Currently browsing posts about: Avocados

I so appreciate the Obesity and Energetics newsletter that comes out every week, and particularly its occasional listing of “Headlines versus Study.”  This one is from a couple of months ago, but I am just getting to it.

• Headline: The Largest Study Ever on Avocados Has Some Good News for Your High Cholesterol: “Eating one avocado per day could lower LDL cholesterol and improve overall diet quality, according to a new study published in the Journal of the American Heart Association.”
• Press Release: Daily Avocados Improve Diet Quality, Help Lower Cholesterol Levels: “Eating one avocado a day for six months was found to have no effect on belly fat, liver fat or waist circumference in people with overweight or obesity, according to a new study. However, it did lead to a slight decrease in unhealthy cholesterol levels.  In the randomized trial, the team — including Penn State researchers — also found that participants who ate avocados had better quality diets during the study period.”
• Study Results: The primary outcome, change in visceral adipose tissue volume during the intervention period, was not significantly different between the Avocado Supplemented and Habitual Diet Groups…No significant group differences were observed for the secondary outcomes…Changes in the other additional and post hoc measures (body weight, body mass index, insulin, very low‐density lipoprotein concentrations, and total cholesterol:high‐density lipoprotein cholesterol ratio) were similar between the 2 groups.
• Conclusions:  Addition of 1 avocado per day to the habitual diet for 6 months in free‐living individuals with elevated waist circumference did not reduce visceral adipose tissue volume and had minimal effect on risk factors associated with cardiometabolic disorders.

This is a classic example of putting a favorable spin on no-effect results.  The study was NOT funded by the avocado industry and I cannot find a Haas Avocado Board comment on it.

The authors were quite clear about “no effect.” The press release is another matter.

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Coming soon!  My memoir, October 4.

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One of the points of my Monday “industry-funded study of the week” posts is that companies usually get the results they want.  Exceptions do exist.  Here’s one of those rare ones.

The study: Changes in Biomarkers of Non-Alcoholic Fatty Liver Disease (NAFLD) upon Access to Avocados in Hispanic/Latino Adults: Secondary Data Analysis of a Cluster Randomized Controlled Trial.  Lorena S. Pacheco, Ryan D. Bradley, Cheryl A. M. Anderson and Matthew A. Allison.  Nutrients 2022, 14(13), 2744; https://doi.org/10.3390/nu14132744

Rationale: Non-alcoholic fatty liver disease (NAFLD) is a common cause of abnormal liver functions tests and of increased increased risk for morbidity and mortality.  Monounsaturated fatty acids such as those in avocados havew been associated with improved NAFLD-related markers.

Hypothesis: “We hypothesized compared to low avocado intake, high avocado intake would have a beneficial effect on oxidative stress and hepatic health indicated by greater reductions in liver function tests and NAFLD fibrosis score.”

Results: “No statistically significant differences were observed between low and high avocado allotment groups” in anything measured.

Conclusion: “Varied intake of avocados resulted in no effects on biomarkers of NAFLD in healthy adults, free of severe chronic disease.”

Funding: “The parent research was funded by The Hass Avocado Board.”

Conflicts of interest: “The authors declare no potential conflict of interest. All authors report the grant from the Hass Avocado Board….The Hass Avocado Board funded the parent trial and provided all the trial’s avocados at no cost to study participants. The parent trial funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.”

Comment: The authors say they have no conflicts of interest but I think they do; the Hass Avocado Board paid for a study of the effects of avocados on NAFLD markers.  Such payments are well established to predict results that favor the sponsor’s interests.

Nevertheless, the results came out contrary to those interests, and the authors were unambiguous in saying so.  In this case, the assertion that the sponsor had no role seems credible, even though it often is not.

High marks to the authors. 

It’s been more than a year since I last wrote about avocado industry funding of research but the Avocado Nutrition Center has been sending out press releases so it’s time for another look.

Given the Superbowl—105 million pounds of avocados consumed that day by one estimate—you might not think that the avocado industry would have to work as hard as it does to convince you that avocados are a superfood.

But maybe what it is trying to do is to get us to ignore the effects of our demand for avocados on deforestation and social unrest in Mexico.

The avocado industry is a good example of how to fund research for marketing purposes.  It funds the Avocado Nutrition Center’s research program.

The program’s website covers dozens of industry-funded studies that demonstrate benefits of avocados for cardiovascular health, weight management, type 2 diabetes, and healthy living at every age.

Here’s how the Center uses them.

Another recent study of 2,886 older adults, published in Frontiers in Nutrition, examined cognitive function among older American avocado consumers compared to nonconsumers.

On that basis, the Center produced a fact sheet: Proactive thinking on cognition.  

The Center also lists a few independently funded studies that produced equally beneficial results.

I picked one at random and looked it up: Avocado Consumption and Risk of Cardiovascular Disease in US Adults.

• Conclusion: Higher avocado intake was associated with lower risk of CVD and coronary heart disease in 2 large prospective cohorts of US men and women. The replacement of certain fat-containing foods with avocado could lead to lower risk of CVD.
• Funding: mostly by NIH
• Conflicts of interest: the lead author reports having “collaborated in the Hass Avocado Board–funded trial Effects of Avocado Intake on the Nutritional Status of Families during 2016 to 2019 as a graduate student researcher, but the present study was not supported or endorsed by the Hass Avocado Board. The remaining authors have no disclosures to report.”

And here’s the most recent study: Effect of Incorporating 1 Avocado Per Day Versus Habitual Diet on Visceral Adiposity: A Randomized Trial

• Conclusion: Addition of 1 avocado per day to the habitual diet for 6 months in free‐living individuals with elevated waist circumference did not reduce visceral adipose tissue volume and had minimal effect on risk factors associated with cardiometabolic disorders.
• Funding: This work was supported by the Avocado Nutrition Center.

Why be concerned?  Aren’t avocados good for you?

Sure, and I love them.  But superfoods?  All fruits and vegetables have useful nutrients, but some have fewer calories (a serving size is one-third of an avocado) and most are less caught up in ecological damage.

I discuss the scientific reasons for concern in my book, Unsavory Truth: How Food Companies Skew the Science of What We Eat.  In it, I review the literature on the “funding effect”—the observation that research sponsored by food companies almost invariably produces results favorable to the sponsor’s interests.  Research on conflicts of interest also demonstrates that recipients of industry funding do not recognize its influence, did not intend to be influenced, and deny the influence, despite vast amounts of research to the contrary.

You might not think that avocados need any special sales efforts, but the Haas Avocado marketers are particularly aggressive in funding research to demonstrate the health benefits of this food.

I’ve written about Haas-funded avocado research previously (most recently, here and here) but here’s yet another, this time initiated by a tweet:

I think avocados are fine foods, love them, but wish their marketers would not do this.  Here’s the Good News Network headline: “An Avocado a Day May Keep Your Gut Microbes Happy, Study Shows.”  As always, the operative word is “may.”  The headline would be equally correct saying “may not.”

The study: Avocado Consumption Alters Gastrointestinal Bacteria Abundance and Microbial Metabolite Concentrations among Adults with Overweight or Obesity: A Randomized Controlled Trial. Sharon V Thompson, Melisa A Bailey, Andrew M Taylor, Jennifer L Kaczmarek, Annemarie R Mysonhimer, Caitlyn G Edwards, Ginger E Reeser, Nicholas A Burd, Naiman A Khan, Hannah D Holscher.  The Journal of Nutrition, Volume 151, Issue 4, April 2021, Pages 753–762.

Conclusions: “Daily avocado consumption resulted in lower fecal bile acid concentrations, greater fecal fatty acid and SCFAs, and greater relative abundances of bacteria capable of fiber fermentation, providing evidence that this nutrient-dense food affects digestive physiology, as well as the composition and metabolic functions of the intestinal microbiota.”

Funding: Support for this research was provided by the Hass Avocado Board and the USDA National Institute of Food and Agriculture, Hatch project 1009249.

Author disclosures: NAB, NAK, and HDH received grant funding from the Hass Avocado Board.

Comment: All fruits and vegetables provide nutritional value and the best way to get the nutrients you need is by eating a variety of them.  If you like avocados, include them in that variety.  If not, don’t.

The Haas marketers want you to think that avocados are a superfood.  Alas, there is no such thing.  All fruits and vegetables provide nutritional value.  By that criterion, all fruits and vegetables are superfoods.

Here’s an example of how Haas advertises:

Did you know fresh avocados can be part of the MyPlate food guide?

• Make half your plate fruits and vegetables.

Avocados are a nutrient-dense fruit with naturally good fats and are easily incorporated into various meals and snacks. One serving (50g or one-third of a medium avocado) has only 80 calories and contributes nearly 20 vitamins, minerals, and phytonutrients along with dietary fiber.

The same could be said for most other fruits and vegetables, although most will be lower in calories.

The study: A Moderate-Fat Diet with One Avocado per Day Increases Plasma Antioxidants and Decreases the Oxidation of Small, Dense LDL in Adults with Overweight and Obesity: A Randomized Controlled Trial.  Li Wang, Ling Tao, Lei Hao, Todd H Stanley, Kuan-Hsun Huang, Joshua D Lambert, Penny M Kris-Etherton.  The Journal of Nutrition, nxz231, https://doi.org/10.1093/jn/nxz231  Published: 14 October 2019

The Press release: One avocado a day helps lower ‘bad’ cholesterol for heart healthy benefits  (thanks to reader Effie Seftel for sending).

Conclusions: “One avocado a day in a heart-healthy diet decreased oxLDL [oxidized LDL]in adults with overweight and obesity, and the effect was associated with the reduction in sdLDL [small-density LDL–the bad kind]…Avocados have a unique nutrient and bioactive profile that appears to play an important role in reducing LDL oxidation, hence decreasing LDL atherogenicity.”

Funding:  “Supported by a grant from the Hass Avocado Board.”  [I’ve written previously about other studies funded by this Board].

Author disclosures: LW, LT, LH, THS, K-HH, and JDL, no conflicts of interest. PMK-E received funding from the Hass Avocado Board to conduct this study and is a member of the Avocado Nutrition Science Advisory. The Hass Avocado Board had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript.

Comment: Thanks to Jeff Nelson for sending this one (his interview with me is online).  He points out that the diet of the group eating one avocado a day also ate less saturated fat and more fiber, which could help to account for the favorable result.  I love avocados (who does not?) but worry about what our demand for them is doing to Mexican food culture and personal safety.  Does the Hass Board really need to do this?

Addition, October 31

The London Daily Mail has, of all things, a critique of this study:  “Eating an avocado a day will NOT cut your cholesterol: Statistician debunks the ‘hilariously unimpressive’ results of study funded by ‘big avocado’.”

The study: Using the Avocado to Test the Satiety Effects of a Fat-Fiber Combination in Place of Carbohydrate Energy in a Breakfast Meal in Overweight and Obese Men and Women: A Randomized Clinical Trial.  Zhu L, et al.  Nutrients 2019, 11, 952; doi:10.3390/nu11050952.

Conclusions: Replacing carbohydrates in a high-carbohydrate meal with avocado-derived fat-fiber combination increased feelings of satiety mediated primarily by PYY [peptide YY] vs. insulin. These findings may have important implications for addressing appetite management and metabolic concerns.

Funding: This research was supported by the Hass Avocado Board, Irvine, CA, USA.

Comment: Why does the Hass Avocado Board fund studies like this?  Because it generates headlines like this one: “Study finds avocados curb appetite and help with weight loss.”

Oops.  This is not what the study actually found.  As I learned from Obesity and Energetics Offerings (an exceptionally useful weekly compendium of articles having to do with energy balance), the discrepancy between what the study’s findings and what got reported merited its inclusion in OEO’s “Headline vs. Study” category.

• Headline: Study finds avocados curb appetite and help with weight loss.
• Study: This was a 6-hour RCT [randomized clinical trial] demonstrating effects on short-term reports of hunger – neither effects on actual food intake nor on body weight were studied.

Sponsored research is often about headlines, not science.

It’s also about advertising.  Here’s an ad that the Hass Avocado people sent out to all members of the Academy of Nutrition and Dietetics.  Although the Academy noted this was an advertisement, here’s what it looked like (thanks to my colleague Lisa Sasson for sending):

I love avocados but wish the Hass people would stick with how delicious they are and fund research on something more useful, like resistance to pests or climate change, maybe.

No such luck.  Here’s the request for proposals I just received:

President Trump’s threat to close the border with Mexico will have a major effect on one beloved food: avocados.

Thanks to the USDA’s Economic Research Service, the impact we can expect is obvious from this one chart:

US production has not changed much since 1990 or so.  If anything, it has dropped in recent years.

Pounds of avocados available per capita have increased from less than one in 1990 to more than seven pounds now.  That’s the pounds available to every man, woman, and baby in the country, less exports, plus imports.

All of the increase comes from imported avocados.

Of imported avocados, more than 89 percent come from Mexico.

Reuters says if the border closes, we run out of avocados in three weeks.

The Washington Post says if the border closes, avocados could be—toast (I’m quoted).

Ouch.