Search results: research bias

I learned about this one from an article in FoodNavigator: Study: Walnut consumption linked to improved life expectancy

New research from the Harvard T.H. Chan School of Public Health funded by the California Walnut Commission has found a possible link between higher walnut consumption and increase in life expectancy among older US adults.

The article quotes the senior author:

What we’ve learned from this study is that even a few handfuls of walnuts per week may help promote longevity, especially among those whose diet quality isn’t great to begin with. It’s a practical tip that can be feasible for a number of people who are looking to improve their health, which is top of mind for many people.

Washington Post columnist Tamar Haspel tweeted about this study: “I have a pretty big beef with nutritional epidemiology, and there’s a new study on walnuts that pushes all my button[s].”

Her beefs:

• Difficulties interpreting information from food frequency questionnaires
• Complications of correcting for confounding variables (18 in this case)
• Implications of causation (“lots of talk about the cardioprotective aspects of walnuts”)
• The study was not pre-registered
• It was funded by the walnut industry

Her view (with which I concur):

• “Studies like the [sic] have helped create the mess that is nutrition advice”
• “We DO NOT have the tools to assess the health impact of specific foods.”
• “Eat a wide variety of whole-ish foods you enjoy in quantities consistent with the weight you want to be.  Eat walnuts if you like them.”

The study: Association of Walnut Consumption with Total and Cause-Specific Mortality and Life Expectancy in U.S. Adults.  Xiaoran Liu, Marta Guasch-Ferré, Deirdre K. Tobias, Yanping Li.

Method: Correlated information on dietary intake of walnuts from two large epidemiological studies  with mortality.

Conclusions: We reported that higher consumption of walnut was associated with a lower risk of all-cause mortality and CVD mortality in two large prospective studies of U.S. elder adults, especially among those with suboptimal dietary quality. We estimated a greater life expectancy at age 60 of 1.3 years in women and 1.26 years in men, among those who consumed walnuts more than 5 servings/week compared to non-consumers.

Conflicts of interest: Li has received research support from California Walnut Commission. The funder has no role in the design and conduct of the study, in the collection, analysis, and interpretation of the data, and in the preparation, review, or in the decision to publish the results. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Comment: In addition to Haspel’s comments, I would add that the statement that the funder had no role is difficult to evaluate.  Industry funders generally do not pay for research likely to come out with results unfavorable to their products and much evidence suggests that influence is exerted at an unconscious level.  I provide evidence for this and other observations about industry “funding effects”—observations that research sponsored by food companies almost invariably produces results favorable to the sponsor’s interests but that recipients of industry funding typically do not recognize its influence—in my book, Unsavory Truth: How Food Companies Skew the Science of What We Eat.

I must also point out that walnuts are not the only nuts singled out for specific health benefits.  See, for example, “Pecan-Enriched Diets Alter Cholesterol Profiles and Triglycerides in Adults at Risk for Cardiovascular Disease in a Randomized, Controlled Trial” in a recent issue of the Journal of Nutrition.  Its sponsor was the Georgia Pecan Commission.

The bottom line: eat whatever nuts you like.

The study: Impact of low-fat and full-fat dairy foods on fasting lipid profile and blood pressure: exploratory endpoints of a randomized controlled trial.  Kelsey A Schmidt, et al. The American Journal of Clinical Nutrition, nqab131, https://doi.org/10.1093/ajcn/nqab131.  Published: 13 July 2021

Background: “Dietary guidelines traditionally recommend low-fat dairy because dairy’s high saturated fat content is thought to promote cardiovascular disease (CVD). However, emerging evidence indicates that dairy fat may not negatively impact CVD risk factors when consumed in foods with a complex matrix.”

Method: “Participants were then randomly assigned to 1 of 3 diets, either continuing the limited-dairy diet or switching to a diet containing 3.3 servings/d of either low-fat or full-fat milk, yogurt, and cheese for 12 wk.”

Conclusions: “In men and women with metabolic syndrome, a diet rich in full-fat dairy had no effects on fasting lipid profile or blood pressure compared with diets limited in dairy or rich in low-fat dairy. Therefore, dairy fat, when consumed as part of complex whole foods, does not adversely impact these classic CVD risk factors.”

Funding: “National Dairy Council, Dairy Farmers of Canada, Dutch Dairy Association (Nederlandse Zuivel Organisatie), Dairy Australia, and the French Dairy Interbranch Organization (CNIEL),” and NIH and others.

Conflict of interest: “This study was initiated by the principal investigator (MK). The dairy-related funding organizations suggested changes to details of the study design prior to the conduct of the study, some of which were implemented. Otherwise, the funding organizations had no impact on the design or conduct of the trial or the analysis and interpretation of study data.”

Comment: Let’s give these investigators high marks for disclosing that the dairy funders influenced the design of the study, which, as we know from the data of Lisa Bero and her colleagues, is the place where biases caused by industry funding most typically show up.  Food companies that fund research are looking for benefits; they won’t risk study designs that might yield inconvenient results.

Reference: For a summary of research on the “funding effect”—the observations that research sponsored by food companies almost invariably produces results favorable to the sponsor’s interests and that recipients of industry funding typically did not intend to be influenced and do not recognize the influence—see my book, Unsavory Truth: How Food Companies Skew the Science of What We Eat.

On July 19, I did a post on a recent study comparing the nutrient composition of plant-based meat alternatives to that of grass-fed beef.  I was not surprised that the study found nutritional differences; they are to be expected.

I was surprised that “From the abstract and conclusion, the study appears to suggest that meat is nutritionally better,” but the authors said the two types “could be viewed as complementary in terms of provided nutrients. It cannot be determined from our data if either source is healthier to consume.”   That confused me.  I also was confused by the authors’ reported conflicts of interest and said so.

One reader wrote to say that I was being unfair to the authors, who are excellent scientists.

Indeed, the authors followed up with an explanation, which I offered to post here without further comment.  They agreed to that.

Dear Dr. Nestle,

Many thanks for posting about our work. We have the utmost respect for your work and we have cited your work in our papers and books (e.g., Provenza’s Nourishment). You are an influential and well-respected person, and as you noted, your followers wanted you to inform them about this paper. When reading the post about our work, we were particularly surprised that you didn’t send us an email to fact-check your points, especially since we were introduced by email on 7/7 that noted: “I’ve copied two of the researchers involved Stephan van Vliet and Fred Provenza. That way if you have any further questions, you can pose those to the researchers directly.” If you disagree, c’est la vie, but at least that would have enabled you to write an informed critique, rather than one that is speculative and, at times, incorrect.

An off-hand and speculative statement such as this one: “maybe the vegetarian was responsible for the hedging comments?” would easily have been addressed by simply sending us an email inquiring about this. We would have gladly told you that it was three of the omnivores (SVV, FDP, SK) who were particularly concerned that people would over extrapolate the data. We were especially concerned that people would interpret our data as beef being “better”. That is not what the data indicate (more on what the data does indicate below). Hence our clear and repeated statement: “It cannot be determined from our data if either source is healthier to consume.”

We are writing you this friendly note to put some context to the points that you made. We hope that you will take them as our attempt to reinforce points that we were careful to develop so our paper was not one-sided.

“So, they’re framing everything with the baseline that animal meat is “proper nutrition” which seems like a pretty obvious bias right out of the gate…”

The two words you quoted are from a much more nuanced sentence, which reads: “This has raised questions of whether plant-based meat alternatives represent proper nutritional replacements to animal meat”. This statement refers to a number of papers by different research groups (see our paper for citations) who pose that very question, which we were interested in exploring. This is much more nuanced statement than what you suggest in the blogpost, which simply states animal meat is “proper nutrition”, which, to us, feels like a twisting of our carefully chosen words.

That we are not framing meat as “proper nutrition” is further illustrated by the stated goal of this work at the end of the introduction: “Given the scientific and commercial interest in plant-based meat alternatives, the goal of our study was to use untargeted metabolomics to provide an in-depth comparison of the metabolite profiles of grass-fed ground beef and a popular plant-based meat alternative, both of which are sometimes considered as healthier and more environmentally friendly sources of “beef”.

Furthermore, we also have to be realistic here and not dance around the obvious; the goal of plant-based meat alternatives is to provide a sensory and nutritional replacement for meat, as illustrated in press releases such as Impossible’s “We are Meat”. If one were to add carotenoids and fiber to a meat sausage (see Arby’s Marrot https://www.foodandwine.com/news/arbys-meat-carrots) and consider this a replacement to a carrot…. We would ask the same question: to what extent do a carrot and a meat-based carrot alternative differ nutritionally? It would be reasonable to take the carrot as the benchmark. All in all, we argue that our framing of the research question is much more nuanced than you suggested in your blogpost. “

To the question of nutritional differences, duh, indeed. Why would anyone not expect nutritional differences? From the abstract and conclusion, the study appears to suggest that meat is nutritionally better.”

As we acknowledge in the abstract “Important nutritional differences may exist between beef and novel plant-based alternatives; however, this has not been thoroughly assessed.” Please give us some credit. One of us (Fred Provenza) has studied plants and animals for over 50 years. Of course, we expected meat from a cow to differ from meat from soybeans, but the extent to which this may be the case had not been studied. Nor is this clear to the consumer who is simply looking at Nutrition Facts panels, another very important reason why we did the research. Another issue is that foods are often considered equivalent simply based on their protein content (even in dietary guidelines), but “protein foods” can be vastly different in terms of the non-protein nutrients they provide. We recommend Dr. Courtney-Martin’s editorial in AJCN titled “Is a peanut really an egg”. (https://academic.oup.com/jn/article/151/5/1055/6217441). She discusses these issues in such an elegant way.

We do not suggest that meat is nutritionally better, we clearly state the following in the abstract (something you cite in your blogpost): “Amongst identified metabolites were various nutrients (amino acids, phenols, vitamins, unsaturated fatty acids, and dipeptides) with potentially important physiological, anti-inflammatory, and/or immunomodulatory roles—many of which remained absent in the plant-based meat alternative when compared to beef and vice versa. Our data indicates that these products should not be viewed as nutritionally interchangeable, but could be viewed as complementary in terms of provided nutrients. It cannot be determined from our data if either source is healthier to consume.”

The italicized portions are key: we state that some nutrients are not found in the plant-based meat alternative and some nutrients are not found in the meat. Nothing more and nothing less. We also clearly state that we cannot determine from this metabolomics analysis if one is healthier than the other. We intend to pursue that question in research with people, but based on current research we also have to be realistic and we, therefore, highlight the following: “Further work is needed to inform these discussions; however, we consider it important to not lose sight of the “bigger picture” in these discussions, which is the overall dietary pattern in which individual foods are consumed. That is arguably the predominant factor dictating health outcomes to individual foods. Of note is a recent 8-week randomized controlled trial that found that a “flexitarian approach” (swapping moderate amounts of meat with novel plant-based alternatives as part of an omnivorous diet) may have positive benefits in terms of weight control and lipoprotein profiles (e.g., LDL-cholesterol).” (https://doi.org/10.1093/ajcn/nqaa203).

We are not particularly touting the superiority of meat in the discussion. We mention many of the potential health benefits of the compounds found in plant-based meat alternatives such as phytosterols, tocopherols, and other phenolic anti-oxidants, which were more abundant or exclusively found in the plant-based meat alternative.

“Really? If they can’t figure out which is better, why do this study?”

It is not a question of which one is better. It is about understanding potential similarities and differences. Is an almond better than an orange? That depends on the types of nutrients you are looking to get. If you want Vitamin C, an orange is preferred over an almond. If you want Vitamin E, consume the almonds. But there is also nutritional overlap, because both provide fiber and they have complementary phytonutrient profiles. A silly example perhaps when you put it like that, but that’s analogues to what we are stating in the paper.

“As for the conflicted interests: My first reaction to seeing this study was to ask: “Who paid for this?”

No funding was received for this work. The cost of the meat and plant-based meat alternatives (~$600) was paid with my [Dr. Stephan van Vliet] personal credit card (I am a post-doc and had no grant or start-up funds when I first arrived at Duke). The cost of metabolomics (~$200 per sample) was waived by Duke Molecular Physiology Institute’s Metabolomics Core. This was generously done to provide an early career investigator like myself to generate pilot data for a publication and grants.

The North Dakota Beef Association grant that I am the PI on [Dr. Stephan van Vliet] is $135k (not a very big grant) and supports a 4-week RCT that studies cardiovascular risk biomarkers and metabolome profiles in response to eating beef as part of a traditional (whole food) vs standard American diet. Various epidemiological studies suggest that when red meat is consumed as part of a whole foods diet, the associated risk with CVD becomes neutral, whereas eating red meat as part of a standard American diet is associated with increased disease risk. We are testing/falsifying this hypothesis prospectively in a short-term RCT and are exploring potential mechanisms by which this may or may not be the case. This work has nothing to do with plant-based meat alternatives.

The Turner Institute of Ecoagriculture ($27.5k) and the Dixon Foundation ($12.5k) are pilot grants to run metabolomics on grass-fed vs grain-fed bison and beef, respectively. The USDA-NIFA-SARE grant is collecting both plant (crops + fruit) and animal (eggs + beef) food samples from farms that use agroecological principles such as integrated crop-livestock systems. Here we are asking the question: How do practices that potentially stimulate soil health and plant diversity impact the healthfulness of animal and plant foods for human consumption? To be clear, we are also studying crop samples (soy, corn, and peas) some of which may go into alternative protein production.

My [Stephan van Vliet] conflict-of-interest policy is also essentially similar to yours: I accept funding for travel, hotels, meals, and meeting registrations, but I do not accept personal honoraria, consulting fees, or any other financial payments from such groups. A simple email could have cleared that up, but I will make sure that I state this more clearly in future papers.

Of course, we understand the public suspicion about research funding and undue influence. If a certain funding agency doesn’t like the data or the proposal and they don’t want to fund any of our projects then that is what it is, but we would not risk our reputation and career for a few research dollars or to please the funding agency. That’s why we are pushing back on this. Fred Provenza, especially, has been critical of the way beef is produced in confinement feeding operations (e.g., see recent paper https://doi.org/10.3389/fsufs.2021.547822), so the suggestion that we are beef industry defendants rather than independent scientists does sting a bit.

At the same time, we would also be lying if we didn’t think about where funding comes from. However, the harsh reality is that without foundation/commodity funds for scientific research, there would be much less research, much of which has also proven valuable over time. Even with our USDA grant, one could argue that the reason we are funded is because we wrote a good proposal, but also because our proposed work can presumably benefit the US Farm Bill. Is that true independence? All we know is that we should be transparent (hence our detailed competing interest statement) and let the data speak for itself (hence we attached our full data set as supplementary materials and deposited raw data files on metabolomics workbench), which is what we aimed to do in our Sci Rep paper.

We appreciate your concerns. We will certainly take these into account as we move forward and continue to be critical of our work. We hope you also consider our concerns and are willing to keep an open and friendly dialogue.

Sincerely,

Stephan van Vliet

Fred Provenza

Scott Kronberg

So many readers have asked me to comment on the recent study comparing the nutrient content of meat versus plant-based alternatives that I thought I better get to it.

For example, Andrew Wilder of eatingrules.com writes:

They conclude that there are nutritional differences…My first thought was “Duh!”… so I started wondering why they would even do this study…Surprise surprise, two of the authors have connections to the beef industry.  I also thought it was interesting that in the Abstract, they say “This has raised questions of whether plant‑based meat alternatives represent proper nutritional replacements to animal meat.” So they’re framing everything with the baseline that animal meat is “proper nutrition” which seems like a pretty obvious bias right out of the gate…

Indeed it does.  But the study is a bit more complicated than that, and definitely worth a look.

The study: A metabolomics comparison of plant‑based meat and grass‑fed meat indicates large nutritional differences despite comparable Nutrition Facts panels. Stephan van Vliet, James R. Bain Michael J. Muehlbauer, Frederick D. Provenza, Scott L. Kronberg, Carl F. Pieper & Kim M. Huffman. Nature Scientific Reports (2021) 11:13828.

The research question: Do plant‑based meat alternatives represent proper nutritional replacements to animal meat?

The method: The study compared 190 metabolites (chemical compounds capable of being used by the body) in meat and plant-based alternatives.

Result: Big differences.

Conclusion:  “In conclusion, metabolomics revealed that abundance of 171 out of 190 profiled metabolites differed between beef and a commercially-available plant-based meat alternative, despite comparable Nutrition Facts panels. Amongst identified metabolites were various nutrients (amino acids, phenols, vitamins, unsaturated fatty acids, and dipeptides) with potentially important physiological, anti-inflammatory, and/or immunomodulatory roles—many of which remained absent in the plant-based meat alternative when compared to beef and vice versa. Our data indicates that these products should not be viewed as nutritionally interchangeable, but could be viewed as complementary in terms of provided nutrients. It cannot be determined from our data if either source is healthier to consume [my emphasis].”

Competing interests: “S.V.V. reports a grant from the North Dakota Beef Association to study the impact of diet quality on the relationship between red meat and human health. S.V.V reports additional grant support from USDA-NIFA-SARE (LS21-357), the Turner Institute of Ecoagriculture, and the Dixon Foundation for projects that link agricultural production systems to the nutritional/metabolite composition of foods and human health. S.V.V also reports having received honoria [sic] for talks linking food production systems to human health, which was used to support scientific research. F.D.P. reports receiving honoraria for his talks about behavior-based management of livestock. J.R.B., M.J.M., S.L.K., C.F.P., and K.M.H report no conflicts. S.V.V., J.R.B., M.J.M., F.D.P., S.L.K., and C.F.P. consume omnivorous diets; K.M.H. consumes a vegetarian diet.”

Comment: To the question of nutritional differences, duh, indeed.  Why would anyone not expect nutritional differences?  From the abstract and conclusion, the study appears to suggest that meat is nutritionally better.

But then, the authors throw in those hedge-betting comments.

Really?   If they can’t figure out which is better, why do this study?

Andrew Wilder’s analysis and mine too: the underlying purpose of this study is to demonstrate the nutritional superiority of meat and the lack of equivalence of plant-based substitutes.

As for the conflicted interests: My first reaction to seeing this study was to ask: “Who paid for this?”

But the reported conflicts are somewhat confusing.  The lead author has meat-industry funding to do studies of this type.  But most of the other authors report no conflicts, and one is a vegetarian.

Maybe the vegetarian was responsible for the hedging comments?

I read about this one in NutraIngredients.com.

While previous animal studies have suggested a significant impact of the gut microbiota on the development and maturation of brain networks that underlie emotional behaviour, fewer studies have been conducted on humans. Intake of a galacto-oligosaccharides (GOS) prebiotic over 3 weeks has been shown to lower the secretion of the stress hormone cortisol and emotional processing in healthy adults, suggesting that GOS intake may be useful in modifying anxiety-related psychological mechanisms. However, reviews and meta-analyses on the efficacy of prebiotics for reducing anxiety symptomology are mixed, calling for further well controlled trials in human participants.

I am always curious to know who pays for this kind of research, so I looked up the study.

Anxiolytic effects of a galacto-oligosaccharides prebiotic in healthy females (18-25 years) with corresponding changes in gut bacterial composition.  Nicola Johnstone , Chiara Milesi , Olivia Burn, Bartholomeus van den Bogert, Arjen Nauta , Kathryn Hart , Paul Sowden, Philip W J Burnet, Kathrin Cohen Kadosh.   Sci Rep 2021 Apr 15;11(1):8302.

The study: “We examined multiple indices of mood and well-being in 64 healthy females in a 4-week double blind, placebo controlled galacto-oligosaccharides (GOS) prebiotic supplement intervention and obtained stool samples at baseline and follow-up for gut microbiota sequencing and analyses. We report effects of the GOS intervention on self-reported high trait anxiety, attentional bias, and bacterial abundance, suggesting that dietary supplementation with a GOS prebiotic may improve indices of pre-clinical anxiety.”

Conflict of interest statement: AN is an employee of FrieslandCampina, Amersfoort, The Netherlands. BvdB reports co-ownership of MyMicroZoo, Leiden, The Netherlands with no financial benefit from contributions to this manuscript. NJ, CM, OB, KH, PS, PWJB and KCK declared no financial or potential conflicts of interest.

Comment:  Probiotics are microorganisms that maintain a healthy microbiome.   They are typically found in fermented foods like yogurt.  Prebiotics are substances in food—or, in this case, supplements—that feed probiotic microbes.  This prebiotic supplement is GOS, a complicated chain of sugar molecules that is found in milk.

Why would an employee of FrieslandCampina want to do this study?  “Milk is the foundation of everything we do at FrieslandCampina.”

Why would a co-owner of MyMicroZoo be interested?  “The MyMicroZoo analysis shows the composition of your microbiota, and gives insight into how to improve your vitality.”

I’m all for eating yogurt (but watch out for the added sugars).  But GOS supplements?  Pardon my industry-induced skepticism.

The review:  Do Refined Grains Have a Place in a Healthy Dietary Pattern: Perspectives from an Expert Panel Consensus Meeting .  Yanni Papanikolaou, Joanne L Slavin, Roger Clemens, J Thomas Brenna, Dayle Hayes, Glenn A Gaesser, Victor L Fulgoni, III.  Current Developments in Nutrition, Volume 4, Issue 10, October 2020, nzaa125.

Method: “A scientific expert panel was convened to review published data since the release of 2015 dietary guidance in defined areas of grain research, which included nutrient intakes, diet quality, enrichment/fortification, and associations with weight-related outcomes.

Results: 

1) whole grains and refined grains can make meaningful nutrient contributions to dietary patterns,

2) whole and refined grain foods contribute nutrient density,

3) fortification and enrichment of grains remain vital in delivering nutrient adequacy in the American diet,

4) there is inconclusive scientific evidence that refined grain foods are linked to overweight and obesity, and

5) gaps exist in the scientific literature with regard to grain foods and health.“

Supported by the Grain Foods Foundation.  The sponsors (Grain Foods Foundation) had no role in the design of the study or in the collection, analyses, or interpretation of the data.

Author disclosures: YP, as President of Nutritional Strategies, provides food, nutrition, and regulatory affairs consulting services for food and beverage companies and food-related associations and collaborates with VLF on NHANES analyses. VLF, as Senior Vice President of Nutrition Impact, provides food and nutrition consulting services for food and beverage companies. VLF also conducts analyses of NHANES data for members of the food industry. JLS, RC, JTB, DH, and GAG all received an honorarium and travel expenses in the current scientific collaboration.

Comment: The Grain Foods Foundation commissioned the panel and paid the panel participants for their service and travel.  For the authors, this was a paid gig.  The Foundation got what it paid for.  About results #1, 2, and 5, there can be no argument.  #1 and #2 are obvious and did not require a scientific panel to come to those conclusions: even refined grains have nutritional value, not least because they are fortified with several key nutrients.   That’s why these authors consider fortification and enrichment to be “vital.”

What this really is about is to demonstrat that refined grains are healthy and do no harm (#4).  But refined grains are major components of ultra-processed foods, which cause people who eat them to take in more calories than they recognize or need (see Hall et al, 2019) and are strongly associated with higher levels of obesity, chronic disease, and mortality.  Despite dozens of studies consistently linking ultra-processed foods to these conditions, this industry-sponsored panel says the evidence is inconclusive.

The underlying purpose of this study, therefore, is to cast doubt on the connection between refined grains, ultra-processed foods, and weight gain.

With independently funded research, even by biased researchers, the underlying purpose is usually explicit.

–Thanks to Lisa Young for alerting me to this one.

US and UK Consumer Adoption of Cultivated Meat: A Segmentation Study.  Keri Szejda, Christopher J. Bryant, Tessa Urbanovich.  Foods 2021, 10(5), 1050.

Background: “Despite growing evidence of the environmental and public health threats posed by today’s intensive animal production, consumers in the west remain largely attached to meat. Cultivated meat offers a way to grow meat directly from cells, circumventing these issues as well as the use of animals altogether.”

Purpose: “The aim of this study was to assess the overall consumer markets and a range of preferences around cultivated meat in the US and the UK relating to nomenclature, genetic modification, health enhancements, and other features.”

Conclusion: “there are solid consumer markets for cultivated meat in the UK and the US, despite an overall lack of familiarity with the product. Younger generations are the most open to trying cultivated meat, and government seals of approval are considered important. Consumers tend to prefer non-GM cultivated meat, and while nutritional enhancements do not add much to consumer appeal overall, they may be an effective way to provide tangible benefits to more skeptical consumers.”

Funding: “This work was supported by Aleph Farms. Aleph Farms participated in the study design, but not other aspects of the project.”

Conflicts of interest: “The authors report no conflicts of interest.”

Comment: Aleph Farms produces cell-based meat substitutes: “We’re paving a new way forward in the field of cultivated meat, growing delicious, real beef steaks from the cells of cows, eliminating the need for slaughtering animals or harming the environment.”

The company paid for consumer research to find out how to sell its product.   The authors perceive no conflicted interests in this kind of paid research.  The biases induced by paid research are often unconscious and unrecognized.  The result of this study is an implied suggestion to add nutrients to cell-based meat products as a means to convince people to buy them.

This is marketing research.

Thanks to Michele Simon for sending a query about this paper.

The study: Investigating walnut consumption and cognitive trajectories in a representative sample of older US adults.  Nicholas J. Bishop and Krystle E. Zuniga.  Public Health Nutrition , Volume 24 , Issue 7 , May 2021 , pp. 1741 – 1752.

Purpose: To estimate the association between whole walnut intake and cognitive change in a sample of 3632 US adults aged 65 years and older.

Method:  This was a secondary analysis of dietary data and health outcome from the Health and Retirement Study and Health Care and Nutrition Study.

Conclusions: “We identified an association between walnut consumption and cognitive function in older adults, although we did not find that walnut consumption was protective against age-related cognitive decline.”

Financial support: This research was funded by the California Walnut Commission.

Comment: Eating walnuts tracks with cognitive function in this sample, but has no particular effect on it.  As I read them, the conclusions put a positive spin on a null finding, a classic example of “interpretation bias.”  The Walnut Commission paid for the study and this interpretation helps to sell walnuts.  I think walnuts are great but wish the California Walnut Commission would stay out of this kind of marketing research.