A degenerative disease causing pain and swelling of the knee joints, knee osteoarthritis currently has no cure. But researchers say drinking milk every day has been linked to reduced progression of the disease.
Publishing their results in the American College of Rheumatology journal Arthritis Care & Research, the researchers say while their findings show that women who regularly drank fat-free or low-fat milk experienced delayed progression of knee osteoarthritis (OA), those who ate cheese actually experienced an increase in progression of the disease.
They also note that their findings are not applicable to men, and that yogurt did not affect OA progression.
The Centers for Disease Control and Prevention (CDC) say that OA, which is characterized by degeneration of the cartilage and its underlying bone in a joint, is believed to result from "mechanical and molecular events in the affected joint."
However, the actual causes of the disease are unknown. Treatment for the condition aims to relieve symptoms and improve function, which can include physical therapy, weight control and medications.
According to the CDC, as of 2005, an estimated 27 million adults in the US over the age of 25 had OA.
The researchers found that the more milk a woman consumed, the better her joint space width was.
The study authors say milk consumption has been acknowledged as playing an important role in bone health, but until now, its role in the progression of knee OA has been unknown.
As such, lead investigator Dr. Bing Lu - from Brigham & Women's Hospital in Boston, MA - and colleagues conducted the largest study to date to investigate the effect of dairy consumption on progression of knee OA.
A total of 2,148 individuals with knee OA - and 3,064 knees - were used as part of the Osteoarthritis Initiative. After collecting dietary information at the start of the study, investigators measured joint space between the medial femur and tibia of the knee with X-ray, to assess progression of OA.
'First evidence linking milk consumption with slowed progression of knee OA'
Subjects for the study included 888 men and 1,260 women, all of whom were followed up at 12, 24, 36 and 48 months, and the team notes that milk consumption was evaluated with a Block Brief Food Frequency Questionnaire.
Fast facts about knee OA
- By age 85, nearly 1 in 2 people may develop knee OA.
- Around 2 in 3 obese people are likely to develop the condition in their lifetime.
- In the US, an estimated 27 million adults have OA.
The researchers found that, in women, as milk intake increased (from none to less than 3, 4-6, and more than 7 glasses per week), the joint space width decreased (by 0.38 mm, 0.29 mm and 0.26 mm, respectively).
Additionally, they say there was no association between milk consumption and joint space width decreases in men.
When asked why their study revealed that women who consumed cheese showed increased progression of OA, Dr. Lu told Medical News Today that the high saturated fat acids in cheese could be to blame.
"A recent study reported that increased consumption of saturated fatty acids was associated with an increased incidence of bone marrow lesions," he added, "which may predict knee OA progression."
In a linked editorial, Shivani Sahni, PhD, and Dr. Robert McLean, from the Harvard-affiliated Hebrew SeniorLife Institute for Aging Research, write:
"With the aging population and increase in life expectancy, there is an urgent need for effective methods to manage OA. The study by Lu et al. provides the first evidence that increasing fat-free or low-fat milk consumption may slow the progression of OA among women who are particularly burdened by OA of the knee, which can lead to functional disability."
The team concludes their study by noting that further studies are needed to demonstrate how increasing milk consumption leads to delayed knee OA progression.
In 2013, Medical News Today reported on a study suggesting knee OA could be improved by combined diet and exercise.