Discovering the Best Sources of Magnesium Is Easy

How much is too much magnesium?

By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital
Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily
Magnesium rich foods
Magnesium is derived from our food sources; more than 300 enzymes in the body require it as an activator and several metabolic processes are supported by it. Photo By YARUNIV Studio / Shutterstock

Magnesium as a Mineral

Magnesium is an essential mineral and the fourth most abundant in the human body. As a mineral, magnesium plays a role in bone mineralization, energy metabolism, muscle contraction, and nerve impulse transmission. 

About 50% of the body’s total magnesium is housed in the bone. The other 50% is located in cells of tissues and organs. 

Only 1% is in the blood; the body keeps this fraction as a constant. Thus, when a mineral is in the blood, the body’s going to have a lot of defense mechanisms to keep that blood value normal. 

More than 300 enzymes require the use of magnesium. This includes all enzymes that use or make ATP, the energy currency of the body, as well as those that use nucleotides, or the building blocks needed to create DNA and RNA. 

Reactions catalyzed by magnesium include, among others, fatty acid synthesis, glucose metabolism, and protein production. Magnesium also enhances the absorption of calcium in the intestine, so these two minerals work as partners. Increasingly, research has suggested that magnesium may be used to treat, manage, and prevent disorders such as cardiovascular disease, diabetes, and hypertension.

Sources of Magnesium

Just like iron is the central molecule in hemoglobin, magnesium is the central mineral in chlorophyll. This means that anything that’s green and has chlorophyll in it is going to be a source of magnesium. 

Another source of magnesium can be tap water. The amount varies according to whether the water supply is hard, meaning it has a lot of dissolved minerals, or soft. Hard water usually naturally contains more minerals, including magnesium, than soft water.

A half a cup of almonds has 238 milligrams, one ounce of unsweetened chocolate has 88 milligrams, and a half a cup of cooked spinach has 66 milligrams. Whole grains are a great source of magnesium. 

However, when the grains are refined and the outer bran is removed, magnesium and B vitamins are lost. The B vitamins are replaced or fortified back into that grain, but magnesium is not.

Daily Requirements and Toxicity

The daily magnesium requirement for men ages 19 to 30 is 400 milligrams (mg), men ages 31 to 70 is 420 mg, and women ages 31 to 70 it is 320 mg. The upper limit for magnesium intake is around 350 mg per day, and that’s from supplements. 

It’s the supplements that confer the toxicity. Excess magnesium is filtered through the kidneys, so it’s hard to overdose from dietary sources. However, people with renal disease are prone to toxicity because magnesium balance is regulated by the kidneys. 

Typical symptoms of excess magnesium again include nausea, vomiting, and diarrhea. If the state of excess continues for a prolonged period of time, the toxicity can result in cardiovascular and muscle irregularities. 

Avoiding Deficiency

Magnesium deficiencies are not prevalent in Americans, and the concern about under-consumption of magnesium does not seem to be high among health care providers. However, dietary surveys have proposed that Americans do not have enough magnesium in their diet. 

Optimal magnesium intake may protect against cardiovascular disease and immune dysfunction. As with all minerals, a deficiency can be compounded by other conditions including acidosis, which occurs when your kidneys and lungs can’t keep your body’s pH in balance.

Alcohol abuse, the use of diuretics that your physician might have prescribed for high blood pressure, and kidney or renal disease can all cause a deficiency of magnesium. Low, as well as high, protein intake can also interfere or inhibit magnesium absorption.

Symptoms of magnesium deficiency include confusion, hallucinations, nervousness, and muscular weakness, plus tremors and swallowing difficulties when values are exceptionally low. Deficiency rarely occurs with diet but can occur with some of the other confounders. Suboptimal levels of magnesium increase the likelihood of metabolic syndrome and type 2 diabetes. 

Some medications can cause magnesium deficiency, including antibiotics and antineoplastic medications used to treat cancer, particularly cisplatin. During 1999-2000, and back in 1988-1994, National Health and Nutrition Examination Survey (NHANES) results suggested that older adults are at increased risk for magnesium deficiency. 

Are Supplements Ever Necessary?

Magnesium supplements may benefit individuals who have trouble controlling their diabetes, particularly individuals who most often experience an increased magnesium loss in their urine, as well as alcoholics. Thirty to 60% of alcoholics and 90% of patients experiencing alcohol withdrawal demonstrate low blood levels of magnesium.

Additionally, individuals exhibiting such malabsorptive disorders as Crohn’s disease as well as  potassium and calcium deficiencies may also benefit from magnesium supplements. Individuals who have had intestinal surgery, including gastric bypass, may need supplemental magnesium to keep their values normal. 

Keep in mind that minerals interact with vitamins, fiber, and each other. Think about it in terms of setting up dominos. If you knock one down, because you’re taking too much of one, you can influence the bioavailability of other ones. Your body needs to be in balance. If you take a significant excess of magnesium or calcium, your body will not be healthy and correction will be needed. 

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.

Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.

About Kate Findley 408 Articles
Kate is a writer, novelist, and blogger living in Los Angeles. She has been writing for The Great Courses since 2017. It incorporates her two favorite things: writing and learning.