Sticking to a healthy diet over many years may protect against rheumatoid arthritis

Women with a healthy diet may be less likely to develop rheumatoid arthritis

Rheumatoid arthritis is a chronic inflammatory disease that affects a person’s joints, causing pain and disability. It can also affect internal organs. Rheumatoid arthritis is more common in older people, but there is also a high prevalence in young adults, adolescents and even children, and it affects women more frequently than men. Food and diet are one of the many things that can contribute to the development of rheumatoid arthritis. It has been suggested that eating a healthy diet rich in fish, olive oil and cooked vegetables may protect people from going on to develop rheumatoid arthritis.

What did the authors hope to find?
The authors hoped to find out whether having a better quality diet for a long period of time could be linked to having a reduced risk of developing rheumatoid arthritis.

Who was studied?
The study looked at almost 170,000 women from two health studies in nurses. Everyone included was a registered nurse, and nobody had been diagnosed with any kind of autoimmune disease.

How was the study conducted?
This was a prospective cohort study using information from two long-running nurse’s health studies that started in 1976 and 1984. At the beginning of each study, the women filled in a questionnaire about their lifestyle and medical history. The questionnaire was repeated every 2 years. Every 4 years they also filled in a questionnaire about their eating habits, such as how often they ate, how many calories they consumed each day, and what sort of foods they chose. The authors used this information to create a scoring system called the Alternative Healthy Eating Index 2010 (shortened to AHEI-2010) to measure the overall quality of each person’s diet over time. They then looked to see whether there was a link between the AHEI-2010 scores, and whether someone went on to develop rheumatoid arthritis. Unhealthy foods included red meat or processed meat, drinks with added sugar, and foods with a lot of salt or trans-unsaturated fatty acids (also called trans fats). Trans fats occur in only very small amounts in nature, but are found in high levels in processed foods such as snacks or fast foods. Healthy foods included nuts, fruit and vegetables, whole grains and foods with polyunsaturated fats or omega-3 fatty acids. Moderate alcohol intake was also classed as being healthy.

What were the main findings of the study?
Over the course of the study, 1007 women developed rheumatoid arthritis. The authors found that women who ate a better quality diet were less likely to develop a type of arthritis called seropositive rheumatoid arthritis before the age of 55. The women with the very best diets were 33% less likely to get rheumatoid arthritis compared with the women who had the worst diets. However, this link was not as strong for women over 55, with only a 15% reduction in risk for the very best diets.

Are these findings new?
Yes, this is the first time that a study has linked a person’s overall diet quality and their risk of rheumatoid arthritis in this way. Many other previous studies have looked at individual foods or nutrients rather than a person’s diet as a whole.

What are the limitations of the study?
It is possible that some unmeasured or unknown lifestyle or diet factors could be affecting the results. Also, the study does not tell us what the best diet or foods are to help people avoid rheumatoid arthritis. Finally, it is not possible to apply the results of this study to everyone. The women in this study were mostly white, well-educated healthcare professionals in the United States, so their diet quality may not be representative of what is eaten by people from other backgrounds and countries.

What do the authors plan on doing with this information?
This study has shown that a better quality diet could reduce the risk of younger women getting rheumatoid arthritis. People do not often maintain the same diet quality over time and it is natural for some people to change their diet quality, especially as they get older. It would be interesting to do a study to see whether making changes to diet could have an effect. If this is the case, it would be an important message for people with bad diets who are at risk of developing rheumatoid arthritis. Since diet can be modified, people may be able to simply reduce their risk of getting rheumatoid arthritis by improving the quality of their diet.

What does this mean for me?
If you are concerned about your risk of developing rheumatoid arthritis, it is possible that having a better diet quality may reduce the risk. If you already have rheumatoid arthritis, changing your diet might help. This is because some foods and nutrients have anti-inflammatory properties that could help to relieve the symptoms. For example, you could try to drink only a moderate amount of alcohol, and limit how much red meat, salt and sugar you eat. Try to include lots of fruit and vegetables and whole grains, as well as healthy nuts and oils.

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Date prepared: August 2017

Summary based on research article published on: 30 January 2017 From: Hu, Y. et al. Long-term dietary quality and risk of developing rheumatoid arthritis in women. Ann Rheum Dis 2017;76:1357–1364. doi:10.1136/annrheumdis-2016-210431

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