How bad are carbs, really?


There is a fear that carbohydrates are detrimental to health. As a result, low carb diets have become popular, especially for weight loss. In this Honest Nutrition feature, we explain what carbohydrates are, look at healthy vs. unhealthy options, and discuss whether a diet rich in
Carbohydrates are considered essential nutrients for the body to function properly by several global health organizations, including the World Health Organization (WHOTrusted Source). Their primary role is to provide energy to all cells in the body. In the absence of carbohydrate intake, the body will use an alternative fuel source called ketones.
The word “carbohydrate” is an umbrella term that describes various types of sugar-containing molecules present in foods.
Types of carbohydrates
Generally, there are three types of carbohydrates: sugars, starches, and dietary fiber.
It is possible to classify them further as simple or complex carbs, depending on the number and type of sugar molecules — such as glucose — that each structure contains.
Simple carbs
Also called “simple sugars,” “sugars,” or “saccharides,” these carbohydrates contain between one and 10 sugar molecules and are present in fruits, vegetables, and dairy products. Those with one or two sugar molecules are called monosaccharides and disaccharides, respectively, while those containing up to 10 sugar molecules are called oligosaccharides.
Lactose — the main sugar in animal milk — is a disaccharide comprising the monosaccharides glucose and galactose.
Oligosaccharides, however, are mid-length prebiotic carbohydratesTrusted Source that are in fiber-rich foods and human milkTrusted Source.
Complex carbs
Complex carbohydrates are made up of polysaccharidesTrusted Source, which are longer, intricate chains of sugar molecules. Complex carbs include both starches and dietary fiber.
Starches are the storage carbohydrates in peas and beans, grains, and vegetables, and they provide the body with energy.
Dietary fiberTrusted Source, or roughage, is the indigestible part of plants — in whole grains, fruits, vegetables, nuts and seeds, and legumes such as peas and beans — that supportsTrusted Source good gut health.
Are there ‘healthy’ and ‘unhealthy’ carbs?
Carbohydrates often get a bad rap due to the associationTrusted Source of their excessive consumption with weight gain, obesity, metabolic syndrome, and diabetesTrusted Source.
This phenomenon, which some researchers call “carbotoxicityTrusted Source,” promotes the idea that the excessive consumption of all types of carbohydrates favors the development of chronic diseases.
For this reason, many low carbohydrateTrusted Source diets have become popular among people interested in losing weight or managing blood sugar levels. They are even in favor among seasoned athletesTrusted Source.
However, several other studiesTrusted Source have demonstrated that the qualityTrusted Source of carbohydrates that people consume is as important as the quantity.
This finding suggests that rather than all carbs being “created equal,” some options are better than others for health.
‘Unhealthy’ carbs
Carbohydrates that people may consider unhealthy because they are less nutritious include:
• refined carbohydrates, such as polished rice and flour
• sugar-sweetened beverages, such as sodas and juices
• highly processed snacks, including cookies and pastries
According to existing research, a diet with a higher intake of these types of carbohydrates and fewer of the more nutritious options can increase markers of inflammationTrusted Source and perpetuate hormonal imbalancesTrusted Source in people with polycystic ovary syndrome (PCOS).
The excessive consumption of simple added sugarsTrusted Source is also linked with an increased risk of insulin resistance, non-alcohol-related fatty liver disease, heart disease, stroke, diabetes, and cancer.
However, studies distinguish that added sugars and simple sugars that occur naturally in foods may not have the same negative effects.
A 2018 studyTrusted Source even suggests that natural sourcesTrusted Source of sugar, such as honey, may be effective in reducing blood sugar levels and lowering the risk of developing type 2 diabetes.
Emerging research continues to shine a light on the adverse health effects of these so-called unhealthy carbohydrate foods.
Experts recommend eating a balanced diet that consists primarily of nutritious foods and includes these types of carbohydrates only in moderation.
‘Healthy’ carbs
More nutrient-dense sources of carbohydrates that people typically see as healthy include:
• fruits, such as bananas, apples, and berries
• nonstarchy vegetables, such as spinach, carrots, and tomatoes
• whole grains, such as whole grain flour, brown rice, and quinoa
• peas and beans, such as black beans, lentil peas, or garbanzo beans
• dairy and dairy products, such as low fat milk, and yogurt
Research has linked diets rich in these complex carbohydrates — such as the Mediterranean dietTrusted Source — with anti-inflammatory benefits, lowered insulin resistance, and a reduced risk of chronic diseases.
The researchers attribute many of these benefits to the dietary fiber content of complex carbohydrates.
For instance, the dietary fiber in whole fruits improvesTrusted Source long-term weight management and supports regular bowel movements and healthy aging.
Furthermore, boosting the quality of the diet by including more complex carbs and dietary fiber can lead toTrusted Source improvements in some of the effects of PCOS, such as insulin resistance and elevated androgens.
A 2020 reviewTrusted Source found that the dietary fiber in whole grain foods confers several health benefits, including a reduced risk of heart diseaseTrusted Source, gut disorders, cancer, and diabetes.
Deciding which carbs are the ‘healthiest’
The glycemic index (GI)Trusted Source and glycemic load (GL)Trusted Source are two measures that people have used to establish the quality of carbohydrate foods and categorize them as “healthy” or “unhealthy.”
The GI is a measure of the blood sugar-raising potential of a single carbohydrate food compared with pure glucose.
Low GI foods, which primarily consist of complex carbs, have minimal effects on blood sugar levels. They include whole grains and nonstarchy vegetables. High GI foods include potatoes and foods with added sugars.
Likewise, people use the GL to assess how much a particular meal is likely to increase blood sugar levels.
Although people have used both the GI and GL for decades to guide meal planning and manage blood sugar levels for people with diabetes, the science is inconclusiveTrusted Source.
Many studies suggest that an increased intakeTrusted Source of low GI foods improves health outcomes, but other studies demonstrate that differencesTrusted Source in daily glucose tolerance and individual responses are responsible for blood sugar levels rather than the GI of the foods themselves.
A food’s GI may, therefore, not be a direct predictor of an individual’s glycemic response.
Differences in glycemic response between individuals make it challenging to determine which carbs are truly the healthiest, since even whole grains may not beTrusted Source a consistent and reliable measure of GI and GL.
Are diets rich in carbs good for you?
Despite the popularity of low carbohydrate dietsTrusted Source, they are not suitable for everyone, and some populations still benefit from a carbohydrate-rich diet.
For example, endurance athletic performance becomes compromisedTrusted Source on a low carbohydrate diet, and a high carbohydrate intake remains the most evidence-backedTrusted Source choice for elite athletes.
Among members of the general population with high carbohydrate intake, significant reductionsTrusted Source in blood sugar levels — potentially promoting the remission of prediabetes — occur when the daily intake of carbohydrates is reduced.
Therefore, for populations that consume 65–75% of their daily calories from carbohydrates, experts recommendTrusted Source reducing carbohydrate calories to 50–55% of daily intake and increasing protein.
A carbohydrate restriction of 45% or less of daily calories is more effectiveTrusted Source for short-term blood sugar control, but it may be unsustainable and does not provide greater long-term results than a range of 50–55% of daily calories from carbohydrates.
Before making changes to their diet, people should speak with a doctor or registered dietitian to determine their specific carbohydrate needs to optimize their health outcomes.