Nutritional Epidemiology: Specification Curve Analysis

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Did you look up quadrillion? It’s a 1 with a whole lot of 0s—15 to be exact.

When I finished Saturday’s Memo, the researchers had chosen an area of nutritional epidemiology to focus on: the analytics used to analyze the data. They began with the premise that there are many ways to analyze any data set. They then identified published research studies that examined the consumption of red meat and mortality. They identified 15 publications reporting on 24 studies that examined the effect of red meat on all-cause mortality.

They weren’t doing a meta-analysis to see all the results of all the studies combined; they used a newer technique called specification curve analysis. They identified the type of data used in the analysis, the number of variables, the number of covariates, as well as demographic data. From that information, they then calculated the total number of ways each data set could be analyzed—the specification curve analysis. Turns out that number is 10 quadrillion! That exceeds the capacity of the computing power of a small country, and I can’t even imagine how much electricity that would consume.

They decided to take a randomized sample of the possible ways to analyze the data with specific variables and covariates in each and came up with 1,440 different approaches to analyzing the data. They ran additional tests on the data and eliminated 232 approaches because the data exceeded norms.

Then they ran the remaining analytic approaches on data from several years of the NHANES study. What did they find?

  • The median hazard ratio (HR) was 0.94 for the effect of red meat on all-cause mortality. That means the mortality risk was decreased 6% if the subject ate red meat.
  • HRs ranged from 0.51 to 1.75; 435 approaches yielded HRs more than 1.0 (increased risk) and 773 less than 1.0 (decreased risk). Most analyses showed that eating red meat reduced the HR, and thus reduced the risk of dying.
  • Of all the results, 48 (almost 4%) were statistically significant; of those, 40 indicated that red meat reduced all-cause mortality and 8 that red meat increased all-cause mortality.

Does this mean that eating red meat decreases your risk of dying early? We’re not done yet. We’ll put it all in perspective on Saturday.

What are you prepared to do today?

        Dr. Chet

References:
1. https://www.sensible-med.com/p/the-definitive-analysis-of-observational
2. Journal of Clinical Epidemiology 168 (2024) 111278

Nutritional Epidemiology: The Problem

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The health headline shouts: “Fish oil increases your risk of heart disease.” The next week, “Fish oil beneficial for reducing risk of Alzheimer’s disease.” It makes one wonder what is going on in research. I’ve felt that way for a long time, and I know you have as well. I think I’ve found part of the problem, and I’m going to talk about in the next three Memos. As I said, this involves statistics, but I’ll keep it as simple as I can; we’ll be talking about some heavy duty statistical analytics, but there’s no math in my approach.

The frustration with conflicting research outcomes is especially prevalent in nutrition studies. It also happens in other fields as well including treatments for cardiovascular disease. Dr. John Mandrola, a cardiologist, wrote about a paper that examined why nutritional epidemiology is subject to conflicting results. After reading his post, I listened to the interview he had with the principal investigator of that study; then I read the paper itself. Statistics are not my forte but putting aside the high-level math, what they did was pretty amazing. By reviewing the paper here, I think you’ll get a better understanding of why research papers yield differing results even when using the same database of subjects.

Let’s begin with what has become accepted in the nutritional literature: eating red meat increases your risk of all-cause mortality. I know that many readers have given up or severely restricted red meat because so many physician, dietetic, and other health organizations have said it’s bad for your heart, among other organs. But is it really?

I used the phrase “nutritional epidemiology.” Those are studies that use some form of diet record, usually a Food Frequency Questionnaire, to track the food intake of a large group of people. Then they are tracked for 5, 10, even 20 or more years to see the differences in mortality between groups who ate red meat and those who did not. This contrasts with randomized controlled trials; they generally have as few as six subjects up to several hundred. They’re difficult to do because of the labor intensity of collecting data and ensuring subjects adhere to the protocol, whether a diet, specific foods, or dietary supplement.

With that in mind, the researchers examined all the nutritional epidemiological studies on the relationship of eating red meat and all-cause mortality. They then calculated all the ways that the data could be analyzed given the number of outcome variables and covariates used. We’ll pick it up on Tuesday, but as a tease, look up how much a quadrillion is.

What are you prepared to do today?

        Dr. Chet

References:
1. https://www.sensible-med.com/p/the-definitive-analysis-of-observational
2. Journal of Clinical Epidemiology 168 (2024) 111278

How Did You Do in the Holiday Challenge?

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Did you keep track of the fruits and veggies you ate over the holiday weekend (or July 4–7 for those of you outside the U.S.)? Remember to email me your results. Some people didn’t need reminding—I have already gotten replies.

I didn’t do as well as I would have liked. Here are my lists:

  • Vegetables: tomatoes (multiple varieties), lettuce, asparagus, artichokes, cucumber, red onion, shallots, avocado, mushrooms, prickly pear, basil.
  • Fruit: oranges, grapes, cherries, apples, blueberries, raspberries, watermelon, corn on the cob, potatoes, raisins, garlic.
  • Condiments: ketchup and mustard

I know that technically tomatoes and avocado are fruit, but savory is savory in my head. I bought a couple that I haven’t used before, fresh ginger and daikon radish, but then never worked them into the menu. Both last, so I’ll have them soon. That brings my total to 24 for the weekend. I’m guessing many of you are going to exceed my attempt—and that would be great.

Saturday I’m going to begin a three-Memo arc on statistics. This applies to the study on ultra-processed food as well as the recent one on multivitamins. Even though it’s about statistics, you’ll be able to understand it. It’s important for you to have this foundation to make sense of the studies that you hear about these days.

What are you prepared to do today?

        Dr. Chet

Start Your Lists!

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A reminder that today is the beginning of the Holiday Fruit and Vegetable Challenge. There will be three prizes this time:

  • The most plant-based foods (but you have to exceed JB’s record of 28 vegetables, fruits, and herbs)
  • The greatest number of different vegetables
  • The greatest number of different fruits

Start keeping track this morning and keep going until bedtime Sunday. I’m keeping my list as well.

Winners can choose between a free six-month Insider membership or the digital Optimal Performance program.

What are you prepared to do today?

        Dr. Chet

The Holiday Challenge, Part 2

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I enjoyed the Memorial Day Challenge so much, I want to see if you can do better. I want more of you to respond this time, so I’m going to make it a little more enticing for you by handing out more prizes. This time, I’m going to reward the person who eats the most plant-based foods, but because there is an extra day, you have to exceed the past winner’s record of 28 vegetables, fruits, and herbs. I’ll also reward the person with the greatest number of different vegetables as well as the greatest number of different fruits. Just start keeping track the morning of July 4th and keep going. It was almost all women who responded last time—men, you need to step up and get in the game.

Expand your horizons and try some new veggies. Challenge yourself to eat something other than Romaine or iceberg lettuce for salads, although they certainly count. Try arugula or bok choy, or switch it up and grill some peaches or eggplant. For this challenge, corn on the cob counts as a vegetable instead of a grain. Melon, tomatoes, berries of all types, as well as bananas and apples count.

The goal is to increase your phytonutrient intake by a massive amount. Vegetables and fruit all have some nutrients you need, and summer is the easiest time to get them. You can prepare them any way you want; grill watermelon or pineapple or caramelize onions for your burgers. Creamy coleslaw also works. Cooked or raw doesn’t matter; cooking may change the form of phytonutrients but doesn’t destroy them. Remember that condiments count. Ketchup, mustard, and relish—sweet or dill—all have specific phytonutrients in them. People are becoming obsessed with pickled veggies. They count, of course.

As for how much of each food counts, use common sense. You might reasonably count the sprinkling of chives on your eggs, but adding one leaf of basil isn’t how people cook (except for maybe the tweezer-wielding chefs on TV).

Using the honor system, send me a list of everything you ate with the total fruits and veggies, the number of vegetables, and the number of fruits. I’ll offer a free six-month Insider membership or the digital Optimal Performance program to the person with the highest total in each category. Have fun, be safe, and I’ll be back next week.

Stocking up on podcasts for this holiday weekend? You can binge my podcast Straight Talk on Health, available on Spotify and other podcast sites.

What are you prepared to do today?

        Dr. Chet

A Closer Look at Ultra-Processed Food Risk

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I think the results of the UK Biobank ultra-processed food (UPF) study were interesting, as I relayed on Tuesday, but the researchers went further. They estimated how substituting non-UPF plant-sourced foods for any of the other three sources of food resulted in a reduction of cardiovascular disease (CVD) morbidity and mortality. Further, and what got the headlines, substituting UPF plant-sourced foods for any of the other three increased the risk of CVD morbidity and mortality.

That led some experts to speculate about how processing destroyed fiber and phytonutrients and may even increase the amounts of negative chemicals that have been associated with disease in UPF plant-sourced foods. The problem is that there are no randomized-controlled trials to prove that. Here are a few things that stood out to me.

Theoretically…

The most important issue was this: The determination made about UPF increasing or decreasing the risk of CVD was theoretical and based on calculations. They used a 10% substitution for the non-UPF or UPF plant-sourced foods to calculate the expected raising or lowering of risk. What they could have done was divide the subjects into actual groups based on percentage of nutrients they actually ate instead of running theoretical statistical formulae. My impression is that so few people were diagnosed or died from CVD during the nine-year observational period that they wouldn’t have enough subjects for each group.

So few subjects were diagnosed or died? In the entire subject population—over 118,000 subjects followed for nine years—there were only 7,806 people diagnosed with CVD and only 529 deaths from CVD. Only? Most of the subjects were between 40 and 70, prime time for being diagnosed with some form of CVD.

When looking at the percentage of UPF-plant-sourced foods, the highest percentages were from industrialized packaged breads (9.9%),

pastries, buns, and cakes (6.9%) and biscuits (the kind called cookies in the U.S.) at 3.9%. That’s over half the amount of UPF-plant based foods on the list provided in the research paper. While wheat and other grains were certainly stripped of nutrients in the ultra-processing, that’s nothing new—that’s been happening to flour for over 100 years. What was missing were any fruits or vegetables processed in that manner.

The Bottom Line

Should you take the corn chips and vegan burgers out of your cart? Don’t get the impression that I think UPF plant-based foods should be eaten in mass quantities. I don’t. But I don’t think this study provided much direction in a reasonable response to the issue. On top of that, the analysis of the data may be just plain wrong. We’re not done yet, but we’ll get to that after the 4th of July. One more holiday challenge coming up on Tuesday.

What are you prepared to do today?

        Dr. Chet

Reference: DOI:
https://doi.org/10.1016/j.lanepe.2024.100948


Is Ultra-Processed Food Worthless?

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Ultra-processed food (UPF) has been in the news again: researchers have found a relationship between plant-based UPF and cardiovascular disease (CVD) and mortality. Health news writers were brimming with opinions on what the study meant. The comment that got my attention was that UPF manufacturing destroyed good nutrients found in plant foods to the point that there was no benefit to eating them. For example, store-bought cereals and cookies are worthless no matter how much fruit or nuts are added.

Is that true?

Let’s begin by looking at the study. Researchers used data from the UK Biobank database. They selected only the participants who completed at least two 24-hour dietary recalls—118,397 subjects. All participants were part of the healthcare system in the UK, so the researchers were able to collect diagnostic and mortality data from electronic medical records.

Researchers divided the dietary data into four groups:

  • Non-UPF plant-sourced foods (fresh grapes or canned corn)
  • UPF plant-sourced foods (corn chips or vegan burgers)
  • Non-UPF animal-sourced foods (ground beef or canned tuna)
  • UPF animal-sourced foods (chicken nuggets or ice cream)

The two main findings were that the more UPF plant-sourced foods were eaten, the higher the risk of CVD and CVD mortality; second, the increase of non-UPF plant-sourced foods reduced the risk of CVD and mortality. I think those results were to be expected. In Saturday’s Memo, we’ll take a closer look at whether the expert diatribes about negating the benefits of UPF-plant-sourced foods were warranted.

Don’t forget that the Men’s Health Webinar is this Wednesday evening. If you want to participate, respond by tonight to get the login information. The live webinar is free.

What are you prepared to do today?

        Dr. Chet

Reference: DOI:
https://doi.org/10.1016/j.lanepe.2024.100948

Free Men’s Health Webinar

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June is National Men’s Health month. My first thought was to do a series of Memos on the key points of men’s health, but because I can talk faster than I can type (and you may not want to read that much), I decided to do a Men’s Health webinar next Wednesday night, June 26 at 8 p.m. Eastern Time. All you have to do is reply to this email and say something like “I’m in” and I’ll add you to the email list. I’ll send out the login information the day before, with a reminder in Tuesday’s Memo.

While cardiovascular disease and type 2 diabetes can cause the most serious negative outcomes if untreated, men don’t completely understand prostate issues, especially prostate cancer. Most men’s way of dealing with it is to ignore it. I’m a prostate cancer survivor, so I’ll talk about my experience. I’ll provide the top five things you can do to decrease your risk of all the major diseases and conditions that afflict men and what you can do when you’re diagnosed. You’re never too young or too old to take your health into your own hands; there’s always something you can do to be healthier.

Men—you don’t want to miss this webinar. Women are welcome as well.

The live webinar is free next Wednesday, and then I’ll consider having it as a product for a nominal fee. Hearing it live is better, and I know it’s short notice, but so is the warning for a stroke, and none of us need that. Join me next week.

What are you prepared to do today?

        Dr. Chet

Memorial Weekend F&V Challenge

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It’s time to reveal the consumer of the largest variety of fruit and vegetables over the Memorial Day weekend, but before I do, a couple of comments.

If you would have typically eaten the vegetables and fruits anyway, good job. I know that readers who perceive themselves as eating enough servings were probably more likely to respond, but still, good job.

For those of you who went out of your way to add more vegetables and fruit, I hope you’ll continue to find a way to increase your typical intake.

For those of you who didn’t try, there is no question that eating more plant-based foods is healthier for you. Taking great supplements fills gaps, but it doesn’t replace eating food as well.

The winner for the largest variety of fruit and vegetable intake was J.B. with a whopping total of 28 different vegetables and fruits. There were a number of readers who hit 20, but 28 was tops. Great job! We’ll issue the challenge again for the 4th of July holiday weekend.

Insider Call Tomorrow

Omega-3 fatty acids have been in the news lately; recent research has shown an association with omega-3 intake and the development of atrial fibrillation. I’m going to look at this in detail to see if there’s anything there. I’m also going to answer Insider questions. For those of you who aren’t Insiders, you have until 8 p.m. Eastern to join and participate in the call at 9 p.m.

What are you prepared to do today?

        Dr. Chet

SIT to Get Fitter

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Here are the results of the study on sprint interval training or SIT. There was an 11% increase in max VO2 after the first cycle, reduced down to 6.4% after the second cycle, and finished at an 8% increase. Were the subjects fitter? Max VO2 notwithstanding, they absolutely were fitter. The reason we know that is because during succeeding sessions, their heart rates were lower for a given workload. They were working just as hard, but they didn’t need to use as much energy to do it.

Is there an explanation for the apparent dip in the max VO2 increase? I think the reason the results appear stymied was that they overtrained. Athletes do intervals of any type once, maybe twice per week. The subjects trained every other day for six weeks—and the max VO2 test is like another sprint training session. If someone were healthy enough and had the doctor’s permission, doing a sprint interval training session once every two weeks is enough. I know it sounds so easy: “It’s just 15 seconds! I get to rest for two minutes.” Trust me, with 30 years as a runner and an exercise physiologist: you get shredded every time you do it. You need complete recovery after that kind of session whether cycling, sprinting on a track, on an elliptical, or whatever.

The Bottom Line

I hope you’ve enjoyed the progression of these recent studies. From a walking program to get fitter and sustain muscle mass in exercising muscles, to the comparisons of bike HIIT intervals versus running HIIT intervals to sprint intervals to get fit a little faster, there’s something for everyone. Just make sure you have your physician’s approval to exercise at the level of each type before you begin.

What are you prepared to do today?

        Dr. Chet

Reference: Medicine & Science in Sports & Exercise. 56(5):876-884, May 2024.