What Science Can Tell Us About Diet and Health

Most of the medical research on diet, rheumatoid arthritis (RA), and systemic lupus erythematosis (SLE) relies on patients reporting what they eat. In these studies, called observational studies, patients may complete surveys or questionnaires about their usual diet in the past week or past year, and about their symptoms. While observational studies can be relatively easy to carry out, they cannot prove a cause-and-effect relationship between diet and RA/SLE symptoms. What we choose to eat is strongly linked to individual factors – such as personal tastes, cultural background, medical conditions, cigarette smoking, income, etc. – that can also affect our health and how we feel. As an example, many people eat chicken soup when they have the flu, but nobody would say that eating chicken soup causes the flu. Similarly, people with RA/SLE who have worse symptoms may choose to eat differently than those with milder symptoms, in which case it would be wrong to say that their dietary choices are causing more severe disease.  

What kind of medical research can tell us which diets or foods cause less severe RA/SLE symptoms? Randomized clinical trials allow researchers to randomly assign different diets to different patients. Meals are often provided so that the researchers can be sure that participants are eating the diet “as prescribed.” A trial allows us to test whether a particular diet causes better or worse RA/SLE symptoms because individual factors (e.g., medical conditions, mild versus severe disease) are equally balanced in the randomly-assigned diet groups. The downside of clinical trials is that they are harder to carry out: they are more expensive, take longer, and it can be more difficult to find patients willing to participate.  

Some of the information here comes from observational studies and some comes from clinical trials. The dietary advice in the FAQs comes from clinical trials, and we have provided references on each page for readers who are interested in learning more, including a thorough review of dietary interventions that have been tested in people with RA [1]. 

Reference

1. Hagen, K.B., et al., Dietary interventions for rheumatoid arthritis. Cochrane Database Syst Rev, 2009(1): p. CD006400.