Why Your Vitamin D Supplements Aren’t Effective

Jennifer O'Donnell-Giles | March 16, 2018

So you found out that your vitamin D levels were low, and now, you’re taking vitamin D supplements. That’s great! It’s an important supplement to take when your body doesn’t get enough vitamin D. However, did you know that vitamin D needs magnesium in order to be metabolized? If you’ve been taking vitamin D for a while now but you’re not feeling the benefits, read on to find out how you can make the most out of your vitamin D supplements.

A review article published in the March issue of The Journal of the American Osteopathic Association stressed that many people don’t know that taking vitamin D without adequate magnesium is not beneficial.

Magnesium is a mineral that activates hundreds of enzymes in our bodies related to crucial biological reactions, including the enzymes that play a role in vitamin D metabolism.

A national survey between 2005 and 2006 found that about half of all Americans do not consume adequate magnesium. The National Institute of Health, or NIH, recommends a magnesium intake of 400 to 420 milligrams per day for men, and 310 to 320 mg a day for women.

Interestingly enough, past research found that consuming magnesium can reduce the risk of vitamin D deficiency.

Good foods sources of magnesium include almonds, bananas, beans, broccoli, brown rice, cashews, egg yolk, fish oil, flaxseeds, green vegetables, milk, mushrooms, nuts, oatmeal, pumpkin seeds, sesame seeds, soybeans, sunflower seeds, sweet corn, tofu, and whole grains.

There are dangers is consuming too much magnesium – more than the daily recommended amount – such as diarrhea, nausea, and abdominal cramping. Extremely high intakes can lead to irregular heartbeat and cardiac arrest, according to the NIH. Before taking synthetic supplements, it is best to gradually increase food sources of magnesium in order to control the amount that is consumed at one time.

This is yet another example of how good health and longevity are never found in one nutrient alone. They’re found in a delicate balance of many nutrients that are best consumed in whole food form. So, if you find that your vitamin D supplements aren’t working for you, talk to your doctor and start introducing healthy foods that are rich in magnesium to your balanced diet!


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Jennifer O'Donnell-Giles

Jenn Giles, R.D., C.S.S.D. is all about health and wellness. She has over 15 years’ experience, including a dual master’s degree in Nutrition and Exercise Physiology from Columbia University. She is a Registered Dietitian (RD) and a Board Certified Specialist in Sports Dietetics (CSSD). She supplements all of this with her spin instructor certification and USATriathlon Level I Coach Certification.

Jennifer is passionate about (actually, obsessed with) the sport of triathlon. She has been personally participating in triathlons since 2000 and running road races since 1992. She is a two-time Ironman finisher and has completed countless numerous marathons. She has been a member of Power Bar Team Elite since 2006 and competed as a member of the 2006 Aquaphor/Active.com Sponsored Athlete Team. She was ranked as USAT All American Honorable mention in 2006 and 2011. Jennifer does all of this along side of her husband, Patrick, who is an equally accomplished triathlete and runner. They try as hard as they can to do all of their training and racing together.

She will tell you, however, that her most important, most rewarding and most challenging job is as a mother of four. She knows first hand the challenges of maintaining optimal fitness, overall good health and achieving goals while raising a family - of which good nutrition is the cornerstone.

Most importantly, she knows how to motivate, inspire and challenge athletes based on their own abilities, strengths and everyday lifestyles. She believes there is an athlete in everyone - no matter what their abilities are – and if those abilities are manifold, then there is an even better athlete in there!

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