Is a low-carb diet a nutritious diet? Yes, new study shows

 

Over the last decade, low-carbohydrate (i.e., low-carb) eating patterns have doubled in popularity.1 Substantial research also suggests a low-carb lifestyle is an effective way to support overall health, including managing or even reversing type 2 diabetes.2-6 Yet, skepticism remains around the nutritional quality of low-carb diets, with some arguing that reducing carb intake leads to over-consuming protein or fat and under-consuming essential nutrients.

That misconception has been put to rest with a new study in Frontiers in Nutrition, which demonstrated that well-constructed low-carb eating patterns can meet, and sometimes even safely exceed, people’s nutrient needs.

The study assessed the nutrient adequacy of three different 7-day low-carb meal plans: two ketogenic diets – one that averaged approximately 20 grams of net carbs per day, one that provided an average of about 40 grams of net carbs per day – and one more liberalized plan that contained an average of around 100 grams of net carbs per day. (Net carbs equate to total grams of carbohydrate minus total grams of fiber consumed.)  All three plans met the consensus definition of a low-carb diet, which includes less than 130 grams of carbs per day.6

All three low-carb meal plans safely exceeded nutrient needs for vitamins A, C, D, E, K, thiamin, riboflavin, niacin, folate and vitamins B6 and B12 for both men and women aged 31-70.

“Many Americans struggle get the nutrients they need from typical food choices,” notes study co-author Beth Bradley, PhD, Department of Nutrition and Food Sciences, University of Vermont. “Our findings suggest that, in addition to their well-established ability to support weight management, low-carb eating patterns can actually help promote better diet quality and close critical nutrient gaps.”

Only for certain sub-populations with higher needs did a few nutrients fall slightly short in the low-carb meal plans (e.g., iron for younger women and calcium for older adults).

Notably, the two meal plans containing 40 grams and 100 grams of net carbohydrates, respectively, also provided more than enough fiber for women aged 31-70. Given low-carb diets are especially popular among middle-age women, meeting the nutrients needs of this population is especially relevant.1

“The idea that a low-carb diet must also be low in fiber is simply not supported by the data,” Dr. Bradley explains. “High-fiber foods are actually an important part of a low-carb lifestyle, in part because fiber-rich food choices can help lower net carbohydrate intake. Non-starchy vegetables, nuts and seeds, and, in moderation, even higher-carb fruits, starchy vegetables and whole grains can contribute fiber to the diet while keeping overall net carb intake in check, especially in the more liberal low-carb approach.”

While all three of the low-carb meal plans were higher than the Recommended Dietary Allowance (RDA) for protein, protein levels still fell within the Acceptable Macronutrient Distribution Range of 10-35% of daily calories. In other words, the meal plans provided more protein than what is needed to prevent deficiency but did not deliver an excessive amount that would be considered unsafe.

Though lower in saturated fat and sodium compared to the average American diet, the meal plans also slightly exceeded recommendations for saturated fat and sodium. However, they also offered more beneficial omega-6 to omega-3 and sodium to potassium ratios.

“Nutrition is often more complex than simply tallying the totals you see on a menu or a food label,” says Dr. Bradley. “Which foods your nutrients come from and how they fit within the broader context of your overall diet may play a more important role in determining health outcomes. For example, a better omega-6 to omega-3 ratio has been linked to a lower risk of cardiovascular disease and type 2 diabetes. And similarly, a more optimal sodium to potassium ratio may help lower risk of high blood pressure and heart disease.”

The latest study findings add to the robust and growing evidence base demonstrating the role a lower-carb lifestyle can play in supporting good diet quality, overall well-being and the management or reversal of diet-related disease. While some people (e.g., younger women, older adults) may benefit from dietary supplements to meet all of their individual needs, the low-carb diet provides a strong nutritional foundation for health.