New Harvard Study Links “Western Diet” to Knee OA

A “Western diet,” as defined for this new Harvard Study, is a diet with fried foods, processed/red meats, refined grains, poultry, pizza, and snacks.

The new study found evidence that certain foods in the Western diet may be associated with knee osteoarthritis (OA) incidence or progression. The resulting paper, “Dietary patterns and risk of developing knee osteoarthritis: data from the osteoarthritis initiative,” was published in the June 1, 2021 edition of Osteoarthritis and Cartilage.

The team worked from their prior study showing that a Western diet as measured by principal component analysis (PCA)—a way to incorporate all food groups for dietary pattern analysis—was associated with increased knee OA progression. In their current study, the researchers undertook the first prospective study on the association between PCA-derived dietary patterns and the risk of knee OA.

Using data from the Osteoarthritis Initiative’s four clinical sites, the investigators were able to collect data from 2,842 participants (4,573 knees) and then follow-up at 12, 24, 36, 48, and 72 months. The authors note that more than 83% participants had at least four follow-up visits.

The authors categorized Western dietary items as French fries, processed/red meats, refined grains, poultry, pizza, and snacks. The authors then categorized a “prudent” dietary pattern as being one with vegetables, beans, fruits, fish, whole grains, and legumes.

Co-lead author Chang Xu, M.D., with the Division of Rheumatology, Inflammation and Immunity at Brigham and Women’s Hospital, Harvard Medical School, and the Rutgers University School of Public Health, explained the study to OTW. “Previous studies have found that dietary factors may be associated with knee OA progression. There is also evidence showing that single foods or nutrients (such as saturated fat, dietary fiber, and soft drinks) may contribute to the incidence of knee OA.”

The authors separated all participants into increasing quartiles of the Western and prudent dietary pattern scores.

Individuals who most adhered to a Western diet (i.e., included in highest quartile, Q4) tended to be “younger, more frequently depressed, and less educated than those in the lowest quartile (Q1),” they wrote. “They are also more likely to be African American, NSAIDs [non-steroidal anti-inflammatory drugs] users, and current smokers. They tended to have more energy intake per day and be overweight or obese. Meanwhile, participants who were more following prudent dietary pattern (i.e., included in Q4) had higher education levels and fewer suffered from depression. They were less likely to be current smokers, and more likely to exercise more, and consume more total calories per day.”

The investigators found that 385 (418 knees) developed knee OA within 72 months.

Dr. Xu told OTW, “The most important result of this study is that following a Western dietary pattern may be associated with an increased risk of knee OA while following a prudent pattern was associated inversely.”

We asked Dr. Xu to explain further the association of diet to OA and the role of body mass index (BMI). “Dietary factors may affect BMI, and BMI is a major risk factor for knee OA. The actual effect of dietary patterns includes two parts: the direct effect and the effect through BMI changes. Therefore, we conducted the mediation analysis to assess the allocation of these two effects. We found that BMI might explain about 30% of the detected association.”