Older people who eat the most fiber are at lower risk of developing knee pain and stiffness due to osteoarthritis (OA), new research shows.
Diets rich in fiber from plant-based foods have clear health benefits, such as lower cholesterol, better-controlled blood sugar, and a healthier weight, but most people in the U.S. don't eat enough fiber, lead author Dr. Zhaoli Dai of Tufts University in Boston told Reuters Health.
The current average fiber intake among U.S. adults is about 15 grams, she noted. "This is far below the recommended level, which is 22.4 grams for women and 28 grams per day for men 51 years and above," Dai said.
OA, which occurs when wear and tear on the joints degrades cartilage and leads to bone abnormalities, is extremely common in people 60 and older. It can be painful, and is also a leading cause of disability. There is no treatment for OA, aside from joint replacement, and therapies to address symptoms, such as anti-inflammatories for pain and swelling.
Given that dietary fiber is known to help prevent obesity and reduce inflammation, both of which are associated with arthritis, Dai's team looked at diet and arthritis risk over time in two study groups. In the Osteoarthritis Initiative, which included 4,796 men and women with OA or at risk for OA, people who consumed the most dietary fiber at the start of the study were 30 percent less likely than those who ate the least fiber to develop knee pain, stiffness or swelling due to OA, or to worsening of OA, during four years of follow-up.
In the Framingham Offspring Study, which included 1,268 adults in their early 50s, on average, the top quarter of fiber consumers had a 61 percent lower risk of knee OA symptoms nine years later than the bottom quarter.
There are many mechanisms through which increased fiber intake could help ease knee arthritis symptoms, Dai said, for example by reducing inflammation and helping people to maintain a healthy weight. Fiber can also act as a pre-biotic, she added, meaning that it can help fuel the growth of beneficial microbes in the gut, which in turn also reduces inflammation.
"This is the first study to show that consuming more dietary fiber is related to lower risk of painful knee osteoarthritis," Dai said. "Changing diets by increasing intake of dietary fiber seems to be one of the most economic ways to reduce the risk of knee osteoarthritis."
Older adults, especially those who are overweight or obese, should consider increasing their fiber intake, she added.