Starchy vegetables are an important source of carbohydrates and other nutrients, but they have often been treated with caution as low-carbohydrate diets have become more popular.
Unlike non-starchy vegetables, which generally contain fewer carbohydrates and calories, starchy vegetables contain more carbohydrate, mainly in the form of starch. Potatoes, sweet potatoes, cassava, plantains, maize and yams are common examples, although the nutritional composition varies from one food to another.
The distinction matters, but it does not mean starchy vegetables should automatically be excluded from a healthy diet.
It starts with carbohydrates
Carbohydrates are one of the main sources of energy in the diet. They include sugars, starches and dietary fiber, although the body handles each type differently.
Digestible carbohydrates are broken down during digestion into smaller sugar molecules, including glucose. The glucose can then be used by cells for energy or stored for later use.
Starch is a complex carbohydrate made up of chains of glucose molecules. It is found naturally in many plant foods, including potatoes, maize and other starchy vegetables.
Fiber is also a carbohydrate, but unlike starch and other digestible carbohydrates, most dietary fiber is not broken down and absorbed in the small intestine. Instead, it moves through the digestive system, where different types of fiber can help regulate digestion and support the gut microbiome.
Cellulose, which forms part of plant cell walls, is one type of dietary fiber. It is not produced by simply reversing the bonds in starch, as is sometimes suggested. Starch and cellulose are both made from glucose units, but their molecular structures and the way those units are linked are different.
Why starchy vegetables can be part of a healthy diet
Starchy vegetables provide carbohydrates that the body can use for energy. They can also provide fiber, vitamins, minerals and other plant compounds, depending on the vegetable and how it is prepared.
The nutritional value of a starchy vegetable is also different from that of a highly refined food made primarily from starch. Whole or minimally processed plant foods generally retain more of the components that occur naturally in the food.
Fiber is particularly important. It can help food move through the digestive system, support regular bowel movements and, depending on the type, slow digestion and the rise in blood glucose after a meal. Some forms of fiber are also fermented by bacteria in the large intestine, producing compounds that support the health of the gut.
That does not mean every starchy food has the same effect. Processing, cooking method and the amount of fiber in a food can influence how quickly its carbohydrates are digested and how much blood glucose rises after eating. Highly refined foods such as white bread generally contain less fiber than many whole plant foods and can be digested more quickly.
Starchy does not mean unhealthy
The growing popularity of low-carbohydrate diets has sometimes created the impression that foods containing starch should be avoided. Nutrition research instead places considerable emphasis on the quality and source of carbohydrates.
Whole and minimally processed carbohydrate-rich foods, including vegetables, fruits, legumes and whole grains, can provide fiber and other nutrients that are limited in many highly processed foods.
Some starchy vegetables can therefore have a useful place in a balanced diet. The important distinction is not simply whether a food contains starch, but what else comes with that carbohydrate and how the food is prepared.
For example, a whole yam or sweet potato provides starch along with other nutrients and, depending on the food, fiber. A heavily processed food made from refined starch may provide considerably less fiber and other naturally occurring nutrients.
Starchy vegetables are therefore not simply a category of foods to avoid. They are carbohydrate-rich plant foods that can contribute energy, fiber and nutrients to the diet, particularly when eaten as part of an overall balanced eating pattern.
