Did Leading Nutrition Experts Knowingly Use Fatally Skewed Data?

JAMA Internal Medicine published the first-ever study comparing butter to seed oils. But they skewed the data to the point of absurdity.

Time and again, I’ve seen supposedly peer-reviewed studies making conclusions that defy common sense. Especially seed oil studies. This latest journal is one of the worst examples I’ve come across. I’m going to break down what they did and how they got away with it in this article.

Their paper is especially important. It’s the first, to my knowledge, to compare seed oils head to head with butter. More than 70 years have passed since health authorities started recommending we swap out butter for seed oils. In all that time, our authorities said they had studies showing that seed oils had health benefits over butter. But they didn’t.

Previous studies lumped butter in with other animal fats. Or they investigated saturated fat rather than any whole food. Similarly, they lumped the collection of problematic seed oils I call the Hateful Eight together with olive oil and other plant fats. Or they investigated linoleic acid rather than any whole food.

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So this truly is a first. At least to my knowledge.

Let’s start by talking about the claim that’s making headlines.

Exchanging 10 grams of butter for seed oil reduces total mortality and cancer mortality by 17%, while also reducing heart disease mortality.

That’s a huge effect. But let’s think about what they’re saying here for just a bit. 

Total mortality includes cancer mortality and heart disease mortality. So when they say total mortality and cancer mortality can be cut by 17 percent by avoiding butter, that suggests all the excess deaths the seed-oil eaters avoided come from cancer. But, wait. The authors also claim that heart disease deaths were reduced as well.  That would mean seed oils confer a less than zero chance of dying.

Now, I’m no statistician, but that’s pretty improbable. When I posted this on social  media, experts came out of the woodwork to say things like “I can’t even begin to say how wrong that is.” Hmmm. If it’s that hard to explain, maybe you should question it. 

I think we all know that statisticians can make 17 minus 17 not equal zero any day of the week. They can make a bunch of extrapolations and adjustments. They can use a skewed data set. And the editors rarely require them to reveal the raw data that they adjusted and extrapolated. That’s true in this case (no raw mortality data provided), and the butter and oil intakes were skewed to the point of ridiculousness.

Let’s start with a look at the skewed data.

Quartiles Became Levels

Normally, studies like this break people’s consumption into groups that are evenly sized. They did not do this here. They intended to, but because butter and oil intakes were highly right-skewed, meaning most data points were clustered at the lower end, but a few extremely high values pulled the mean to the right of the median. (This comes from the inaccurate reporting problem discussed below.) The authors acknowledge this directly in the Statistical Analysis section, where they state:

“Participants were initially categorized into quartiles of intake levels; however, due to the right-skewed distribution of these exposures, the sample sizes within each category were uneven. Therefore, we labeled the categories as levels 1 to 4 instead of quartiles 1 to 4.”

This is an admission that these are not quartiles in any meaningful sense. Just to show you one example of the imbalance using the Nurses’ Health Study butter intake data:

Number of participants in each level:

• Level 1: 53,415 

• Level 2: 6,488

• Level 3: 2,156

• Level 4: 1,049

That is not remotely quartile-like. There should be roughly 15,000 in each quartile. This is so out of the ordinary and flawed that one scientist has said, “such skewed allocation is absurd and the ‘research’ should have stopped there.” I couldn’t agree more.

Now let’s move on to understanding why that “highly right-skewed” data is a big problem in and of itself.

Butter and Seed Oil Intakes Difficult to Believe.

Reported butter intake from the Nurses’ Health Study is skewed low.

According to Table 1, a pound of butter would feed most families for years.

Zooming in to look at the butter intakes, we see this:

According to Table 1, the median butter serving among most of the participants surveyed in 2002 (63,108 of 53,415) was 0.1 grams per day. In a year, they’d eat 36.5 grams. But wait, the average butter consumption in the US around that time was 60 times higher, 2.2 kg per year. [See table 2 in this article, which reports 1999 data] So they’re asking us to believe that the vast majority of study participants, 82% or so, consumed so much less butter than average that it’s statistically a miracle that they found so many of them.

It’s been a while since I took my two-credit course on statistics in med school, but I think the proper term to describe that kind of result starts with a B and ends with an S.

Another part of Table 1, not shown here, also reports butter consumption from two other very large data sets: the Nurses’ Health Study II (NHSII) and the Health Professionals Follow-up Study (HPFS). The results are also much lower than average and difficult to believe.

Next, let’s look at the seed oil data from the Nurses’ Health Study.

The paper reports that the median serving of seed oil for a majority, 37,266 of the 63,108 people surveyed, in 2002 was 1.8 grams per day. In a year, they’d consume 657 grams. That’s just under half of one of those 24-ounce bottles you can buy for $4 or so. But here again, when we compare to the average person’s estimated consumption, we see a discrepancy [see figure 1 in this paper].

According to more reliable data, in 1999, the average person’s soy and canola consumption was 20 times higher than the majority of Nurses’ Health Study participants.

(The same goes for the data in the two other studies the authors analyzed. In the interest of space, I’m not going to break them down.)

According to Zhang et al, a majority of participants consumed so much less seed oil than average that their total reported consumption amounts to a rounding error in the average consumption at that time.

How do they get away with this?

I’m going to show you in the next section.

What should we make of these reported butter and seed oil consumption discrepancies?

These discrepancies are huge. Yooooj. Why didn’t the authors mention them?

I can think of two reasons. Either they were completely unaware of average consumption levels. Or they did not want to highlight the fact that their data appears to deviate so far from reality that it’s simply not believable. If it’s option one, then we have people calling themselves nutrition experts who are not. If it’s option two, we have dishonest people running the nutrition conversation. Heck, they might even fill in the data tables with fake numbers if they think they can get away with it!

I don’t actually think they printed fake consumption data. I do think they intentionally skewed the data.

Let’s focus on how they skewed the butter intake data.

The authors knowingly underestimated true butter intakes.

According to the authors, “Total butter intake was calculated by multiplying the frequency of consumption by 5 g per pat from the sum of 3 FFQ items: butter from butter and margarine blend, spreadable butter added to food and bread (excluding cooking), and butter used in baking and frying at home.”

They did not asses any butter used as cooking fat, or melted and added to vegetables, pancakes, puddings, frostings, cookies, cakes, muffins, desserts, etc. They did not assess any butter consumed outside the home. Restaurants use butter for all of the above purposes. Bakeries use a ton of butter.

The know-it-alls on social media have told me that I’m wrong to suggest any malfeasance here. They say this is just a problem with food frequency questionnaires, which are notoriously inaccurate. They don’t realize they are making my point, which is this: we shouldn’t be using data from flawed food frequency questionnaires to draw any conclusions.

The average calorie intake is also strikingly low.

Check out the calorie data reported under “Total energy intake, kcal/d” in the table I copied above. Participants, who are all women in this study, ate 1682 calories per day. At the time, the average American woman was getting 1877 calories daily. This represents 200 calories fewer than average.

Again, no mention of this either. The authors understandably would not want to draw attention to the flaws in their dataset. It’s understandable. But it’s not ethical.

The biggest names in nutrition science are misleading us.

You might expect that a deviant article like this would come from a group of hacks at a minor university. But take a look. The authors include some of the biggest names in nutrition science, and five of the six are at Harvard. Walter Willett has over 2,000 publications, and Frank Hu has over 1500.

Here’s the bottom line: Nutrition science is no longer science.

Leading nutrition scientists chuffed out a fundamentally flawed article and are not being held accountable (so far). This article is being used to support the continued production and usage of seed oils by every consumer and every processed food company. This is hardly the first flawed article reporting on seed oils. It’s time for dietitians, doctors, and patients who trust these licensed health professionals to wake up. Nutrition science has been completely hijacked by the processed food industry, which fuels the diseases that the pharmaceutical industry feeds upon.

Want to know who to trust? Trust your own sense of logic. Trust you.

Related Posts:

Read about the real cause of heart disease. It’s not butter.

Read about the harms of cholesterol-lowering drugs: here, here, here, and here.

Have a burning question about good fats and bad? The answers are on this page.

Want to know why seed oils are so unhealthy? I’ve answered those questions, too, right here.