Stop me when this starts to sound familiar:
This New Year, you resolved to clean up your eating act. Your colleague/trainer/friend has been raving about intermittent fasting, so you finally decided to break up with breakfast and start your eating day to noon. Or maybe all the keto hype finally captured your attention and you broke up with carbs and sugar in favor of meat, nuts and cauliflower-turned-everything. Perhaps you’ve been reading about austere elimination diets purported to help with inflammation and decided to try breaking up with multiple food groups at once, from grains and beans to nuts and seeds to dairy. Or you saw a documentary and took the plunge into a fully whole foods, plant-based – or minimally-processed vegan – diet.
But as the saying goes, “No good deed goes unpunished.”
Because whatever the nature of your big, seemingly healthy eating change, there’s been another unexpected and wholly unwelcome change that accompanied it: You’re suddenly constipated, and you simply cannot figure out why.
While it may seem counterintuitive, it’s not at all uncommon for people to experience a downgrade in their digestive regularity alongside big change in their diet, even when that change seems to be a healthy one. Here are four of the most common reasons why people become constipated in response to shifting diet patterns – and how to fix them, including what foods help with constipation.
4 Reasons You’re Constipated
1. You’re skipping breakfast.
Hormonally speaking, morning presents the perfect pooping conditions. (In my second book, “REGULAR,” I actually refer to morning as “the window of poop-ortunity” for most people.). Thanks to natural rises in cortisol that start at dawn and peak by around 10 a.m., our bowels are waking from their overnight slumber and become responsive to many stimuli that the day presents: a surge of stress as you hurry to get your kids out the door for the school bus, the chemical jolt of chlorogenic acid delivered by your morning coffee and, importantly, the digestive system nerve reflex that is triggered by the act of eating.
Eating at any time of day provokes the gastrocolic reflex, a nerve signal from the upstream part of your GI tract to the colon, urging it to contract and move things along to accommodate the meal which is currently being consumed and heading into the pipeline. But for many people, eating in the morning, when cortisol has already primed the colon, is more likely to produce a contractile wave that results in a bowel movement than eating at other times of the day.
In other words, for some, the morning window of poop-ortunity is their only window of poop-ortunity all day … and skipping breakfast makes them more likely to miss it. If this is you, then intermittent fasting or other breakfast-skipping protocols may not be the best fit for your system.
2. Your new diet lacks soluble fiber.
Many popular diet regimens – like keto, Whole30, the specific carbohydrate diet and the AIP diet – completely cut out grains. And some involve a reduction in root vegetable and fruit intake as well. These foods, which are rich in a type of fiber called soluble fiber, are often replaced by lower-carb alternatives like leafy greens, berries and nuts, which are rich in a type of fiber called insoluble fiber.
Swapping one type of fiber for another may seem like an even trade, but in fact, the two types of fiber behave very differently in your digestive tract. Soluble fiber can hold onto water, serving to plump up your poops and help keep them bulky and soft, no matter how long their journey to the exit may last. The insoluble fiber that predominates in “roughage” like lettuce, veggie skins, berries, nuts and seeds, on the other hand, can’t really hold onto water as it passes through the digestive tract. Therefore, if you’re someone whose bowels trend toward the slower side, there’s a fair chance that a diet heavily distorted to insoluble fiber may result in poops prone to being hard and dried out by the time they reach the end of their digestive journey.
Oatmeal and beans are among the best sources of dietary soluble fiber, but if you’re committed to staying away from grains and legumes, other sources include:
- Root veggies, like beets, carrots and sweet potatoes.
- Winter squashes and pumpkin.
- Chia seeds.
- Melons, apples, pears, mangoes, papayas and kiwifruit.
- Zucchini, string beans, mushrooms and broccoli.
If these aren’t an option, then magnesium supplements in doses of 400 to 800 milligrams taken at night will help draw extra water into your bowel and speed your stool along to help promote softer, more expeditious evacuations. This is particularly helpful for people experiencing tiny, hard balls of stool.
If your stools are large but just too hard to pass comfortably, an over-the-counter stool softener like docusate sodium (Colace) may help them hold on to moisture better. Another potentially helpful option is a bulking fiber supplement, like psyllium husk or calcium polycarbophil (Fibercon).
3. Your new diet is too low in fat.
When people make dietary changes like giving up meat, dairy, switching from eggs to egg whites or adopting a fully plant-based diet, it can result in a whole lot less fat. What you may not know, however, is that fat plays a role in stimulating motility – or forward motion – in the colon, which in turn promotes more regular bowel movements. So, giving up cheese and avocado in your salad in favor of fat-free balsamic vinegar for a dressing; or those veggies sautéed in broth instead of oil; or replacing 2% milk with almond milk in your latte or cereal may result in fewer fat-provoked motility signals being sent to the colon.
This goes back to the gastrocolic reflex we just learned about; it’s one way that our upstream digestive organs (the stomach and small intestine) communicate with the downstream digestive organs (namely, the colon) to let them know what is on its way so they can prepare.
Consolidated meals and foods that contain some fat stimulate this communication reflex, essentially informing the colon that a significant amount of food has just entered the system. In response to the gastrocolic reflex, the colon ramps up its motility to make some room for what’s headed its way. The gastrocolic reflex is one reason why very, very high-fat meals can cause an urgent need to poop – and even diarrhea – soon after a meal in some people.
When your healthy diet pattern happens to also be a low-fat diet pattern, then you may sometimes find that your meals don’t provoke as robust of a digestive system response as they used to and you become constipated. If you’re not sure what to eat when constipated, try including healthy fats with your meals more often: avocados, nut butters, pumpkin or sunflower seeds, tahini, hummus, an extra drizzle of olive oil or fatty fish like salmon are all good choices. Some people find that fish oil or flaxseed oil supplements can provide a modest benefit as well.
4. Your new diet ditches natural sugars.
Some of the more restrictive diet regimens in circulation these days take a pretty hardline approach to foods that have more than a minimal amount of naturally-occurring sugar, like milk or yogurt; sweeter fruits like bananas, grapes, mango, cherries or watermelon; dried fruits like apricots and even certain root veggies like carrots and beets, none of which, for the record, are even remotely “like eating a candy bar,” despite what joy-killing online wellness influencers would have you believe.
However, many of the natural sugars contained in such foods – the lactose in dairy foods, the fructose or sorbitol in certain fruits – can exert a mild laxative effect in our colons by attracting water into the bowel. So if you’d been eating foods on this list regularly, you may not have realized to what extent they were contributing to your previously smooth digestive function in the form of softer stools … until you gave them up.
I don’t advocate for restricting any whole fruits, vegetables or unsweetened dairy products on the basis of their natural sugar content; I’ve never seen someone gain excess weight or develop Type 2 diabetes because they ate too many carrots or fresh mango. And for what it’s worth, research suggests that restricting fruit intake among people who actually do have Type 2 diabetes doesn’t actually seem promote weight loss or improve glycemic control; it just results in poorer diet quality.
But if you are adamant about avoiding such foods for any reason, you might benefit from finding another way to attract some extra moisture into your plumbing. Magnesium in doses of 400 to 800 milligrams taken at night often does the trick in a natural way, though may not be suitable for people with impaired kidney function.
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