A Registered Dietitian's Take on the Food Combining Diet


Recently it’s come to my attention that there’s a growing trend of “influencers” promoting a dietary pattern known as food combining. I decided to do some research and the further I delved, the angrier I became. This is not just a case of someone on instagram saying “I’m eating this way and I feel great and it works for me!”... these people are SELLING PROGRAMS prescribing this way of eating to their followers. Not only is this irresponsible, it’s also illegal… but I won’t get into that today.

Let’s dive in…

What is food combining?

The concept of food combining has roots in ayurvedic medicine but can also be traced back to “The Hay Diet” which was a nutrition method created by physician, Dr. William Howard Hay in the 1920’s. He claimed that different foods require different pH levels to be digested and also have different transit times in the GI tract which could lead to digestive issues, weight gain and toxin build up. 

Essentially, the claim is that certain food combinations are more difficult for our bodies to digest which would then decrease nutrient absorption and would also cause gas, bloating and “toxin build=up” because the food isn’t moving through the digestive tract quickly enough. *Right…*

Dr. Hay claimed that carbohydrate rich foods need alkaline conditions for digestion so they shouldn’t be combined with acids (like citrus fruits) because the acid would neutralize and they also shouldn’t be combined with protein because protein “excites” hydrochloric acid in the stomach during digestion.

Okay… I’m already confused

The Hay Diet separates foods into 3 categories: Acid, Alkaline or Neutral and other adaptations of his diet follow suit with similar categories.

Proponents of food combining diets have specific recommendations for what types of foods can be eaten together and which should be eaten separately. Here’s a list of some of the common food combining rules.

Common Rules of Food Combining:

1. Always eat fruit on an empty stomach
2. Protein can be paired with non-starchy vegetables
3. Fats can be paired with non-starchy vegetables
4. Carbohydrates  can be paired with non-starchy vegetables
5. Always wait 3-4 hours between meals before switching categories
6. Only consume dairy on an empty stomach.

1. Starches and protein should never be eaten together at the same meal.
2. Fats and proteins should never be eaten together at the same meals
3. Melons should be eaten alone and never paired with other fruits
4. Don’t drink liquids with meals
5. Don’t combine starches with acidic foods
6. Don’t combine different types of protein
7. Eat fruits and vegetables at the same time.

First of all, there’s no scientific evidence to support any of this. Notwithstanding the lack of scientific evidence (more on this in a second), this just isn’t the way the human body works. Anyone who’s taken biochemistry can tell you that.

The first step of digestion occurs in the mouth. Once food enters the mouth and we start chewing, enzymes are released to break that food down. The enzymes that are released in the mouth are amylase (which breaks down starch) and lipase (which breaks down fat.

The food then enters the stomach where hydrochloric acid and more enzymes are released. Again lipase and amylase are released for fat and starch respectively, and pepsin joins the party to break down protein.

Proponents of food combining suggest that eating one category of food at a time will prevent pH imbalance but our bodies are extremely complex and when we eat anything, the appropriate enzymes are sent out to break the food down. We don’t just break down one food at a time… and even if we DID, most foods are a combination of multiple macronutrients.

Food leaves the stomach as one big mish-mash (aka “chyme”) which is then released into the small intestine at which point, the pancreas releases digestive enzymes and bicarbonate (a base) to neutralizes the stomach acid. Another example of our bodies innate ability to regulate pH intrinsically.

The pancreas releases these enzymes in reaction to the drop in pH that happens when the acidic content of the stomach makes its way to the small intestine. In theory, the more acid your stomach makes, the more bicarbonate the pancreas will secrete. The pancreas has us covered! The pH level in your body is tightly regulated.

So now that we don’t have to worry about regulating pH, let’s talk about the idea that food combining can help food to move through the digestive tract more quickly.

While this is true. It’s also asinine.

Why would we WANT our food to go through the GI tract quickly? Ultimately, the longer it takes for food to go through our system, the more satisfied we feel and the less often we eat.

Satiety aside, eating a balance of macronutrients at a meal helps to regulate blood sugar.

The only time I would really recommend eating carbohydrates without a protein and fat is if we’re discussing pre or intra workout nutrition, (or maybe if you need a quick energy boost). There’s no PROBLEM with occasionally eating carbohydrates on their own but as a rule of thumb, pairing your carbohydrate with a protein and/or fat is going to improve blood sugar control and keep you fuller longer.

The food combining diet suggests that fruit should be eaten on it’s own which might be fine for someone without blood sugar control issues but for people with insulin resistance, this is terrible advice. Even if you aren’t insulin resistant, this still is shoddy science. Adding protein or fat to a meal with carbohydrates will help slow the breakdown of carbohydrates, causing a smaller spike in blood sugar. Not only that, but foods that contain fat soluble vitamins (Vitamin A, D, E and K) actually REQUIRE fat to be absorbed by the body.

It seems that most people who practice food combining espouse the digestive benefits of the practice, which makes sense...but not for the reasons they describe.

Digestion might be improved by eating this way because ultimately, you’re eating less food in a sitting. This is also why it might be effective for weight loss. If you normally pair your apple with peanut butter, you’re now just eating the apple by itself and ultimately, taking in less calories. Here’s the clincher… you don’t need to follow food combining rules to eat less.

If you are dealing with chronic bloating or digestive issues, you should talk to a f*cking doctor, not buy a 21 day reset on instagram.

If you DO see weight loss benefits, it likely has nothing to do with the principles of food combining and everything to do with the fact that maybe you’re eating more fruits and vegetables. Maybe you’re not overeating high calorie foods because your meals are boring AF because who wants to eat a chicken breast by itself?

This isn’t meant to attack anyone. You do you. But it would be irresponsible not to share the science behind this. There was actually one study that I was able to locate in the International Journal of Obesity which looked at weight loss between two groups. One group was put on a food combining diet and the second group was put on a “balanced eating”plan. Both groups were assigned 1100 calories per day. Both groups lost weight and the conclusion was that food combining offered no weight loss benefits compared to a general balanced diet.

Sure, that doesn’t mean that people might not have improved digestion from this but to me, it seems like permission to practice disordered eating for “health reasons”.

Ultimately, food combining creates food rules, which people love. To me, these rules seems extremely stressful (just google food combining chart and just try to make sense of all the arbitrary rules).

As I always say, a lack of scientific evidence via research isn’t enough of a reason to discredit something. But a complete disregard for biochemistry and our understanding of human digestion is enough of a reason not to jump on board this trend.