NEW ENGLAND JOURNAL OF MEDICINE
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Volume 355:1991-2002

November 9, 2006

Number 19


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Low-Carbohydrate-Diet Score and the Risk of Coronary Heart Disease in Women

Thomas L. Halton, Sc.D., Walter C. Willett, M.D., Dr.P.H., Simin Liu, M.D., Sc.D., JoAnn E. Manson, M.D., Dr.P.H., Christine M. Albert, M.D., M.P.H., Kathryn Rexrode, M.D., and Frank B. Hu, M.D., Ph.D.




ABSTRACT

Background Low-carbohydrate diets have been advocated for weight loss and to prevent obesity, but the long-term safety of these diets has not been determined.

Methods We evaluated data on 82,802 women in the Nurses' Health Study who had completed a validated food-frequency questionnaire. Data from the questionnaire were used to calculate a low-carbohydrate-diet score, which was based on the percentage of energy as carbohydrate, fat, and protein (a higher score reflects a higher intake of fat and protein and a lower intake of carbohydrate). The association between the low-carbohydrate-diet score and the risk of coronary heart disease was examined.

Results During 20 years of follow-up, we documented 1994 new cases of coronary heart disease. After multivariate adjustment, the relative risk of coronary heart disease comparing highest and lowest deciles of the low-carbohydrate-diet score was 0.94 (95% confidence interval [CI], 0.76 to 1.18; P for trend=0.19). The relative risk comparing highest and lowest deciles of a low-carbohydrate-diet score on the basis of the percentage of energy from carbohydrate, animal protein, and animal fat was 0.94 (95% CI, 0.74 to 1.19; P for trend=0.52), whereas the relative risk on the basis of the percentage of energy from intake of carbohydrates, vegetable protein, and vegetable fat was 0.70 (95% CI, 0.56 to 0.88; P for trend=0.002). A higher glycemic load was strongly associated with an increased risk of coronary heart disease (relative risk comparing highest and lowest deciles, 1.90; 95% CI, 1.15 to 3.15; P for trend=0.003).

Conclusions Our findings suggest that diets lower in carbohydrate and higher in protein and fat are not associated with increased risk of coronary heart disease in women. When vegetable sources of fat and protein are chosen, these diets may moderately reduce the risk of coronary heart disease.


Source Information

From the Departments of Nutrition (T.L.H., W.C.W., F.B.H.) and Epidemiology (W.C.W., J.E.M., F.B.H.), Harvard School of Public Health, Boston; the Department of Epidemiology, University of California, Los Angeles, School of Public Health, Los Angeles (S.L.); and the Division of Preventive Medicine (J.E.M., C.M.A., K.R.), the Channing Laboratory (W.C.W., J.E.M., K.R., F.B.H.), and the Cardiovascular Division (C.M.A.), Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston.

Address reprint requests to Dr. Hu at the Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115, or at frank.hu~channing.harvard.edu .

I have to laugh, I was just reading this headline:
Low carb, low fat diets pose similar heart disease risks.
Interesting how the headlines are written differently.

.
Low-carb diet doesn't raise heart risk
By LINDA A. JOHNSON, Associated Press Writer
http://news.yahoo.com/s/ap/20061108..._low_carb_study


Eating a low-carb, high-fat diet for years doesn't raise the risk of heart disease, a long-term study suggests, easing fears that the popular Atkins diet and similar regimens might set people up for eventual heart attacks

The study of thousands of women over two decades found that those who got lots of their carbohydrates from refined sugars and highly processed foods nearly doubled their risk of heart disease.

At the same time, those who ate a low-carb diet but got more of their protein and fat from vegetables rather than animal sources cut their heart disease risk by 30 percent on average, compared with those who ate more animal fats.

The findings came from researchers at Harvard University's schools of medicine and public health who reviewed records of 82,802 women in the ongoing Nurses' Health Study over 20 years. The women were not dieting to lose weight. In fact, on average they were slightly overweight and increased their body-mass index roughly 10 percent during the study.

Conventional wisdom says risk of heart disease should increase for those eating the lowest-carb, highest-fat diet, said lead author Thomas Halton.

"It didn't, which was a little eye-opening," he said.

Halton said that may be because the women eating the fewest carbs were compared directly to the group eating the highest-carb, lowest-fat diet.

"Neither diet is ideal," he said. "You need to take the best of both."

The findings, reported in Thursday's New England Journal of Medicine, came from an analysis of food questionnaires the nurses filled out every two to four years starting in 1980. The nurses also reported their use of aspirin, vitamins and hormones for menopause symptoms, and on any history of smoking and heart problems.

The researchers calculated the percentage of calories coming from carbohydrates and animal and vegetable fats and proteins, then divided the nurses into 10 groups, from the lowest to the highest calorie percentage from carbs.

The lowest-carb group ate carbohydrate amounts similar to the maintenance program of the Atkins diet, less extreme than the early phase of the diet, said dietitian Geri Brewster, former nutrition director at the Atkins Center for Complementary Medicine in Manhattan.

Still, she said most women in this study ate fewer carbohydrates than traditional diets recommend. While she thinks the Atkins diet allows too much animal fat, Brewster said reducing carbohydrates works because it forces the body to convert stored fat into an energy source and can curb appetite.

American Dietetic Association spokeswoman Susan Moores, a dietitian in St. Paul, Minn., said that because the study only included women, many going through menopause and taking hormones, it is unclear how it applies to men.

For Moores, the key finding was that women reduced heart disease risk by eating more protein and fat from vegetable sources.

"That was the biggest, "Aha!'" she said.

Dr. Robert Eckel, immediate past president of the American Heart Association, said the study was well done, but noted that the nurses' recall of what they ate likely isn't perfect.

Eckel, an endocrinologist at University of Colorado School of Medicine, said many studies have shown heart disease risk is cut by eating less fat and more whole grains, fresh fruit and vegetables — the approach of the government's food pyramid. He said medical guidelines won't be changed by the new study, although it raises questions about the role of refined sugar.
.
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A LITTLE eye-opening??!!!!!!

They just can't stand it- they (the authors of these studies, and the AHA and ADA) bend over backwards to try and explain away the findings- they just don't get it. "Eye opening." So now they complain that you can't compare the lowest fat group to the lowest carb group? HELLO!!! What have they been telling us to eat all these years- LOW FAT. Thank goodness they are comparing! And it only applies to women!!!! HELLO!!!! Last time I checked I was a woman!!!! AAAARG!!!

This is a great article.

http://www.msnbc.msn.com/id/15625548/

yes for once huh!!?

I can't find a link to this, it's probably not officially out yet, but I got an online NEJM table of contents summary today for the upcoming edition with a link to an abstract of a study by our old friend Walter Willet. It's a re-analysis of the women's health study that looks at the rates of incident heart disease as a function of the percentage of carbs in the diet. Sorry I don't have exact numbers-- I'm going on memory here!

They divided the women into quintiles (lowest 20% to highest 20%) of % carb intake as estimated by food frequency questionnaires or diet recall questionnaires. ( I know there are huge problems with these kinds of studies).

The lowest quintile of carb intake (LC-high fat) compared to the highest quintile of carb intake had a relative risk of heart disease of 0.94 (approximately), with a confidence interval of something like 0.8 to 1.16, in other words, not a statistically significant difference. (But a trend toward lower risk!) But mainly it means that the low carb diet is not significantly more likely to cause heart disease than a low fat diet, which the current paradigm would predict. This was approximately a 10 year study.

Willett also specifically looked at the quintile of lowest carb and highest animal fat, with the same relative risk and intervals. Seemed kind of surprised at that.

Of course they also looked at the lowest % carb intake along with the highest percentage of plant-derived protein and plant-derived fat, (compared to ???)and that comparison showed a RR of 0.70, and it was highly significant (p value 0.002).

The last item was I think highest GI diet vs lowest GI. The RR was 1.9 if I remember correctly.

So for Willett, I think this is the most we can expect. A grudging admission that Atkins isn't dangerous (for post-menopausal women), but a joyous proclamation that plant derived protein and fat is far superior to animal-derived.

Hmm, I don't see these results as fantastic for my very animal-foods based diet though. Am I missing something?

i've saved the original article here . you'll find the trumpeted link between reductions of coronary incidences and consumption of vegetable sources of protein and fat by "experts" in the associated press article is tempered quite a bit in the OA...

The spin doctors are out in force to twist this "surprising" study against saturated fat, but even if the food pyramidists squirm, ultimately they can't hide. I wonder how much of the leftover/spin indictment of saturated and animal fats in LC diets is due to the traditional lumping of trans-fatty and processed foods in with them.

By DAN CHILDS
ABC News Medical Unit


Nov. 8, 2006 — Americans have been debating the risks and benefits of different diets, specifically low-fat versus low-carbohydrate diets, even decades before the Atkins Diet and the South Beach Diet swept the nation.

Now, a new study has answers to an old question: Is a low-carbohydrate diet bad for the heart?

No, suggests new research published in today's issue of the New England Journal of Medicine, and it's not any worse than a diet high in carbs.

The study, which involved more than 82,000 women from across the country over 20 years, confirms what previous research has suggested: Low-carbohydrate diets do not increase heart-disease risk.

Even though low-carb dieters might tend to eat more fats and other heart-unhealthy foods, over time their risk of coronary heart disease (CHD) did not exceed that of their counterparts who instead consumed a low-fat, low-cholesterol diet.

The study's researchers say the results suggest that low-carb diets are at least on equal footing with other forms of dieting when it comes to heart health.

"This study suggests that neither a low-fat dietary pattern nor a typical low-carbohydrate dietary pattern is ideal with regards to risk of CHD. Both have similar risks," said study researcher Tom Halton, a former doctoral student in the Department of Nutrition at the Harvard School of Public Health in Boston.

"However, if a diet moderately lower in carbohydrates is followed, with a focus on vegetable sources of fat and protein, there may be a benefit for heart disease," Halton said.

Backing the findings are data from three trials published in 2003, which showed that low-carb diets do not increase cardiovascular risk factors.

In those studies, the Atkins Diet, a bellwether regimen on the low-carb scene, was compared to a different diet emphasizing a low intake of fat and cholesterol.

The results? Those on the Atkins Diet actually had greater improvements in insulin sensitivity, HDL (good) cholesterol and triglyceride levels than did the low-fat, low-cal dieters.

The findings, however, come with a caveat common to many of the other studies on high-protein, low-carb diets. In short, don't go crazy on the red meat.


"This study doesn't mean that you should load your plate with steak and bacon," said the study's senior author Frank Hu, associate professor of nutrition and epidemiology at Harvard School of Public Health.



"The quality of fat and carbohydrate is more important than quantity. A heart-healthy diet should embrace healthy types of fat and carbohydrates," Hu said.


Some experts remain skeptical of the study.



"This is an observational study, not a randomized trial," said Dr. Neal D. Barnard, president of the Physicians Committee for Responsible Medicine in Washington, D.C.


"We already have randomized trials of low-carb diets, and they clearly show that approximately one in three low-carb diets has a significant increase in LDL [bad] cholesterol. Such findings are far more relevant than observational studies to the question of what effects do low-carb diets have," Barnard said.




Adding to the skepticism of some experts are the limitations of the study — specifically, that it only looked at female nurses, and that the self-reporting method used could be considered unreliable.


"A strong limitation of this study is that since the subjects were nurses who may make more informed food choices that other women, the results may not be applicable generally," said Carla Wolper of the Obesity Research Center at St. Luke's Hospital in New York.


"In other words, these nurses may have chosen healthier forms of protein [fish, leaner meats, skim milk and lower-fat cheeses]. Thus, even with increased protein intake, they may not have increased intake of saturated fats so damaging to coronary health."

Wolper says the study, which defies conventional wisdom on the consumption of high-protein (and often high-fat) foods, could be puzzling to average consumers who are just hoping to eat healthier.

"As for patients, they are confused, and this study will confuse even more," she said. "If you include obesity in the picture, with all its inherent health risks, and then add a poor diet, heart disease increases. Americans are already overweight or obese, and choosing a high-fat diet will increase coronary risk."

Oddly, the study does NOT show any issue with animal fat or animal protein at all. . .

"Total fat, animal fat, total protein, animal protein,
and vegetable protein were not significantly associated
with the risk of coronary heart disease
according to multivariate analyses."

Carbs are, however. . .

"Total carbohydrate intake was
associated with a moderately increased risk of
coronary heart disease (P for trend for the comparison
of the 10th decile with the 1st decile
= 0.06). For the comparison of the 10th with
the 1st decile, there was a significant direct association
between dietary glycemic load and coronary
heart disease (relative risk, 1.90; 95% CI,
1.15 to 3.15; P for trend = 0.003). The overall dietary
glycemic index had a direct association
with the risk of coronary heart disease (relative
risk comparing extreme deciles, 1.19; 95% CI,
0.91 to 1.55; P for trend = 0.04)."

The effect of 'vegetable protein' was actually rather small, however. (A RR of .70.)

Oddly, too, the vegetable protein consumption was tiny across the board, averaging 5% of calories (which isn't surprising, since you can't find a whole lot a protein in plants, except in beans and nuts.) That's maybe 90 calories' worth.

The difference between those who ate a LOT of veggie protein and those who at LESS, seems to be about 1% of calories.

Which is, what, a mouthful of beans??

Sounds to me that someone was tweaking the math very hard to put some sort of anti-meat spin to this.

Does anyone else find this sentence a little bizarre?



What exactly IS the criteria for "heart-unhealthy"???

I think the study was a fantastic advance for low carb, BUT, the spin they put on the findings is totally outrageous!

They say that the low carb group was eating the equivalent of Atkins maintenance, which allows plenty of meat sources of protein and fat and then turn it around to show that they got most of the protein and fat from vegetable sources. Not on any Atkins "diet" I've ever seen and I've read all his books.






I bet they were in seventh heaven to get a quote from the former nutrition director at the Atkins Center for Complementary Medicine stating she thinks Atkins allows too much fat from animal sources! If these nurses were actually doing Atkins maintenance, then they were getting considerable animal fat and protein.