Does the Atkins Diet Increase Cardiovascular Risk?
In short, the answer is not clear. But a recent study suggests it might.
The Atkins diet is higher in saturated fat (and probably cholesterol, too) than standard American fare. It’s the classic low-carbohydrate diet. Current dietary dogma is that high intake of saturated fat promotes atherosclerosis - hardening of the arteries - which in turn leads to premature heart attacks, strokes, and death. Whether related or not, it’s pretty clear that higher saturated fat intake leads to higher blood cholesterol levels. This is a major concern about the Atkins diet and other low-carb plans among traditional medical practitioners and dietitians.
The postulated relationship between high dietary saturated fat (and cholesterol) and higher rates of atherosclerotic complications is often called the Diet-Heart Hypothesis.
The aforementioned study compared effects of the Atkins diet, South Beach diet, and Ornish diet in healthy people. Fat content of the diets was 50% (in Atkins), 30% (South Beach), and 10% (Ornish). Researchers wanted some idea of how the diets affect specifice cardiovascular risk factors in the maintenance phase of these diets.
Methodology
The 18 healthy study participants were in the normal weight range (average body mass index 22.6). Participants tried each of the three diets for four weeks. So they served as their own controls.
In between diet runs, participants went back to their usual dietary patterns for four weeks. Weight loss was not a goal; adherence to the specified diets was.
At the start and end of each four-week diet, researchers measured cholesterol levels, C-reactive protein, and a test of blood vessel functioning (brachial artery testing of flow-mediated vasodilation). Three-day food records were examined at the end of each diet phase to check for compliance.
Results
Participants ate about 30 grams of saturated fat daily on the Atkins diet, about 14 grams on South Beach, and 3 grams on Ornish.
The 8% increase in LDL cholesterol seen with Atkins was not statistically significant. [This means there is a good chance the 8% increase was due to chance alone rather than a true effect of the Atkins diet.]
LDL cholesterol decreased by 12% on South Beach, and by 17% on Ornish. These were statistically significant.
As saturated fat intake increased, flow-mediated vasodilation decreased (p=0.016, meaning statistically significant). Compared with Atkins, the other groups showed statisically significant decreases in apolipoprotein B.
Conclusion of the Researchers
These data suggest that during weight maintenance, less favorable biological effects are observed during a simulated, high-fat Atkins diet when compared to the South Beach and Ornish diet. The findings support additional study in subjects with visceral obesity and the metabolic syndrome, in whom an increased risk of coronary disease at baseline may be accentuated with chronic consumption of a diet that exhibits unfavorable effects on lipids and endothelial function.
Comments from Atkins Nutritionals (as reported by HealthDay on April 1, 2009)
Representatives from Atkins Nutritionals took exception with the study, however. In a statement, Colette Heimowitz, vice president of nutrition and education at Atkins Nutritionals, noted that, “given the short duration of his study, the very small sample size and the weak correlations, drawing conclusions about possible long-term health risks tied to fat consumption in the maintenance phase of any weight control program is not good science.” She also questioned whether the participants were actually following a true Atkins diet.
My Comments
I regret that I only have access to the article abstract, not the entire article. C-reactive protein results were not reported in the abstract, nor were HDL and total cholesterol levels.
The observed blood lipid changes would tend to favor the South Beach and Ornish diets over Atkins, in terms of future cardiovascular health. But Heimowitz is right: this was a very small, short-term study, so it’s difficult to apply the results to common clinical situations. There is ligitimate cause for concern, however.
If the Diet-Heart Hypothesis is wrong, then the observed lipid changes don’t matter.
I’m not very familiar with brachial artery testing of flow-mediated vasodilation. It would make sense that “healthy vessel dilation is important to proper blood flow” (from the HealthDay article). But that doesn’t mean it is so.
South Beach’s maintenance phase is similar to the traditional Mediterranean diet, although lower in carbohydrates and higher in protein. [If interested in my review of South Beach, click here.]
Last time I checked, the Ornish diet was vegetarian.
Hundreds of thousands of people have been eating low-carb/Atkins-style for years. What we need is a study comparing their long-term health and longevity outcomes with a group of people following a standard American diet.
The United States’ National Institutes of Health should fund it.
I don’t care if low-carb eating outperforms the Mediterranean, DASH, Ornish, paleo, vegetarian, Dr. Siegal’s Cookie Diet, or any other diet. Actually, I do care; I want to know. My ego can easily handle it if Atkins beats Mediterranean.
Just show me the data.
References:
Miller, Michael, et al. Comparative Effects of Three Popular Diets on Lipids, Endothelial Function, and C-Reactive Protein During Weight Maintenance. Journal of the American Dietetic Association, 109 (2009): 713-717.
Moens, A.L., et al. Flow-mediated vasodilation: a diagnostic instrument, or an experimental tool? Chest, 127 (2005): 2,254-2,263.
April 7th, 2009 at 10:01 am
Thanks for the great analysis. There are so many food and diet studies, it’s difficult to keep up. I have a bias against the Atkins diet because it just doesn’t make sense to me.
April 10th, 2009 at 5:29 am
Dr. Hubbard,
I used to be biased against low carb too, until I read about it. Hopefully you would be open to reading Good Calories, Bad Calories, by Taubes. It really opened my eyes.
April 10th, 2009 at 6:46 am
Agree we need a long term study, because the long term study that we have had in place over the past 30 years has clearly not gone well.
Here is a study from the journal Lipids from 2 years ago which determined that a higher saturated fat diet results in lower levels of saturated fatty acids in the blood, as well as reduced inflammation markers. YOU ARE WHAT YOUR BODY DOES WITH WHAT YOU EAT — eating fat does not make you fat, eating carbohydrate tells your body to start packing away fat for winter.
April 10th, 2009 at 7:13 am
Sorry to flood your blog but I forgot the link to the journal.
http://www.ncbi.nlm.nih.gov/pubmed/18983673?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_PMC&linkpos=2&log$=citedinpmcarticles&logdbfrom=pubmed
April 10th, 2009 at 10:51 am
No problem, Matt! I appreciate the effort. I think you may have used the wrong link to the article. Consider this tinyurl:
http://tinyurl.com/cyo7hs
It should take you to the abstract of “Comparison of low fat and low carbohydrate diets on circulating fatty acid composition and markers of inflammation” by Forsythe et al, in Lipids, 43 (2008): 65-77. Authors are at the U. of Connecticut.
Their summary: “…a very low carbohydrate diet resulted in profound alterations in fatty acid composition and reduced inflammation compared to a low fat diet.”
July 16th, 2009 at 7:13 am
Dr. Parker - thanks so much for the helpful information. I’ve had difficulty finding good info on this subject.
I have spend several years using (and then not using) a high protein/ low carb diet. I am currently on it now to lose some weight. During times when I used it, my cholesterol was good. 178/65/113. Cholesterol did increase when off it, on a high carb eating pattern. (We saw increases in LDL and decreases in HDL.)
My diet differs from Adkins in that I consume very lean meats & low-fat, high protein foods, so it is not that high in fat. I don’t eat a lot of cheese, or rich sauces.
I’ve been concerned about the statements of Adkins causing heart problems, so am currently having my heart-health checked. I wonder if my modification to Adkins makes it more healthy. I know it makes me feel so much better.
After I’ve reduced my weight back to a healthy place, I will probably switch to something more similar to the Mediterranian diet, because it seems like a healthier, more well-rounded diet. But in a state of being highly-metabolically resistant currently, I have not been able to lose weight on it.
Please continue to research these things as there is so many conflicting medical reports here in the US pertaining to healthy eating & obesity.
March 10th, 2010 at 7:47 pm
The latest Atkins’ book by Drs. Eric Westman, Jeff Volek, and Stephen Phinney cites over 200 (I believe) articles that support a low-carb/high-fat diet. I’m not savvy enough to ascertain what kind of studies were done - randomized, repeated, with controls or whatnot. I suspect that if one loses weight (and perhaps exercises) that CAD risk factors would go down. But does that really mean the arteries are not plaqueing while reducing weight?
I wish I could recall the study…who, when, where…but within the last 12 months or so a researcher (biochemist???) was involved in a study where rats were fed a low-carb/high-fat diet. The rats showed remarkably improved triglycerdies and HDL. However, when the arteries of the rats were examined, their arteries had significantly plaqued during the diet. The researcher himself had been following a low-carb diet and immediately abandoned it. Remember that news article?
March 10th, 2010 at 9:44 pm
Hi, LynneP.
That article doesn’t ring a bell. It does point out the very real possibility that just because some heart disease risk factor improves with intervention, actual disease rates are another thing altogether.
I try to focus on human studies, as opposed to lab animals, when able. I also like to see hard clinical endpoints such as heart attacks, strokes, cancer, overall death rates.
The new book by Westman, Phinney, and Volek has several chapters discussion the science of low-carb eating. Here’s a link to my formal review of the book:
http://diabeticmediterraneandiet.com/2010/03/07/book-review-the-new-atkins-for-a-new-you/
March 12th, 2010 at 8:13 pm
Thanks for the link, Dr. Parker. I found your review very interesting. By the way, I ordered your book and can’t wait to read it! I love Mediterranean food. Very interested in the latest science.
March 12th, 2010 at 8:20 pm
Hi Dr. Parker,
I found a link regards the research on mice fed a low-carb diet. The research was carried out at Beth Israel Hospital in the Rosensweig cardiology unit. Dr. Anthony Rosensweig, director of the unit, was on a low-carb diet himself and abandoned it after results were revealed in the mice.
http://www.saga.co.uk/health/news/low-carb-diets-may-clog-up-arteries-031.asp
March 13th, 2010 at 9:01 am
Thank you for that link, LynneP. Hope you like the book.
I imagine that mice in a natural habitat would eat a high-carb diet, and relatively high-fat if they can find seeds and nuts. If they don’t do well on a low-carb diet, the lesson might be that we (and mice) should eat what we are adapted to eat, not something totally artificial.
Also note that different strains of lab mice may respond differently to any given condition.
-Steve