Diet and Rheumatoid Arthritis Development
Diet and Rheumatoid Arthritis Development
Studies regarding consumption of foods of plant origin in relation to RA risk are also limited.
Fruits and vegetables play an important role in diet owing to their protective action against several chronic diseases – from cancer to cardiovascular diseases. Since cardiovascular diseases may have an inflammatory response similar to RA, fruits and vegetables could also prevent the development of RA, especially thanks to their high content of antioxidant nutrients.
Studies on the association between fruits and vegetables and RA are limited, and results from case–control and prospective studies are not concordant. A case–control study conducted in Washington (DC, USA) found no association between fruit and vegetable consumption and RA risk. However, a more recent case–control study in Greece found an inverse association between cooked vegetables and RA (OR: 0.39; 95% CI: 0.20–0.77, for >85 vs <20 servings per month), but not for raw vegetables. Among prospective studies, an inverse association, although not statistically significant, was observed in the IWHS between fruit (RR: 0.72; 95% CI: 0.46–1.12, for >83 vs <52 servings per month) and vegetable (RR: 0.74; 95% CI: 0.48–1.14 for >97 vs <60 servings per month) consumption and RA. Among fruits, oranges and grapefruit juice consumption showed the lowest relative risks, while among vegetables, cruciferous vegetable consumption was associated with the lowest risk. No associations with fruits or vegetables were observed in the DCH cohort.
In line with the Iowa cohort study, the EPIC-Norfolk study showed that a low intake of fruits and vegetables (OR: 1.9; 95% CI: 1.0–4.0, for <167 vs >275 g/day) was associated with increased risk of inflammatory polyarthritis.
Antioxidants. Fruits and vegetables are rich in antioxidants that may protect against oxidative stress. Products of free radical oxidation are present in the synovial fluid of patients with RA, indicating a role of free radicals and oxidative stress in the RA inflammation process.
Among the four studies examining associations between antioxidants and RA, only one prospective study observed an inverse association. Several antioxidants were examined in the IWHS, where inverse associations were observed for vitamin C and β-cryptoxanthin (carotenoid) with RA, while no associations were found for vitamin E, or other specific carotenoids (α- and β-carotene, lycopene and lutein/zeaxanthin) and total carotenoids. No association was observed in the DCH cohort or in the NHS and NHS IIwith antioxidant (vitamin A, C and E, α- and β-carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin) intake from foods and supplements.
No association was observed in the case–control study conducted in Washington (DC, USA) between vitamins A, C and E and RA risk. The EPIC-Norfolk study reported that low intake of vitamin C (OR: 3.3; 95% CI: 1.4–7.9, for <55.7 vs >94.9 mg/day) was associated with increased risk of inflammatory polyarthritis, while the intake of vitamin E, β-carotene, and retinol were not associated with inflammatory polyarthritis. A subsequent study based on the new cases arising from the same cohort, confirmed the inverse association between vitamin C and inflammatory polyarthritis, and also showed a decreased risk associated with intake of β-cryptoxanthin.
The association between antioxidants and RA was also examined using serum antioxidant concentrations in three studies. Two nested case–control study conducted in Finland observed an elevated risk of RA for low levels of serum α-tocopherol, and β-carotene, but none of the associations were statistically significant. A case–control study in Washington County (MD, USA) analyzed the difference in serum concentration of α-tocopherol and β-carotene between RA cases and controls, finding a statistically significant decrease only for β-carotene.
A randomized, double-blind, placebo-controlled trial conducted in USA, The Women's Health Study, also evaluated vitamin E supplementation and found no association with RA.
Consumption of whole-grain cereals has been shown to reduce levels of inflammatory markers (C-reactive protein and IL-6). In addition, legumes have been found to decrease levels of inflammatory biomarkers (high-sensitive C-reactive protein, TNF-α and IL-6). However, only one case–control study has analyzed the association of high-fiber cereals with RA and observed no association, while no studies have analyzed the association of legume consumption with RA.
Olive oil is a major component of the Mediterranean diet and is considered to be associated with many health benefits. The health-related effects of olive oil are attributed to its richness in oleic acid and natural antioxidants. Oleic acid has been reported to have modulatory effects in a wide variety of physiological functions, and a beneficial effect on cancer, autoimmune and inflammatory diseases. Oleic acid is a n-9 monounsaturated fatty acid that is converted to 8,9,11-eicosatrienoic acid under restriction of n-6 fatty acids. Oleic acid and its metabolite 8,9,11-eicosatrienoic acid may have an anti-inflammatory effect with a mechanism similar to fish oil.
However, results from epidemiological studies are inconclusive. Two hospital-based case–control studies conducted in Greece found an inverse association between high consumption of olive oil and risk of RA (OR: 0.39; 95% CI: 0.19–0.82, for high vs low). However, this finding was not confirmed in the prospective DCH cohort.
Foods of Plant Origin
Studies regarding consumption of foods of plant origin in relation to RA risk are also limited.
Fruit & Vegetables
Fruits and vegetables play an important role in diet owing to their protective action against several chronic diseases – from cancer to cardiovascular diseases. Since cardiovascular diseases may have an inflammatory response similar to RA, fruits and vegetables could also prevent the development of RA, especially thanks to their high content of antioxidant nutrients.
Studies on the association between fruits and vegetables and RA are limited, and results from case–control and prospective studies are not concordant. A case–control study conducted in Washington (DC, USA) found no association between fruit and vegetable consumption and RA risk. However, a more recent case–control study in Greece found an inverse association between cooked vegetables and RA (OR: 0.39; 95% CI: 0.20–0.77, for >85 vs <20 servings per month), but not for raw vegetables. Among prospective studies, an inverse association, although not statistically significant, was observed in the IWHS between fruit (RR: 0.72; 95% CI: 0.46–1.12, for >83 vs <52 servings per month) and vegetable (RR: 0.74; 95% CI: 0.48–1.14 for >97 vs <60 servings per month) consumption and RA. Among fruits, oranges and grapefruit juice consumption showed the lowest relative risks, while among vegetables, cruciferous vegetable consumption was associated with the lowest risk. No associations with fruits or vegetables were observed in the DCH cohort.
In line with the Iowa cohort study, the EPIC-Norfolk study showed that a low intake of fruits and vegetables (OR: 1.9; 95% CI: 1.0–4.0, for <167 vs >275 g/day) was associated with increased risk of inflammatory polyarthritis.
Antioxidants. Fruits and vegetables are rich in antioxidants that may protect against oxidative stress. Products of free radical oxidation are present in the synovial fluid of patients with RA, indicating a role of free radicals and oxidative stress in the RA inflammation process.
Among the four studies examining associations between antioxidants and RA, only one prospective study observed an inverse association. Several antioxidants were examined in the IWHS, where inverse associations were observed for vitamin C and β-cryptoxanthin (carotenoid) with RA, while no associations were found for vitamin E, or other specific carotenoids (α- and β-carotene, lycopene and lutein/zeaxanthin) and total carotenoids. No association was observed in the DCH cohort or in the NHS and NHS IIwith antioxidant (vitamin A, C and E, α- and β-carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin) intake from foods and supplements.
No association was observed in the case–control study conducted in Washington (DC, USA) between vitamins A, C and E and RA risk. The EPIC-Norfolk study reported that low intake of vitamin C (OR: 3.3; 95% CI: 1.4–7.9, for <55.7 vs >94.9 mg/day) was associated with increased risk of inflammatory polyarthritis, while the intake of vitamin E, β-carotene, and retinol were not associated with inflammatory polyarthritis. A subsequent study based on the new cases arising from the same cohort, confirmed the inverse association between vitamin C and inflammatory polyarthritis, and also showed a decreased risk associated with intake of β-cryptoxanthin.
The association between antioxidants and RA was also examined using serum antioxidant concentrations in three studies. Two nested case–control study conducted in Finland observed an elevated risk of RA for low levels of serum α-tocopherol, and β-carotene, but none of the associations were statistically significant. A case–control study in Washington County (MD, USA) analyzed the difference in serum concentration of α-tocopherol and β-carotene between RA cases and controls, finding a statistically significant decrease only for β-carotene.
A randomized, double-blind, placebo-controlled trial conducted in USA, The Women's Health Study, also evaluated vitamin E supplementation and found no association with RA.
Cereals & Legumes
Consumption of whole-grain cereals has been shown to reduce levels of inflammatory markers (C-reactive protein and IL-6). In addition, legumes have been found to decrease levels of inflammatory biomarkers (high-sensitive C-reactive protein, TNF-α and IL-6). However, only one case–control study has analyzed the association of high-fiber cereals with RA and observed no association, while no studies have analyzed the association of legume consumption with RA.
Olive Oil
Olive oil is a major component of the Mediterranean diet and is considered to be associated with many health benefits. The health-related effects of olive oil are attributed to its richness in oleic acid and natural antioxidants. Oleic acid has been reported to have modulatory effects in a wide variety of physiological functions, and a beneficial effect on cancer, autoimmune and inflammatory diseases. Oleic acid is a n-9 monounsaturated fatty acid that is converted to 8,9,11-eicosatrienoic acid under restriction of n-6 fatty acids. Oleic acid and its metabolite 8,9,11-eicosatrienoic acid may have an anti-inflammatory effect with a mechanism similar to fish oil.
However, results from epidemiological studies are inconclusive. Two hospital-based case–control studies conducted in Greece found an inverse association between high consumption of olive oil and risk of RA (OR: 0.39; 95% CI: 0.19–0.82, for high vs low). However, this finding was not confirmed in the prospective DCH cohort.
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