The link between osteoarthritis and obesity

Historically, osteoarthritis was considered to be a degenerative, wear-and-tear disease. Early researchers believed that damage to bone and articular cartilage was purely mechanical, occurring as a result of loading on joints, perpetuated by age and excessive body mass; the two leading risk factors for OA.

Introduction

However, obesity is also a risk factor for OA in non-weight-bearing joints such as the hand and wrist, suggesting more than mechanical factors are at play.

Nowadays it is widely accepted that obesity induces low-grade systemic inflammation. Patients with OA have been found to have significantly higher amounts of proinflammatory molecules, including adipokines (such as leptin, resistin, and adiponectin) and cytokines (such as TNF-a and IL-6), in their synovial fluid when compared with healthy controls. Of these, leptin is well documented to be detrimental in OA, with higher serum levels independently and consistently associated with reduced cartilage thickness.5 It has been hypothesised that elevated leptin may contribute to an overexpression of proinflammatory cytokines that promote the progression of OA through cartilage damage.

While traditional management of OA has focused on alleviating the symptoms of the condition through the use of pharmaceuticals, optimal management should manage symptoms while also attempting to slow down disease progression. Given recent advancements in the understanding of OA, dietary strategies should be taken into consideration as a complementary treatment. While there is no designated diet for OA, there is preliminary evidence that adherence to the Mediterranean diet can lower levels of pro-inflammatory markers, which in turn can slow down cartilage degeneration.

Mediterranean diet

Below are just a few key foods from the Mediterranean diet that can be recommended to patients who are interested in trying complementary management strategies for OA.

FRUIT AND VEGETABLES

Fruits and vegetables are loaded with antioxidants, vitamins and polyphenols, food chemicals that protect against oxidative stress and inflammation.7 There is an excellent catalog of research outlining each specific nutrient and their mechanism of action, with some research directly linking specific food chemicals to OA.

However, when it comes to recommending fruit and vegetable intake for patients, variety should be emphasised. Each colour worn by a fruit or a vegetable indicates an abundance of a specific food chemical. Therefore patients should be encouraged to consume a wide variety of antioxidants through consuming at least 7 serves of different coloured fruits and vegetables per day.

WHOLE GRAINS AND LEGUMES

Whole grains and legumes provide dietary fibre, possibly the most essential nutrient for good health. Fibre’s role in the anti-inflammatory process stems from the link between the gut microbiome and the immune system. Although fibre is resistant to human digestive enzymes, fermentable fibres are able to be digestible by gut microbes, which then produce byproducts that can affect the development of immune-cell precursors. In a healthy gut environment, short-chain fatty acids such as butyrate are produced, which prevent an excessive immune response and inhibit pro-inflammatory pathways. Alternatively, when the normal gut microbiome is altered, the immune system can overreact leading to the activation of inflammatory mediators associated with OA.

Patients can be recommended to consume 25-30g of fibre-rich whole grains and legumes each day, which can include whole-wheat breads and cereals, brown rice, quinoa, lentils and chickpeas.

FISH

Fish contains the essential polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These omega-3s decrease the production of proinflammatory cytokines, while conjunctively generating anti-inflammatory molecules. While currently there is insufficient evidence to determine the specific effect of fish consumption in patients with OA, the anti-inflammatory mechanisms of EPA and DHA are well established.

As such, patients should be recommended to consume 2-3 servings of fatty fish per week, this can include salmon, herring, sardines, tuna, trout, and mackerel.

EXTRA VIRGIN OLIVE OIL

Extra virgin olive oil (EVOO) provides an excellent source of healthy fat as well as biologically active polyphenols. One of these compounds, oleocanthal, has similar properties to ibuprofen in which it inhibits the production of COX proinflammatory enzymes. By inhibiting these enzymes, the body’s pool of inflammation and pain is lessened.

In order to procure the benefits, patients should be recommended to consume 2-3 tablespoons of EVOO each day.

NIGHTSHADE VEGETABLES

Eggplants, capsicums, tomatoes and potatoes are all members of the nightshade family, which contain the chemical compound solanine. There are anecdotal reports this particular compound can trigger arthritis pain and inflammation. However, there are no scientific studies that have demonstrated a connection between nightshade vegetables and inflammation.