Don't get us wrong: Switching to a vegan diet has its benefits. We know it's better for the environment, it can be less expensive (plant-based proteins tend to be cheaper than animal proteins) and, if done properly, a vegan diet does a body good.
The downside, though? It may also require a big shift from the way you were eating before, which can have a big affect on your digestive system. That's why a common complaint people have when starting a vegan diet is constipation.
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Here's why your bathroom habits may suddenly change on this plant-based eating plan and what you can do about it.
Dietary Fiber and Digestion
Adopting a vegan diet can alter your fiber intake pretty drastically, which can lead to pretty noticeable changes in your poop.
Fiber is the part of a (typically plant-based) food that, for the most part, is not digested in the GI tract. There are two main types of dietary fiber — soluble and insoluble. They're both important for digestion but they do not behave the same way in your body, according to the Linus Pauling Institute.
Soluble fiber: This type of fiber dissolves in water, so once in the GI tract, it soaks up water and turns into a gel. This slows down digestion, making you feel full longer. Food sources include oat bran, nuts, seeds, beans, lentils, peas and some fruits and veggies.
Insoluble fiber: This type of fiber does not dissolve in water so it adds bulk to stool and appears to speed up the passage of foods through the stomach and intestines. It also helps to "sweep" the GI tract clean of carcinogens and other toxins. Food sources include wheat bran, vegetables and whole grains.
The recommended daily intake of fiber is a minimum of 25 grams for women and 38 grams for men under the age of 50, according to the Academy of Nutrition and Dietetics.
Why Going Vegan Can Lead to Constipation
Here, we'll break down two of the most likely reasons you're constipated on a vegan diet and how to remedy your situation.
1. You're Getting Enough (or Too Much) Fiber and Not Enough Water
Healthy vegan diets tend to be higher in fiber. Indeed, a March 2014 paper published in Nutrients compared the nutritional quality of a vegan diet to vegetarian, semi-vegetarian, pescatarian and omnivore diets. The researchers found that the vegan dieters consumed the most fiber — about 41 grams each day — while the omnivore diet consumed the least with 27 grams a day on average.
This builds on older research showing vegan diets tend to be higher in fiber, even compared to vegetarian diets.
Getting enough fiber is crucial for keeping you regular, but it only works if you're also getting enough water. (This is why it's always recommended to drink plenty of fluids when taking fiber supplements.) Water makes stools softer and easier to pass, and getting too much fiber without enough water can actually make you constipated.
The fix: To prevent this, make sure you're getting enough fluids. The Institute of Medicine recommends women consume 2.7 liters (or nearly 11.5 cups) of total water per day (includes food, beverages and drinking water) and men drink 3.7 liters per day (about 15.5 cups).
These are general guidelines, but every person is different and various factors like exercise, illness and your environment can all affect your hydration.
2. You're Not Eating Enough Fiber
OK, we just said vegan diets tend to be higher in fiber, but hear us out: Over the past few years, the plant-based foods category has exploded in supermarkets, from meat alternatives to frozen dinners, to yogurts, cheese and jerky, and the list goes on. Sales in this category topped $5 billion in 2019, according to the Good Food Institute and the Plant Based Foods Association.
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 are predominately highly processed, which means they typically don't offer the same level of nutrition as whole foods (and keep in mind that much of the research done on the benefits of a vegan diet has been based on whole foods).
These newer plant-based products may decrease the amount of fiber (and other nutrients) you're consuming for two reasons:
- They lack fiber themselves
- They're replacing fiber-filled foods from your diet
The fix: If you're new to a vegan diet or if you've been on a vegan diet and begin to incorporate some of these more processed plant-based foods, keep a handle on how much you're including and how it balances with the other whole foods in your diet.
If you're experiencing constipation, keep track of how much fiber you're consuming and try cutting back on these more processed foods.
- Nutrition: "Comparative Effectiveness of Plant-Based Diets for Weight Loss: A Randomized Controlled Trial of Five Different Diets"
- Circulation: "Anti-inflammatory Effect of Whole-Food Plant-Based Vegan Diet vs the American Heart Association - Recommended Diet in Patients With Coronary Artery Disease: The Randomized EVADE CAD Trial"
- Linus Pauling Institute: "Fiber"
- Nutrients: "Comparison of Nutritional Quality of the Vegan, Vegetarian, Semi-Vegetarian, Pesco-Vegetarian and Omnivorous Diet"
- The American Journal of Clinical Nutrition: "Health Effects of Vegan Diets"
- Institute of Medicine: "ietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Total Water and Macronutrients"
- Good Food Institute and the Plant Based Foods Association: "Plant-Based Food Retail Sales Hit $5 Billion"
- Academy of Nutrition and Dietetics: "Fiber"
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.