A normal diet contains both insoluble and soluble fibers. The American Dietetic Association recommended a mix of these fibers in ratios of 50:50, 60:40 and 70:30, depending on a person’s health.

Most studies show soluble fiber is beneficial to heart health, although a few also give such credit to insoluble fiber — a point of controversy, according to Rajen S. Mehta, PhD, senior director, fiber applications, SunOpta Ingredients Group, Chelmsford, MA. “But for colon health and reducing cancer risks, more studies show the benefits of insoluble fiber,” he said.

The description of a given fiber as soluble or insoluble refers to specific analytical methods. Some dissolve readily in water, while others remain stubbornly in suspension or precipitating out of solution. Solubility affects viscosity, a characteristic that can guide applications.

Many vegetable fiber sources contain both forms. For example, sugar beet fiber is one-third soluble and two-thirds insoluble.