My hope is to answer this question today….
“Why is there so much contradictory information out there regarding nutrition”?
And while there may be a couple reasons for this, I believe there is a main overriding factor that plagues the fitness industry in providing bad information without true context behind the facts. This factor and main contributor is correlation vs. causation. This may get a bit long winded, but stick with me.
Let’s dive into what correlation vs. causation is. According to a quick Google search, these are the definitions of each:
Correlation: “a mutual relationship or connection between two or more things.” (1)
Causation: “the action of causing something.” (2)
Now reading those two definitions, it is very apparent there is a difference, yet many articles on nutrition seem to not be able to distinguish the difference between the two. Correlation shows a relationship or connection between two or more things, but in no way signifies that these two things cause each other to occur, whereas causation signifies a direct interrelation, where one thing causes the other. At this point you may still be confused, so let me get into an example of how correlation can be an inaccurate way of coming to conclusions, and then some specific nutrition examples that have consistently had this exact issue.
There is a famous study that many go to in regards to the possible downfalls of using correlation to assume causation, or in other words, assuming because something has a relation to another issue, that it means it causes that issue as well. This study showed that an increase in ice cream sales had a direct correlation with an increase in murder rates, which raised the question, “Does ice cream cause people to kill?”. (3) I don’t think I need to spend much time on answering that question, as we all can understand that ice cream does not cause someone to kill. Even though there was correlation, there was something else that was the actual issue, and that was found to be the warmer weather in the months of July to September. Warmer weather then is the middle ground that is associated with causing both to occur, resulting in more ice cream to be bought and for murder rates to rise.
So how does this apply to fitness? Let’s take a look at two specific examples that I believe are the most abused when it comes to taking a correlational effect and then assuming it is also the cause. The first one we will look at is diet soda. I will be the first to say there is nothing inherently good about diet soda and I am not here to recommend that it would be a good option for you to consume. But I also can say with 100% certainty that diet soda does not CAUSE weight gain, as so many articles and research studies have tried to claim or hint at. Research has shown that there is a direct CORRELATION between diet soda and being overweight, but let’s break this down so we can understand the truth. When it comes to the question “Does diet soda CAUSE weight gain?”, I have a simple answer…..”Diet soda has ZERO calories” (mic drop). Weight gain is caused by a surplus of calories over our needed amount, so if something has zero calories, it cannot physiologically CAUSE weight gain, it is just not biologically possible. So if currently you have quit drinking diet soda in the fear of gaining weight from it, I am hear to tell you that you no longer have to worry. What research has shown though, is that there is a CORRELATION between people who drink diet soda and those people being overweight. And to me there is a simple answer to what this correlation means. People who are overweight tend to drink diet soda! This does not mean that diet soda is causing them to be overweight. What it means is that diet soda is not the healthiest of choices in regards to its contents, and those who are overweight usually are not choosing the best of options, so diet soda is a logical option they are probably gravitating towards. Now in my own personal experience, I have very rarely seen diet soda be an issue within someone’s weight loss, and have at times found a small benefit. People crave sweet things, and if a diet soda once in awhile can calm those cravings and give you that “sweet” satisfaction with zero calories, that is going to be a much better option than what could occur, which is eating candy and junk food that actually contains calories. Again, I do not recommend drinking diet soda, as there is nothing beneficial about it physiologically, but if mentally it can satisfy sweet cravings, I definitely would consider it the lesser of two evils in regards to eating candy and junk food.
The second big correlation vs. causation mishap I see is the demonization of sodium and its apparent role in causing obesity. Unlike diet soda, we actually need sodium, and there are health benefits in regards to sodium, so demonizing it is a dangerous thing to do. But just like any substance, if we over consume sodium, there can be health risks. Sodium is definitely something that can be an issue for those with heart related issues or high blood pressure, and at that point needs to be closely monitored. But for the sake of this article, I want to just hone in on the much talked about CORRELATION between sodium and obesity. A quick Google search of “sodium and obesity” comes up with 17,600,000 hits, with page after page filled with articles saying the sodium is strongly linked with obesity. But I have the same exact answer, as with diet soda, to this issue as well….
”Sodium has ZERO calories” (mic drop).
Just like diet soda, sodium cannot cause weight gain, yet the general fitness industry is trying to convince us it does, so what gives? Let’s look at the real issues with sodium and why this correlation has arised. I am going to look at myself as an example. I eat on average around 3,500 calories a day, and consume around 3,500mg of sodium as well. The vast majority of what I eat would be considered healthy, and I eat out on very rare occasions. According the general health standards, it is recommended to be somewhere in the range of 1500-2500mg of sodium for your daily intake, but that is also based off a 2,000 calorie diet. So if I am using those standards (which I do not completely agree with, but will use for this example) then I am right about where I should be, which is 1mg of sodium for every 1 calorie. But now let’s look at an entrée from a popular restaurant chain that will go unnamed.
Chicken Bowl /w Rice (sounds like it could possible be healthy, but it’s not)
That one single meal is more sodium than I consume in an entire day, and I eat 3,500 calories! If the suggested amount of sodium is 1:1 ratio of sodium to calories, this meal is 1:4.35, or four times the amount of sodium we should probably consume with that amount of calories. Going down the menu for this popular restaurant chain, most entrees are above 2,000mg of sodium, with probably the average being somewhere around 3,000mg. No matter what, we are going to hit our allotted sodium goal in just one sitting, while also consuming a very high calorie meal (the 880 chicken bowl w/ rice was one of the lower calorie options, most were over 1,000 calories). So what does this all mean? If you are consistently eating out or eating a lot of processed foods, you will be consuming a lot of sodium. And what do you think happens to people who are eating out a lot and are consuming processed foods? They gain weight. Sodium did not cause this weight gain, and just like the instance with ice cream and murder rates, there is a middle ground actually causing both, and in this case it is eating out and processed foods. So what can we gain from these correlational studies on sodium? Do not eat out so much and limit your processed foods, as those have been shown to have a causation effect with obesity due to their high calorie nature. Unless you have high blood pressure or a heart related issue, if the vast majority of your food is home-cooked, you do not need to worry about sodium in the slightest.
The list could go on about examples of correlation vs. causation getting abused within the fitness industry, but what I hope you got from this is a new way of thinking about the research in these articles claiming that X correlates with Y, so X must cause Y. Look for keywords like “linked, “correlates”, “strongly associated” or “associated with”, “may increase” or “may raise”, “tied to”, or other terms that try to hint at a causation effect, but are truly just correlational. This doesn’t mean all correlational effects are wrong, but what I am saying is that if you see those keywords, make sure to challenge the thought process of the claims before accepting them as truth.