The hype on delaying or preventing osteoarthritis by drinking more milk or eating more cheese does not always necessarily work. Before people start to guzzle more milk, there are many factors to consider other than dairy intake that influence the progression of the joint disease or the likelihood of getting osteoarthritis. A recent study that was published in Arthritis Care & Research showed that milk consumption in the sample population of 1,260 women showed some benefits in delaying osteoarthritis in the knee, but the sample population of 888 men showed no significant benefits. Each group had follow-ups at every 12 months for four years.
The results after the study showed that women who drank more milk from zero to less than three, four to six, and more the seven 8-ounce glasses a week, the joint space width in the knee also decreased respectively by 0.38mm, 0.29mm, and 0.26mm. Factors that may influence the results, such as diet, body mass index, and disease severity, were already considered. The men, unfortunately, showed no such trend and benefit as the women did. Researchers concluded that there is a correlation between higher milk consumption frequency and the reduction of osteoarthritis in women. However, they were cautious about their findings, stating, “Replication of these novel findings in other prospective studies demonstrating the increase in milk consumption leads to delay in knee OA (osteoarthritis) progression are needed.”
Many may think that maybe drinking more milk is better to prevent or delay osteoarthritis, but this is not always true. “I always look at who funded the studies,” said registered dietitian Angelique Crandall, M.S., who practices in Albuquerque New Mexico. She suggests that consumers ask questions considering the study. “Would this group studied have any other good habits or qualities that promote health besides the fact that they drank milk? What is the trade-off for drinking milk? Is it associated with any adverse effects (allergies, digestive issues, other diseases, etc.)? It’s very important to remember that correlation does not equal causation. Ice cream sales go up in the summer and so do shark attacks. Does that mean one caused the other? Go back to original study and examine the data. So many times the headlines do not match what the study can actually say about a given topic. Remember the purpose of these headlines is to grab the readers’ attention but they often don’t match up. Researcher Pedro Bastos and his colleagues have a ton of data on dairy; the good, the bad and the ugly.”
Osteoarthritis is a disease that mostly causes the inflammation of the joint cartilages, which could lead to the wearing down of the thin membranes that cushion the joint. It not only affects the knees, but also affects the wrists, hand, fingers, lower back and hips. According to the Mayo Clinic, risk factors include aging, obesity, repetitive movements based occupation or physical activities, joint deformities, gender, joint injuries, and having other diseases, such as diabetes, gout, and Paget’s disease. While it affects over 15 million people in the United States, there is no cure currently. There are treatments and lifestyle changes that can delay the progress of osteoarthritis and improve the quality of life. Although calcium and other nutrients found in milk and dairy products could benefit from delaying osteoarthritis, it may not always be that simple. Here’s why.
Nutrition 101: No nutrient works by itself
Milk contains a high amount of calcium, protein, and vitamin D, which makes it an ideal “one-stop-shop” for obtaining these nutrients that bones need. However, drinking more milk does not necessarily mean the body will absorb more nutrients and use them to prevent osteoarthritis and other related diseases. Calcium is one of the major nutrients that is essential for maintaining bone health. However, it doesn’t work alone to do its job. Vitamin D, a fat-soluble vitamin, assists the body in absorbing calcium and maintains a narrow range of serum calcium levels for normal functioning of the nervous system, bone growth, and maintaining bone density.
According to the Linus Pauling Institute Micronutrient Research at Oregon State University, the serum calcium levels are regulated by the parathyroid glands that are located in front of the trachea at the throat. When calcium levels drop too low, they secrete parathyroid hormone (PTH), which increases activity of an enzyme in the kidney called 25-hydroxyvitamin D3-1-hydroxylase or CYP27B1. This causes a chain reaction of chemical interactions that results in increased production of 1,25-dihydroxyvitamin D, an active form of vitamin D that the body can use, and changes in gene expression that normalize calcium levels by increasing the absorption rate of calcium in the intestines, reabsorption rate of calcium filtered by the kidneys, and transportation of calcium from bones when there is a dietary deficiency of calcium. Therefore, diet and maintaining a normal functioning hormonal and renal system could affect the progress of osteoarthritis.
Cutting back on soda intake could maintain healthier bones and decrease the risk of osteoarthritis. In a study that was published in the British Medical Journal Open on the July 18, 2013, researchers assessed the daily diet and soda consumption of over 2,100 participants with osteoarthritis in the knee. They evaluated the questionnaires and the width of the joint space in the knee based on radiographs. What they found was that in most of the cases, higher soda consumption led to decreases in joint space. Those who drank one serving of soda or none per week had a mean decrease of 0.39 and 0.31mm, respectively, while those who drank two to four servings and more than five servings per week had a decrease of 0.34 and 0.60mm, respectively. What was even more interesting was that obese men who also had very high soda consumption showed significant decreases of joint space while no such associations occurred in women. Like the milk consumption study, the soda researchers concluded, “Replication of these novel findings in other studies demonstrating the reduction in soft drink consumption leads to delay in OA progression is needed.”
The Linus Pauling Institute stated that one of the culprits in soda that causes calcium reduction in bones is phosphorous in the form of phosphoric acid. Diets that are low in calcium and high in phosphorus are associated with increased PTH secretion, which increases the amount of calcium leeched from the bones. So it doesn’t really matter how much milk or dairy products one consumes if the soda consumption offsets the benefits that milk provides. Therefore, more milk consumption — one single factor — does not necessarily prevent osteoarthritis and maintain bone health if the rest of the diet is poor.
Don’t forget to move
Even with the perfect dose and balance of nutrition intake, it still doesn’t improve the quality of life or bone and joint health if exercise and movement aren’t addressed. Exercise physiologist Len Kravitz, Ph.D., from the University of New Mexico, stated that resistance exercise training — including weightlifting and body-weight exercises — can stimulate hormones to increase calcium absorption to increase bone density. In the September 2013 issue of British Medical Journal, a review of 60 trials — 44 of these include the knee — of over 8,200 patients with osteoarthritis in the knee or hip showed that those who performed strength training exercises had significant improvements in pain relief and lower-body strength, endurance, and flexibility than those who did no exercise. Another review published in March 2014 of Arthritis & Rheumatology also had very similar results among 48 trials.
Some people fear that more exercise could lead to more pain or worsen the condition, but a meta-analysis in the January 2014 issue of Arthritis Care & Research showed that middle-age and elderly adults who met the 2008 exercise guidelines (more than 150 minutes per week) established by the Department of Health and Human Services (HHS) did not significantly increase the risk of worsening the disease. Those who had the highest levels of physical activity (more than 300 minutes per week) had higher risk than those who met the minimum HHS requirements, yet the data wasn’t statistically significant enough to prove that more exercise increased risks of osteoarthritis in the knee.
Understanding the relationship between nutrition, exercise and movement, and lifestyle can help anyone increase the chances of preventing osteoarthritis, and drinking more milk or adhering to any one factor does not necessarily guarantee positive results. The biggest question one could ask about the study is, “Why did the men not benefit from drinking milk?” Thus, this may be the evidence indicating that correlation does not necessarily equate to causation.
By Nick Ng
Oregon State University
Arthritis Care & Research
Arthritis & Rheumatology
British Medical Journal
Oregon State University
University of New Mexico
Interview with Angelique Crandall, M.S., R.D.