You reference the term "high intake" when talking about studies that looked at consuming turkey vs red meat. How is high intake defined?

You might expect a very simple answer to this question about "high" intake of meat, but unfortunately, research studies as a group do not provide us with any simple answer to this question. It turns out that the definition of "high" is actually quite complicated.

In many studies, participants are divided into groups according to the amount of meat that they consume. "High" intake in these studies is often defined as whatever amount of meat is eaten, on average, by participants whose meat consumption falls into the top 20% of all participants. (This top 20% is referred to as the study's "highest quintile" group.) The meat intake of this "high" group is then compared to the meat intake of the "low" group, namely, the average meat intake of participants whose meat consumption falls into the bottom 20% of all participants. (This bottom 20% is referred to as the study's "lowest quintile" group.) From a statistical research perspective, this comparison of the top 20% of participants to the bottom 20% of participants makes good sense. But it doesn't always leave us with a practical health guideline about what counts as "high" or "low" intake, because "high" and "low" intakes as defined in these studies are based exclusively on the happenstance personal preferences of participants in the studies.

Additional factors are relevant in understanding classifications of meat intake in large-scale diet studies. One way to measure "high" intake is to ask study participants about their frequency of meat intake, without actually measuring the amount of meat that they consumed. In this research approach, participants simply report how many servings of meat they eat per day, per week, or per month. In most of the studies that we have seen that make use of this methodology, "high" intake of meat usually translates into 1.75-2.5 servings per day or higher. (By contrast, "low" intake of meat usually translates into 0.5 servings per day or less.) In some studies, the amount of meat that constitutes one serving is carefully defined for the study participants before they report the number of meat servings that they consume. In these studies, "1 serving" is usually defined as either 1, 2, or 3 ounces of meat, depending on the decision of the researchers. Yet another approach in some studies is to measure the actual amount of meat consumed in terms of some unit of weight (usually grams), and usually on a daily basis. Approximately 100-200 grams of meat per day is typically classified as "high" intake in most of the diet studies that follow this methodology. Depending on the fat content and other characteristics of the meat in question, 100-200 grams usually translates into approximately 3-1/2 to 7 ounces of meat.

One of the reasons for this methodological diversity in diet studies on meat intake is related to the diversity in nutrient factors related to meat intake. Researchers are sometimes most concerned with the saturated fat content of meat. Sometimes they are focused on other nutrient or processing factors, including total fat content, heme iron content, or degree of meat processing that might involve use of preservatives like nitrites or nitrates. These nutrient and processing factors might lead researchers to adopt a particular measurement of "high" or "low" intake that would make accurate evaluation more likely.

As you can see, determination of "high" meat intake in dietary studies can be a complicated and confusing research issue! Our own take-away from the studies as a whole is as follows:

References

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