Background/Purpose:

Some specific diets have been shown to ameliorate rheumatoid arthritis (RA). However, there is generally a lack of studies on any possible dietary impact on the efficacy of anti-rheumatic therapies such as methotrexate. We hypothesized that some dietary nutrients may affect the treatment response. Thus, the aim of this study was to investigate dietary impact on treatment results of methotrexate (MTX) in patients with RA.

Methods:

We used data from the Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study as well as from the Swedish Rheumatology Quality (SRQ) register. In EIRA, data on dietary intake at baseline were collected using a previously validated dietary questionnaire. DAS28 values at baseline and at 3 months were obtained from the SRQ and used to calculate EULAR responses.

Statistical analysis was performed using IBM SPSS Statistics 20 and included independent samples t-tests and ANOVA.

Results:

This study included 293 RA patients from the EIRA study who started treatment with MTX. 70.6% were females. Mean age was 52.7 years. Most patients were RF positive (63.3%) and ACPA positive (70.0%). In 55.4%, MTX was combined with glucocorticoids (GC). At baseline, 59.3% had high disease activity and 36.4% had moderate disease activity.

Mean DAS28 scores decreased significantly from 5.4 (±1.2SD) at baseline to 3.4 (±1.3SD) at 3 months (p<0.001).

After 3 months of MTX treatment, 45.1% of patients had a good EULAR response. Average daily folate intake was 326.9µg in good responders and 318.5µg in moderate/non-responders (not significant). In contrast, the daily intake of long-chain fatty acid C22:5 was higher in good responders versus moderate/non-responders (0.069±0.035 vs. 0.058±0.032, p=0.011). In patients who were not on GC at baseline, good responders had significantly higher vitamin D intake compared to moderate/non-responders (6.58±3.45 vs. 5.01±2.33, p=0.004). Associations were also found between therapeutic response and the intake of other fatty acids and of niacin and selenium in different subsets of patients (table).

 

		Good response		Moderate/Non-response
Patient subset	Nutrient	N	Mean ± SD	N	Mean ± SD	p value
Total study sample	Fatty acid C22:5 (g)	119	0.07 ± 0.3	151	0.06 ± 0.03	0.011
Overweight/Obese	Fatty acid C20:4 (g)	57	0.12 ± 0.05	80	0.10 ± 0.05	0.034
Ex smoker	Polyunsaturated fatty acids (g)	46	11.32 ± 4.92	49	9.44 ± 3.64	0.036
Ex smoker	Niacin (mg)	46	17.89 ± 5.71	49	15.58 ± 4.89	0.036
No GC at baseline	Total fat (g)	39	76.21 ± 29.18	85	63.01 ± 27.71	0.017
No GC at baseline	Monounsaturated fatty acids (g)	39	25.73 ± 9.77	85	21.13 ± 8.99	0.011
No GC at baseline	Selenium (µg)	39	36.49 ± 16.37	85	29.85 ± 12.15	0.013
No GC at baseline	Vitamin D (µg)	39	6.58 ± 3.45	85	5.01 ± 2.33	0.004

Conclusion:

In early RA, the therapeutic response to MTX at 3 months might be linked to several nutrients. Perhaps surprisingly, daily folate intake did not influence the response to MTX. In contrast, higher intake of C22:5 in the whole cohort, and the intake of various other nutrients, including higher vitamin D, in specific subsets of patients were significantly related to better clinical responses. In conclusion, dietary habits may affect treatment results.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/dietary-impact-on-treatment-results-of-methotrexate-in-patients-with-rheumatoid-arthritis/