What image comes to mind when you think of fiber? Wimbi porridge? A proper bowel movement? Spinach? Fiber has enjoyed celebrity status in nutrition circles for a long time. It had been revered and recommended by everyone from your mother, to top scholars in nutrition science.
For decades, a high fiber diet has been linked to a host of good health outcomes. More recently, a number of these alleged benefits have come under intense scrutiny.
Most of us have suffered a bout of constipation at least once in our lives. For many others, constipation is a daily plague, significantly impacting on their quality of life. Many people describe constipation as not having a bowel movement every day. Others describe it as passing very hard stools. Let’s start by defining this ‘elephant in the room’ that millions suffer from but hardly anyone speaks about.
Diagnosis of constipation tends to rest on an individual’s perception or on clinical criteria developed by a group of experts. One group defined chronic (longstanding) constipation as passing fewer than 3 hard stools per week, associated with the need to strain or the sensation of incomplete evacuation, for more than 6 months. This definition is often of little consolation to patients who ‘just know’ what is normal for them and what is not.
This article seeks to debunk the commonly held belief that fiber is both necessary and sufficient to prevent or treat constipation. I submit to you that a lack of fiber does not cause constipation and that for many people, adding more and more fiber to the diet actually makes constipation worse. I realise that this is quite counterculture, but allow me to explain.
What causes Constipation?
The first thing that we must understand is that our bowels consist of muscles and nerves that work in a co-ordinated fashion to push waste along. This happens regardless of the presence or absence of fiber or water. Fiber holds onto water and increases the volume of the waste. This can make stool softer and increase the frequency of bowel movements – for some. For many others, fiber seems to aggravate digestion and constipation.
The large intestine is responsible for absorbing water and delivering the stool to the rectum, where it can be evacuated comfortably. If there is a delay with the movement of stool along the colon, constipation can result. This is known as ‘slow transit constipation’. Colonic transit is heavily influenced by the heavily networked nervous system within the gut. We have all felt ‘butterflies’ when we are excited or anxious. Many develop diarrhoea in this situation due to an increase in stool transit time.
Our bowels consist of muscles and nerves that work in a co-ordinated fashion to push waste along.
Many women have experienced brief constipation during pregnancy, or during the pre-menstrual week leading up to their period, due to the flux of reproductive hormones. It is interesting to note that constipation affects twice as many women as men.
Travelling also disrupts our toilet activities, with many complaining of seized-up bowels for the first few days into their holiday. Any new change in diet can also cause havoc to your system and the bowel frequency can go either way.
In addition, a sedentary lifestyle can impact the frequency of bowel movements, as can medications, particularly blood pressure pills, painkillers, and antidepressants. Furthermore, underlying medical conditions such as diabetes and hypothyroidism are frequently implicated.
The Fiber Myth
Therefore, before one can implicate their diet, it is imperative that these other contributing causes are identified and dealt with. Foods often cited to be notorious in causing constipation are grains, nuts, seeds, legumes and cruciferous vegetables like cauliflower. Dairy is another culprit. What is interesting about this list (which is by no means exhaustive) is that it is almost all plant-based, and by extension, contains fiber.
All plant foods contain a combination of soluble and insoluble fiber (roughage). Grains, seeds, nuts, and vegetables are high in roughage. We are encouraged to eat lots of roughage because it bulks up the stool and ‘sweeps our intestines clean’, en-route to the outside world. But let’s think about this logic for a moment.
Only plant foods contain fiber.
Imagine, if you may, a long stretch of bumper-to-bumper traffic on a 4-lane highway. The traffic is a result of a bottleneck downstream caused by an impromptu police check. They are only letting one car pass at a time. You are in charge of relieving the blockage. You decide, based on ‘conventional wisdom’ to add more cars upstream. This analogy helps reveal the circular logic behind adding more and more fiber to an already full lower intestine.
Fiber – More is not always Better
As much as we want to believe that fiber is universally useful for treating constipation, the evidence, in fact, contradicts this idea. Several good-quality studies have demonstrated that low fiber intake does not necessarily equate to constipation. In addition, individuals with chronic constipation tend to have a similar fiber intake to those without. They can have worsening symptoms when dietary fiber intake is increased, and report significant improvement when fiber is eliminated or reduced.
We all know people who eat meat-heavy diets – with few or no vegetables – who are never afflicted with constipation. We also know of those who eat a plant-heavy diet yet suffer routinely with colonic inertia.
The effectiveness of dietary fiber on constipation is inconsistent. For too many people, fiber causes constipation, flatulence, and pain. Eating should be a pleasurable, comfortable activity. If fiber plays havoc with your digestive system, rendering you bloated, gassy, blocked up and in pain, you might be better off avoiding it. Remember that fiber is a carbohydrate, and, unlike fats and proteins, there are no essential carbohydrates.
If you can tolerate fiber, you are better off choosing vegetables that grow above the ground. These have a far better fiber to carbohydrate ratio, and are undoubtedly a healthier way to consume fibre, in comparison to eating commercial bran cereals or using laxatives. Exercise is often very helpful. A short walk outside can certainly help move things along inside. It is equally important not to ignore the urge to ‘go’. Listen to your body and go when you need to go.
An abridged version of this article was published in print and online by The Star, Kenya on 16th September 2019.