Tatiana V. Macfarlane, Hadeel M. Abbood, Ejaz Pathan, Katy Gordon, Juliane Hinz, and Gary J. Macfarlane
Published: 25th October 2017
“The question of whether diet plays a role in the onset of ankylosing spondylitis (AS) or can affect the course of the disease is an important one for many patients and healthcare providers.
The aims of this study were to investigate whether: 1) patients with AS report different diets to those without AS; 2) amongst patients with AS, diet is related to severity; 3) persons with particular diets are less likely to develop AS; 4) specific dietary interventions improve the AS symptoms…
… Evidence on a possible relationship between AS and diet is extremely limited and inconclusive due to the majority of included studies being small, single studies with moderate-to-high risk of bias, and insufficient reporting of results.”
“Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease with estimated prevalence per 10,000 of 23.8 in Europe, 16.7 in Asia, 31.9 in North America, 10.2 in Latin America, and 7.4 in Africa.
AS adversely affects patients in terms of symptoms such as pain and fatigue, leading to impaired function and diminished quality of life (2, 3). Despite the development of biological therapy, which has revolutionized the treatment of AS, many patients explore complementary treatments such as dietary therapy.
There is overwhelming evidence of the importance of diet in the etiology of a wide range of diseases such as rheumatoid arthritis (RA), cardiovascular disease, and cancer (5–7). An examination of dietary patterns in a large cohort of nurses in the United States found that dietary patterns characterized by high intakes of fruit, vegetables, legumes, whole grains, poultry, and fish, were associated with a reduced risk of RA.
In contrast, dietary patterns typical of industrialized countries (high intake of red meats, processed meats, refined grains, French fries, desserts and sweets, and high-fat dairy products) were associated with an increased risk of RA.
A meta-analysis of placebo-controlled trials in patients with RA reported that that dietary fish oil has a modest effect in reducing tender joint count and morning stiffness, an effect attributed to the anti-inflammatory mechanism of omega-3 polyunsaturated fatty acids.
It has been suggested that a low starch diet leads to lower AS disease activity and that Klebsiella pneumoniae, which can be influenced by starch consumption, is a triggering factor involved in the initiation and development of AS.
Although some publications have considered the evidence linking AS with diet, there have been no systematic evaluations of the evidence.
The objectives of this systematic review were to investigate whether:
- Patients with AS report different diets to those without AS;
- Amongst patients with AS, diet is related to severity;
- Persons with particular diets are less likely to develop AS;
- Specific dietary interventions improve the symptoms of AS.”
“The search of the databases yielded 582 publications. After the removal of irrelevant papers (n=512) and duplicates (n=18) and having found 10 additional papers from other sources including searching the references of full-text papers, 58 full-text published papers, 2 letters, and 5 conference abstracts were considered.
After further consideration, 3 abstracts were removed because they did not include the necessary information and 46 full-text articles were removed because they did not report AS (n=3), did not look at relationship between AS and diet (n=2), included children (n=1), had a very small sample of AS patients (n=4), contained case reports (n=3), did not report information on diet (n=1), was in the Chinese language (n=1), did not report diet (n=25), did not report information on AS (n=2), and were non-systematic reviews (n=3) and thesis (duplicate publication, n=1).
There were a total of 16 studies included in the review, 10 of which were full-text papers, two were letters, two studies were summarized in review articles, and two were conference abstracts (25–40).”
Description of the Included Studies and Participants:
“Multiple studies were conducted in Sweden and United Kingdom, and individual studies in Norway, Belgium, France, Australia, New Zealand, China, Portugal, and Turkey and were published between 1991 and 2014 (25–35, 37–40).
Eight of the included studies were case series; four were treatment outcome studies with all the participants receiving intervention, three were randomized clinical trials, one was a case-control study, and one study investigated the gene-environment interaction using a case-only design (25–35, 37–40). All of the studies were conducted in a hospital setting, except one study that recruited participants via a Web site.
Eight studies only reported inclusion criteria, while three others only reported exclusion criteria.”
Objective 2: Diet and Severity of AS (observational studies):
“Overall, the evidence interlinking diet and AS severity was limited, and we were unable to perform a meta-analysis due to the lack of reports with data, diversity in outcome, and definition of exposure.
Haugen et al. (25) reported that 78% of AS patients believed that diet influenced the symptoms of their disease and one-third of the patients reported worsening symptoms after the intake of certain foods with 35% mentioning increased swelling of the joints.
Foods most frequently implicated were meat, coffee, sweets, sugar, chocolate, citrus fruits, and apples.
Sixteen percent of the AS patients had been through a fasting period on their own initiative with a majority of them reporting less pain, less stiffness, and less joint swelling.
Twenty-two percent of patients with AS in an attempt to alleviate disease symptoms had previously tried diets such as lactovegetarian or vegan diets.
Of the four studies reporting data on the relationship between foods high in starch and AS severity, two were conference abstracts.
While one study reported a significant association of daily starch intake with BASDAI, BASFI, and BASG, other studies did not find an association between the consumption of foods high in starch and BASDAI.
There was no association of daily starch intake with SF-36, CRP, or ESR. A small proportion of patients (1.8%) reported aggravation of symptoms associated with food rich in flour.
Silva (39) reported that the average starch intake was significantly, positively associated with BASDAI, BASFI, and BASG, but not with SF-36, CRP, or ESR.
The linear regression showed increases of 3%, 3.9%, and 2.9% in BASDAI, BASFI, and BASG scores, respectively, by milligram of ingested starch. The authors concluded that the higher intake of starch was related to increased disease activity and greater functional impairment.
Three studies that reported data on the relationship between the consumption of dairy products and AS did not find any association with BASDAI.
One study that reported a case series did not find an association between the consumption of fish and dietary omega-3 fatty acid and BASDAI.
Sundström et al. reported in a study of 111 patients that 7 patients experienced aggravated arthralgia or AS symptoms associated with a particular foodstuff, most commonly vegetables or fruits (n=2) or food rich in flour (n=2).”
Objective 4: Dietary Interventions and AS Symptoms:
“Appelboom et al. investigated, in a single-arm intervention study of 25 patients, whether a diet that excluded dairy products, was beneficial for the course of the disease or not.
The results after six weeks of follow-up showed relatively good compliance to the diet (72%). Amongst the participants, 52% reported good improvement out of which 62% could discontinue their nonsteroidal anti-inflammatory drugs (NSAID) therapy.
When follow-up of the responders was carried out for 80% out of the 15 patients at 3 months, all the 10 patients at 6 months, and 89% out of 9 patients at 9 months, it was found that they were satisfied and had continued the dietary regime.
The authors reported that six patients were still observing the diet after two years of follow-up and remained free from any other therapy.
Ebringer and Wilson in a single-arm intervention study of a low starch diet in 36 AS patients, reported a significant reduction (p<0.001) in ESR levels over a 9-month period.
Further, a majority of the participants reported that the severity of symptoms declined, and in some cases, disappeared.
Some patients noticed a decrease in the requirement for NSAIDs; however, no precise figures were reported.
The authors reported that they treated over 450 AS patients from 1983 onwards and that over half of these patients did not require any medication at follow-up.
Ebringer et al. reported a decrease in ESR in a single-arm intervention study of low starch, high protein, high vegetable, and fruit diet with 10 months follow-up; however, precise figures were not reported.
Sundström et al. reported a randomized trial of high- versus low-dose fish oil with 21 weeks of follow-up with participants blinded to the dose.
At the end of the study, there was a statistically significant decrease in the BASDAI scores (p=0.038) in the high-dose group and a statistically significant increase in the ESR in the low-dose group (p=0.027), but no other significant differences. However, a statistically significant difference was not found when comparing the high- and low-dose groups.
A small uncontrolled intervention study investigated the effects of giving Lactobacillus acidophilus and Lactobacillus salivarius daily for 4 weeks to 18 patients with quiescent ulcerative colitis but active SpA (36).
Significant improvements were seen in BASDAI (reduction in mean (SD) from 5.8 (1.5) at the baseline to 4 (1.8) at follow-up, p<0.05) and pain VAS (reduction from 58.1 (16.8) to 41.5 (14.3), p<0.05).
However, neither of the two RCTs found a significant effect of probiotic supplementation on the AS outcome such as disease activity, function, wellbeing, BASDAI, BASFI, pain levels, CRP, or ASQoL.”
“This is the first systematic review to examine the association between AS and diet. It has shown that only a few, relatively small, and mainly observational studies have been conducted in this field.
From the 16 articles included in the review, there is little evidence regarding the fact that aspects of diet influence the severity of AS or are part of its etiology.
In particular, there is no evidence that a reduction in starch intake, exclusion of dairy products, consumption of fish and fish oil or probiotic supplementation reduce susceptibility toward AS or diminish AS symptoms.
This review has many methodological limitations. Firstly, there is scarce literature on the topic and 6 out of 16 studies were not published as full reports and, therefore, limited data were available for data extraction.
Several studies did not report the actual figures and analysis results. The studies included in this review vary extensively in design, AS diagnostic criteria, measures of disease severity, exposure measured, measurement instruments, intervention, and duration of follow-up. Therefore, it was not possible to conduct a meta-analysis.
Although we limited our search to publications in the English language, the studies included in this review were from 10 countries. Most studies were conducted in a hospital setting, except one study that used a patient society Web site.
The participation rate and the participants’ selection method were not stated in the majority of the studies and, therefore, it was difficult to determine how representative they were, limiting the generalizability of the findings. Most studies, especially more recent, used appropriate statistical methods and investigated the effects of potential confounding factors.
Retrospective assessment of dietary exposure may introduce recall bias. However, observational studies included in this review seem to evaluate the current dietary habits, except one study that collected information on special diets and food avoidance in the past three months and one study that used a food diary over five consecutive days.
In addition, when assessing dietary risk factors in prevalent cases of AS, it is difficult to ascertain if the diet influences the development of AS over the course of the disease. It is also common for people to change their diets soon after the onset of disease and, therefore, the current diet may not actually represent past dietary intake. A validated FFQ was used in three observational studies from the same research group, and reproducibility was assessed in the study by Haugen et al; however, the reliability and validity of the dietary data collected in the other studies was not clear.
The majority of AS patients (78%) as well patients with other rheumatic diseases (RA, 64%; juvenile rheumatoid arthritis (JRA), 88%; psoriatic arthropathy, 71%; osteoarthrosis, 65%) believe that diet influences their disease symptoms. This suggests that if diet is important, it may influence the inflammatory process across rheumatic diseases.
Studies involving AS and other rheumatic diseases report dietary interventions such as fasting, vegan diet, and lactovegetarian diet. Clinical dietary therapy studies of AS have focused on some form of dietary elimination such as low starch diet and diet that excludes dairy products.”
“In this systematic review, we have determined, from a relatively small number of studies, that the evidence on the relationship between diet and AS is extremely limited and we have highlighted important methodological weaknesses in the studies reviewed.
Many AS patients believe that the aspects of diet affect their symptoms and/or have altered their diets in attempt to improve symptoms.
However, well-designed studies of dietary patterns and nutrients are required before any AS-specific recommendations can be made.
Future prospective, population-based studies using validated dietary assessment methods should focus on dietary patterns that have been implicated in other inflammatory conditions, including cardiovascular disease, to determine whether diet plays a role in the susceptibility to AS and AS severity…
… There is a need for large population-based epidemiological studies investigating the relationship between AS and diet.”