Is Low-Carb Eating Really Better for Blood Sugar?

A review of popular low-carbohydrate diets finds that while restricting carbs can reduce blood sugar in the short run, evidence in support of long-term benefits is lacking.

Low carb eatingIs low-carb eating really better for blodd sugar? Review of popular low-carb diets says yes but only in the short term.

While very low carbohydrate diets (LCD) promise to cut blood sugars, a review of popular LCDs finds that while very low-carb eating can reduce blood sugar in the short run, little evidence exists to show long-term benefits.

The study, published online in the Journal of the American Osteopathic Association, reports that while LCDs may be “slightly better than low fat diets for weight and triglycerides management” they are “not superior for the management of blood glucose, blood pressure, or cholesterol levels.”

However, researchers note that physicians should be aware that “available evidence for LCDs is limited because of variable definitions, lack of long-term studies, and lack of patient adherence.”

Diets considered ranged from very low carb—less than 20 to 60 grams per day—to less restrictive diets that averaged about 130 grams per day. The American Diabetes Association says diets should be tailored to individual needs, but recommends starting at 45-60 grams of carbohydrates per meal.

“Patients can likely follow a version of the low carbohydrate diet for longer than the studies suggest, but we don’t know the health effects of a very low carbohydrate ketogenic diet of less than 20 grams of carbs per day,” says Heather Fields, MD, an author of the study and a doctor of integrative medicine at the Mayo Clinic in Phoenix, Arizona. “With so few people adhering to a truly ketogenic diet long term [more than a year], we will likely never be able to study the health effects in a meaningful way.”

Dr. Fields finds that if type 2 patients have not had success with a plant-based, whole-foods diet with moderate calories and avoidance of processed foods, they might consider a very low-carbohydrate diet to “get back on track.”

But eventually, she suggests people incorporate whole grains, legumes, vegetables and fruits in moderate portions, “because we know these foods have key nutrients including fiber, antioxidants and phytochemicals that are protective and restorative.”

“Low carbohydrate diets may be easier for some due to increased satiety and overall lifestyle, but once they reach a reasonable weight, I advocate for incorporating a variety of whole foods and plants,” says Dr. Fields.

Long-term Diet Studies Problematic

The problem in researching low-carb diets is that people do not use the same definition of low carb and very few studies go beyond a year, says DiabeticLifestyle Editorial Board Member Amy Hess Fischl, MS, RD, LDN, BC-ADM, CDE. Hess Fischl agrees with previous proposals to standardize the language rgarding low carb diets: very low carb are those that use 10% of calories from carbs (20-50g); low carb about 26% (130g); moderate carb about 45% and high carb over 145 grams per day.

As a point of comparison, she notes that the average American man consumes about 47% of his diet from carbs (283g) and the average woman about 49% (228g). “What we can agree on is that the average American eats too many carbs, which can cause a rise in problems with blood glucose control,” says Hess Fischl, who is also a diabetes educator at the University of Chicago Kovler Diabetes Center.

When it comes to the difficultly of researching low-carb diets long-term, Hess Fischl notes that such studies are expensive and often limited due to self-reported data. “The best approach for people with type 2 diabetes is to meet with a dietician and to see what really helps them,” she says. “When it comes to type 2 diabetes carbs are the first component to look at but we have to find a healthy balance of fats, proteins and vegetables and fruits.”

Being Selective About Carbs Might Make a Difference

Hess Fischl points out that finding the optimal diet can take some trial and error since everyone’s body and metabolism are so different.

“The reality is that every plan needs to be individualized,” says Hess Fischl. “Rather than focusing on very low carb, we should focus on being ‘carb selective.’”

“Short term a very low carbohydrate diet could work to lose weight,” she said. “But food is a component of everything and we need a healthy relationship with food.”

“The American diet is simply too high in sugar,” says Susan Delaney, ND, an integrative medicine doctor who practices at The Wellness Alliance in  Carrboro, North Carolina. Rather than focus her type 2 diabetes patients on very low carbohydrate eating she also tries to concentrate on eating real food and avoiding processed foods that are packed with sugar and low in nutrients.

“It often depends on what a person normally eats,” says Dr. Delaney. “If it’s chips and bagels, then we want to shift their diet to more nutrient dense foods. The body needs carbohydrates, but not processed carbohydrates.”

Her best bet for type 2 patients is the Mediterranean diet, which is high in soluble fats, but she says she is not opposed to the revised low carbohydrate Atkins or South Beach diets, as long as fruits and vegetables are incorporated into the eating plan. 

“I do object to the Paleo diet,” she says, “since it lacks variety and is too heavily weighted toward protein.”

Dr. Fields says the takeaway from her study is that “the most important contributor to healthy eating and long term success is to eat a variety of real food on a consistent basis.”

“If type 2 patients can adhere to low-carbohydrate diets that are whole foods and plant based over the course of several years, they could certainly benefit,” she says.

Updated on: July 12, 2018
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