A recent article in Frontiers in Nutrition evaluates the nutritional sufficiency of three low-carbohydrate diets with varying carbohydrate levels.
Background Low-carbohydrate diets are gaining popularity globally, particularly among middle-aged women. These diets typically restrict carbohydrate intake to less than 130 grams per day or 10-25% of total energy. Very low-carbohydrate diets reduce this further to 20-50 grams per day, equating to less than 10% of energy from carbohydrates.
Numerous studies have demonstrated that low-carbohydrate diets effectively manage chronic metabolic conditions, such as type 2 diabetes, metabolic syndrome, obesity, and polycystic ovarian syndrome.
Additionally, the study highlights that these diets could help address health disparities among historically marginalized racial, ethnic, socioeconomic, and cultural groups. Despite this, the Recommended Dietary Allowance (RDA) for carbohydrates is 130 grams per day, which has been a barrier to incorporating low-carbohydrate diets into standard dietary recommendations.
Study Design Researchers analyzed the nutrient content of three low-carbohydrate diets over seven days: a very low-carbohydrate diet providing 20 grams of carbohydrates per day (VLCD20), another very low-carbohydrate diet offering 40 grams (VLCD40), and a low-carbohydrate diet with 100 grams (LCD100). They assessed the diets using data from the US Department of Agriculture Food Data Central.
Key Findings The study found that the VLCD20 and VLCD40 diets provided 91% and 94% of the RDA for energy, respectively, for females aged 31-70 years, while LCD100 met the RDA. For older females (51-70 years), VLCD20 and VLCD40 met the RDA, and LCD100 exceeded it by 12%. None of the diets met the RDA for energy in males across all age groups.
In terms of dietary carbohydrates, VLCD20, VLCD40, and LCD100 provided 37%, 55%, and 98% of the RDA, respectively. VLCD40 and LCD100 offered more dietary fiber than the RDA for females aged 31-70 years, but VLCD20 did not. For older females, VLCD20 met the RDA for fiber, while VLCD40 and LCD100 exceeded it by over 20%. None of the diets met the fiber RDA for males aged 31-70, although VLCD40 and LCD100 did for older males.
All three diets provided more protein than the RDA, falling within the acceptable macronutrient distribution range of 10-35% of total energy. They also slightly exceeded the RDA for saturated fat and sodium. However, the ratio of omega-6 to omega-3 fatty acids was lower than in the average American diet, potentially offering protective health benefits. The sodium-to-potassium ratio in all diets was favorable, which is beneficial for cardiovascular health.
Micronutrient Adequacy The diets exceeded the RDA for several essential vitamins and minerals, including vitamins A, C, D, E, and K, as well as calcium in adults aged 31-50 years. These levels were below the Tolerable Upper Intake Levels.
Significance of the Study The study suggests that low-carbohydrate diets, when carefully designed, can meet or even surpass nutritional requirements for essential micronutrients, particularly for females aged 31-50. This challenges the notion that low-carbohydrate diets are nutritionally inadequate. Furthermore, the study underscores the importance of considering the quality of diets, not just carbohydrate quantity, in dietary guidelines. The beneficial ratios of omega-6 to omega-3 fatty acids and sodium to potassium could be crucial for individuals with metabolic health issues, potentially reducing the risk of chronic diseases.
