Milk may delay knee osteoarthritis in women
7th April 2014 – Drinking skimmed or semi-skimmed milk may delay the progression of osteoarthritis in women, according to new research.
The same was not true for other dairy products, the study found. Yoghurt did not protect against osteoarthritis, while women who ate cheese tended to see their condition worsen more rapidly.
Milk did not appear to affect the advance of knee osteoarthritis in men.
Swelling and deformity
Osteoarthritis is a condition in which the natural cushioning between joints - cartilage - degenerates. Small injuries within joints triggers an immune reaction, which causes inflammation that leads to a breaking down of cartilage tissue leading to pain, swelling and deformity.
It is estimated that around 8.5 million people in the UK are affected by joint pain from osteoarthritis. In those aged over 45, knees are the joints most often affected by osteoarthritis, and women aged 75 and over are the group with the highest prevalence of knee pain.
Milk is an excellent source of vitamins and minerals, dairy calcium and protein, and has long been recognised for helping promote bone health. However, the authors of the latest study, published in the journal Arthritis Care and Research, say little work has been done on establishing a link between diet and osteoarthritis (OA) of the knee.
"Milk consumption plays an important role in bone health,” lead author Dr Bing Lu explains in a statement. "Our study is the largest study to investigate the impact of dairy intake in the progression of knee OA."
Joint space width
The researchers examined data from 1,260 women and 888 men involved in the Osteoarthritis Initiative – a long-term study aimed at promoting new treatments for the condition.
The diet of the volunteers was recorded at the start of the study and X-rays were taken to measure the width of the joint space – an indication of how much cartilage has been lost. All the volunteers were assessed each year for the next 4 years.
The researchers found a correlation between how much fat-free or low-fat milk women drank and joint space width in their knee. Those who drank no milk saw their joint space decrease by an average of 0.38mm compared with 0.29mm for those who drank up to six 8 oz glasses each week and an average of 0.26mm for those who drank more than 7 glasses each week.
These results remained valid even after the researchers took account of disease severity, body mass index (BMI) and other dietary factors.
"Our findings indicate that women who frequently drink milk may reduce the progression of OA," concludes Dr. Lu. However, he adds: "Further study of milk intake and delay in OA progression are needed."
Professor Alan Silman, medical director of Arthritis Research UK, says the findings of the US study are "extremely interesting", but cautions that it is too early to send out the message that women with knee osteoarthritis should drink more milk to prevent their condition getting worse.
In a statement he says: "Although the link between levels of milk consumption and the progression of knee osteoarthritis is not well understood, the researchers suggest that elevated dietary calcium intake may be a factor. We know that vitamin D is needed for the body to absorb and process calcium, and there’s also some evidence that osteoarthritis of the knee and hip progresses more quickly in people who don’t have enough vitamin D.
"We’re currently funding a large clinical trial to find out of if taking vitamin D supplements can stop the deterioration of the knee joint due to osteoarthritis, and we expect the results soon."