Magnesium is an essential mineral involved in hundreds of functions in your body. But if your levels are very low, you could experience negative side effects.
Magnesium plays an important role in maintaining nerve and muscle function, immune health and blood sugar levels. It also keeps the heart beating steady and keeps bones strong. Some research also suggests magnesium could play a role in preventing or managing health problems including diabetes, high blood pressure and heart disease, according to the National Library of Medicine.
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The Office of Dietary Supplements (ODS) estimates that nearly half of Americans get less than the recommended daily intake of magnesium. But falling a little short and actually having a magnesium deficiency aren't the same thing.
"Actual deficiency is not common and may be as low as 2 percent," says Vandana Sheth, RDN, registered dietitian nutritionist and author of My Indian Table.
The only way to tell for sure if you're deficient in magnesium is with a blood test. That said, low magnesium levels can cause noticeable symptoms, some of which are serious.
Early Symptoms of Low Magnesium
Early on, low magnesium levels might not cause any symptoms at all. But in some cases you may start to notice side effects. Per the ODS, signs of mildly low magnesium levels may include:
1. Nausea or Vomiting
Falling short on magnesium could leave you feeling queasy or even cause you to throw up. That's because the mineral is involved in nervous system function.
"Our gastrointestinal nerves may not be conducting correctly, which leads to nausea," explains Dana Ellis Hunnes, PhD, MPH, RD, senior dietitian at UCLA Medical Center and author of Recipe for Survival. "Vomiting is often a side effect of the nausea, which, of course, causes us to lose even more magnesium."
2. Loss of Appetite
Low magnesium can sap your appetite. That could be a direct effect of nausea — it's hard to eat when your stomach is off, Hunnes notes.
Lack of magnesium could also cause the nerves that signal feelings of hunger to work less effectively.
3. Low Energy
Magnesium plays an integral role in cell metabolism — the process where nutrients are converted to energy.
"If we are low in magnesium, we become less effective and efficient at this conversion," Hunnes explains.
That can lead to feelings of weakness, sluggishness and fatigue.
Does Low Magnesium Cause Insomnia?
You may have heard that taking magnesium can help you sleep if you have insomnia, but the evidence here is thin, according to the Cleveland Clinic. A few studies have found that magnesium may make it easier to fall asleep or improve overall sleep quality, but these have all been relatively small. And other research shows some people with low magnesium levels sleep just fine.
Severe Magnesium Deficiency Symptoms
A person is more likely to experience serious symptoms as their magnesium deficiency becomes more severe, the ODS notes. In some cases the effects of extreme magnesium deficiency could be life-threatening.
1. Numbness or Tingling
Trouble experiencing sensation in the hands or feet, or noticing a tingling feeling, can both stem from very low magnesium levels.
"Again, it has to do with magnesium's effect on the nervous system response," Hunnes says.
2. Muscle Cramps
Cramps can occur from imbalances of electrolyte minerals like magnesium (as well as sodium, potassium or calcium).
"Cramps can also occur when low magnesium causes nerves in the body to misfire, leading the muscles to contract and cause cramps," Hunnes says.
3. Personality Changes
Abnormal or uncharacteristic behavior is another problem that can stem from faulty nervous system function, which can happen when a person's magnesium deficiency becomes severe.
If the magnesium deficiency is related to alcohol use (alcohol abuse can lead to magnesium deficiency), the drinking may be affecting the individual's behavior too, Hunnes notes.
"Seizures related to magnesium deficiency likely relate to electrolyte imbalances, which may be caused by poor overall diet quality or the nervous system effects of low magnesium levels," Hunnes says.
There are many possible causes of seizures, though. Call 911 if you or someone you know is experiencing a seizure for the first time, is having trouble breathing or the seizure lasts longer than five minutes.
5. Abnormal Heart Rhythm
"Our heart beats are little nerve firings that lead to the contraction of the heart muscle," Hunnes says.
Because magnesium plays a key role in healthy nerve function and nerve conduction, being deficient could potentially affect the heart muscle nerves and cause a person to experience irregular heartbeat.
Causes of Magnesium Deficiency
Anyone can develop a magnesium deficiency if they don't get enough magnesium-rich foods in their diet (think: leafy greens, beans, nuts and seeds). But certain factors can affect the body's abilities to absorb nutrients like magnesium or increase a person's magnesium needs, which can make it harder to maintain adequate levels.
According to the ODS, some of the most common culprits include:
Older adults are more prone to low magnesium levels too, since body's ability to absorb magnesium decreases with age. These effects can be compounded by taking medications that increase magnesium deficiency risk, says the ODS.
How Much Magnesium Do You Need?
The right amount of magnesium for you depends on your age and whether you were assigned male at birth (AMAB) or assigned female at birth (AFAB).
Here's what's recommended, per the National Library of Medicine:
Infants and Children
- Newborn to 6 months: 30 mg per day
- 6 to 12 months: 75 mg per day
- 1 to 3 years: 80 mg per day
- 4 to 8 years: 130 mg per day
- 9 to 13 years: 240 mg per day
- AMAB 14 to 18 years: 410 mg per day
- AFAB 14 to 18 years: 360 mg per day
- AMAB: 400 to 420 mg per day
- AFAB: 310 to 320 mg per day
- Pregnant people: 350 to 400 mg per day
- Lactating people: 310 to 360 mg per day
Best Foods With Magnesium
You can find magnesium in a wide range of plant and animal foods, but nuts and seeds, leafy greens, whole grains, beans and fortified cereals are some of the best sources, per the Cleveland Clinic.
Magnesium-rich foods include:
- Pumpkin seeds: 168 mg in 1 ounce
- Almonds: 80 mg in 1 ounce
- Spinach: 78 mg in 1/2 cup cooked
- Cashews: 74 mg in 1 ounce
- Fortified soymilk: 61 mg in 1 cup
- Black beans: 60 mg in 1/2 cup
- Soybeans: 50 mg in 1/2 cup
- Peanut butter: 49 mg in 2 tablespoons
- Whole-wheat bread: 46 mg in 2 slices
- Brown rice: 42 mg in 1/2 cup cooked
- Plain yogurt: 42 mg in 1 cup
- Banana: 32 mg in 1 medium
- Milk: 24 to 27 mg in 1 cup
- Salmon: 26 mg in 3 ounces
Should You Take a Magnesium Supplement?
Magnesium supplements can help you meet your nutritional needs, but they shouldn't be your first choice. "Since there are plenty of magnesium-rich food sources, getting it from your diet is best," Sheth says.
Talk with your doctor to determine whether a magnesium supplement is right for you and decide how much magnesium you should be taking.
While it's hard to overdo it on magnesium from food, getting too much magnesium from supplements can cause nausea, diarrhea and stomach cramps, according to the Mayo Clinic. In some cases magnesium can also interact with medications, especially antibiotics.
- National Library of Medicine: "Magnesium In Diet"
- Office of Dietary Supplements: "Magnesium Fact Sheet for Health Professionals"
- Cleveland Clinic: "Magnesium Rich Food"
- Mayo Clinic: "I've heard that magnesium supplements have health benefits. Should I take one?"
- Cleveland Clinic: "Does Magnesium Help You Sleep?"
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Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.