Dairy, inflammation, and commercially funded research

Dairy is somewhat of a controversial topic these days. For example, when searching for “Why is dairy…” on Google, the first two autofill-suggestions are “Why is dairy bad for you?” and “Why is dairy good for you?”. The fact is that some view dairy as a superfood, while others view it as straight-up dangerous. For that reason, I was very interested in the session “Exploring the Links between Diet and Inflammation: Dairy Foods as Case Studies” during the NUTRITION 2020 LIVE ONLINE conference organised by the American Society of Nutrition.

One matter that kept popping up throughout the entire conference was sponsored sessions and commercially funded research, which is inevitable to encounter within nutrition research. During this conference I was confronted with many thoughts about this topic. “Can this research be trusted?” but also “is it fair to disregard research just because it’s funded by commercial actors?“. Due to this, I felt I had to incorporate some discussion about this topic in the blog post.

Diet and inflammation

Charles B. Stephensen (USDA-Western Human Nutrition Research Center) started off the session with a brief introduction to immune activation, and how the process differs depending on the cause. He mentioned how obesity induced inflammation can result in low-grade chronic systemic inflammation as there is no pathogen to resolve, and how inflammatory cells exacerbate disease by causing insulin resistance.

He continued by describing how dietary interventions can dampen inflammation. As an example he brought up PREDIMED, a large Spanish primary prevention trial which showed significant reductions in several biomarkers of inflammation for those following the Mediterranean Diet. He suggested that these results are due to components of the diet that address the underlying cause of inflammation, such as unsaturated fatty acids, phenolics and fiber that may for example diminish damage of adipose tissue depots.

What about dairy and inflammation?

The next speaker, Mario Kratz (Fred Hutchinson Cancer Research Center) continued by presenting some research about the impact of total dairy intake and dairy fat on biomarkers of systemic inflammation.

Dr. Kratz chose to focus on results from a few randomised controlled trials which he deemed to be the most informative and representative. He specifically focused on results about fasting plasma hsCRP, IL-6, TNFalpha and adiponectin, biomarkers which have previously been strongly linked to systemic inflammation.

In a cross-over RCT (funded by the American National Dairy Council), Zemel et al. 2010 found a consistent reduction in biomarkers of systemic inflammation on a low-fat milk intervention compared to a soy drink control among 20 participants, without any differentiating effects on body weight or composition. The study was a cross-over study where both groups received smoothies with either low-fat milk or soy drink, and the biomarkers were measured at 0, 7 and 28 days.

Similar results were found in an RCT with cross-over design by Labonté et al. 2014. Among 112 men and women with elevated hsCRP, both the control and dairy diet decreased biomarkers of systemic inflammation. The dairy diet included low-fat milk and yoghurt, and full-fat cheddar, while the control diet consisted of fruit and vegetable juice, cashew nuts and one cookie per day. The authors conclude that consumption of a combination of low- and high-fat dairy products as part of a healthy diet has no adverse effects on inflammation. The study was funded by the Dairy Research Cluster Initiative. Another similar study (randomised cross-over design) found no difference in biomarkers of inflammation between dairy foods and the control (fruit juice and granola) among the 37 participants.

Dr. Kratz emphasised that these studies were conducted in individuals without dairy allergies, and that the impact would likely be different in those with dairy allergies. He concluded by stating that the current evidence does not suggest that dairy consumption is pro-inflammatory. To the contrary, many studies indicate that it is actually anti-inflammatory! To be honest, I felt that this conclusion was rather sensationalistic and made a mental note to double check the research before forming my own opinion on the topic.

Fermented dairy products and inflammation

Bradley W. Bolling (University of Wisconsin-Madison) rounded off the session by discussing why dairy might not be pro-inflammatory, it contains saturated fat, right? I think he brought up a good point, which is that dairy is extremely complex with a wide array of bioactive components, even more so fermented dairy products. Thus, it is difficult to attribute the health impact of dairy to one single component of it. He then brought up a study about fermented dairy products (yoghurt and cheese) and postprandial inflammation, and stated that there is emerging evidence of yoghurt and cheese improving immune health but that no scientific agreement has been reached yet.

To conclude the take-home messages of this session: Different dietary patterns as well as different individual foods have been found to affect inflammation, with many high quality RCTs indicating that dairy is either neutral or anti-inflammatory. We don’t know yet what the mechanisms behind any anti-inflammatory effects of dairy are. It is important to keep in mind that the molecular composition of dairy is complex, meaning that the health effects are likely not be attributable to one single component.

Dear dairy

In my view, most of the speakers of the session had quite high credibility as they discussed the topic in a very pragmatic way, that is, not sensationalising it and I found the session to be interesting overall. However, one feeling that I did have throughout the entire session was “can these researchers and studies be trusted?”. The entire session was sponsored by National Dairy Council, and all researchers and presented studies had been reimbursed and funded by dairy related organisations.

Funders with commercial interests can affect research in various ways. Of course, they may in some cases just fund research without any involvement in study design and publication, thus not restricting academic freedom. In other cases however, they may have a say in what results get published, sway the interpretation of the results to be favourable for their own interests, or design studies in ways that promote the desired results.

When trying to get an overview of the topic by reading some papers myself, however, I did find that the presented results are in line with current evidence, regardless of how the studies were funded. For example, here’s a quote from Bordoni et al. 2017: “Our review suggests that dairy products, in particular fermented products, have anti-inflammatory properties in humans not suffering from allergy to milk, in particular in subjects with metabolic disorders.“. They do however state that the clinical relevance of inflammatory markers is currently debated among researchers and regulatory authorities, which I thought was very interesting!

It is important to always be attentive when reading research articles and be aware of any bias that may be present, but in my opinion, it is equally important not to disregard certain research simply out of principle. If we doubt everything that we cannot know for sure, we are no wiser than he who did not use his legs but sat still and wasted away because he had no wings to fly with.

June 17, 2020

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Conferences Suzanne Janzi

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