Constipation is a possible side effect of Keto Diet, especially during the first time on a low-carb diet, as your digestive system may need time to adapt.
Here are the three steps to cure it; perhaps you only need the first one:
- Drink plenty of fluid and get enough salt. One common cause of constipation on low carb may be dehydration. This makes the body absorb more water from the colon and thus the contents get dryer, harder and constipation can result. The solution is to drink plenty of water and perhaps add some extra salt.
- Eat plenty of vegetables or another source of fiber. Getting enough good-quality fiber from the diet keeps the intestines moving, which may reduce the risk of constipation. This can be more of a challenge on low carb where many sources of fiber are avoided but eating plenty of non-starchy vegetables may solve this problem. Another, and completely carb-free, option for adding fiber to the diet is psyllium seed husks (can be dissolved in water) or ground flaxseed.
- If the steps above are not enough, take 2 to 4 tablespoons (30-60 ml) Milk of Magnesia (magnesium hydroxide) to relieve constipation.
Reference
Clinics in Colon and Rectal Surgery 2010: Medical management of constipation.