MedicalResearch.com Interview with:
Dr. Clett Erridge PhD
Department of Cardiovascular Sciences
University of Leicester
Clinical Science Wing
Glenfield General Hospital
Medical Research: What is the background for this study? What are the main findings?
Dr. Erridge: We have spent many years seeking potential stimuli that might be responsible for triggering the chronic inflammatory processes that underpin atherosclerosis. Our earlier work focused mainly on the questions of whether and how various molecules related to lipoprotein particles, oxidised lipids and fatty acids interacted with receptors of the innate immune system, which we believe are central players in the initiation of atherosclerosis. However, we were surprised to discover (as a result of some control experiments that we expected to yield a null result), that extracts of some, but not all, foods trigger inflammatory cytokine production in human monocytes via stimulation of the innate immune receptors Toll-like receptor (TLR)-2 and TLR4. The molecules responsible for triggering these responses (collectively termed PAMPs, ‘pathogen-associated molecular patterns’), were found to arise in foods that have been finely chopped and stored at refrigeration temperature or above for some time, as a result of the growth and activity of common food spoilage bacteria. The foods most commonly affected are minced meats, ready chopped vegetables, some cheeses and chocolates.
The present study found that in 11 healthy volunteers who habitually consumed food products rich in PAMPs, switching to a low PAMP diet for 7 days resulted in an 18% reduction in LDL-cholesterol, 11% reduction in white blood cell count, a 1.5 cm reduction in waist circumference and a 0.6 kg reduction in body weight. Switching back to a high PAMP diet, in which the same volunteers were then fed meals tested and proven to be high in PAMPs, for just 4 days reversed these beneficial effects.
A second study in 13 healthy volunteers then showed that PAMPs can exert effects on white cell markers of inflammation within 24 h of consumption, when volunteers were fed either fresh or processed onion-based meals, which were nutritionally identical other than for content of bacteria and PAMPs.
Medical Research: What should clinicians and patients take away from your report?
Dr. Erridge: The implication of the theory, if correct, is that reducing dietary PAMP intake has the potential to reduce risk of developing coronary artery disease and type II diabetes. This fits well with existing data from other groups showing that dietary intake of processed meat is associated with increased risk of developing cardiometabolic diseases, while dietary intake of the same quantity of non-processed (intact) meat is not. If subjects wished to pursue a low PAMP diet, the advice would be to eat food as fresh as possible, and to avoid convenience items containing ready-chopped meat or vegetables that have been stored at refrigeration temperature for extended periods of time.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Erridge: These experiments need to be repeated in larger groups, particularly in patients with existing metabolic disturbances, before the fuller picture emerges. We expect the hypothesis will be most adequately addressed by a combination of approaches, combining evidence from diet-focused epidemiological studies, interventional studies in healthy volunteers and relevant patient groups and mechanistic pre-clinical models.
Medical Research: Is there anything else you would like to add?
Dr. Erridge: We believe it should be possible for food manufacturers to make relatively subtle changes to their processes and procedures, such that almost any food can be prepared with a very low PAMP content, at minimal additional cost and with no changes to ingredients, texture or taste of the final product. Commonly used probiotic organisms, and the vast majority of commensals of the human microbiota, shed very low quantities of soluble PAMPs into their surroundings and can therefore be considered to be of very low inflammatory potential in this context.
Dr. Clett Erridge (2016). Some Bacteria In Stored Food Raise Markers of Inflammation MedicalResearch.com