Carbohydrates: A Complex or Simple Matter?
Roberta Alessandrini, PhD, translated and adapted the following content from this PAN Israel blog article.
Carbohydrates are one of the macronutrients essential for the body, needed in relatively large quantities. They play a crucial role in providing energy and supporting the function of various organs, including the central nervous system.
Plants produce carbohydrates through photosynthesis, which involves combining carbon dioxide and water using the energy from the sun. In a well-balanced diet, carbohydrates are derived from plant sources such as grains, legumes, fruits, and vegetables. However, not all carbohydrates are the same, as they vary in structure. Carbohydrates can be classified into simple sugars (monosaccharides and disaccharides) and complex carbohydrates (polysaccharides such as starch and most dietary fibre).
Why are people scared of consuming carbohydrates?
Carbohydrates obtained from manufactured foods — such as sweets, ice cream, chocolates, and sugary drinks — most of the time contain large quantities of simple sugars and lack dietary fibre. Evidence shows that carbohydrates “packaged” this way are of low nutritional quality and adversely affect health (1). On the other hand, whole plant foods contain carbohydrates in the form of starch and dietary fibre and are rich in vitamins, minerals and phytochemicals. Carbohydrates packaged this way have been shown to have beneficial effects on health.
The consumption of fruit — a whole food naturally containing simple sugars such as monosaccharides and disaccharides — has been shown to reduce the risk of type 2 diabetes (2). In contrast, the consumption of sugary drinks is associated with an increased risk of diabetes. Similar patterns emerge when comparing the health effects linked to the consumption of unrefined whole grains against the consumption of refined grain products such as white pasta and rice (3).
Figure 1: Non-linear dose-response relation between daily intakes of selected food groups and type 2 diabetes risk. From Schwingshackl et al., 2017
What is the recommended carbohydrate intake?
The Atherosclerosis Risk in Communities (ARIC) study examined the relationship between carbohydrate intake and mortality risk (4). The study followed over 15,000 US adults aged 45-64 at study commencement for approximately 25 years. Researchers found that the lowest risk of mortality was observed with a carbohydrate intake of 50%-55% of total calories (4). This percentage aligns with the carbohydrate recommendations from almost all food and health organisations globally. Note that in nutrition and dietetics, macronutrient intake ( such as carbohydrates) is always reported as a percentage of the total calories, not as grams per day. This is because the calorie requirements of individuals vary according to age, sex and physical activity levels.
Figure 2: U-shaped association between the percentage of energy from carbohydrates and all-cause mortality in the ARIC cohort. From Seidelmann et al., 2018
Within the same study, the researchers compared their findings with similar cohort studies and with recent high-quality meta-analyses. The results were clear: individuals who consumed 50-60% of calories as carbohydrates had a lower risk of mortality than those consuming a lower percentage of calories from carbohydrates.
A 2022 Cochrane systematic review and meta-analysis including 61 randomised controlled trials (RCTs) compared low-carbohydrate diets (10-45% of calories) with balanced carbohydrate diets (45-65% of calories)(5). The aim of all the included trials was weight loss, and both arms administered weight-reducing diets.
The review concluded that low‐carbohydrate weight-reducing diets show little difference in weight loss compared to balanced‐carbohydrate weight-reducing diets. No notable differences were found in LDL cholesterol levels and diastolic blood pressure between the intervention of low-carbohydrate diets and balanced carbohydrate diets. The arm including low-carbohydrates diets produced a small but significant difference in weight reduction (1-2 Kg) in the short term compared to balanced-carb diets, but this difference was not present in longer-term studies. The authors suggested that the slight difference in weight might be attributable to reduced body fluid stores due to lower body glycogen content in low-carbohydrate diets (5).
The authors highlighted that low‐carbohydrate diets are implemented differently, but they can often restrict healthy foods such as whole grains, legumes, and other carbohydrate‐containing foods, such as dairy, most fruit and certain vegetables. In these diets, these foods are typically replaced with foods higher in saturated fat and protein, such as meats, eggs, cheese, butter, cream, and oils. Some low‐carbohydrate diets recommend eating as desired, while others recommend restricting the amount of energy eaten. On the other hand, diets with moderate amounts of carbohydrates, protein and fats (in line with current healthy eating advice from the World Health Organization) include plenty of healthy whole plant-based foods and can be safely used for weight reduction (6). People can reduce their calorie intake by reducing their portion size and choosing options with a reduced energy density (e.g. boiled potatoes instead of fried potatoes).
What are the recommendations from dietary guidelines worldwide regarding carbohydrate intake?
Carbohydrate recommendations vary across different settings and countries, as they are influenced by various factors such as dietary guidelines, cultural practices, and health considerations. In general, carbohydrates are considered an essential part of a balanced diet, providing a significant source of energy.
In the United States, the Dietary Guidelines for Americans recommend that carbohydrates should make up 45-65% of total daily calorie intake (7). This range allows flexibility in meeting individual nutritional needs and preferences. Similarly, the recent World Health Organization (WHO) suggests that carbohydrates should constitute 55-75% of the total energy intake for adults (6). These recommendations emphasise the importance of choosing whole grains, fruits, vegetables, and legumes as primary sources of carbohydrates.
The German Nutrition Society (DGE) recommends that carbohydrates should contribute 45-55% of total daily energy intake (8). The DGE recommends consuming various carbohydrate-rich foods such as whole grains, potatoes, legumes, fruits, and vegetables to ensure an adequate intake of essential nutrients and dietary fibre.
Do people eat the recommended intake of carbohydrates?
Surveys from across the globe show that approximately, people consume the recommended intake of carbohydrates (9). However, data shows that the quantity of low-quality carbohydrates is disproportionately high. For example, a study of US adults showed high energy intake from low-quality carbohydrates. Most of them came from refined grains, fruit juice, and potatoes (21.2% of intake), followed by added sugars in foods and beverages (14.4% of intake)(10).
The bottom line
Carbohydrates have positive health implications and are vital for energy and organ function. It is important to recognize that not all carbohydrates are created equal, as their quality and source can significantly impact health outcomes. Whole plant foods such as whole grains, legumes, tubers, fruit and vegetables are excellent sources of dietary fibre, vitamins, minerals, and phytochemicals. Contrary to common belief, low-carbohydrate diets do not result in significantly greater weight loss than balanced carbohydrate diets.
Further information
Diet and Diabetes: Carbohydrate Consensus vs Controversy by Christopher Gardner, PhD.
The following video is a webinar recording from April 13, 2022, as part of our webinar series “A Taste of Healthcare”.
Additional Information:
-
Monteiro C, Cannon G, Lawrence M, Louzada ML, Machado P. FAO. Ultra-processed foods, diet quality, and health using the NOVA classification system. 2019 Aug 1;
Schwingshackl L, Hoffmann G, Lampousi AM, Knüppel S, Iqbal K, Schwedhelm C, et al. Food groups and risk of type 2 diabetes mellitus: a systematic review and meta-analysis of prospective studies. Eur J Epidemiol. 2017 May;32(5):363–75.
O’Hearn M, Lara-Castor L, Cudhea F, Miller V, Reedy J, Shi P, et al. Incident type 2 diabetes attributable to suboptimal diet in 184 countries. Nat Med. 2023 Apr;29(4):982–95.
Seidelmann SB, Claggett B, Cheng S, Henglin M, Shah A, Steffen LM, et al. Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis. Lancet Public Health. 2018 Sep 1;3(9):e419–28.
Naude CE, Brand A, Schoonees A, Nguyen KA, Chaplin M, Volmink J. Low‐carbohydrate versus balanced‐carbohydrate diets for reducing weight and cardiovascular risk. Cochrane Database Syst Rev [Internet]. 2022 [cited 2023 Jun 13];(1). Available from: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013334.pub2/full
Carbohydrate intake for adults and children: WHO guideline [Internet]. [cited 2023 Sep 29]. Available from: https://www.who.int/publications-detail-redirect/9789240073593
Home | Dietary Guidelines for Americans [Internet]. [cited 2023 Jun 13]. Available from: https://www.dietaryguidelines.gov/
DGE-Positionspapier-Richtwerte-Energiezufuhr-KH-und-Fett.pdf [Internet]. [cited 2023 Jun 13]. Available from: https://www.dge.de//fileadmin/Dokumente/WISSENSCHAFT/Positionspapiere/DGE-Positionspapier-Richtwerte-Energiezufuhr-KH-und-Fett.pdf
ChartsBin. ChartsBin. [cited 2023 Jun 21]. Contribution of Carbohydrates in Total Dietary Consumption. Available from: http://chartsbin.com/view/1154
Shan Z, Rehm CD, Rogers G, Ruan M, Wang DD, Hu FB, et al. Trends in Dietary Carbohydrate, Protein, and Fat Intake and Diet Quality Among US Adults, 1999-2016. JAMA. 2019 Sep 24;322(12):1178–87.
