You might've heard too many eggs make you constipated. Influencers on Instagram claim it too . The United Kingdom has slang for it - being " egg bound ".
Author
- Vincent Ho
Associate Professor and clinical academic gastroenterologist, Western Sydney University
Eggs were once blamed for raising blood cholesterol levels, which turned out to be false . Did we get it wrong about eggs and constipation too?
Here's what the mixed bag of evidence tells us.
Starting with constipation
Constipation means different things to different people, and there are many different types.
Let's focus on "functional constipation", when people have hard, infrequent and often difficult-to-pass bowel movements. This constipation isn't due to a physical blockage of the bowel or from disease.
Functional constipation is very common. Globally, about one in ten adults (10.1%) and one in seven children (14.4%) have it at any one time.
Is eating eggs to blame?
Several studies link eating eggs with constipation, but not necessarily how you'd think.
A 2002 study of 1,699 Japanese residents over 40 found Japanese women who ate eggs at least five times a week were less likely to be constipated. Eating eggs didn't affect constipation rates in men. The researchers couldn't explain the difference.
A later study involved 3,770 female Japanese university students who filled in a questionnaire about what they'd eaten over the past month. A Western diet high in foods such as processed meats and eggs was linked to more constipation than a traditional Japanese diet (which has lots of rice but not much bread or confectionary).
Another study looked at middle-aged adults in southern China who ate duck or chicken eggs as part of a Western diet. This was linked to a higher risk of constipation compared with the traditional southern Chinese diet, which has lots of refined grains, vegetables, fruits, pickled vegetables, fish and prawns.
However, such dietary studies mostly rely on participants remembering what they ate. People also don't always fill in dietary questionnaires truthfully, and tend to under-report eating unhealthy food and over-report eating healthy food. So dietary questionnaires aren't always accurate.
They also rarely look at a single food item (such as eggs) in isolation.
Even if these studies mention eggs, the population studied can vary in age, gender and ethnicity. So the findings may not apply universally.
How about other evidence?
Laboratory based experiments looking at how egg proteins are digested in the bowel may offer some clues.
When researchers fed constipated rats protein from egg yolk, their constipation improved. This could be due to an egg yolk protein called phosvitin. This retains water around itself in the colon (the large intestine) and makes the stool bulkier and easier to pass.
How about humans? As far as I'm aware, no specific research involved feeding people eggs to see if this cured their constipation or made it worse. But we know a little about what happens in the gut when people eat eggs.
Although eggs are quite a digestible food for humans, research shows even cooked egg proteins are not completely digested and absorbed in the small intestine.
A small amount reaches the colon where it is linked to increased numbers of good bacteria , such as Bifidobacterium and Prevotella. There's often more Prevotella , in particular, in people with looser stools.
So some research supports the idea eating eggs improves constipation.
What about eating lots of protein?
Eggs are rich in protein. Could a diet with lots of protein cause constipation?
No, protein itself is not to blame, according to research involving adults and children in the United States.
That study found someone eating a diet low in carbohydrate was more likely to be constipated after eating extra protein (the equivalent of an extra two small eggs a day). That's compared with someone eating a moderate amount of carbohydrate.
Why the difference? The researchers said low carbohydrate intake could be linked to less Prevotella in their stools, potentially making the stools firmer.
This makes sense. Fibre is a type of carbohydrate the body can't readily digest. Low dietary fibre is linked to constipation.
If we have adequate fibre in our diet then eat extra protein, this won't worsen constipation. It may actually improve it.
However, not eating enough fibre on a high-protein diet is very likely to increase the risk of constipation.
Kids with allergies
There's also a type of functional constipation associated with kids' food allergies.
A study from Greece tested children with chronic (long-term) constipation to see if they had food allergies.
The children found to have food allergies ate a diet without these foods (including eggs) for eight weeks. Constipation improved in most of these children.
How are food allergies in children and constipation related? A type of immune cell found in people with allergies - known as mast cells - can affect the bowels. These cells can contribute to bowel muscles not contracting well. Food is less able to move along, leading to constipation.
So if all other causes of a child's constipation have been ruled out, and they have a food allergy, their constipation may be allergy-related.
However, it's recommended to try healthy eating, with enough fluid and fibre first. If that doesn't resolve the constipation, the child could try an elimination diet, under medical supervision.
What are we to make of all this?
Overall, there's no firm evidence that eating more eggs leads to constipation.
Provided you eat a diverse diet containing fibre along with your eggs there should be no increased risk of constipation.
If chronic constipation doesn't get better with extra fluids and fibre, talk to your doctor.
Vincent Ho does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
