What Research Can And Can’t Tell You About Optimal Diets

The good folks at are celebrating the 6th birthday of their website today. To celebrate they’re not only having a 50% off sale, but have also written up this must-read on how nutrition research actually works: it provides a great insight into where research fits in in regards to the choice of the foods you eat. A must-read for any fitness enthusiast.

Coach Charles R. Poliquin


If I had a nickel for every time someone asked me a question like “Is low carb better than XYZ diet?”, then I’d have … lots of nickels.

The following is a short explanation of why diets aren’t as comparable as you’d think, especially among different types of people, concluding with how to properly account for research when choosing your eating habits.

Case study #1: The Mediterranean diet

Let’s start with a baseline diet that’s well known for health benefits: the Mediterranean diet. And let’s also ignore the fact that there’s no one single diet by that name, and it’s been misportrayed at various times as meat-free and very low in fat. Regardless of this, people in the Mediterranean region do tend to eat veggies, use olive oil, and eat a variety of foods without resorting to much junk food.

Let’s first apply the diet to sick people. The Mediterranean diet performs well for people with chronic conditions. But for people with more rare conditions, or genetic conditions, it may fall short. Some rare conditions (like Phenylketonuria, otherwise known as PKU) are not amenable to any but the most specialized diet. But even less-rare ailments, such as certain seizure disorders, show the most improvement while on a ketogenic diet, which doesn’t exactly fit into the Mediterranean template.

Those were easy pickings, and not everyone has a rare medical condition. But what about more common conditions? Seafood allergy is not uncommon, and seafood can be a substantial part of the Mediterranean diet. Other than allergy, seafood can be an issue for those with histamine intolerance. Some people are allergic or intolerant to whole grains (e.g., wheat) or legumes. That doesn’t fit well with the most common version of the Mediterranean diet. It isn’t that easy to eat little meat and legume yet get enough protein, especially if you can’t handle dairy well.  

And then there’s the ubiquitous “my gut health sucks, not sure why” condition, sometimes classified as irritable bowel syndrome (IBS). In this case, a variety of foods may cause reactions, and those are often the foods that the Mediterranean diet is richest in! That includes legumes, certain veggies, and whole grains. The specific culprit isn’t always known (Is it lectins? An issue with certain types of fiber due to microbiome imbalances? FODMAPs? Something entirely different?), but IBS is a black box for a reason.

Case study #2: The zero carb diet

There are subtypes of dieters that are well informed, have tried a bunch of different diets, and thrive on diets that you’d never expect. One of the most interesting of these subtypes is the zero-carb eater. Due to their lack of carb intake, they may be in perpetual ketosis. They may have little to no intake of vitamin C. And they don’t feed their guts any fiber at all, which you might think would destroy their gut health.

But published research doesn’t apply very well to this situation. This isn’t a case of “rabbit starvation”, where you eat too much protein without any fat or carbs and build up toxic nitrogenous byproducts. Rather, these people are eating only meat (and sometimes dairy), sometimes for years, without developing dire diseases or massive gut issues. Some even resolve longstanding health issues, possibly for the same reason elimination diets can be effective.

You might doubt those who post in zero-carb forums, but I’ve met some long-time zero carbers who have great bloodwork and no digestive issues. There’s a lot we don’t know about nutrition; while some people may do very poorly on these diets, possibly endangering themselves, others seem to thrive.

So, is research useless?

As you can see, there is no way that a universally applicable “best” diet exists. There are too many different health situations, too many disease states, and too many types of food to allow for the drawing of generalized conclusions. Experimentation is still necessary, no matter how much research is out there on dietary variables.

That’s where research fits in: it provides many additional data points to bolster experimentation and common sense. Without all three working in concert, you can miss major research findings (such as with keto and seizures, fish oil lowering the efficacy of chemotherapy​, etc.), get stuck in diet habits that aren’t great for your health, or keep experimenting with useless or dangerous fad diets.


[from coach Poliquin]: is an education company run by researchers. Along the years, its growing team has reviewed thousands of studies on hundreds of supplements. Today, over two million people visit its website each month.

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