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Bonus Nutrient of Concern: Magnesium

Jennifer Hanes MS, RDN, LD

Magnesium is our bonus nutrient of concern today. This will be the last nutrient I shine a spotlight on! 

You’ll notice that magnesium is not a vegetarian specific nutrient of concern. However, that is because it is actually a nutrient of concern for everyone. Americans are simply not getting enough magnesium in their diet anymore.  

In the past, magnesium was not a nutrient of concern. So what happened? Well, magnesium is a common component of groundwater. When we were drinking from rivers and wells we were getting magnesium (and other stuff!) and preventing deficiency. Now we drink softened tap water and filtered bottled water. The result, among others, is a reduction in magnesium in our water supply!

So does that mean it’s hard to get? Or that we can’t be healthy anymore?

Absolutely not.

Getting enough magnesium is really just a matter of adding some foods that are great for us anyway.

cooked spinach, poached egg, and tomato on white plate. Cooked spinach is a good source of magnesium
Photo by Carissa Gan on Unsplash


Magnesium’s biggest role in our body is as a co-factor. This means that it aids our enzymes in certain processes our body does almost constantly. 

The reason that magnesium is so important is that it is a co-factor for more than 300 different metabolic processes! This includes, but is not limited to protein synthesis, muscle and nerve function, and control of our blood glucose and blood pressure. More functions include energy production, development of our bones, and mood stabilization.

Adequate magnesium intake has been linked to improved blood pressure, decreased risk of developing type 2 diabetes, relief from constipation and indigestion, and increased bone density.

Recommended Intake

According to the RDA, after the age of 18, we should aim to get around 400mg per day from food.

Here’s the thing with these recommendations: they may not be enough. In fact, studies show that as our weight increases, so do our magnesium needs. This is simply not reflected in the current recommendations.

A better estimate of our needs is a simple calculation: 6 mg of magnesium for every kg of body weight per day.

To do this, divide your weight in lbs by 2.2, then multiply by 6. 

So a 130 lb woman would need to take in 355 mg of magnesium per day. 

But let’s say she is obese at 200 lbs. Her needs would increase to 545 mg of magnesium per day.

almonds and fruit in various bowls.
Photo by Josh Bean on Unsplash

Sources of magnesium

Good news! The best sources of magnesium are vegetarian!

Almonds, spinach, cashews, peanuts, and shredded wheat cereal are the top 5 sources for dietary magnesium.

However, if you had one serving of each of those in one day, you would only get 356 mg of magnesium

Other good sources include beans, brown rice, yogurt, and avocado.

For those reading that eat meat, small amounts can be obtained from fish, chicken, and beef as well. However, you will not reach your magnesium needs without including vegetarian sources of this mineral.

This is why I cannot stress enough how important it is for you to vary your diet, and include lots of nuts, seeds, beans, whole grains, and vegetables in your diet. Most vegetables have at least some magnesium in them, so when you vary your diet and eat enough of those high-value foods, you can easily reach your magnesium needs.

Sliced whole-grain bread is a good source of magnesium
Photo by Miguel Maldonado on Unsplash

Symptoms of magnesium deficiency

Because magnesium has so much to do, deficiency symptoms can vary. Loss of appetite, fatigue, weakness, and vomiting can occur.

As deficiency continues, you can develop numbness and tingling, muscle cramps, personality changes, migraines, and abnormal heart rhythms. 

Magnesium deficiency has consistently been linked to worsening symptoms and/or medication resistance in mental health disorders, including depression, anxiety, and schizophrenia.

Magnesium deficiency is hard to diagnose. Symptoms can mimic other conditions, and blood work doesn’t reveal low serum levels until you’ve been deficient for a while. This is because most magnesium is stored inside our cells or bones.

Other tests are available, but nobody’s really loving any of them. They can be expensive, labor-intensive, and still unreliable.

Some evidence exists that the majority of Americans have at least a mild magnesium deficiency. And that’s at the potentially too low recommendations.

Causes of secondary deficiency

Remember that secondary deficiency occurs when you eat enough of the nutrient in question but still have symptoms of deficiency.

Chronic alcoholism, certain medications, intestinal disorders, and type 2 diabetes are all at risk of secondary deficiency of magnesium.

This can be due to either poor absorption or increased excretion of magnesium.

Intense exercise may increase magnesium needs by 10-20 % due to increased magnesium loss in sweat and urine. Almond butter on whole-grain toast may be the perfect post-workout snack you need.

Treatment for deficiency

Treatment for magnesium deficiency is supplementation until serum levels are normal AND symptoms of deficiency are gone.

As you are taking a supplement, you should also be working towards dietary changes that regularly include foods that are good sources of magnesium.

mixed beans in a wooden bowl.
Photo by Milada Vigerova on Unsplash

Symptoms of magnesium toxicity

Magnesium toxicity from food is very unlikely because the kidneys will remove more if you eat more than your body needs.

However, high doses of medications or supplements can cause diarrhea, with or without nausea and abdominal cramping. Stopping the supplementation will cause the diarrhea to stop.

Long-term, excessive supplementation can lead to low blood pressure, nausea, vomiting, ileus (a dangerously slow digestive system), depression, and listlessness. If toxicity is allowed to continue, the person can experience difficulty breathing, irregular heartbeat, heart attack, or death.

Patients with kidney disease are at higher risk of toxicity than other people. This is because the kidneys are responsible for the removal of magnesium. When the kidneys aren’t working normally, the magnesium removal system is impaired.

peanut butter in a barrel shaped jar
Photo by Olia Nayda on Unsplash

Should I take a magnesium supplement?

If you know you have a deficiency, go for it temporarily. The foods that are high in magnesium all have wonderful health benefits, so you should be trying to get them in anyway.  

With almost all the nutrients that we’ve discussed and some that we haven’t, it is almost always better to get them from foods. The health benefits are improved when the nutrient is allowed to intermingle with other compounds in our food

This is especially well documented in cases where magnesium is used to improve symptoms or increase medication response in depression.

What supplementation won’t do

As always, supplementation is not going to negate a poorly planned diet.

Any concern for the omnivores?

Yes, many sources of magnesium are vegetarian, and they’re foods a vegetarian would be more likely to seek out.

Nuts and seeds, beans, and vegetables are good sources of magnesium and something a vegetarian is more likely to reach for.  

Encourage your omnivorous buddies to eat nuts, seeds, beans, whole grains, and vegetables as well!


National Institute of Health

Magnesium and Depression

Magnesium and Schizophrenia

Recommended intake of magnesium

Learn More

Most of this series was focused on nutrients of concern for vegetarians, based on an article I wrote called Are You an Unhealthy Vegetarian?

That article would be a great place to start, and it has links to each other articles in the series!

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