Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the practical application of health information. Nutrition. Exercise. Diet. Supplementation. I look at the science behind them, and let you know whether it’s something to consider or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
The abstract begins simply enough. “Dietary Haem iron intake is linked to an increased risk of Type-2 Diabetes.” Heme iron is sourced from animal meat. But let’s get back to the opening statement. The first question that pops into my mind is “how are they going to measure iron intake from all sources, especially when you consider the scope of the study, with that many subjects?
The research team examined data from over 200,000 potential subjects from three large studies of healthcare professionals: The Nurses’ Health Study I and II as well as the Professional Healthcare study. As you might expect, the nurses studies were predominantly women while the PHS was predominantly men. Some of the subjects were followed for as long as 36 years. Researchers wanted to examine associations between iron intake from all sources and the risk of T2D. They also examined blood markers in a subset of close to 38,000 subjects. The biomarkers were insulin, lipids, inflammation, and uric acid levels.
They found that heme iron intake resulted in a Hazard Ratio of a 26% increased risk for the development of T2D when comparing the highest quintile with the lowest quintile of heme iron intake. The heme iron intake was also correlated with poor blood profiles such as high insulin, hs-C-reactive protein, and lipid levels.
Is it time to reduce meat intake? That’s not my question, at least not yet. My question is how did they measure the heme and non heme iron levels in over 200,000 people? I relied on the press release by the university center that published the paper as well as the abstract published in a reputable scientific journal for most of the information.
They calculated the heme and non heme content by searching the USDA Database for the iron content of every iron-containing animal and plant-based food. If you’ve listened in the past, you know that’s what I always criticize nutritional studies about: finding the specific nutrient within a food that may explain the findings. In this case, they didn’t just look at meat; they sought to find what they felt was the culprit: animal-based iron.
Sometimes, size matters. If you think that study was large, this next study actually precedes the heme-iron paper. Not only in time but in size—with close to 2 million subjects! This was an attempt to check on whether red meat, processed red meat--like bacon and sausage, or chicken are associated with T2D. This was a Herculean task that would never be possible without the type of computers available today. Just examining the results of the observational studies alone was amazing.
The researchers used a statistical technique called a federated meta analyses to test the relationship between meat consumption and Type 2 Diabetes. That allows analyzing the nutritional data while preserving the anonymity of the subjects. One of the problems was that the data for meat intake had to be standardized among the 31 countries covering the Americas, Europe, and Pacific countries.
With 1.9 million adults selected for the study, there were just over 107,00 diagnosed with T2D. The median follow-up time was 10 years with an interquartile range of 7-15 years. The ranges of meat consumption in all categories was as little as 0 grams up to 110 g per day. One thing that surprised me was that the European processed meat intake far exceeded that of the US.
What did they find? Eating more of each type of meat increased the diagnosis of T2D. The HRs were a 10% greater risk for each 100 g of unprocessed red meat, 15% greater risk for each 50 grams of processed red meat but only 8% greater risk for every 100 grams of chicken consumed. The increased risk was found in North America, the European countries, and the Western Pacific regions. Repeated covariates such as age, gender, or BMI were tested to explain the differences with other regions but no clear answers emerged. The conclusion? Eating red meat is a risk factor for developing T2D across all populations.
I often criticize these types of studies because they do not give any reasons or even guesses as to why? They couldn’t explain it but gave one possibility that many people don’t consider. Red meat and chicken with skin contains fat, and processed red meat contains other chemicals used in processing and cooking techniques certainly vary. That’s probably not it. But what they have in common is protein. If someone is not eating enough carbohydrates, they are more likely to make glucose from the amino acid remnants of the protein. That’s why people who claim to eat few carbs and starches will end up with prediabetes and fatty livers. I give the authors credit for that.
The problem is in the tool used to collect the nutritional information in the first place and as you probably guessed, it was the FFQ in most cases. I understand completely why they are used. When a study may contain 500, 5000, or 500,000 subjects, to do a dietary recall of the prior 24 hours using a dietitian to help determine portion sizes would be close to impossible, very difficult at best. Way back when nutritional research became the focus of examining dietary intake in large populations across all age, gender, and ethnic groups, the FFQ was developed to provide a snapshot of what people eat. I say that purposefully because it does only cover one moment in time regardless of the nature of the questions. One of the first times that I noticed it was used was in the Nurses’ Health study. Those studies have been going on close to 50 years or more with repeated measures every few years. Until very recently, they've used the exact same FFQ form as when it was developed 50 years ago.
Let me give you an example of the FFQ. These are the directions: Please fill in your average use during the past year of each specified food. I chose unprocessed meat. There are 4 categories within the unprocessed meat. Let's focus on one. Hamburger. 1 patty. Here are the directions: Please fill in your average use during the past year. Here are the categories: One patty never or less than once per month, one to three patties per month, one per week, two to four per week, five to six per week, a hamburger patty every day, two to three per day, four to five per day, or 6 or more hamburger patties per day.
The problem with this particular choice is that it doesn't define the size of the patty, either by grams or ounces. I know that things have changed as it relates to our meat intake, but whoever ate 6 or more hamburger patties per day? Ever? Or any other kind of meat for that matter? Those categories that I listed for you apply to every food on the questionnaire, whether vegetable, fruit, dairy, seafood, or grains as well. It’s supposed to be indicative of what you ate in a year.
Whether researchers are trying to estimate how much of each type of meat a person eats or trying to calculate the heme content of that meat from the grams of meats people said they ate, the FFQ doesn’t have enough precision to be used in determining those values. Remember, the increase in HR was 10% per 100 grams—that’s 3.3 ounces—of unprocessed red meat per day. If a patty were 100 grams, a reasonable size, that would be 600 grams or over 1.5 pounds of hamburger patties alone per day. Would that raise the risk to a HR of 60% based on that single answer? What about a vegan who gets no heme iron? Would they never get T2D? We know that’s not true either.
What we’re left with is this. There may be a relationship between red meat and subsequently heme iron intake and the risk of T2D. It certainly isn’t a linear relationship. For now, there is no clear and present danger to eating meat and developing T2D, especially if you keep in mind to eat better, eat less, and move more. I’m out of time. This is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
