Low-Carb Diets May Not Be Healthy in the Long Run, Study Says
New research suggests that low-carb diets may not be the best way to achieve long-term health.
Research presented Tuesday at the European Society of Cardiology Congress in Germany found that diets very low in carbohydrates may raise individuals’ risks of premature death over time.
“The message seems to be clear,” wrote study co-author Maciej Banach, president of the Polish Mother’s Memorial Hospital Research Institute, in an email to TIME. “We should avoid diets with extremely low and very low levels of carbohydrates,” specifically those that draw less than 26% of daily calorie intake from carbohydrates. Risks may be even more pronounced when that level dips below 10%, Banach says.
Low-carb diets have become increasingly popular in recent years, largely among people trying to lose weight. But Banach’s research — which comes shortly after a Lancet study that found moderate carbohydrate intake is best for longevity — suggests that weight loss achieved through a low-carb diet may come at the expense of general health, at least when it’s followed for a long period of time.
The new study — which has not been published in a peer-reviewed journal — used diet and health data from almost 25,000 people collected through the National Health and Nutrition Examination Survey between 1999 and 2010. The researchers found that over an average of 6.4 years of follow-up, people who consumed the lowest amount of carbohydrates had a 32% higher risk of total mortality, a roughly 50% higher risk of dying from vascular diseases and a 36% higher risk of dying from cancer, compared to people who ate the most carbs.
The researchers also reviewed seven separate studies on carbohydrates and health, involving around 447,500 people in all. Together, these studies pointed toward similar, if more modest, results. Low-carb diets were associated with a 15% higher risk of total mortality, a 13% higher risk of cardiovascular mortality and an 8% higher risk of cancer mortality, compared to high-carb diets.
It’s not totally clear why low-carb diets are linked to these health risks, and observational studies like this one can never prove cause-and-effect, only uncover patterns in a particular dataset. But Banach says there are always consequences when cutting out an entire food group, especially if it’s not thoughtfully replaced with healthy alternatives. In the case of carbs, the study says, dieters may run into trouble if they eliminate things like nutritious but carb-heavy fruits, or replace carbohydrates with meat and dairy products. Diets heavy in animal products, versus plant products, may increase a person’s risk of heart disease, and processed meat has been linked to cancer.
“All-natural nutrients from the everyday diet are important,” Banach says. “Therefore all interventions aimed to restrictedly limit one of them might be harmful for our health.”
Despina Hyde, a registered dietitian at NYU Langone’s Weight Management Program, agrees with that assessment. “When you’re not eating carbs, you have to eat something. We tend to eat higher protein and higher fat [on a low-carb diet],” Hyde says. Plus, “carbohydrates are the only source we have of fiber, and fiber is great for reducing risk of breast cancer, lowering our cholesterol and making us feel full for longer.”
Don’t take that as license to binge on bread, though. Even though low-carb diets appear to come with more risks than high-carb diets, Banach says plenty of existing data, including that from the recent Lancet study, suggests moderation when it comes to carb consumption. Very high-carb diets tend to be heavy on refined carbohydrates, such as white bread and snack foods, which are low in nutritional value.
Hyde recommends taking a thoughtful approach to carb consumption, no matter how many you eat. “I would include carbohydrates as part of every meal,” she says. “Just choose whole grain, high-fiber carbohydrates” — such as black beans, fruit, quinoa and whole grains — “not necessarily white bread, pasta and cookies.”