Dr. Urvi Shah encourages patients to eat plenty of fiber-rich foods, many of which are also naturally high in magnesium. “Magnesium is a mineral that is important for more than 300 enzymatic reactions and functions throughout the body,” says Dr. Shah.
Magnesium is having a big moment, as its boosters take to social media to tout the mineral’s potential to do everything from relieve anxiety and facilitate sleep to lower blood pressure and cure constipation. Naturally abundant in certain foods and widely available in supplement form (pills, powders, liquids, sprays, patches, and more), magnesium is being promoted as the latest, greatest cure-all for a wide range of symptoms, from muscle aches to migraines. But what does the evidence show: Is magnesium helpful — or is it hype?
Magnesium — first isolated more than two centuries ago — is enjoying the spotlight thanks, in part, to evolving research about the essential role it plays in a variety of functions in the human body. Ongoing studies are also giving us a better understanding of how we absorb magnesium and how intestines and kidneys work together to maintain stable magnesium levels.
Magnesium matters to cancer patients
“Our patients are curious about the pros and cons of magnesium” says hematologic oncologist Urvi Shah, MD, at Memorial Sloan Kettering Cancer Center (MSK). “They want to know whether it can improve treatment outcomes or reduce their risk of cancer.” She cares for patients with plasma cell disorders, including multiple myeloma, and she conducts research aimed at understanding the interplay between nutrition and cancer.
Dr. Shah answers common questions about magnesium’s role in overall health and in cancer treatment and prevention, and she dives into the differences between natural dietary sources and magnesium supplements.
What does magnesium do and how much do I need every day?
Magnesium is an essential nutrient that plays a major role in disease prevention and overall health. “Magnesium is a mineral that is important for more than 300 enzymatic reactions and functions throughout the body,” says Dr. Shah.
It’s essential for nerve and muscle function and for bone health, and it regulates blood sugar levels and blood pressure. Our bodies need magnesium to maintain a healthy immune system and a steady heartbeat, but our bodies can’t manufacture it — so we have to get magnesium from the foods we eat.
The amount of magnesium you need depends on your age and sex. Men should get 400 to 420 milligrams a day, while women require 310 to 320 milligrams a day.
How can I get enough magnesium through food or supplements?
“There are two ways you can get magnesium,” says Dr. Shah. “One is through the diet, and the other is through dietary supplements.”
Foods that are rich in magnesium are also usually fiber-rich foods. Some foods with a high magnesium content include:
- Seeds, such as chia and pumpkin
- Nuts, such as almonds, cashew, peanuts
- Green leafy vegetables, including spinach, kale, and collard greens
- Legumes, such as edamame, tofu, black beans, and lima beans
- Whole grains, such as brown rice, whole wheat, barley, buckwheat, oats
- Soy milk and, to a lesser extent, dairy milk
True magnesium deficiency is rare: The vast majority of people can maintain healthy magnesium levels with a varied diet rich in legumes, nuts, whole grains, and green vegetables.
But research suggests that nearly 50% of Americans don’t get enough magnesium through diet. Studies have found that teenagers and men over 70 are most likely to have low intakes of magnesium in their diets.
What’s the link between magnesium levels and cancer risk?
Researchers know that getting enough magnesium is essential to overall health, but its precise role in reducing cancer risk is still under investigation. Few population studies have shown that individuals with higher dietary magnesium intake have lower risk of certain cancers and death from cancer. It’s not known, for instance, if the cancer-fighting benefits of magnesium derive from the mineral alone or from the fiber-rich plant-based foods that contain it.
Why are cancer patients at risk for low magnesium?
Some cancer patients are at risk for magnesium deficiency.
Especially over the long term, certain types of chemotherapy, such as cisplatin, and some immunosuppressive drugs, including cyclosporine, deplete magnesium and increase the risk of low magnesium levels (hypomagnesemia). Another commonly used drug that can deplete magnesium levels is the long-term use of proton pump inhibitors like omeprazole and pantoprazole.
Additionally, cancer patients with gastrointestinal diseases that lead to chronic diarrhea — such as Crohn’s or celiac disease, which can impact magnesium absorption — or who’ve had surgery to remove a part of their intestines or pancreas, have their magnesium levels monitored.
Patients with type 2 diabetes (especially if it is poorly controlled) and patients with chronic alcohol intake are at an increased risk for deficiency too.
Patients with heart disease at risk of heart rhythm issues usually also have their blood tested for magnesium regularly. “Some studies show that magnesium levels in the normal range may improve blood pressure, thus lower their risk for heart attack or stroke,” says Dr. Shah.
Hypermagnesemia, or magnesium levels that are too high, is a very rare condition, occurring primarily in patients with kidney disease.
Should everyone get their magnesium levels tested?
No. It’s not a routine screening test. It’s a blood test ordered by the medical team when they suspect that a patient’s symptoms, other conditions (for example, type 2 diabetes), or medications are depleting their magnesium levels.
The tests are not straightforward. Most of the magnesium in our bodies is stored in our bones, muscles, and cells — very little is circulating in our blood. If your body detects that you’re not getting enough magnesium through food or supplements, it pulls magnesium out of the bones and sends it to the blood system to regulate hundreds of enzyme reactions. “When you test the blood of a person with a chronic mild deficiency, it may look normal. But the bones are losing magnesium, and the long-term effect can be osteoporosis,” says Dr. Shah.
Researchers are working to develop a simple, rapid, and more accurate test.
What’s a normal magnesium level on a blood test?
Normal levels are measured between 1.8 to 2.4. “So if it’s low on that test, you definitely know the patient has a magnesium deficiency,” says Dr. Shah.
What are the symptoms of low magnesium?
“The most common symptoms that lead me to test a patient for low magnesium are frequent muscle cramps or headaches,” says Dr. Shah. Some other early signs are loss of appetite, vomiting, fatigue, weakness, high heart rate — also symptoms cancer patients may have for a variety of other reasons. As magnesium deficiency worsens and become extreme, numbness, tingling, and abnormal heart rhythms can occur.
Symptoms of low magnesium in otherwise healthy people are uncommon. When healthy people don’t take in enough magnesium, the blood stream pulls magnesium from the bones, and the kidneys help to limit the amount lost in urine.
What’s your guidance for someone who thinks their sleep, mood, or energy might be helped by taking a magnesium supplement?
If you are healthy and your doctor doesn’t think there’s a major reason to avoid magnesium supplements, says Dr. Shah, “it is not unreasonable to try a small dose of magnesium at night to see if it helps in terms of sleeping better or just feeling better overall.”
But it’s not her first choice. Before taking a magnesium supplement, “I would bump up the dietary fiber first,” she says. In our dietary studies we have seen this can help with energy, mood, and sleep too.
Studies have also shown that roughly half the population doesn’t get enough magnesium — meaning, says Dr. Shah, that half of the population, or more, doesn’t eat enough fruits, vegetables, and fiber-rich foods. She encourages her patients to add fiber-rich foods to their diet, ideally 25 to 30 grams of fiber per day.
Do you have a favorite magnesium-packed recipe?
I do! It’s so simple. It’s my favorite recipe for overnight oats.
In a bowl or jar, start with 1 cup of whole grain rolled oats (112mg magnesium), and add:
- 1 cup soy milk (61mg magnesium)
- 2 tablespoons chia seeds (222mg magnesium)
- 2 tablespoons pumpkin seeds (312mg magnesium)
- Your favorite fruit, such as berries, for sweetness and a drop of vanilla extract
Let it sit in the refrigerator overnight to soften. Eat the next day.
It’s delicious and packed with magnesium, and this bowl of goodness will meet your daily magnesium requirements. It’s good for so many things. We’re talking better mood, better sleep, and good for your bones.
What’s a good way to include supplements in your diet?
For patients who do take supplements, Dr. Shah recommends starting with a small dose to minimize the side effect of diarrhea and to take it at night, as it may cause drowsiness and aid sleep. She also recommends taking organic varieties, which are easier for the body to absorb. (Organic varieties include magnesium glycinate, magnesium citrate, magnesium aspartate, and magnesium lactate.)
If, after a few weeks, it’s not clear if the supplements are helping with sleep or mood, then magnesium is probably not benefiting you.
Is there a reason not to take magnesium?
Magnesium supplements should be avoided in patients with certain heart, kidney, or gastrointestinal disorders and should be discussed with their doctor. They should not be used in patients taking bisphosphonates (osteoporosis drugs), antibiotics, diuretics, or reflux drugs because of the potential for drug interactions. Dietary magnesium, however, is not an issue, as the excess is excreted — food is a more reliable source.
What are the different types of magnesium?
There are several different formulations used in magnesium supplements. They may all sound similar, but they do slightly different things, and their absorption varies.
Magnesium l-threonate
Easily absorbed, it may support brain health and help with sleep and mood.
Magnesium malate
Well-absorbed by the body and often taken as a supplement.
Magnesium chloride
Used to boost magnesium levels — usually taken as a pill.
Magnesium lactate
Used in people with magnesium deficiency and often given in slow-release form.
Magnesium glycinate
Used for relaxation, tachycardia, and insomnia, and less likely to cause diarrhea.
Magnesium oxide
Used for migraines and heartburn, but not the best option for correcting magnesium deficiency. Causes diarrhea and may therefore help constipation.
Magnesium citrate
Easily absorbed and widely used for constipation.
Magnesium hydroxide
A primary ingredient in some laxatives. (Milk of Magnesia, for example, provides magnesium hydroxide.) Also included in remedies for heartburn and upset stomach due to acid indigestion.
Magnesium sulfate
Epsom salts. Used for constipation and to soak achy muscles. Used in patients admitted to hospitals when intravenous magnesium is needed.
