There is a decent chance to read about diet soda studies by the day you die. (Odds are extremely good that it won't be the soda that kills you.)
The latest batch of news came last month based on another study linking diet soda to increased risk of death.
As usual, the study (and some of the articles) lacked any important context and raised more concerns than warranted. There are specific reasons why this cycle is unlikely to end.
1. If it is artificial, it must be bad.
But everything is a chemical, including dihydrogen monoxide (this is another way of saying water). These are just words we use to describe ingredients. Some ingredients occur naturally and some are brought into existence. This is not inherently one better than the other. In fact, I argue that studies support the consumption of artificial sweeteners with added sugar. (The last study completes the opposite.)
2. Soda is an easy target
In the age of health, soda became almost stigmatized in some circles (and sales declined as a result).
It is true that no one needs soda. There are millions of varieties and almost no taste in nature. Some, like Dr. Pepper, refute the description.
But there are many things we eat and drink that we do not need. We don't need ice cream or pie, but for many people life would be less enjoyable without these things.
None of this should be considered a license to drink soda cases weekly. The lack of evidence of danger in normal quantities does not mean that consuming one thing is a huge amount is a good idea. Moderation still matters.
3. Scientists must publish in order to keep their jobs
I am a professor of research and am here to tell you that the kingdom coin is grants and documents. You need funding to survive and you need to post to get funding.
As a junior faculty member or even as a doctoral or doctoral student, you must publish research. Often, the easiest step is to take a large data set and publish an analysis of it, showing the relationship between a factor and a result.
This type of research is understandable. So we hear year after year that everyone is dehydrated and we need to drink more water. This is how we hear that coffee affects one way or another. Here's how we end up with a lot of nutritional research finding associations one way or another.
While the culture of science requires results as a measure of success, these studies will emerge. And given that the news media must also publish to survive – if you didn't know, people love to read about food and health – we will continue to read stories about how diet soda will kill us.
4. Prestigious Institutions and the Press
To make the types of analysis described here, you need large amounts of data that researchers can provide. Building a data set is the hardest part of the job.
Analyzing the numbers of hundreds of thousands of people is not a child's play. But collecting data is much more expensive and time consuming.
Therefore, several universities produce a disproportionate amount of research on these topics. They also tend to be the universities with the most resources and the most recognizable names. Because they are also typically prestigious, they attract more researchers and more funding to build larger and newer datasets.
They also receive more media attention because they have access to more researchers, prestige and funding. If research is coming from a super reputable institution, this should be important.
Rather. Rinse. Repeat.
5. We still don't understand the limitations of observational studies
No matter how many times you emphasize the difference between correlation and cause and effect, people still look at "increased risk" and determine that risk produces a poor outcome. For hundreds of thousands of people, observational studies as a whole are the only realistic option. With very few exceptions, they can only tell us if two things are related, not whether one is to blame for the other (as opposed to randomized control trials).
With respect to diet soda, it is plausible that people who tend to drink them also tend to worry about their weight or health; this may be a recent heart attack or other health issues that cause consumption, not the other way around. But you should not assume that diet sodas also cause better health; it may be that healthier people avoid the added sugars.
Many of these new observational studies add little to our understanding. At one point, a study of 200,000 participants is not "better" than one with 100,000 participants, because almost all of them have limitations – often the same – that we can't fix.
Dr. John Ioannidis writes in a seminar paper: "People consume thousands of chemicals in millions of possible daily combinations. For example, there are more than 250,000 different foods and even more potentially edible items, only 300,000 edible plants. "
Yet, he added," much of the literature tacitly assumes the risk of disease "is governed by" the most abundant substances; such as carbohydrates or fats. "We don't know what else is playing, and with the help of observational studies we will never do it.
(Observational studies are still the best way to study risk factors for the population; sophisticated techniques such as breaking regression can even create quasi-randomized groups to try to get closer to understanding the cause-and-effect relationship. Too few of these techniques.)
In addition, too many reports still focus solely on relative risk, not absolute risk. If, for example, Fig This sounds bad, but if the main risk is 0.1 percent, this increase by 10 percent will move the baseline to just 0.11 percent.
Probably would be a public service if we stopped to repeat a lot of this research – and stop reporting on it in a breathless manner. If this is not possible, the best they can do is stop paying so much attention.