Low carbohydrate diet or ketogenic diet – bad for your gut health?
Are low-carbohydrate or ketogenic diets bad
for your gut health?
Hi, this is Dr. Ruscio, and let’s discuss
this question: if low-carb or ketogenic diets
are bad for or could be damaging your gut
In short, the answer is no.
Low-carb or ketogenic diets are not bad for
your gut health.
But there’s confusion around this.
Allow me to dispel briefly why there’s a confusion
and what this means for you.
Again, in short, if you’re doing a lower-carb
or a ketogenic diet and deriving benefit from
it, continue with it.
Now, do not continue with that dietary approach
if you’re feeling fatigued or irritable or
A lower-carb or ketogenic dietary approach
is not going to be the best approach for everyone,
but for some it will be helpful.
Unfortunately, you may come across information
on the internet that tells you a number of
One of which could be that a low-carb diet
can starve your gut bacteria and be bad for
your gut bacterial health.
And this is really misleading because while,
yes, a lower-carb or ketogenic diet may starve
certain populations, or you may see a dwindling
of certain populations of bacteria, other
populations of bacteria may actually bloom
on a lower-carb diet.
There’s debate in terms of what population
of bacteria are better than the others.
That is so littered with speculation that
you as the healthcare consumer should not
bother wading in that confusion.
Rather, we can look to outcome studies—meaning,
what happens when people eat a certain way—for
the answer to the question of what kind of
impact a lower carb diet could have.
I’m going to extrapolate a little bit from
research on the paleo diet.
There has been research published showing
that a paleo-type diet—which is oftentimes,
but not always, lower in carb—reduces colorectal
cancer risk to a similar degree as the Mediterranean
So some good evidence there.
Now there are a number of trials showing that
a lower-carb diet, oftentimes looking at this
through the context of either a paleo diet
or an overtly low-carb diet, can be beneficial
for weight loss, metabolism, and cholesterol
So more good news there.
It can improve your metabolism.
Now, how this ties in with gut bacteria…
some studies have actually looked at a moderate,
low, and very low-carb grouping of patients,
and tracked what happened in their microbiotas
and how that correlated with weight change.
And ironically, in one study in particular,
found that the very low-carb diet group saw
the most weight loss and had a measurable
shift in their intestinal bacteria.
And the higher the carb intake went, the less
the change on the intestinal bacteria, and
the less the weight loss.
So this thinking—that if a diet impacts
or causes a dwindling of certain bacterial
populations, it’s going to automatically be
bad for you—is really an erroneous premise
that doesn’t have good evidence to support
Further yet still—and I review this evidence
extensively in Healthy Gut, Healthy You—when
you look at fiber content in the diet, as
compared to what’s known as all-cause mortality
or morbidity (so, your chances of dying from
any disease or having any disease), there
is no general trend showing that eating more
fiber is better for your health.
There are about as much data showing that
higher fiber intake is good for you as there
are data showing higher fiber intake has no
impact on your health.
So there’s no need to subject yourself to
a higher fiber diet if you don’t feel good
on that diet.
Now, fiber and carb intake in the diet don’t
share this direct relationship.
But oftentimes what you’ll see is, when someone
is doing a ketogenic diet, their fiber intake
may become a little bit lower.
If that ends up being you, that’s nothing
to necessarily worry about.
I do think it’s a good idea to make sure you’re
not eating an unhealthy version of a low-carb
or ketogenic diet, and making sure that you
get an ample amount of vegetables in your
diet and some fruits.
When we look at the data comparatively, vegetarian
diets do tend to have a higher fiber intake
than lower-carb diets, but what that means,
I think, is up for debate.
And finally, if you’re someone looking for
digestive relief by employing a low-carb or
ketogenic diet, (if we look at a low FODMAP
diet as a proxy) we see that those on a low
FODMAP diet—a diet that by design reduces
the amount of fermentable carbohydrates, so
many forms of fruits and vegetables are reduced—we
actually see that that can be very helpful
for many people with digestive maladies like
gas, bloating, constipation, heartburn, diarrhea,
loose stools, abdominal pain, and what have
More evidence showing that a diet that, by
design, restricts foods that feed healthy
bacteria can actually cause you to be healthier.
That tells us there’s quite an ample amount
of evidence showing you do not need to directly
feed gut bacteria in order to be healthy.
The posit that I put forth in Healthy Gut,
Healthy You is that it’s not about just feeding
gut bacteria and hoping that those gut bacteria
make you healthy, but rather eating in such
a way that makes you the host as healthy as
you can be.
And when you are healthy as the host that
houses the microbiota—your bacteria—a
healthier host means a healthier environment,
means healthier bacteria can grow.
That is what you should be focusing on.
Whether it be feeling better on a lower-carb
or ketogenic type diet, or on the other end
of the spectrum, someone who feels better
on a moderate to higher carbohydrate diet.
The carbohydrate diet needs to be personalized
to the individual.
If you as an individual are feeling better
on a lower-carb diet, and that’s creating
a healthier you and healthier environment,
then ostensibly you will see healthier bacteria
Conversely, if you’re someone who feels better
on a higher carb diet, then you will likely
have a healthier internal ecosystem that will
harbor healthier bacteria, and that will work
well for you.
In short, there is no good evidence to my
knowledge—and this is after a fairly extensive
review of the literature—showing that a
lower-carb or ketogenic diet is bad for your
In fact, there’s more evidence showing that
it could be quite good for your gut health.
But remember not to be dogmatic regarding
If you try that type of diet and don’t feel
well, then you may want to try a moderate
to higher-carb diet and see how you feel.
So the answer: no, a low carb or ketogenic
diet is not bad for your gut health.
This is Dr. Ruscio, and hopefully this information
helps you get healthy and get back to your life.