Why can’t I digest corn? And why does poo change colour?

Some foods agree with our digestive tracts and some foods don’t. Everyone’s digestive adventures are a little bit different, and there are a variety of processes that go on to get food from our mouths to the other side. Why do foods agree and disagree? Is it the food, or is it us?

A food that nearly everyone knows about that finds its place in our motions is corn.

Corn is a staple in many countries across the world, and is a delicious and versatile product. Think of all the things can be get from one plant? Snacks, breads, pasta, flour, flavours, something that binds and holds food together. But most of the time, we find whole corn coming out the other end looking like how we put it in (just a little more worse for wear). Why does this happen? Is it being digested?

Corn is a vegetable, which means it has a variety of components that make it up, such as vitamins, minerals, fibre content, moisture, and the ability to make us feel nice and full. The outer skin of the corn is thicker and of a different consistency than many other vegetables we eat, and our bodies lack the enzymes to be able to break down the skin of corn properly (and also we don’t always chew particularly well), which means the skin travels through our digestive system pretty much intact. The inner parts of the corn are easily absorbed and contains lots of good nutrients which help feed our bodies and the good bacteria in our gut.

We can get the goodness from corn, but the skin is just too tough to breakdown. So enjoy your corn, and know what to expect in the next 24 hours or so as it heads to the other side.

Speaking of the other side, it is interesting to know that the colouring of poo can be different depending on what you eat. Normal colour ranges from light yellow to brown or even black! The normal colour of poo is a mix of by-products from your digestive process, as well as other cells that need to be removed from the body. But what colours are normal, and when should you be concerned?

What colours can poo be and why –

Green – this can happen after consuming food or drink that has blue or green food colouring in it, or if food travels through your digestive tract too quickly and bile doesn’t get properly absorbed.

Pale/clay coloured – this can occur with anti-diarrhoeal medication, or when digestive products affect the liver, gall bladder or pancreas.

Yellow (greasy) – this can also smell really bad, and this is a sign of food malabsorption. It can be related to gut infections or medical conditions, so please consult a doctor if concerned.

Red – this can be related to having too much red food colouring, or can be because of bleeding in the lower gastrointestinal tract.

Black – this is one colour to pay a lot of attention to. It can be related to bleeding in the stomach or upper gastrointestinal tract which loses oxygen and becomes darker as it travels through your system. It can also be a side effect of taking iron supplements, or eating too much food such as licorice.


Most people know the colouring of regular motions and won’t be concerned by slight changes in colour. If you do have any concerns, take a photo of your motion (not the prettiest idea), and book in to see a GP and discuss it. If needed, a dietitian can assist you after all investigations have been completed.