You Really Are What You Eat: Can Food Actually Have an Impact on Health and Disease?

I get a lot of questions from patients about food. There’s a lot of interest lately in using food to treat disease. Now, we know that “eating right” is “healthier” in that too much of anything can make us gain weight, and being obese can put us at risk for heart disease and diabetes, for example. But more and more people are asking me if certain foods can reduce inflammation in the body, reduce cancer risk, and actually change their risks for certain diseases – not just based on the caloric content and impacts on their weight.

Along those same lines, I am seeing more and more patients who tell me that a certain dietary change had a major impact on something totally unrelated and unexpected – like their otherwise hard to treat skin condition, or their child’s behavior in school.

Is there any validity to this?

Though the temptation is to dismiss these associations as coincidence, our growing understanding of the human microbiome has opened our eyes to ways in which food might possibly have a major impact on determining our health and disease states.

What is the microbiome?

The human microbiome is the genetic blueprint of all the organisms (viruses, bacteria, fungi, etc – also called microbiota) that live within the human body. Typically, we think of “bugs” as causing infections. But there are a few areas in our bodies that organisms call home, such as the gut, vagina, lungs, and skin. They feed off of our bodies, and often help us out in various ways in exchange. In recent years, there have been efforts in Europe, the US, and China to sequence and characterize the human microbiome. And what we’ve found is that it’s rich and diverse. You thought humans had a lot of genes? The human microbiome has at least 30 times the number of genes as the human genome!

So now that the human microbiome has been sequenced, the next step is to slowly understand what all the different genes and organisms do.

What determines a person’s microbiome?

The specific organisms living in a person’s gut and the genes that those organisms carry are different from those found in that same person’s lungs, and different from those found in another person. But we’ve noticed that there are also a lot of commonalities. And the people who have more similar microbiota to one another tend to either be related, or live near each other. We’ve also noticed that people who have the same illnesses also have similar changes in their microbiome.

No one knows exactly what determines a person’s microbiome, but we know it’s complicated. It’s likely a combination of genetics and environmental determinants. We know that antibiotics and chronic inflammation can alter the microbiome, as can food.

So why does this matter? Well, it’s hard to change our genetics, and often hard to change a lot of things in our environment. But we can change what we eat, and in turn manipulate our microbiome.

Why does our microbiome impact our health?

As we begin to understand the role of the different microbiota, we’re starting to understand the important role the microbiome plays in maintaining the “status quo” of our bodies. We’re also starting to see that these organisms play a role in how our bodies develop immunity and mediate inflammation.

For example, some of the genes in some of the organisms in our gut are responsible for allowing our bodies to digest certain foods. Without these genes or these organisms, we would not be able to digest these foods. This would be both a nuisance because we would feel sick or bloated when we ate them, but would also lead to significant nutritional deficiencies if these foods were supposed to be major parts of our diets. So why is this concept unique? Because that isn’t our genes that allow us to digest our food – it’s a gene that belongs to a bacteria, that lives inside of us.

On the negative, some of the microbiota in our guts are responsible for releasing from our foods certain compounds that can signal tumours and cancers to grow. Again – these aren’t our genes doing this – these are genes that belong to a bacteria, living in our gut.

I know what you’re wondering – if certain organisms cause inflammation and cancer, and others are good and promote health, why can’t we just eat differently and create a more favourable microbiotic environment?

Food as Medicine?

Believe it or not, this is concept that isn’t far off. We already know that taking antibiotics can decrease the richness of the gut microbiota and can lead to overgrowth of a bacteria called clostridium difficile, that can lead to a severe diarrheal illness. We also know that repopulating the microbiota can treat a stubborn clostridium difficile infection – we do this by transplanting stool from an uninfected person into a person with the infection. A less dramatic example is using a probiotic to treat infectious diarrhea or irritable bowel syndrome.

We know that people with fewer species making up their microbiota have more obesity, diabetes, high cholesterol, and inflammation. We also know that diets with more fiber, fruits, and vegetables lead to a richer microbiome. And we’ve shown a positive association between diets high in fiber, fruits, and vegetables, and  a lower risk of inflammatory bowel disease.

What next?

The problem is, we have a lot we still need to understand about the human microbiome, and the complex role it has in health and illness. We need to recognize that the microbiome is only one piece of the puzzle – we also have to contend with different genetic predispositions to certain diseases, and a whole host of other factors. But the more we understand, the closer we are to being able to actually change one major determinant of our health, and we can potentially do that by modifying what we eat.

So for the time being, when people ask me what they can do to “be healthier” – eat a diet high in fiber, fruits, and vegetables.  Consider reducing the amount of meat. And most importantly, stay tuned, because in the next few years, we will likely have gained a much better understanding of how to use food as medicine. But for now, there are very few conditions we can treat with diet alone. That being said, when people come in telling me that changing their diet lead to a major improvement in a symptoms or condition they have, I believe it! And I think it’s likely because they changed their microbiome.

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