Mediterranean, Vegan Diets Reduce Constipation

If you’ve ever struggled to poop, you know how annoying, and sometimes painful, it can be. Constipation is clinically defined as having fewer than three bowel movements a week. But that’s not all. If your stools are hard, dry or lumpy, or you have to strain to get them out, you might be constipated. And if you’re able to go but feel like you can’t get it all out? That’s also a sign of constipation. 

If you can relate to any of this, know that you’re not alone. About 16% of American adults have symptoms of constipation. This number increases to 33% for those over 60. And constipation can be costly. Some experts estimate that people with constipation and commercial health insurance average $8,700 more annually in health care costs compared to people without constipation.

Typically, increasing fiber and fluid intake are two things that are recommended to help get things moving. But a new study done by researchers at Mass General Brigham in Boston has a few more suggestions regarding diet and which foods may help. They published their findings in the journal Gastroenterology. Let’s break down what they found.

How Was This Study Conducted?

Researchers drew data from three large, previously conducted, long-term U.S. studies: the Nurses’ Health Study (NHS), the Nurses’ Health Study II (NHSII) and the Health Professionals’ Follow-Up Study (HPFS). The NHS started in 1976 and included 121,700 female nurses; the NHSII included over 116,400 female nurses and began in 1989. Starting in 1986, the HPFS enrolled just over 51,500 male health care workers. 

From these cohorts, researchers pulled data on participants who met their criteria, resulting in almost 28,000 women from the NHS with an average age of 78, about 56,000 women from the NHSII with an average age of 61, and over 12,200 men from the HPFS with an average age of 79. 

They also took data on demographics, including age, sex, race, smoking status, physical activity, medical history, medications, supplements, BMI and socioeconomic status.  

Constipation was assessed in biannual questionnaires, asking, “In the past year, have you been bothered by constipation for at least 12 weeks (not necessarily consecutive)?”

Individuals with irritable bowel syndrome with constipation subtype (IBS-C) were identified by answering yes to the constipation question, plus to “If yes, were your bowel movements associated with abdominal pain?” Researchers defined chronic constipation as having a bowel movement every three or more days. 

In all three cohorts, food frequency questionnaires were completed every four years. The FFQs included 131 food and beverage items, asking how often and how much participants ate. Responses were converted into average servings per day. Researchers then applied this to five different eating patterns, resulting in scores for each one, including the alternate Mediterranean diet (aMED) score, plant-based diet index (PDI), low-carb diet (LCD) score, Western diet and the empirical dietary inflammatory pattern (EDIP) score. The EDIP attempts to quantify the amount of inflammatory food you eat by tracking 18 food groups that may raise inflammatory markers in the body.

Based on their scores, participants were placed into groups called quintiles. The quintiles ranged from low to high scores. 

What Did This Study Find?

During the study follow-up periods, which were 25 to 30 years, there were over 7,500 cases of chronic constipation. After running statistical analyses, including adjusting for confounding factors (e.g., demographics and fiber intake), researchers found:

• Compared to the lowest groups, the groups that scored highest on Mediterranean diet and plant-based diet experienced a 16% and 20% decreased risk for constipation, respectively.
• The groups that scored highest on the inflammatory diet scale (EDIP) and Western diet scale were associated with a 24% and 22% increased risk for constipation, respectively. 
• Among the individual dietary components, higher intake of all types of vegetables, nuts and salad dressing were associated with lower risks for constipation.
• Comparing the highest quintile (Q5) to the lowest (Q1), greater adherence to the Mediterranean diet and a plant-based diet were associated with a 25% and a 27% decreased risk for irritable bowel syndrome with constipation, respectively.

These results suggest that greater adherence to the Mediterranean diet or a plant-based diet reduces the risk of chronic constipation. This is independent of fiber intake. In other words, researchers adjusted for total fiber intake and still found that, even by taking away any influence fiber might have on constipation, these eating patterns still helped reduce the risk of constipation. 

In particular, they found that tomatoes, cruciferous vegetables, leafy green vegetables and dark yellow vegetables appeared to be the primary dietary components driving the protective associations between the aMED and PDI with reduced risk of constipation.

Eating patterns that increased the risk of constipation included the Western diet and EDIP. The Western diet, sometimes referred to as the typical American diet, is characterized by high intake of red or processed meats, refined grains, french fries, high-fat dairy products, sweets, desserts and butter. 

How Does This Apply to Real Life?

In addition to vegetables, researchers also found strong associations between nuts and healthy fats with reduced risk of constipation. Since researchers adjusted for fiber, they essentially removed fiber’s effects on constipation for analysis. This suggests that there is some other component in these foods that is responsible for reducing the risk of constipation. 

“Although the study did not specifically address the mechanisms by which these diets were protective, we suspect that bioactive compounds found in vegetables and nuts—such as polyphenols, antioxidants and healthy fats (e.g., monounsaturated fats)—likely contribute to constipation prevention,” says senior study author Kyle Staller, M.D., M.P.H. “These benefits are most likely driven by the way they impact our gut microbiome, the community of bacteria and other microbes that live in our gut. It’s possible that these foods promote the growth of beneficial gut bacteria that produce compounds that we think may be beneficial to the lining (and therefore function) of the gut, like short-chain fatty acids.”

Still, Staller says that fiber is still a key nutrient for avoiding constipation and supporting a healthy gut.

If you’re not ready to go all in with the Mediterranean or plant-based diets, you can start adding the foods that seem to have more influence over constipation, according to this study: tomatoes, cruciferous vegetables, leafy green vegetables, dark yellow vegetables, nuts and healthy fats, like olive oil. Need some inspiration? Try our Roasted Squash & Lentil Kale Salad to get your leafy green/cruciferous and dark yellow veggies, plus olive oil. Or our mouthwatering Tomato Salad with Lemon-Basil Vinaigrette to get your fill of tomatoes and olive oil. 

If you’re ready to go for it, a great place to start is with our 7-Day Mediterranean Diet Meal Plan for Beginners or our 7-Day Mediterranean Diet Meal Plan for a Healthy Gut. The Mediterranean diet is loaded with fruits, vegetables, whole grains, legumes, nuts, seeds, seafood, lean protein, healthy fats and a little dairy. 

If you’re interested in trying a meal plan with no meat, but a little yogurt or kefir, check out our 7-Day Plant-Based Diet Meal Plan for Beginners. If you think plant-based means boring, this will change your mind!

Other habits that can influence constipation include physical activity, stress and fluid intake. And while alcohol may help you go, these study authors caution against using it as a constipation cure, since it can have negative consequences on your gut health and other organs, including your brain. Plus, in the long run, regularly imbibing can increase chronic inflammation, which, in turn, increases disease risk—exactly the opposite of what you’re trying to accomplish. 

Our Expert Take

This study suggests that the Mediterranean and plant-based diets are associated with lower rates of constipation. On the other end of the spectrum fall the Western diet and inflammatory diets, which are associated with higher rates of constipation. According to these researchers, it’s not just fiber that contributes to a reduced risk of constipation. The antioxidants in vegetables, nuts and healthy fats also appear to contribute. There are many reasons the Mediterranean diet has been ranked as the healthiest eating pattern for several years. Following the Mediterranean diet also helps reduce disease risk, including heart disease, dementia, osteoporosis and macular degeneration. Now we can add constipation to the list.