A meta-analysis of the results of 2 longitudinal studies has shown that consuming a high-fiber diet may lower the risk for developing symptomatic osteoarthritis (OA; Dai Z, et al. Ann Rheum Dis. 2017;76:1411-1419). Dietary fiber has been shown to lower patients’ risk for coronary heart disease, diabetes, obesity, and premature death because it can lower serum cholesterol, slow glucose absorption, improve insulin sensitivity, and promote weight loss by increasing satiety and decreasing caloric intake. Patients whose diets are high in fiber have also been shown to have lower levels of C-reactive protein, a marker of inflammation that has been linked to rheumatoid arthritis, among other diseases.
“To our knowledge, this was the first study in the literature investigating the association between dietary fibre and OA outcomes,” said lead investigator Zhaoli Dai, PhD, MS, T32 Postdoctoral Researcher, Clinical Epidemiology Research and Training Unit, Boston University School of Medicine, MA, and colleagues.
Using data from 2 US trials, Dr Dai and colleagues performed a meta-analysis with the goal of determining whether dietary fiber may have any bearing on risks for x-ray evidence of knee OA, symptomatic knee OA (eg, pain and stiffness), and worsening knee pain.
The first clinical trial was the OA Initiative (OAI), a multicenter, long-term, prospective study of 4796 men and women aged 45 to 79 years with or at risk for OA who were enrolled between 2004 and 2006. The goal of OAI was to create a diverse cohort of patients who could help researchers gather more information about the physiologic changes that occur before the onset of OA symptoms, or before the disease progresses.
The second trial was the Framingham Offspring cohort study, which was designed to provide a more in-depth assessment of diet. It consisted of >1200 adults who were the offspring of patients who once participated in the Framingham Heart Study, as well as their spouses. Patients in the Framingham Offspring cohort study had their regular dietary intake documented at baseline and at year 4.
Dietary fiber intake in both trials was measured using responses to the food frequency questionnaire.
Data regarding symptoms and x-ray evidence were collected every year for 4 years in the OAI, and assessed at 9 years in the Framingham Offspring trial. Data were also collected on potentially influential factors, such as history of knee injury and surgery, medication usage, and particulars of the patient’s lifestyle, including tobacco and alcohol use and exercise. For the purposes of the meta-analysis, total dietary fiber was calculated by the sum of fiber generated from cereal grain, fruit and vegetables, and legumes and nuts.
In the OAI trial, at the end of the 4-year period, investigators observed 861 cases of symptomatic OA of the knee and 152 cases of radiographic OA of the knee. In addition, knee pain worsened in 1964 patients.
In the Framingham Offspring cohort, at the end of the 9-year period, there were 143 cases of symptomatic OA of the knee and 175 cases of radiographic OA of the knee.
Analysis of the data showed that consumption of more fiber was associated with a lower risk for symptomatic OA. Compared with the lowest intake (bottom 25% of participants), the highest intake (top 25%) was associated with a 30% lower risk for symptomatic OA in the OAI trial and a 61% lower risk in the Framingham Offspring cohort. However, more fiber intake was not associated with risk for radiographic OA.
In addition, among patients in the OAI trial, eating more fiber in general, as well as having a high cereal fiber intake, were associated with a significantly lower risk for worsening knee pain. These findings held true, regardless of other potentially influential factors.
“These data demonstrate a consistent protective association between total fibre intake and symptom-related knee OA in two study populations with careful adjustment for potential confounders,” Dr Dai and colleagues concluded.