by Marion Nestle

Currently browsing posts about: Nuts

May 2 2022

Industry-influenced study of the week: diet and brain atrophy

Thanks to a reader in Israel, Yehuda Ben-Hur, for sending this one.

The study: The effect of a high-polyphenol Mediterranean diet (Green-MED) combined with physical activity on age-related brain atrophy: the Dietary Intervention Randomized Controlled Trial Polyphenols Unprocessed Study (DIRECT PLUS) .  Alon Kaplan, Hila Zelicha, Anat Yaskolka Meir, Ehud Rinott, Gal Tsaban, Gidon Levakov, Ofer Prager, Moti Salti, Yoram Yovell, Jonathan Ofer, Sebastian Huhn, Frauke Beyer, Veronica Witte, Arno Villringer, Nachshon Meiran, Tamar B Emesh, Peter Kovacs, Martin von Bergen, Uta Ceglarek, Matthias Blüher, Michael Stumvoll, Frank B Hu, Meir J Stampfer, Alon Friedman, Ilan Shelef, Galia Avidan, Iris Shai.  The American Journal of Clinical Nutrition, nqac001, https://doi.org/10.1093/ajcn/nqac001 Published: 11 January 2022.

Objectives: We aimed to explore the effect of a Mediterranean diet (MED) higher in polyphenols and lower in red/processed meat (Green-MED diet) on age-related brain atrophy.

Methods:  Abdominally obese  participants were randomly assigned to follow one of three diets: (1) healthy dietary guidelines (HDG), (2) MED, or (3) Green-MED diet.  The two MED groups consumed 28 g walnuts/d.  The Green-MED group consumed green tea , mankai (100 g frozen cubes/d as a green shake).  After 18 months, participants got MRI scans.

Results: Indicators of brain atrophy were attenuated in both MED groups, with the best outcomes among Green-MED diet participants.  Therefore, greater Mankai, green tea, and walnut intake and less red and processed meat were significantly and independently associated with reduced atrophy decline .

Conclusions: A Green-MED (high-polyphenol) diet, rich in Mankai, green tea, and walnuts and low in red/processed meat, is potentially neuroprotective for age-related brain atrophy.

Funding: Supported by German Research Foundation, Israel Ministry of Health, Israel Ministry of Science and Technology, and the California Walnut Commission (to I Shai, the senior author). “None of the funding providers were involved in any stage of the design, conduct, or analysis of the study, and they had no access to the study results before publication.”

Comment: I hardly know what to make of this study, which involves so many variables: mankai, (duckweed, supposedly a polyphenol-rich “supergreen”), green tea, walnuts, and low red/processed meat.  The MED groups were instructed to consume a calorie-restricted Mediterranean diet “rich in vegetables, with poultry and fish partly replacing beef and lamb.”  Physical activity instructions (and gym memberships) as well nutrition counseling was also part of this mix.

My questions:

  • Why not test the Mediterranean diet on its own without all those polyphenol additives?
  • Why walnuts as opposed to any other polyphenol-containing food?  Could sponsorship have anything to do with this choice?
  • Why Mankai, which is traditionally a component of Asian diets, not Mediterranean?    Why are Israeli scientists so interested in this plant?
  • Don’t classic Mediterranean diets provide enough polyphenols to be protective against brain atrophy?

I will be intersted to see further studies along these lines.

Dec 20 2021

Industry-influenced (and not influenced) studies of the week: nuts

Two studies of the role of nuts in health.

I.  This one comes from ObesityandEnergetics.org’s “Headline vs. Study.”

Headline: Maximum Wellness: Walnuts are a Life-Extension Food: Looks like your [sic] nuts not to include walnuts in your diet. For more information and to read this study…go to maxwellnutrition.com, where you can find top wellness and nutrition products made in the United States – shipped to your door.”  [Comment: Clearly, we are dealing here with marketing]

Study: Association of Self-Reported Walnut Consumption with Total and Cause-Specific Mortality and Life Expectancy in U.S. Adults. Maximum Wellness nor Causation Necessarily Established.  Liu, X.; Guasch-Ferré, M.; Tobias, D.K.; Li, Y.  Nutrients 2021, 13, 2699. https://doi.org/ 10.3390/nu13082699

Conclusion: A greater life expectancy at age 60 (1.30 years in women and 1.26 years in men) was observed among those who consumed walnuts more than 5 servings/week compared to non-consumers.  Higher walnut consumption was associated with a lower risk of total and CVD mortality and a greater gained life expectancy among U.S. elder adults.  [Comment: association, not causation, and the difference is small].

Conflict of interest: The last (senior?) author reports having received research support from California Walnut Commission, but states that ” 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.”  [Comment: That’s what they all say, but research often demonstrates otherwise, as I review in my book Unsavory Truth].

And now for the second:

II.  Association of nut consumption with risk of total cancer and 5 specific cancers: evidence from 3 large prospective cohort studies.  Zhe Fang, You Wu, Yanping Li, Xuehong Zhang, Walter C Willett, A Heather Eliassen,1Bernard Rosner,
Mingyang Song, Lorelei A Mucci,and Edward L Giovannucci.  The American Journal of Clinical Nutrition, Volume 114, Issue 6, December 2021, Pages 1925–1935, https://doi.org/10.1093/ajcn/nqab295

Conclusion: In 3 large prospective cohorts, frequent nut consumption was not associated with risk of total cancer and common individual cancers.  [Comment: What? An industry-funded study that finds no benefuts?]

Funding: Supported by the California Walnut Commission and Swiss Re Management Ltd (to YL),… and NIH grants U01 CA167552 (to LAM and the Health Professionals Follow-up Study), UM1 CA186107 and P01 CA87969 (to the Nurses’ Health Study), and U01 CA176726 (to AHE and the Nurses’ Health Study II). The funding sources did not participate in the study design; or
collection, analysis, or interpretation of the data; or preparation, review, or approval of the manuscript.

Here’s how the authors explain their highly unusual no-benefit result:

Given the scarcity of available high-quality data, our findings add to current evidence to more precisely determine the relation between nut consumption and cancer risk. So far, the population based evidence has not been strong enough to conclude that nut consumption is protective against total cancer and these 5 common cancers. Future studies on other cancer sites are still needed to examine the benefits of nuts on cancer development.

Really?  Why?  Do the authors not believe their own data?  Their findings ought to settle the matter and encourage the authors to move on to more significant research.  “More research needed” keeps the California Walnut Commission busy.

Research funded by food companies always requires a degree of skepticism, no matter what the results.

Sep 27 2021

Industry-sponsored study of the week: walnuts

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.

Sep 2 2021

Will almonds prevent skin wrinkles? The Almond Board wants you to think so.

I know I’ve already posted one of these this week, but this one is too good not to share.

Let’s start with the press coverage: Snack yourself young: Study investigates the effects of daily almond consumption on wrinkles

A study by American research found that eating almonds daily reduces wrinkle severity – along with improving skin pigmentation – in postmenopausal women.

The 2021 study – published in Nutrients and funded by the Almond Board of California – expands upon findings of a 2019 study​ that found there may be more than one reason to add almonds to a daily skin care routine.

And here’s the study in question: Prospective Randomized Controlled Trial on the Effects of Almonds on Facial Wrinkles and PigmentationAuthors: Sivamani RK, Rybak I, Carrington AE, Dhaliwal S, et al.  Nutrients. 2021; 13(3):785

This is not their first on this topic.  See: Prospective randomized controlled pilot study on the effects of almond consumption on skin lipids and wrinklesAuthor: Sivamani RK, Foolad N, Vaughn AR, Rybak I, et al   Phytother Res. 2019 Dec;33(12):3212-3217

Nor are these the first studies to link specific foods to wrinkle prevention.  I’ve written previously about a study on mangos and wrinkle prevention, sponsored—of course—by a mango trade association.

I wish companies and trade associations would stop doing studies of one food and some health outcome. Diets that contain reasonable proportions of fruits, vegetables, and whole grains are demonstrably healthy.  Can any one food really make all that much difference?

The sellers of these foods would like you to think they are “superfoods.”  Alas, no such thing exists.  But it’s a great marketing strategy.

As for sponsored research in general?

For a summary of research on the “funding effect”—the observation 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—see my book, Unsavory Truth: How Food Companies Skew the Science of What We Eat.

Jun 28 2021

Industry-funded study of the week: Almonds

By this time, a great many research studies have associated eating nuts—of any kind—with good health.  Nuts have fats and, therefore, calories (150-200 per ounce).

The nut industry would like to minimize concerns about fats and calories.  It funds research to demonstrate that nut fats are healthy (which they are) and that you don’t have to worry about the calories (which you do, depending on what else you eat).  Hence:

The study: Almond Bioaccessibility in a Randomized Crossover Trial: Is a Calorie a Calorie?  Nishi SK, et al.  Mayo Clinic Proceedings, 2021;nn(n):1-12, Published April 11, 2021.

Methods: This is a clinical trial in which subjects with hyperlipidemia consumed about 1 or 2 ounces a day of almonds versus muffins with equivalent calories.

Results: “Almond-related energy bioaccessibility was 78.5%±3.1%, with an average energy loss of 21.2%±3.1% (40.6 kcal/d in the full-dose almond phase).”

Conclusion:  “Energy content of almonds may not be as bioaccessible in individuals with hyperlipidemia as predicted by Atwater factors, as suggested by the increased fat excretion with almond intake compared with the control.”

Comment #1: The authors went to a lot of expensive trouble to demonstrate what has been known for a long time: almonds as typically consumed have only about 80% of the calories listed in standard tables.  This is because some of the fat is excreted rather than absorbed.  Chewing is not as efficient as machine grinding in separating fat from fiber.  When nuts are machine ground, their fats are more fully released and their calories similar to values obtained in calorimeters.

So guess who paid for this?

Grant Support: …the Almond Board of California…[and several other sources].

Potential competing interests: Where to begin?  The list takes three full columns of printed page.  Several of the authors report grants or consulting arrangements with entities such as the Almond Board of California, American Peanut Council, International Nut & Dried Fruit Council (INC), International Tree Nut Council Research and Education Foundation, California Walnut Commission, Peanut Institute, and the International Tree Nut Council.  But authors also report funding relationships that seem irrelevant to this study, such as the Dairy Farmers of Canada, Ocean Spray, the Saskatchewan & Alberta Pulse Growers Associations, and Beyer Consumer Care.  Even odder are reports of an honorarium from the USDA for a lecture; travel support from the Canadian Society of Endocrinology and Metabolism to produce mini cases for the Canadian Diabetes Association (CDA); and, most unnecessarily, a book about vegetarian diets published by the daughters of one of the authors.

Comment #2:  I think disclosure statements like these are disrespectful of the disclosure requirement.  In this case, because several of the authors have so many financial relationships with food and drug companies, a listing of the nut-industry connections would have sufficed.  These alone would make it clear that these authors have conflicted interests that might deserve consideration in interpreting the study results.

May 10 2021

Industry-funded study of the week: Walnuts and cognitive decline

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.

Oct 5 2020

Overhyped food of the week: peanuts!

The Peanut Institute is working overtime to convince you to eat more peanuts.

Disclaimer: I love peanuts and think they are great to cook with and make an excellent snack—peanut butter too—but I see no need to overhype them, as this press release does.

Research Reveals Daily Dose of Peanuts Delivers Body and Mind Benefits: Americans Encouraged to Pause for Peanuts…Peanuts are a superfood so just a small amount can fend off mid-morning hunger, help eliminate the afternoon slump and deliver much-needed brainpower.

“Superfood,” I must remind you, is a marketing term.  It has no nutritional meaning.  All fruits, vegetables, grains, beans, and, yes, nuts, have nutritional value.  On that basis, all plant foods are “superfoods.”

The press release makes these claims, and provides references for most of them:

  • Regular peanut consumption has been associated with a reduced risk of heart disease, diabetes and numerous kinds of cancer.
  • An ounce of peanuts packs more protein than any other nut.
  • Peanuts stimulate peptide YY, a hormone that decreases appetite.
  • Peanuts also have a low glycemic index that helps stabilize blood sugar to prevent the feeling of ‘crashing’ in the afternoon.
  •  A single serving of peanuts is packed with 19 vitamins and minerals, including the antioxidant resveratrol, which has been shown to increase blood flow to the brain.
  • Peanuts also contain high levels of niacin and are a good source of vitamin E – two nutrients that support brain health and have long been known to protect against Alzheimer’s disease and age-related cognitive decline
  • Eating peanuts twice a week can reduce the risk of premature death by 12% and reduce the risk for certain cancers, including colorectal, gastric, pancreatic and lung cancers.
  • Regular consumption can also reduce the risk of death due to heart disease by 24%, respiratory disease by 16%, infections by 32% and kidney disease by 48%.

As I read the research on peanuts, it associates eating nuts of all types with good health.   Is there something distinctive about peanuts as compared to other kinds of nuts?

I doubt it—all nuts are worth eating.

A basic prinicple of nutrition is to vary food intake.  You love peanuts (as I do)?  Eat them, but go easy on the salt.

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Jul 6 2020

Annals of food marketing: pistachios have amino acids (duh)!

I was fascinated to see this ad in the June 8 & 15 issue of the New Yorker inside the back cover:

I like pistacchios, but never thought of them as a protein source and in any case so what?  Protein is anything but lacking in American diets.

I went right to the website, AmericanPistachios.org: “Breaking News: Pistachios are a complete protein.”  I read more: A study shows that pistachios have all 9 essential amino acids.

Here’s the study:

I assumed that the study was paid for by the pistachio association, but if so, the funding was well laundered.  The disclosure statement says: “This study was funded by a Specialty Crop Grant from the US Department of Agriculture.”  The USDA supports pistachio marketing.

OK.  Here’s why I think this ad is absurd.

  • Americans consume roughly twice the amount of protein needed.
  • Most food proteins, even those from plants, contain all 9 essential amino acids.
  • Pistachios are already known to contain the essential amino acids (see the USDA food composition data base).
  • 100 grams of pistachios contain 21 grams of protein BUT also 572 calories.
  • Other nuts have all those amino acids too (see composition data for walnuts, for example).

I suppose it’s good to educate New Yorker readers about how plants have protein—they do!—but the emphasis on protein makes no nutritional sense.

The Pistachio trade association must think whatever this ad costs is worth the expense.*  Let’s hear it for marketing!

*What does it cost?  This depends on the size of the market—the circulation in a particular area—which can vary from one borough of New York to the whole country, and must be highly negotiable.