The all-too-common magnesium deficiency limits levels of active vitamin D
As everyone knows by now, vitamin D is key to healthy bones.
Far fewer folks know that vitamin D is a key element in “innate” immunity — our first line of defense against infection.
And low levels of this hormone-like nutrient have been linked to higher risks for breast cancer, colon cancer, prostate cancer, heart disease, autoimmune disorders, depression, and weight gain.
Unfortunately, most Americans lack optimal blood levels of vitamin D, as we’ll detail below.
We produce vitamin D when UV sunrays strike our skin, but a prominent anti-skin-cancer campaign — urging people to curb sun exposure and slather on sunscreen — has likely limited many Americans’ blood levels.
Emerging evidence now shows that we also need adequate dietary magnesium to effectively use the vitamin D we get from UV sunrays, fatty fish, fortified foods, and supplements.
The magnesium/vitamin D link
The authors of a new evidence review conclude that our bodies can’t metabolize vitamin D efficiently without sufficient levels of magnesium.
As they wrote, “Magnesium assists in the activation of vitamin D, which helps regulate calcium and phosphate … to influence the growth and maintenance of bones. All of the enzymes that metabolize vitamin D seem to require magnesium ...”.
And, as they noted, “Deficiency in either of these nutrients is … associated with various disorders, such as skeletal deformities, cardiovascular diseases, and metabolic syndrome. It is therefore essential to ensure that the recommended amount of magnesium is consumed to obtain the optimal benefits of vitamin D.” (Uwitonze AM et al. 2018)
Unfortunately, attempts to address that problem with vitamin D supplements create their own concerns. Insufficient bodily magnesium can increase your calcium and phosphate levels — which can lead to risky calcification of artery walls.
As study co-author Mohammed Razzaque explained, “People are taking vitamin D supplements but don’t realize how it gets metabolized. Without magnesium, vitamin D is not really useful or safe. By consuming an optimal amount of magnesium, one may be able to lower the risks of vitamin D deficiency and reduce dependency on vitamin D supplements.”
His team's finding echoes the results of a Japanese rodent study, in which magnesium deficiency impaired the enzymes necessary to produce usable vitamin D — the same enzymes employed by humans (Matsuzaki H et al. 2013)
The little-known connection between the humble mineral and vitamin D matters because many Americans — nearly half — don’t get the recommended daily allowance (RDA) for magnesium.
And, due to their magnesium shortage, much of the vitamin D in those Americans’ bodies remains in an inactive, storage form, making it essentially unavailable for use.
As the authors of the new evidence review also noted, people with optimum levels of magnesium need less vitamin D to maintain healthy levels.
In addition, magnesium can reduce the risk of osteoporosis, which is of course associated with vitamin D deficiency.
Getting enough magnesium? Many Americans don’t
Magnesium is often called an “orphan” nutrient, overlooked in the focus on things like omega-3s, vitamin D, and calcium.
But there’s growing evidence that magnesium plays a far bigger role in human health than previously thought.
In fact, low magnesium intakes are linked to greater risks for accelerated aging, diabetes, metabolic syndrome, chronic inflammation, hypertension, cardiovascular disease, sudden cardiac death, osteoporosis, migraine headache, asthma, and colon cancer.
For more on that topic, see Mighty Magnesium for Bones, Hearts, Mood, & More and its links to related reports.
Nearly one in two Americans (48%) falls short of the recommended daily allowance (RDA) for magnesium — 420 mg for men and 320 mg for women — and even fewer enjoy optimal body levels.
It’s difficult to determine your levels of magnesium, because most bodily magnesium is sequestered in our cells and bones, making blood tests unreliable measures — making it critical to ensure adequate intakes.
Over the past 30 years, the intake ratio of calcium to magnesium from foods has been rising among adult Americans — and that excludes average calcium intake from supplements, which greatly outweighs intakes of supplemental magnesium.
When they analyzed data from the National Health and Nutrition Examination Survey, researchers from Vanderbilt University and Rutgers University reported that Americans’ calcium intakes rose at a rate 2-2.5 times higher than their magnesium intakes between 1977 and 2012 — probably due to growing use of calcium supplements for bone health (Deng X et al. 2013).
Yet, as they reported, “High intake of total, dietary or supplemental magnesium was independently associated with significantly reduced risks of vitamin D deficiency and insufficiency respectively.”
They also found that the link between low vitamin D levels and higher risk of death from cardiovascular disease was lower among people who lacked sufficient vitamin D but whose intakes of magnesium were higher than the national average (Deng X et al. 2013).
The increasing calcium-magnesium imbalance may help explain why rates of type 2 diabetes rose sharply between 1994 and 2001 — a time frame when the ratio of calcium-to-magnesium in American diets also rose (Rosanoff A et al. 2012).
Luckily, magnesium is a nearly automatic side benefit of diets focused on whole plant foods, seafood, and poultry, such as the Mediterranean diet or non-dogmatic, nutrition-savvy versions of the Paleo diet.
Top magnesium sources
Nuts, seeds, leafy greens, whole grains, fish, and most foods high in fiber are relatively rich in magnesium.
Other good food sources include yogurt, avocado, bananas, milk, chicken, legumes (beans and lentils), red meat, and seaweed.
This table shows the magnesium content of various foods (USDA data):
- Cocoa powder – 456mg per 3 oz (27mg per Tbsp)
- King salmon – 122mg per 3 oz, cooked
- Swiss Chard – 86mg per cup, cooked
- Almonds or cashews – 75-80mg per oz
- Sablefish – 71mg per 3 oz, cooked
- Yellowfin tuna – 42mg per 3 oz, cooked
- Yogurt – 27-39mg per 8 oz
- Sockeye salmon – 36mg per 3 oz, cooked
- Silver salmon – 36mg per 3 oz, cooked
- Albacore tuna – 33mg per 3 oz, canned in water
- Pacific cod – 30mg per 3 oz, cooked
- Halibut – 28mg per 3 oz, cooked
- Chicken breast – 22mg per 3 oz, cooked
Vitamin D deficiency is common, and America’s magnesium shortage worsens things
Deficiencies — or sub-optimal levels — of magnesium and vitamin D are both common.
About a decade ago, the National Health and Nutrition Examination Survey found that 41.6% of Americans were deficient in vitamin D, with the highest rates seen among black (82.1%) and Hispanic Americans (69.2%).
The finding about ethnic differences is unsurprising because darker skin contains more UV-blocking melanin pigment. People in Middle Eastern countries also tend to suffer vitamin D deficiency — partly due to darker skin color, and partly because women stay indoors and cover their heads and bodies more than in most other regions.
Vitamin D deficiency was more common among those without a college education, obese or unhealthy people, people with hypertension or unhealthful cholesterol profiles, and those who didn’t drink milk daily (milk is typically fortified with 100 IU of vitamin D per 8 ounces).
And last year, the California-based authors of an evidence review concluded that nearly one billion people worldwide suffer from vitamin D deficiency — generally due to lack of sufficient sun exposure (Pfotenhauer KM, Shubrook JH 2017).
As study co-author Dr. Kim Pfotenhauer, D.O. of Touro University said, “People are spending less time outside and, when they do go out, they’re typically wearing sunscreen, which essentially nullifies the body’s ability to produce vitamin D. While we want people to protect themselves against skin cancer, there are healthy, moderate levels of unprotected sun exposure that can be very helpful in boosting vitamin D.”
It’s also worth noting that certain chronic diseases — including type-2 diabetes, kidney disease, Crohn’s disease, and celiac disease — can impair the body’s ability to produce vitamin D from foods and supplements.
- Budhathoki S et al. Plasma 25-hydroxyvitamin D concentration and subsequent risk of total and site specific cancers in Japanese population: large case-cohort study within Japan PublicHealth Center-based Prospective Study cohort. BMJ. 2018 Mar 7;360:k671. doi: 10.1136/bmj.k671. PubMed PMID: 29514781; PubMed Central PMCID: PMC5838719.
- Deng X, Song Y, Manson JE, Signorello LB, Zhang SM, Shrubsole MJ, Ness RM, Seidner DL, Dai Q. Magnesium, vitamin D status and mortality: results from US National Health and Nutrition Examination Survey (NHANES) 2001 to 2006 and NHANES III. BMC Med. 2013 Aug 27;11:187. doi: 10.1186/1741-7015-11-187.
- Henninger N, M.D. Low vitamin D predicts more severe strokes, poor health post-stroke.” American Stroke Association Meeting Report Abstract W MP62, 11 Feb 2015.
- Matsuzaki H, Katsumata S, Kajita Y, Miwa M. Magnesium deficiency regulates vitamin D metabolizing enzymes and type II sodium-phosphate cotransporter mRNA expression in rats. Magnes Res. 2013 Apr-Jun;26(2):83-6. doi: 10.1684/mrh.2013.0341.
- Miller JW, Harvey DJ, Beckett LA, Green R, Farias ST, Reed BR, Olichney JM, Mungas DM, DeCarli C. Vitamin D Status and Rates of Cognitive Decline in a Multiethnic Cohort of Older Adults. JAMA Neurol. 2015 Nov;72(11):1295-303. doi: 10.1001/jamaneurol.2015.2115.
- Pfotenhauer KM, Shubrook JH. Vitamin D Deficiency, Its Role in Health and Disease, and Current Supplementation Recommendations. J Am Osteopath Assoc. 2017 May 1;117(5):301-305. doi: 10.7556/jaoa.2017.055. PubMed PMID: 28459478.
- Rosanoff A, Dai Q, Shapses SA. Essential Nutrient Interactions: Does Low or Suboptimal Magnesium Status Interact with Vitamin D and/or Calcium Status? Adv Nutr. 2016 Jan 15;7(1):25-43. doi: 10.3945/an.115.008631. Print 2016 Jan. Review.
- Rosanoff A, Weaver CM, Rude RK. Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutr Rev. 2012 Mar;70(3):153-64. doi: 10.1111/j.1753-4887.2011.00465.x. Epub 2012 Feb 15. Review.
- Uwitonze AM, Razzaque MS. Role of Magnesium in Vitamin D Activation and Function. J Am Osteopath Assoc. 2018 Mar 1;118(3):181-189. doi: 10.7556/jaoa.2018.037. PubMed PMID: 29480918.