How to Ease Low-Carb Diet Constipation

In studies of low-carb diets, one of the side effects that people sometimes experience is constipation. If you started to become constipated after starting a low-carb eating plan, rest assured there are many things you can do to ease your problem. (Note that there are many causes of constipation, from medications to neurological disorders, but if your constipation started with your diet change, it makes sense to focus on that as the probable cause.)

What Is Constipation?

Constipation is basically difficulty in passing bowel movements. The stool is often hard and drier than normal. Fewer than three bowel movements per week is also considered to be constipation.

How Can a Low-Carb Diet Cause Constipation?

People who become constipated with a dietary change usually are eating less fiber (soluble fiberinsoluble fiber, or both). This is sometimes due to mistaken ideas about what a low-carb diet is. For example, people sometimes don't realize that the norm on a low-carb diet is to double or triple the amount of non-starchy vegetables eaten. They may also not realize that although fiber is a carbohydrate, on most low-carb diets the fiber is not counted as part of the carbs eaten since it doesn't affect blood sugar. There are many foods that are high in fiber and nutrients, but low in digestible carbohydrate.

Now we'll look at things you can do to ease constipation on a low-carb diet.

Drink Plenty of Water

Drinking water
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This is a good idea anyway, but it is very important for preventing a tendency to become constipated. If we aren't fully hydrated, our bodies will suck water out of our colons. Also, drinking lots of water with fiber supplements or flax seed is essential.

Eat Plenty of Non-Starchy Vegetables


Photo: Alexandra Shytsman

In particular, green leafy vegetables are low in digestible carbs while being high in fiber and lots of nutrients. In fact, some low-carb diets don't even count leafy greens, since there is so little carb wrapped in so much fiber that blood sugar is not usually affected unless large amounts are eaten. Some fruit can be helpful, particularly low-sugar fruits such as berries.

This vegetable list is listed from the lowest to the highest in carbs, and there are links to carb and fiber counts along with other information about each one.

Eat Nuts and Seeds, Especially Flax and Chia

nuts and seeds

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Nuts and seeds have lots of fiber (as well as lots of other nutrients).  Flax seeds and chia seeds are especially good choices because they have quite a bit of soluble fiber

Fiber Supplements

fiber supplement capsules
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It's best to get your fiber from food, but there can be a role for supplements. The most common ones (e.g. Metamucil and Fiberall) are made from psyllium husks. The problem with them from a low-carb perspective is that the powders that you mix with water mostly contain a fair amount of sugar. There are "sugar-free" versions, but they mostly contain ​maltodextrin which raises blood glucose just as much as sugar does. Alternatives include psyllium capsules (you have to take quite a few to equal the powder - be sure to consume plenty of water with them) or getting psyllium husks in bulk (your local health food store may carry it in the bulk section). Psyllium provides mostly soluble fiber but has a fair amount of insoluble fiber as well. The powder must be mixed in with water and drunk rather quickly, as it forms a thick sort of sludge as the fiber absorbs the water.

Another popular fiber supplement goes by the name Benefiber, although there are also store brands. It is almost entirely soluble fiber, and has the advantage that it can be dissolved in water or mixed in with soft foods such as yogurt, and doesn't change the texture.

There are other fiber supplements made from sources of fiber that is mostly insoluble, such as wheat bran. Just watch the carbs, because some starch tends to come along for the ride in many of them.

Check Your Dairy Consumption

Cottage cheese

Photo: Alexandra Shytsman 

Some people get constipated if they eat too much dairy food, and there can be a tendency to increase the amount of cheese, cottage cheese, and other dairy foods on a low-carb diet. If this rings true for you, try cutting back on the cheese and see if it helps.

Are You Getting Enough Magnesium?

Fresh Soy Beans
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Magnesium is a nutrient that low-carbers often lack in their diets, and one of the results can be a tendency to become constipated. There are a lot of low-carb foods that are good sources of magnesium, such as green vegetables, nuts and seeds, soybeans (and other beans), fish, and yogurt.

Magnesium supplements are another possibility, but it can be important to steer towards forms of magnesium that are well-absorbed (otherwise you could end up with diarrhea, which is not the goal). The Fact Sheet put out by the Institutes of Health says that magnesium oxide and magnesium sulfate are probably not absorbed as well as other forms.

Try Probiotics

yogurt with blueberries
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The research on this is admittedly far from conclusive, but some preliminary work indicates that yogurt and kefir (and possible other probiotics such as sourkraut) can help regulate our colons, including bowel movements. Which probiotics for what situation? Too early to tell, but it may be worth a shot, and certainly we are learning the importance of gut health, so it's worth paying attention to in any case.

Try Fish Oil

Fish Oil
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Again, it's not clear, but some experts suggest that if we aren't eating enough omega-3 fats we may be more likely to be constipated. If you don't eat much oily fish such as salmon, you might try a fish oil supplement.

What About Laxatives?

Senna laxative tablets in blister pack

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For constipation caused by diet, it makes sense that the cure should ideally be with diet. Laxatives work by stimulating the muscles of the colon to get a move on, but using them for more than a few days can be a bad idea (unless your doctor has told you to, of course). They can even have a boomerang effect by causing the muscles of the bowel to become weaker over time and then causing more constipation.

If a dietary change is causing constipation, the steps I've outlined should help. If they don't, be sure to consult your physician.

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