successes over dozens of years, totaling thousands of patients.”
He also points out that, unlike what the Fentons say, low-fat advice was not based on good science and that due diligence is required before continuing (emphasis his) the current guidelines.
He continues by pointing out that those who have received funding for RCTs have had the opportunity to include low-carb and have not done so.
Finally, Dr. Feinman wraps up with the speculation that “what is really bothering the Fentons, as it bothers my medical students, is the idea that a large part of the medical establishment has gotten things very wrong.”
- 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., Jorgen 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. ↩
- Very low-carb ketogenic diet (VLCKD) 20-50 grams per day or <10% total calories whether or not ketosis occurs | low-carb diet <130 grams per day or <26% total calories (which is the ADA’s recommended minimum) | moderate-carb diet 26-45% total calories (roughly the upper limit prior to the obesity epidemic) | high-carb >45% (ADA’s recommendation and roughly the average American diet) ↩