Don’t get me wrong: switching to a vegan diet has its benefits. We know that it is better for the environment, it can be less expensive (plant-based protein tends to be cheaper than animal protein) and, if done correctly, a vegan diet is beneficial to the body.
The disadvantage? It can also require a big change from the way you were eating before, which can have a big effect on your digestive system. That is why a common complaint that people have when starting a vegan diet is constipation.
Dietary fiber and digestion
Adopting a vegan diet can alter your fiber intake quite dramatically, which can lead to quite noticeable changes in your poop.
Fiber is the part of a food (typically of plant origin) that, for the most part, is not digested in the gastrointestinal tract. There are two main types of dietary fiber: soluble and insoluble. Both are important for digestion, but they don’t behave the same way in your body.
Soluble fiber
This type of fiber dissolves in water, so once in the gastrointestinal tract, it absorbs water and turns into a gel. This slows down digestion and makes you feel full longer. Food sources include oat bran, nuts, seeds, beans, lentils, peas, and some fruits and vegetables.
Insoluble fiber
This type of fiber does not dissolve in water, so it adds bulk to the stool and appears to speed up the passage of food through the stomach and intestines. It also helps “sweep” the gastrointestinal tract clear of carcinogens and other toxins. Food sources include wheat bran, vegetables, and whole grains.
Why going vegan can lead to constipation?
You get enough (or too much) fiber and not enough water
Healthy vegan diets tend to be richer in fiber. In fact, a March 2014 article, published in Nutrients, compared the nutritional quality of a vegan diet with vegetarian, semi-vegetarian, pescatarian, and omnivorous diets. The researchers found that people on a vegan diet consume the highest amount of fiber , about 41 grams per day, while the omnivorous diet consumes the least with 27 grams per day on average.
This builds on previous research showing that vegan diets tend to be higher in fiber, even compared to vegetarian diets.
Getting enough fiber is crucial to staying regular, but it only works if you also get enough water. (This is why drinking plenty of fluids is always recommended when taking fiber supplements.) Water makes stool softer and easier to pass, and getting too much fiber without enough water can cause it to narrow.
The solution: To avoid this, make sure you get enough fluids. The general guidelines recommend about 2-3 liters of water daily, but each person is different and various factors such as exercise, illness and your environment can affect your hydration.
You are not eating enough fiber
We just said that vegan diets tend to be higher in fiber, but in recent years, the plant-based food category has exploded in supermarkets, from meat alternatives to frozen dinners, yogurts, cheese, and jerky.
This innovation and growth offers options and flexibility for vegans, vegetarians, and plant-based eaters, but these new foods are not always the healthiest. They’re predominantly highly processed, meaning they generally don’t offer the same level of nutrition as whole foods (and note that much of the research done on the benefits of a vegan diet has been based on whole foods).
These new plant-based products can decrease the amount of fiber (and other nutrients) you eat for two reasons:
- They lack fiber themselves.
- They are replacing the fiber-rich foods in your diet.
The Solution: If you’re new to a vegan diet or you’ve been on a vegan diet and start incorporating some of these more processed plant-based foods, control how much you’re including and how you balance it with the other whole foods in your diet.
If you experience constipation, keep track of how much fiber you are consuming and try to cut down on these more processed foods.
