Discover how strategic low-carb meal plans not only meet your daily nutritional needs, but also improve your heart health by optimizing the balance of essential fatty acids, sodium, and potassium, challenging conventional nutrition theory.
Study: Nutritional analysis of three low-carb diets that differ in carbohydrate content. Image Credit: Chinnapong / Shutterstock
An article published in Limits in nutrition provides a detailed overview of the nutritional adequacy of three low-carbohydrate diets with different carbohydrate content.
Background
Low-carb diets are becoming increasingly popular worldwide, especially among middle-aged women. Low-carb diets contain less than 130 grams of carbohydrate per day, or 10-25% of energy from carbohydrates. Similarly, very low-carb diets contain 20-50 grams of carbohydrates or less than 10% of energy from carbohydrates per day.
A large number of studies have shown that low-carbohydrate diets are clinically effective in treating several chronic metabolic diseases, including type 2 diabetes, metabolic syndrome, obesity, and polycystic ovary syndrome.
A disparity in the prevalence of cardiometabolic diseases has been observed among people belonging to historically marginalized racial, ethnic, socioeconomic, and cultural backgrounds. As noted in the study, well-planned low-carbohydrate diet plans can serve as an effective intervention to address such health disparities.
The recommended daily allowance (RDA) for total carbohydrates is 130 grams per day, estimated from the average amount of glucose the brain uses each day. This standard has been a major barrier to incorporating low-carb diets into current dietary guidelines, despite clinical evidence supporting their benefits.
In this study, scientists estimated the macro- and micronutrient contents of three 7-day low-carb diet plans to investigate the nutritional adequacy of different forms of carbohydrate restriction.
Study design
The study analyzed the nutritional value of two very low-carb diets and one low-carb diet, which provided 20, 40, and 100 grams of net carbs per day, respectively. Net carbs refer to the total nonfiber saccharides that are digestible by humans.
The nutrients of public health concern, as identified in the 2020 Dietary Guidelines for Americans, were considered when selecting foods for diet plans. These diet plans were specifically designed based on dietary patterns used in studies of ketogenic and low-carb diets, as well as commercial low-carb diets.
The nutritional value of the diet plan was analyzed using the Food Data Central of the United States Department of Agriculture. This central database contains five different data types that provide information about food and nutrient profiles.
Important observations
Energy and nutrient analysis of three diet plans showed that two very low-carbohydrate diets containing 20 grams and 40 grams of carbohydrates (VLCD20 and VLCD40) and the low-carbohydrate diet containing 100 grams of carbohydrates (LCD100) provided 91%, 94%, and 100% of the RDA for energy, respectively, in women aged 31 to 70 years.
In older women aged 51 to 70 years, VLCD20 and VLCD40 met the RDA for energy; however, LCD100 provided 12% more energy than the RDA. In men, none of the diet plans met the RDA for energy across all age groups.
In both men and women aged 31 to 70 years, VLCD20, VLCD40 and LCD100 provided 37, 55 and 98% of the RDA for dietary carbohydrate, respectively. In women aged 31 to 70 years, VLCD40 and LCD100 provided 9 and 16% more dietary fiber than the RDA, respectively. However, VLCD20 failed to meet the RDA for dietary fiber in this age group.
In older women aged 51 to 70 years, VLCD20 provided adequate dietary fiber, and VLCD40 and LCD100 exceeded the RDA by more than 20%. In men aged 31 to 70 years, none of the diet plans met the RDA for dietary fiber; however, VLCD40 and LCD100 did meet the requirement in older men aged 51 to 70 years.
All three diet plans provided higher amounts of protein than the RDA in men and women aged 31-70 years. However, the amounts were within the Acceptable Macronutrient Distribution Range of 10-35% of energy.
In terms of saturated fat and sodium, all diet plans slightly exceeded the RDA. However, the study highlights that despite this, the ratio of omega-6 to omega-3 fatty acids was significantly lower than the average American diet, which may offer protective benefits against chronic disease. The sodium-to-potassium ratio in all three diets was also favorable, remaining well below unity, which is considered beneficial for cardiovascular health. This is particularly notable given that most American diets exceed the recommended sodium intake and fall short in potassium, a pattern associated with increased cardiovascular risk.
Essential micronutrients
All three diet plans exceeded the RDA for vitamins A, C, D, E, and K, thiamin, riboflavin, niacin, B6, folate, and B12 in adults aged 31 to 70 years, and the RDA for calcium in adults aged 31 to 50 years. However, all values remained below the Tolerable Upper Intake Level.
In women aged 31 to 50 years, all three diet plans met or exceeded estimated average requirements for protein and essential micronutrients.
Study meaning
The study found that low-carb diets, which are deliberately designed to provide fewer carbohydrates than the recommended daily amount, can provide Americans with adequate fiber and micronutrients.
Furthermore, the findings suggest that these well-designed diet plans not only meet but may even exceed dietary requirements for essential micronutrients in specific populations, particularly women aged 31–50 years, who are most likely to follow these diets. This challenges the common perception that low-carb diets are nutritionally inadequate and underscores the importance of considering diet quality, not just carbohydrate quantity, in dietary guidelines.
The study also highlights the importance of the ratios of omega-6 to omega-3 fatty acids and sodium to potassium provided by the diets, particularly for individuals with existing metabolic health conditions. These ratios may play a critical role in reducing the risk of chronic diseases, such as cardiovascular disease, in populations adhering to low-carb diets.