PEN eNews 13(5) May 2023 - Low Histamine Diet
eNews is a monthly e-newsletter shared with the global PEN Community and created to help dietitians position themselves as leaders in evidence-based nutrition practice. In addition, users of the PEN System will find articles on the new evidence, resources and features available and how to maximize one's use of PEN.
Histamine Intolerance and the Effectiveness of a Low Histamine Diet
The QuestionDo individuals with a suspected histamine intolerance experience symptom relief on a low histamine diet?
Limited evidence suggests that individuals with a suspected histamine intolerance can determine their tolerance for ingested histamine by briefly restricting and then slowing reintroducing their intake of histamine-containing foods.
Limited evidence suggests that a histamine-free diet may reduce serum histamine levels and improve symptoms of chronic urticaria (CU) in adults.
Grilling and frying can increase the amount of histamine in some foods, whereas boiling can decrease or have no effect on histamine content.
The 2021 joint guidelines from five German, Swiss and Austrian allergology and immunology societies recommend that individuals with a suspected histamine intolerance restrict the intake of histamine-containing foods for 10 to 14 days and then reintroduce these foods as tolerated over a six-week period to determine individual histamine tolerance. The guidelines emphasize that the primary goal is helping individuals to avoid unnecessary, long-term dietary restrictions. Recommendations are limited by the dearth of evidence.
A 2018 pre-post study found that a four-week histamine-free diet reduced serum histamine levels and improved symptoms of CU in adults but did not impact serum diamine oxidase (DAO) activity or participant use of topical steroids or oral antihistamines. Results were limited by participant use of oral and topical medications, the short duration of the study, the challenges associated with following a histamine-free diet, the small sample size and that results may not be generalizable to individuals without CU.
A 2017 study found that grilling and frying increases the amount of histamine in certain foods, while boiling either decreases histamine concentrations or has no impact. Results are limited by the small number of foods included in the study and that a food’s nutritional profile is influenced by a variety of factors.
Grade of Evidence C
Histamine intolerance is thought to be caused by the reduced ability of the body to degrade histamine when DAO, the main enzyme that breaks down histamine in the gut, does not work properly. Individuals with a suspected histamine intolerance may report bloating, flatulence, severe itching and other non-specific symptoms. Evidence for histamine intolerance is significantly lacking and diagnostic criteria do not exist.
A low histamine diet may be one strategy to prevent symptoms in individuals suspected to have a histamine intolerance, although there is no consensus on what a low histamine diet entails. Most low histamine diets recommend avoiding cured and semi-cured cheese, grated cheese, oily fish, canned and semi-preserved oily fish and their derivatives, dry-fermented meat products, spinach, tomatoes, fermented cabbage, citrus, strawberries, wine and beer. Other low histamine diets recommend avoiding shellfish, eggs, fermented soy derivatives, eggplant, avocado, banana, kiwi, pineapple, plum, nuts, chocolate, milk, lentils, chickpeas, soybeans and mushrooms. Individuals with a suspected histamine intolerance have been known to report symptoms after eating foods that do not contain histamine, perhaps because of the “histamine-releasing” ability of some foods or because of the presence of other biogenic amines.
To see the full practice question, including the Evidence Summary, Evidence Statements, Comments, Rationale and References, click here.
What is the Latest on the Alkaline Diet and Chronic Disease Risk, Prevention and Treatment?
The QuestionDoes an alkaline diet have a role in the risk, prevention or treatment of chronic diseases such as obesity, cardiovascular disease, hypertension and diabetes?
A recommendation about the use of an alkaline diet to prevent or treat obesity, cardiovascular disease, hypertension or diabetes cannot be made because evidence is not available.
Limited evidence from observational studies suggests that a high dietary acid load is associated with higher blood pressure, serum insulin, obesity prevalence and diabetes risk and prevalence, but a conclusion about causation cannot be made.
Two systematic reviews and meta-analyses examining the association between dietary acid load and cardiometabolic risk factors conducted by the same research group found that higher dietary acid load (measured by potential renal acid load (PRAL) and/or net endogenous acid production (NEAP)) was associated with higher blood pressure, serum insulin, obesity prevalence and diabetes risk and prevalence but not other cardiometabolic risk factors, such as fasting blood glucose, A1C, BMI, waist circumference or LDL, HDL or total cholesterol. Findings may be limited by differences between studies (e.g. dietary assessment tool, sample size, gender, country/continent in which studies took place), the use of non-validated dietary collection tools in some studies and the use of observational data, which prevents conclusions about causation.
Grade of Evidence C
No studies investigating the potential role of an alkaline diet in the risk, prevention or treatment of chronic diseases were identified.
An alkaline diet has a low dietary acid load and emphasizes the consumption of alkaline-producing foods, such as vegetables, fruit, nuts and legumes and limits the consumption of acid-producing foods including meat, poultry, dairy products and refined grains.
To see the full practice question, including the Evidence Summary, Evidence Statements, Comments, Rationale and References, click here.
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Our Challenges in Updating PEN’s Obesity Content
While I doubt anyone disagrees with the goal of decreasing weight stigma, the concept of obesity has become a polarizing topic. Dietitians approach it from very different practice paradigms that impact the terminology they use, whether weight is monitored as part of the nutrition care process or whether weight loss would ever be considered as a treatment goal. Some practitioners choose not to use the word obesity as they consider it offensive and stigmatizing based on the etymology of the word (from latin, meaning ‘to eat oneself fat’). Instead, they find other terms or write O* and often include a trigger or content warning for content related to obesity and/or weight loss.
For the past several years, the Practice-based Evidence in Nutrition: PEN® Team has been on its own learning journey in the area of weight and obesity. Starting in 2019 with the publication of the Weight Stigma Background, the team then started updating our knowledge pathways in light of the Canadian Adult Obesity CPGs and other high quality research. I’m now delighted to share that most of the weight/obesity content has been updated on the PEN System and new content has been added, including the most recent addition:
Although our approach to updating this content was the same evidence-based process that we use for all our content, the weight/obesity content was especially challenging because of the sensitivity of the topic area and evolving discourse around language and practice paradigms within the dietetic community. As always, the PEN Team is dedicated to providing unbiased, synthesized summaries of the best available research evidence but updating this content prompted many philosophical, ethical, practical and semantic discussions. In this article, I share with you some of the challenges we faced, the decisions we made, and how PEN content was impacted as a result. By sharing this information with you, I am hopeful that you will gain a better understanding of our approach to developing and updating this content.
Challenge 1: Terminology
As already alluded to, one of the first challenges we faced was terminology. Would we continue to use the term obesity? What other terms could be used to describe individuals with larger bodies who may or may not fit the clinical diagnostic criteria for obesity? What terms do individuals living in larger bodies want health care professionals to use? How can we continue to accurately describe the evidence (i.e. using the precise language of the original authors) while still pushing for progress on inclusive, non-stigmatizing language? What stigmatizing language (e.g. ‘normal weight’) needed to be removed from our content during updating?
Our first course of action was to develop a new practice question dedicated to terminology: When discussing weight with an individual, what language should a dietitian use?. We then used this evidence as a jumping off point to develop our Guiding Principles for Obesity Terminology and update our PEN Handout Style Guide. Although we continue to use the term obesity in our content, we added a Message to Our Readers acknowledging that the term is dichotomizing and that we are committed to following best practices as the evidence landscape continues to evolve.
Challenge 2: BMI as an Indicator of Obesity
In 1995, the World Health Organization developed a BMI classification system based on visual inspection of aggregated mortality data that was soon integrated into clinical practice guidelines for identifying, evaluating and treating obesity in adults (Komaroff, 2016). Since then, practitioners and researchers have used the classification system as a diagnostic criterion for obesity (i.e. BMI ≥30 kg/m2). The new Canadian Adult Obesity CPGs, however, indicate that “BMI at the recommended cut-offs should serve only as a simple screening measure. When used together with other clinical indicators such as WC [waist circumference] and cardiometabolic and other obesity-related complications, BMI can help identify individuals who may benefit from obesity management” (Rueda-Clausen et al, 2020). The evolving definition of obesity has presented challenges for the PEN Team because there is no longer consensus in terms of how obesity is defined or applied throughout the literature and we need to accommodate the shift in definition in a transparent manner.
Using the new diagnostic criteria for obesity, the PEN Team made two decisions when dealing with research that used BMI as a sole diagnostic criterion for obesity. First, wherever possible, terms such as ‘overweight’ or ‘obese’ will be replaced with BMI ranges defined by the authors. Second, in detailed descriptions of individual research studies we will use terminology consistent with the published article. In the Practice Recommendation, however, we will use the term ‘higher weight’ instead of ‘obesity’ if BMI is the only metric used in the evidence base. Furthermore, we added a second Message to Our Readers acknowledging the limitations of using BMI as a diagnostic measure.
Challenge 3: Divergent Practice Paradigms
As objective as we like to think evidence analysis is, there is always room for interpretation. That’s why the GRADE system uses an evidence-to-decision framework; it elucidates some of the many judgements involved in making health care decisions such as (Alonso-Coello et al., 2016):
- Is the problem a priority?
- How certain is the evidence?
- What value is placed on obtaining the desirable anticipated effects? On avoiding the undesirable anticipated effects? Is there uncertainty or variability in how people will value the main outcomes?
- Do the desirable effects outweigh the undesirable effects?
- How would health equity be impacted?
- Would the recommendation be acceptable and feasible?
The purpose of the evidence-to-decision framework is not to remove subjective judgements from the process, but rather to make these judgements transparent and systematic.
Judgements in health care decision-making are heavily informed by practice paradigm. The Weight Stigma Backgrounder describes three practice paradigms to understanding body weight (weight-centric, health/complication-centric, and critical or non-weight-centric) but also acknowledges that these views exist on a spectrum (Dietitians of Canada, 2019). Through the lens of practice paradigm, it’s not difficult to see how the same research might be interpreted differently and used to make different practice decisions. For example, someone from a non-weight-centric paradigm might place a higher value on avoiding the anticipated negative mental and emotional impacts of weight loss, whereas someone from a health/complication-centric paradigm might judge that these anticipated negative effects are outweighed by the anticipated positive effects of improved health.
Integration of multiple practice paradigms within the PEN System has been challenging and our approach has been twofold. First, we are working to include PEN content that supports dietitians in understanding the different practice paradigms. In addition to the Weight Stigma Background, we are working with non-weight-centric practitioners to develop a Weight-Inclusive/HAES® Background and anticipate its publication this fall. Second, acknowledging that the PEN Team predominantly subscribes to the health/complication-centric paradigm, we have been intentional in finding reviewers from other practice paradigms to help strengthen the weight content and broaden its practice applications.
Progress, not Perfection
Every year we learn more as a society, but one thing that doesn’t change is the importance of language. The PEN Team is committed to choosing our words carefully and we are continually working on updates to help make the language used in the PEN System more inclusive. These changes are time-intensive and require a lot of background work, so please be patient with us. In the interim, if you identify content that you think needs revision, please reach out through our contact us page or by emailing me directly.
Two years of hard work have brought us closer to our goal of translating and presenting scientific literature in a way that is not only evidence-based and precise, but also equitable, inclusive and safe. As science, research and language evolve, so too does our work. We humbly acknowledge that this process is a journey and that our best efforts represent progress, not perfection.
- Komaroff M. For researchers on obesity: historical review of extra body weight definitions. J Obes. 2016;2016:2460285. doi: 10.1155/2016/2460285. Abstract available from: https://pubmed.ncbi.nlm.nih.gov/27313875/
- Rueda-Clausen CF, Poddar M, Lear SA, Poirier P, Sharma AM. Canadian adult obesity clinical practice guidelines: Assessment of people living with obesity. 2020. Available from: https://obesitycanada/ca/guidelines/assessment.
- Alonso-Coello P, Schünemann HJ, Moberg J, Brignardello-Petersen R, Akl EA, Davoli M, et al. GRADE Evidence to Decision (EtD) frameworks: a systematic and transparent approach to making well informed healthcare choices. 1: Introduction. BMJ. 2016 Jun 28;353:i2016. doi: 10.1136/bmj.i2016. PMID: 27353417. Available from: https://www.bmj.com/content/353/bmj.i2016
- Dietitians of Canada. Weight Stigma Background. In Practice-based Evidence in Nutrition [PEN]. 2019 Dec 3. Available from: https://www.pennutrition.com/KnowledgePathway.aspx?kpid=803&trid=28010&trcatid=38. Access by subscription only.
PEN® Backgrounds – Ready for You When Needed
Backgrounds provide general information about a topic for new practitioners as well as for experienced health professionals.
Here are the new or newly updated backgrounds:
Want to know what else is new and updated? Bookmark these pages:
New Knowledge Pathway Content (Knowledge Pathways, Practice Questions, Summary of Recommendations and Evidence, Practice Guidance Toolkits, Backgrounds)
Tools and Resources.
May 2023 Volume
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