Functional Medicine Doctor Recommends Magnesium for Everyone. Where’s the Evidence?

Ask Dr. Jen

An article by a functional medicine doctor said that everyone should take a magnesium supplement because 80% of people are deficient in magnesium. That doesn’t seem right. What are your thoughts?

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Quick Take

Your instincts are right, 80% of people are not deficient in magnesium and everyone should not be taking a magnesium supplement. 

Go On…

Magnesium is an essential mineral that is involved in multiple biochemical reactions in the body, for example muscle and nerve function, control of blood sugar, and synthesis of DNA. It is also an essential component of bone. Most of our magnesium is stored in bone and other tissues and only about 1% is in the blood. Because most of the magnesium is stored in tissues, blood levels don’t always give us the full picture about whether a person has enough magnesium in their body. To know if someone is magnesium deficient may require more than a simple blood test. 

The recommended magnesium intake per day for women ages 19-30 years is 310 mg and for those over the age of 30 it is 320 mg. It is true that only 50% or so of people in the United States get the recommended amount of magnesium in their diet, however, this does not mean that 50% of people are deficient in magnesium. The kidneys are very good at hanging onto magnesium to prevent magnesium deficiency. There has not been a study of magnesium levels in the general population in the United States for decades, so that “80%” number from the functional medicine doctor seems literally pulled out of their ass. 

Some people are more at risk for magnesium deficiency than others. For example, magnesium deficiency is more likely to happen when someone has a gastrointestinal disease that affects how they absorb magnesium. Others at increased risk for magnesium deficiency are people with alcoholism, people with type 2 diabetes, and the elderly. Whether these people need a magnesium supplement is something they should decide with their health care providers.

It is true that diets that are higher in magnesium appear to be linked with lower rates of several medical conditions, such as heart disease and osteoporosis, but as magnesium is present in many healthy foods it is hard to sort out what is a reflection of a high quality diet in general and what is specifically magnesium related.

Magnesium supplements can help certain medical conditions, for example magnesium has a laxative effect. It is due to the fact that a lot of the magnesium in these supplements stays in the bowel, so instead of getting absorbed into your bloodstream it hangs around in your stool, increasing how your stool absorbs water. This makes the stool softer, which is easier to pass, and bulkier, which stimulates the bowel to move the stool along. The magnesium that is more likely to treat constipation or cause diarrhea (depending on how formed your stools were to begin with) are magnesium oxide, magnesium carbonate, magnesium chloride, and magnesium gluconate. Magnesium supplements, 300 mg a day, may also be helpful for migraine prevention and there are some low quality studies that suggest magnesium supplements might be helpful for menstrual cramps. Magnesium is frequently recommended for muscle cramps, like a calf cramp, but studies show it is ineffective. 

Besides potentially causing diarrhea, the downsides of taking magnesium are the potential for negative interactions with some medications and magnesium toxicity, meaning taking in too much magnesium, which could lead to serious health problems. This is usually only seen with very large doses or when people have kidney damage and their kidneys can’t get rid of excess magnesium, so it accumulates. 

Here’s the deal. Magnesium is in a lot of foods, especially foods that are associated with lower risks of heart disease and diabetes and overall good health, so the bigger question is why does a functional medicine doctor recommend an unnatural supplement to otherwise healthy people when they could simply recommend some dietary changes? The answer is because most make their money by doing a battery of unnecessary blood tests, diagnosing non existent deficiencies, recommending supplements based on the unnecessary blood work, and then have you continue in that cycle of blood work to “check your levels'' and subsequent “fine tuning” adjustments in perpetuity. Eventually, people realize the therapy is placebo and they are actually not improving or they run out of money.

Many simple dietary changes can help you meet your magnesium requirements, but there is little money in saying, “Add a couple of tablespoons of pumpkin seeds to your salads, snack on almonds or cashews, have chia seeds for breakfast, choose brown rice over white, reach for some yogurt, and have more spinach.” Lots of plant based proteins are good sources of magnesium (just another reason to have more plant based protein) and most fortified cereals have 10% of the daily requirement. I made this amazing vegan coconut, red lentil, sweet potato soup from the New York Times for lunch (you should really try it, I am not a huge fan of vegan food, but I absolutely love this soup). If I have added all the ingredients up correctly a serving should give me about 100 mg of magnesium. I will be having a salad with dinner tonight and will throw in some pumpkin seed for crunch, flavor, and nutritional value. 

The person to consult if you are worried about dietary magnesium intake is a registered dietician, not a supplement pusher. If you have a medical condition that you think might affect your ability to absorb magnesium, then you should see a specialist in that area and also still consult with a registered dietician, as the right food choices can help many medical conditions. And if you are having symptoms that are associated with magnesium deficiency, for example fatigue, weakness, numbness, an irregular heart beat, or seizures–certainly not an exhaustive list), your doctor may check your magnesium level as part of the work up. 

Bottom line: Magnesium deficiency due to diet is uncommon for otherwise healthy people and there are no studies that support the idea that the general population needs a magnesium supplement. 

References

1. Magnesium Fact Sheet for Health Care Professionals. Office of Dietary Supplements (ODS). Accessed 10/16/2021.

2. S Holland, S D Silberstein, F Freitag, et. al. Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society. Evidence-based guideline update: NSAIDs and other complementary treatments for episodic migraine prevention in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society. Neurology 2012 Apr 24;78(17):1346-53.

3. H Mori, J Tack, H Suzuki. Magnesium Oxide in Constipation. Nutrients. 2021 Feb; 13(2): 421.

4. S Garrison, CS Korownyk, MR Kolber, et. al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020 Sep; 2020(9): CD009402.

5. Pattanittum P, Kunyanone N, Brown J, Sangkomkamhang US, Barnes J, Seyfoddin V, Marjoribanks J. Dietary supplements for dysmenorrhoea. Cochrane Database of Systematic Reviews 2016