"Incorrectly" combining foods causes the body to struggle, leading to toxic waste build-up that sits there... and rots in your gut.

Sounds grim, right?

You've probably seen posts and articles online or heard people saying things like:

“Your gut issues are from eating the wrong foods together.”
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They’ll tell you it’s all down to ‘bad combinations’.

A juicy steak and chips? A digestive and health disaster! Apparently. So is a chicken sarny. And don’t even think about adding sugar to your coffee if you’re eating protein.

These food combining theories claim that bad combos cause gut symptoms like indigestion, heartburn, wind, bloating, constipation, and stomach cramps.

But it doesn’t stop there.

It also gets blamed for a ridiculous list of other conditions, including migraines, colitis, rheumatoid arthritis, psoriasis, multiple sclerosis, coeliac disease, heart disease, Type 2 Diabetes, infections, the common cold, and even mental health problems.

One website even claims that allergic reactions don’t happen if you combine your foods "properly". Shocking.

But is this the amazing fix it claims to be? Or just a 90 year old theory dressed up with modern buzzwords?

Let’s break it down, so you can make an informed decision based on actual science, not sketchy claims.

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So food combining is based on the idea that you can’t eat certain foods together, like protein and carbs, otherwise there’s going to be dramas.

The theory goes that it's because your body (supposedly) can’t digest different types of food at the same time.

*rolls eyes*

And I’ve come across so many people, social posts, ads, and websites talking about how all your gut issues (along with loads of other health issues), is caused by eating the wrong foods together!

*sighs deeply, putting face in hand*

And they often throw around fancy scientific words to sound convincing, but unless you know anatomy and physiology, it’s unfortunately easy to get drawn in.

The "rules" vary depending on the guru, but typical ones include:

Their logic?

They say your digestive system can’t handle several food types at once because different enzymes work best at different pH levels (that last bit is true by the way). Like pepsin, an enzyme that breaks down protein in the acidic environment of your stomach (Marieb & Hoehn, 2023).

Whereas the small intestine is alkaline.

So there’s a nugget of truth. But they cock up the fact that your body already accounts for this - digestion happens in stages, not all in one place. There’s no clash or conflict. It’s co-ordinated.

And actually, as a Dietitian, for example, say someone is malnourished and struggling to eat safely, we use the pH as a guide to check whether the feeding tube is in the right place.


Back to food combining...

The claim is that mixing foods causes a “traffic jam” in your gut, leading to fermentation, toxin build-up, and a long list of health issues.

Sounds dramatic, right.

But does your body actually work that way? 

Think about it...

For example, what macronutrients (fats, carbs, protein) do you find in beans, like baked beans? Or what about Brussel sprouts? Or chia seeds?

We don’t eat individual nutrients in isolation. We eat foods! And most foods contain a mix of macronutrients, so good luck with avoiding mixing carbs and protein.

The concept has ancient roots in Ayurvedic (pronounced “i-ur-vay-dic”) medicine, but it was made popular in the West by Dr William Howard Hay in the early 1900s.

In his book, “A New Health Era”, first published in 1935, he explained the principles and the so-called science behind food combining.

He also shares stories of supposedly miraculous health recoveries.

To be fair to Dr Hay, he made some decent points, like eating less highly processed foods and more whole foods. And I agree with that.

He tried to head-off criticism by saying doctors and scientists will reject his ideas (and the diet), but encourages readers to try it for themselves for a few weeks.

That same tactic pops up in modern food combining books as well...

Like one author who, upfront tries to combat objections by warning you that your doctor will likely fob it off (just like Dr Hay said), and that Dietitians, because of their scientific training, will also object to the diet!

Then they go on to say that you don’t need scientific evidence… just look at all the people who’ve tried the diet! Whhaaaat?!

That’s a red flag there.

Spoiler: I don’t recommend the diet. Because there’s zero current (or quality) scientific evidence that supports it, and modern physiology shows us why it doesn’t work.

Dr Hay got backlash from his fellow physicians – supposedly because it was about preventing disease, and that flew in the face of the medical profession at the time, which was focused on treating disease.

So it’s like if you’ve got this fella, Dr Hay cutting about and helping people prevent illness and disease, so these doctors felt threatened, thinking he’s going to put them out of a job!

In his book, he also writes:

“It is not strange that the doctor is not interested in health, for health is the direct antithesis of everything on which he has concentrated his best thought, and his interest must always be in disease, the opposite of health.

And so the patient is interested in his health, the doctor in his disease, and the interests of these two must always conflict.”

Even if Dr Hay had nailed the science for his time – it’s seriously outdated.

The book is nearly a CENTURY old!!

And unless we compare his ideas against the best scientific research of his era (which would be a whole project in itself), he may have got it totally wrong.

But either way, we now know waaaay more about the human body, digestion, nutrition, health, and disease.

Using food combining as your roadmap today is like trying to navigate with a 1930s map – outdated and misleading.

Still, people follow these rules today, like they’re cutting-edge science, when really, they’re just recycled beliefs.

But if you don’t know much about nutrition or how the body works, it’s understandable, especially when they weave in just enough facts with fiction to sound convincing.

👉 Which is exactly why it’s wise to speak to your (non-quack) doctor or Dietitian if you want up-to-date, evidence-based information and tailored support.

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Let me be clear, this isn’t about criticising the spiritual or cultural side of Ayurveda. But when ancient philosophies get repackaged as hard science, that’s when we’ve got to hit pause.

A 2019 review did try to link Ayurvedic concepts of incompatible foods with autoimmune disease, based on traditional principles like the ‘six tastes’ and body ‘humours’ (Bali & Utaal, 2019).

But here’s the key:

These are philosophical frameworks, not evidence-based models of human physiology. And modern science just doesn’t support most of their claims about what happens when you eat mixed foods.
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Well, there’s a really old study from 2000 (Golay et al., 2000) that compared a food combining diet to a regular mixed diet (as in eating foods containing fats, carbs and protein together) with the same calories and macros.

The result?

No difference in weight loss. So people went through the hassle of separating foods… For nothing!

So no, there’s no scientific evidence that food combining boosts weight loss, improves digestion or prevents disease. It appears it’s mostly based on recycled ideas from Dr Hay… from NINETY YEARS ago!

Let's keep it simple:

Your body doesn’t get confused. It was built to digest mixed meals.

And no, food doesn’t “rot” in your stomach if you mix the wrong foods. That’s not how the body works.

Your stomach is extremely acidic (- on the pH scale from 0-14 where 0 is the most acidic, 7 is neutral, and 14 is most alkaline, stomach acid is about 1.5-3pH (Marieb & Hoehn, 2023)) and kills most bacteria.

Fermentation happens much later in your large intestine, where your gut bacteria breaks down fibre to produce beneficial compounds like short chain fatty acids, and in turn, you benefit. Help them to help you!

But you get fermentation in the wrong place if you have SIBO (Small Intestinal Bacterial Overgrowth), where excess bacteria end up in your small intestine.

SIBO can cause bloating, stomach cramps, diarrhoea, and nutrient deficiencies like iron, calcium or vitamin B12. But it’s a medical condition, not the result of “bad food combining” (Pimentel et al., 2020).
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Yes. But they’re based on science, not pH clashes or “digestion chaos”.

For example:

Also, if you’ve got IBS and think you’re lactose intolerant (- the natural sugar found in milk and dairy products), research shows that having dairy products as part of meal rather than on its own can improve tolerance (Facioni et al., 2020; Fassio et al., 2018; Heaney, 2013; Shaukat et al., 2010).

Another thing to keep in mind, if you’re cutting back on dairy because of lactose, you’re also cutting back on calcium (unless you’re having calcium-rich alternatives).

And a diet low in calcium not only increases your risk of weak bones and teeth, and poor muscle and nerve function, but also kidney stones (National Kidney Foundation, 2025).
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Food combining might seem harmless, but here’s why I’m cautious:

Plenty of people say they feel better on a food combining diet. But why might this be the case?

Well, it might be that they’re making better food choices like eating more whole foods and veggies and less highly processed foods, it could be that they’re eating more mindfully, watching their portions or cutting back on chaotic eating patterns.

So yeah, they might feel better, but it’s probably NOT because they were food combining!

If you want to feel better, skip the complicated and outdated food rules.

Instead of separating your foods, focus on things like:
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And if someone tells you your gut issues (including IBS) are caused by mixing protein with carbs?

Send them this article 👍

​…and then enjoy your chicken sarny in peace.