Can My Meal Replacement Shake Cause Constipation?

By Matt Smith

Published: April 8, 2025

There are many causes of constipation that can range from physical, mental, and lifestyle-related. But can my meal replacement shake cause constipation? This article will help you to find out what causes constipation, whether meal replacement shakes are to blame, and how to avoid constipation wherever possible.

Good quality meal replacement shakes should actually reduce the likelihood of constipation thanks to their high fiber content. However, poorly-made meal replacement shakes and ones that have specific macronutrient ratios could lead to constipation and other digestive issues.

This article will take an in-depth look at the most common causes of constipation, how to reduce your risk of constipation, and how meal replacement shakes can sometimes be the cause.

What is Constipation?

Constipation is defined as having fewer than three bowel movements in a week and finding it difficult to achieve. There are many causes of constipation, but the most common is a lack of fiber.

Early meal replacement shakes were often very low in fiber, and constipation was a common side effect. However, most meal replacement shakes now contain a lot of fiber, both for its digestive benefits and its many health and weight management benefits.

What are the Common Causes of Constipation?

Before we look at how meal replacement shakes could be the cause of constipation, it is important to look at what the common causes of constipation are. Some of these are related to meal replacement shakes, while others have no connection.

Lack of Fiber in Diet

The most common cause, by far, of constipation, is a lack of fiber in your diet. Eating a lot of fruit, vegetables, whole grains, and pulses is important if you want to maintain a healthy digestive system. Fibre is used by the body to soften and increase the size of your stool. This helps to regulate the digestive process, reducing the risk of constipation.

Not having enough fibre can lead to harder, looser stools which can slow down the process and be difficult to pass. It doesn’t take many days of low-fibre food before you begin to notice the difference. Many subsequent medical issues can be exacerbated by low-fibre diets.

Stress and Anxiety

The idea that your hormones can affect your bowel movement may seem a little crazy at first, but hormones have a huge impact on your digestion. Serotonin is a hormone that is very much affected by stress and anxiety. When you are stressed, your brain can flood your body with serotonin as a response.

This has many benefits, but it can lead to a build-up of serotonin in your gut, where it can either lead to an increase in digestive speed (which can result in diarrhoea) or a slowing down of the process entirely (constipation).

But it isn’t just the hormonal impact of stress that can cause constipation. Stress can affect how we live our lives, it can reduce our activity levels, and it can lead to us reducing our water intake. Stress can affect sleep and can lead to you seeking out poor nutritional choices such as junk food [1].

Prolonged stress and anxiety may lead to depression, which can require medication, which may further increase your risk of constipation. As you can see, stress and anxiety can lead to multiple different causes of constipation on this list.

Dehydration

The connection between your water intake and your bowel movements may not be obvious, but a lack of hydration can absolutely lead to constipation. For your stool to travel at a good pace through your digestive system, it needs to be soft and smooth.

When you become dehydrated, your body can remove some of the water from your stools, making them harder and less smooth. This slows down motility and can lead to constipation.

Interruption of Normal Routine

If you have ever experienced constipation while travelling (or in the week after travelling), then you will be unsurprised to learn that changes to your normal routine can seriously affect bowel movements.

You might not have realised it, but if you have a healthy digestive system, you will have a routine time when you move your bowels. We’re not talking to the minute here, but early morning, late afternoon, you get the idea.

Your body adapts to this, and so do you. When you feel the need to go, you tend to go as soon as possible.

However, life has a way of messing up your routine. If you have family around, you may not feel like going just because you need to. Or if you are on a plane and don’t fancy taking a risk of turbulence ruining your day.

This interruption can lead to constipation and often does. Provided your diet and mental health are in check, you should get back to normal within a day or so, but for some people, this can affect you for weeks afterwards.

Lack of Exercise/Activity

Walking is one of the best activities you can do when constipated. Not only does the movement help to improve digestion, but it can also help improve your mental and physical health over time. People who lead more active lives are less likely to suffer from constipation unless they have other issues mentioned in this list.

Medication

Many medicines can cause constipation, as can undertaking medical procedures such as surgery. These are, of course, unavoidable, but they are still a common cause of constipation and justify a place on this list. If you are constipated due to the medication that you are taking, it is a good idea to stay hydrated, walk as often as you can, and talk to your doctor about whether you should increase your fiber intake or not.

Health Conditions

IBS, Colorectal cancer, diabetes, and many other health conditions can all increase your likelihood of suffering from constipation.

Can My Meal Replacement Shake Cause Constipation?

The first question to answer is whether following a meal replacement shake diet can itself cause constipation. Because this was a common argument against meal replacement shakes during the early 2000s.

The truth is that switching from a diet that is low in nutritional value to a diet that revolves around high-fiber highly-nutritious shakes can lead to a little bit of digestive discomfort for the first few days. This is because the increased fibre can speed up motility and can affect your routine (as mentioned above, a change in routine can easily lead to constipation).

However, in the long term, a well-made meal replacement shake can actually reduce your risk of constipation.

Badly made meal replacement shakes that are either very low in fiber or very high (more on this in the following section) are more likely to cause constipation for the wrong reasons, and you should certainly try to avoid them.

The following causes are based on badly designed meal replacement shakes.

Low in Fiber

When meal replacement shakes first took off, many of the products were pretty poor. They would be packed full of cheap ingredients, and the macronutrients were often terrible. They would contain almost no fiber whatsoever.

Finding meal replacement shakes that are low in fiber is a lot more difficult today, as it’s a pretty simple issue to fix. But there are still meal replacement shakes that may be low in fibre. If you are replacing a meal with a low-fiber shake, then you will soon see an increased likelihood of suffering from constipation.

Back in the day, companies used to offer a fiber supplement to take alongside their shakes, but now many companies use ingredients that provide natural fiber, such as oats.

Low in Carbohydrates

This is a very similar issue to the one above. In fact, they are related. There are a number of meal replacement shakes on the market that are aimed at the ketogenic market. Meaning that they are very high in fat and protein but have little to no carbohydrates (and therefore fiber).

We’re not here to debate the pros and cons of the ketogenic diet, but it is a well-known fact that very low carbohydrate diets can cause constipation. Some foods are low in carbohydrates and high in fiber, which can be used for meal replacement shakes (flaxseed, chia seed, nuts, berries), so it is possible to have a low-carb, high-fiber shake. But it is not always the case.

Too High in Fiber

As we have established, it is very important to get enough fiber into your diet as it can help to prevent constipation. However, too much fiber can also be an issue. There are a few meal replacement shakes that have a very high fiber-to-calorie ratio, meaning that if you consume too many of them, your fiber intake would be too high.

This would also be an issue if you already have a lot of fiber in your diet or if you are simultaneously taking a fiber supplement. If this is an issue, then check how much fiber is in your meal replacement shake and drop the fiber supplementation if you are taking it.

Contain Artificial Sweeteners

Artificial sweeteners and sugar alcohols are used by meal replacement shake companies as a way to increase the sweetness and improve the taste of their shakes without raising the calorie intake. For some people, this can be a really good thing, but not everyone agrees.

One of the side effects of artificial sweeteners (particularly sugar alcohols) is diarrhoea, which is the exact opposite of constipation. But diarrhoea can lead to:

Dehydration
Irregular bowel movements
Disruption

Which can then lead to constipation. So it could well be your reaction to the artificial sweeteners in your meal replacement shake that causes you to suffer from constipation.

Why Rootana is the Ideal Meal Replacement Shake

Rootana was created so that it could avoid the pitfalls of many meal replacement shakes. It is packed full of healthy carbohydrates and has the ideal amount of fibre per serving. There are no artificial sweeteners or sugar alcohols in its formula; instead, Rootana uses a very small amount of natural coconut sugars to provide a slightly sweet taste.

Check out the full breakdown of Rootana’s ingredients list here

Final Thoughts

Constipation sucks! It can leave you feeling bloated and even nauseated during the day. It is uncomfortable and embarrassing. It can prevent you from truly enjoying your day. The best way to avoid constipation is to exercise regularly, consume enough fibre, stay hydrated, and try to go when you need to, even while travelling (you may have to get over your fear of public toilets for the greater good).

Good quality meal replacement shakes such as Rootana will not contribute to constipation and are much more likely to reduce your risk. However, meal replacement shakes that are low in fibre or that use cheap ingredients could increase your risk, so choose your shake wisely.

References

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4214609/

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