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Delving deeper into carbohydrate diet study

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A recent study demonstrated that low carbohydrate intake was a risk to mortality just as much as a high carbohydrate diet.

Recently carbohydrates were in the news because a large study demonstrated that low carbohydrate intake was a risk to mortality just as much as a high carbohydrate diet. This headline-making observation was a shot in the face to all those who have dropped carbs out of their diets and instead pretend to enjoy the sloppy experience of eating a hamburger between sheets of lettuce. Whereas I, a carbo-lover, toasted the news with a loaf of bread and a bowl of pasta.

But instead of swiping screens, I read the news. There is more to the study than meets the eye. They followed over 15,000 adults ranging from 45 to 64 years old. They looked at their diet and their mortality rate over more than 20 years. The average person in the study had a diet in which carbohydrates comprised 50 percent of their daily caloric intake.

As expected, people with a high carb diet (over 65 percent of their calories) had a higher risk of death than the average consumer of carbohydrates. On average, the high carbohydrate consuming group would die 1.1 years earlier than the average consumer.

The shock of the study was the low carbohydrate consumers. This group gets less than 30 percent of their daily caloric intake from carbohydrates. Their average lifespan was four years less than the average carbohydrate consumer. This is what hit the news.

This is important because low carb or ketogenic diets are so popular. Incidentally, ketogenic diets were originally used in the 1920s for controlling epilepsy. An elevated level of ketones in the blood stream significantly reduces the number of seizures. It wasn’t until much later that Dr. Atkins popularized the diet. In 2003, the height of the Atkins craze, about 9 percent of North American adults were on a low-carb diet.

The researchers knew to look at the low-carb dieters to see what they were substituting for their carbohydrates. The people who were substituting animal protein and fat (bacon, beef, cheese, etc.) for carbohydrates had very different outcomes than the people substituting their carbohydrates with plant proteins and fats (nuts, nut butter, grain breads, chocolate). The animal consumers had an increased risk of death that accounted for all of the negative effects seen on for the low-carb eaters. The people who ate low-carb diets with extra plant proteins and fats actually had the lowest mortality rate of all the groups.

The take-home message is obvious — if you are going to do a ketogenic diet, don’t substitute carbs for extra animal protein or fat. Yes, it will help you lose weight, but in the long run, you’ll actually die sooner.

This large study is not without flaws. It wasn’t a controlled study — that wouldn’t have been feasible — but rather, an observational study that was based on the patients’ self-reporting their diet. Information on diet collecting was collected only every six years. There is a good chance that many of the patients changed diets, or went on fad diets, during those years. In other words, the participants probably had fluctuations in the amount of carbohydrates they ate over the years. That said, people tend to self-report their diet to be healthier than what it is, yet the researchers were able to see significant differences in mortality between these groups. Obviously drawing the line of low-carb diet at 30 percent when the average is less means that these people are actively choosing to eat less calories. It is possible that these carb-conscious people are also making other healthy lifestyle decisions that the study did not explore.

This study looked at all causes of mortality. The researchers did not try to determine which causes of death were related to high-carbohydrate diets. However, there have been other studies that looked at this.  A large Chinese study of nearly 80,000 found that the highest carb diets had increased risk of pre-menopausal breast cancer.

There are a number of mouse studies examining cancer growth and ketogenic diets. For some cancers, mice on ketogenic diets live longer than mice on normal diets. Currently, there are a number of studies trying to reproduce the same findings in humans.

Clearly, a low carb diet with low animal meat and fat is part of healthy living. But some choices are harder to make than others. I won’t be throwing out my spaghetti and meatballs; after all, Italians live on average three years longer than Americans. I just have to eat more vegetables along with the pasta to keep things in balance.

Dr. Salvatore Iaquinta is a head and neck surgeon at Kaiser Permanente San Rafael and the author of “The Year They Tried To Kill Me.” He takes you on the Highway to Health every fourth Monday.


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