Constipation: Is Your Multivitamin To Blame?
Constipation. It happens to too many of us way too often. And a surprising cause of it is your multivitamin.

The definition of constipation is having less than three bowel movements a week. Constipation is a symptom, not a disease. An unbalanced diet, dehydration, inactivity, and stress are just a few causes. 

Your multivitamin could also be the culprit. And a big reason is synthetic vitamins. Many vitamins on the market today are full of synthetic ingredients, dyes, fillers, and artificial flavorings. How our bodies absorb minerals and vitamins from whole food sources is very different than how it is absorbed from synthetic sources.

What's Wrong With My Multivitamin?

Synthetic iron, calcium, and vitamin D can cause an imbalance in our gut resulting in constipation and are among the biggest culprits.


Iron helps transports oxygen throughout the body and is an important component of hemoglobin (found in red blood cells). There are three main sources of iron: 

  • Iron from plants
  • Iron from animals
  • Synthetic iron
Each one is absorbed and processed in the body differently. Organic iron (from plants and animals) is easily absorbed and processed; with iron from meat being the most easily absorbed. Synthetic iron can cause iron toxicity and constipation. 

Organic sources of iron include:

  • Spinach, Swiss chard, and kale
  • Oysters, mussels, and clams
  • Nuts
  • Squash and pumpkin seeds
  • Beans and lentils
  • Blackstrap molasses
  • Red meat
Forms of synthetic iron include:

  • Ferrous citrate
  • Ferrous gluconate
  • Ferrous fumarate
  • Ferrous peptonate
  • Ferrous sulfate
  • Carbonyl iron
These synthetic iron sources are linked to gastrointestinal issues including constipation, diarrhea, and nausea.  

It's estimated that 80% of people are iron deficient. While we try our best to eat a whole food diet rich in minerals and vitamins, most of use need to supplement. A better iron supplement source is ferrous bisglycinate chelated iron. Chelated means the iron is bonded with an organic molecule like amino acids making it easier for your body to absorb. Since ferrous bisglycinate chelated iron is easier to absorb and digest, less gastrointestinal issues occur. 

I take Master Formula for my multivitamin and includes 56% of the recommended daily value of iron in the form of ferrous bisglycinate chelated iron.

Sources: 1, 2, 3


The most common forms of calcium in supplements are calcium carbonate and calcium citrate. Both may cause constipation when not absorbed properly. 

Calcium carbonate is sourced from shells of marine organisms, snails, eggshells, and limestone. Calcium carbonate interferes with your natural production of stomach acid, making it difficult to digest food, resulting in constipation. Calcium citrate is often synthetically manufactured. These forms of calcium, along with other synthetic forms, can leave calcium deposits that our bodies cannot process.

In addition to using a usable source of calcium, we also need magnesium and vitamin D to properly absorb it. Without magnesium and vitamin D, calcium will either be unused or cause constipation.

We need calcium to maintain bone health. Sources of highly usable calcium include:

  • Calcium supplement from algae sources with vitamin D and magnesium (I like Super Cal Plus)
  • Raw milk
  • Dairy
  • Spinach and kale
  • Fish including sardines, mackerel, trout, and salmon
  • Nuts
  • Broccoli
Sources: 1, 2, 3

Vitamin D

Vitamin D is a fat-soluble vitamin meaning we need dietary fat to process it. A low fat diet can result in too much vitamin D stored in the body, which can result in constipation. A diet with healthy fat will help you digest and absorb vitamin D. 

In addition, we need magnesium to activate the enzymes to process vitamin D and maximize absorption. Often what is thought to be an overdose of vitamin D is actually a magnesium deficiency.

Some great sources of vitamin D are:

Sources: 1, 2

Tips for Constipation Relief 

This site is for informational purposes only and is not intended to be medical advice. We hope this information motivates and empowers you to make your own wellness journey decisions based on your own research and partnership with your healthcare provider.
 If you are pregnant, nursing, taking medication, or have a medical condition, consult a health professional prior to use. Information on this site should not replace or substitute professional medical advice, diagnosis, or treatment. The statements here have not been evaluated by the FDA. These products are not intended to diagnose, treat, cure, or prevent any disease.