Mediterranean diet decreases knee OA

High adherence to a Mediterranean diet was found to be associated with significantly less MRI-documented destruction of knee cartilage (see knee arthritis med diet clinrheum2018 in dropbox, or doi.org/10.1007/s10067-018-4075-5).

Details:
-- 783 people in the Osteoarthritis Initiative, a publicly available platform with information from people from 4 cities: Baltimore, Maryland; Pittsburgh, Pennsylvania; Pawtucket, Rhode Island; and Columbus, Ohio. This database included 4796 people, of whom 783 had adequate data for assessment of diet as well as an MRI of their knee
-- 60% female, mean age 62, 85% white, 45% previous or current smokers, 25% had graduate degree, 25% had yearly income less than $50,000, BMI 30, Charlson comorbidity Index 0.5, average energy intake was 1400 cal a day [ie, a pretty healthy white well-off group]
-- dietary assessment was using the Block Brief 2000 food frequency questionnaire of 70 foods/beverages quantified by 9 levels of consumption. This was translated into a Mediterranean diet score

Results:
-- those in the highest quartile of adherence to a Mediterranean diet were significantly older, more likely to be female, white, and have higher educational and  income levels. also lower BMI and fewer medical comorbidities.
--the association between adherence to a Mediterranean diet and knee MRI parameters, adjusted for 10 potential confounders (age, sex, presence of any comorbidities, presence/absence of radiologic/clinical knee osteoarthritis (OA), median BMI, education, income, smoking status, race) were:
     -- a significant increase in the central medial femoral cartilage volume, and the mean central medial femoral cartilage thickness, the mean cartilage thickness of the central medial tibial femoral compartment, and in the cartilage volume of the medial tibial femoral compartment; all were highly statistically significant, mostly p <0.0001)

Commentary:
-- worldwide estimates are that 10% of men and 20% of women over 60 years old have knee osteoarthritis
-- knee x-rays have quite low sensitivity and specificity for assessing knee OA, and have not been recommended in some review articles (see knee arthritis felson nejm 2006 in dropbox, or Felson DT. N Engl J Med 2006; 354: 841)
-- knee MRIs have been used more recently to assess the early detection of articular cartilage damage, menisci, ligaments, synovium, capsular structures, fluid collections, and bone marrow), though this is not used clinically because of its cost and unclear utility
-- cartilage thinning and loss detected by MRI seem to be early features of OA. However, though this makes clear physiological sense, we should always maintain some healthy skepticism about using surrogate markers as definitive evidence of clinical disease. perhaps some of these MRI measurements are not significantly associated with eventual clinical OA (who would have thought that xrays were pretty useless??). perhaps there is a protective repair process that knees undergo which was missed in these MRIs? perhaps it is some common pathway leading to both MRI changes and clinical OA, but the MRI itself is not predictive of clinical disease (ie, the MRI might have changed for reasons not directly tied into progression to clinical OA)
-- diet-induced weight loss has been shown to improve knee OA symptoms more than exercise programs (and this diet is associated with some weight loss)
    -- prior studies have shown that following a Mediterranean diet seems to lower the prevalence of developing knee OA, both clinically and by x-ray findings. in some studies, part of this effect might be from lower BMI associated with the Mediterranean diet
    -- one concern in this study is that those on a Mediterranean diet were also at lower risk of OA, since their BMI was lower and they had fewer medical comorbidities and perhaps attendant medications which might affect the knee cartilage. they did mathematically control for these comorbidities (still finding benefit from the Mediterranean diet), but were there other non-controlled factors?  vitamin D and calcium? exercise type and quantity? quadriceps strength? differences in the anatomy itself (eg eccentric forces on the knee joint)???
-- though this study reveals an association and not causality, a Mediterranean diet is associated with decreased inflammation in the body. It also lowers oxidative stress markers, and there also are data suggesting that that could play a role in remodeling the extracellular matrix (ie, by decreasing inflammation, the Mediterranean diet might help the knee remodel and heal). However these biomarkers were not assessed  in the study.

So, not a definitive study, but it adds yet another plus to the Mediterranean diet. It does seem reasonable to assume that a diet which decreases inflammation and oxidative stress, as well as leading to some weight loss, might be associated with less knee osteoarthritis. and also help prevent or treat other chronic diseases: diabetes, heart disease, cancer, cognitive decline, depression, perhaps even the rate of bone loss in those with baseline osteoporosis (eg see https://www.ncbi.nlm.nih.gov/pubmed/30007343 )…

For some prior blogs on the potential advantages of Mediterranean diet, see:
http://gmodestmedblogs.blogspot.com/2018/06/mediterranean-diet-with-olive-oil-or.html
http://gmodestmedblogs.blogspot.com/2017/08/changing-diet-changes-lifespan.html
http://gmodestmedblogs.blogspot.com/2017/10/mediterranean-diet-helps-nafld.html
http://gmodestmedblogs.blogspot.com/2015/11/mediterranean-diet-and-brain-volume.html
http://gmodestmedblogs.blogspot.com/2015/11/breast-cancer-risk-and-mediterranean.html
http://gmodestmedblogs.blogspot.com/2014/01/mediterranean-diet-and-primary.html
http://gmodestmedblogs.blogspot.com/2014/01/mediterranean-diet-diabetes-prevention.html

geoff

If you would like to be on the regular email list for upcoming blogs, please contact me at gmodest@uphams.org

to get access to blogs since 8/15/17:

1. go to http://gmodestmedblogs.blogspot.com/ to see them in reverse chronological order

2. click on 3 parallel lines top left, if you want to see blogs by category, then click on "labels" and choose a category​

3. or you can just type in a name in the search box and get all the blogs with that name in them

to access older blogs from the BMJ website, from October 2013 until 8/15/17: go to http://blogs.bmj.com/bmjebmspotlight/category/archive/ 

please feel free to circulate this to others. also, if you send me their emails, i can add them to the list