For most people, though, constipation is something that's likely down to a simple cause – or several simple causes.
We know that eating a low-fibre diet can cause constipation. Fibre in foods helps keep our bowels functioning in two important ways: insoluble fibre draws water into the bowel, softening and bulking up the stool so it's easier to move through the bowel. And soluble fibre mixes with water in our gut, forming a gel-like substance and generally promoting good digestion.
There are also other types of fibre. Resistant starch is, as the name suggests, not digested. It's fermented by our gut bacteria instead; it's one of their favourite foods. Resistant starch is especially high in cooked and cooled potatoes and rice, as well as legumes and seeds.
And functional fibre is typically added to foods. We're seeing more of this as food manufacturers look to cash in on fibre's health benefits; we're seeing things like cereals and muesli bars and yoghurts with ingredients like inulin - also called chicory root. Functional fibre also includes fibre supplements, like psyllium husk. There's not really evidence at the moment on whether using these is as healthy as getting fibre from whole foods; it seems to be a case of watch this space.
If you are constipated, though, fibre from food is the first place to start. Try increasing your intake from a range of sources: a real variety of vegetables and fruit, nuts and seeds, legumes and grains. If that's not enough, it might be worth adding something like psyllium to your day. I like the plain powdered husks added to bircher muesli or porridge. Chia seeds are also an easy way to get a fibre boost. I sometimes put these into my scrambled eggs in the morning; they're super high in fibre and a spoonful adds useful fibre to the day.
Once our fibre intake is sorted, though, there are some other things to keep in mind when it comes to constipation. Fluid intake is one; not everyone knows that as well as food, our bowels need water to keep things moving along. Because water is drawn into the bowel to soften stools, if we're not getting enough, stools can get hard and dry, and that of course means they're difficult to pass.
Inactivity is another factor. Like our other muscles, the bowel needs stimulation in the form of exercise to keep it going. It's all about blood flow: more blood flow to the bowel means the muscles can contract better, which helps everything move through more efficiently.
Since our gut is often now called our "second brain" because of its complex connection with the brain via what's known as the gut-brain axis, it shouldn't come as a surprise that stress can also be a cause of constipation. It might not even be conscious stress; have you ever had your regular bowel habits disrupted when you travel, for example? When we're stressed or anxious, blood flow is directed away from the gut, potentially slowing digestion and making constipation more likely.
Gut experts also say we shouldn't ignore the urge to go to the loo – it's that tricky gut-brain axis in action again. I have a friend who calls herself a "home poo-er": she only feels comfortable going in her own bathroom. I suspect she's not alone. But if you have the urge, it's best to follow it if you can. Not doing so can make it more difficult to go when you actually want to.
* • Niki Bezzant is a food and nutrition writer and speaker. Follow her on Facebook or Instagram @nikibezzant