Guidelines for Taking Supplements: Timing, DRIs, and More

why are some supplements preferred over others?

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

Although whole foods are the best way to get vitamins and minerals, sometimes it is necessary to take supplements, especially if you are deficient in a particular nutrient due to a medical condition. Professor Anding answers some questions you may have about proper supplement regimens.

Multiple vitamins stacked together
The daily reference intake (DRI) assigned to vitamins and minerals are designed for the majority of the population, but sometimes need adjustment to correct for a deficiency caused by a chronic illness of an individual. Photo By Valentina_G / Shutterstock

Timing for Taking Supplements

When is the best time to take a supplement? First and foremost, if a vitamin or mineral supplement is going to work, you have to remember to take it. Thus, if you’re more likely to remember to take it first thing in the morning, that might be best for you.

Keep in mind that if you’re taking a supplement, iron can be relatively nauseating, and taking it on an empty stomach may give you significant nausea. What ends up happening is that people stop taking it, saying that the supplement made them sick. The truth is, there was nothing wrong with the supplement itself per say; many people just can’t tolerate it on an empty stomach. 

When you’re looking for a vitamin and mineral supplement, look for one that doesn’t contain more than 100% of the daily value for a particular vitamin or mineral. That limits your body’s ability to end up with any excess.

Uncommon Supplements

Phosphorus, sulfur, and chlorine are essential to life, yet we never hear about taking supplements for them. According to Professor Anding, there’s a good reason for that. 

Phosphorus, for example, is found in almost every food, particularly protein-containing foods, and even in some unlikely sources. In fact, if you look at the list of contents for a soft drink, you’ll see the words “phosphoric acid.” 

Therefore, the reason we don’t see phosphorus, sulfur, and chlorine supplements is not because they’re not important. It just means that a dietary deficiency is unlikely; except perhaps, if you’re taking a medication that interferes with your ability to absorb the minerals. Thus, you might see these minerals on a supplement label, but you’re not necessarily going to see them advertised in the media.

Daily Reference Intake

When it comes to daily reference intake (DRI) for vitamins and minerals, you might be wondering if these recommended amounts are appropriate for everybody. According to Professor Anding, the answer is no.

DRIs are based on body weight, so it’s going to change depending on how old you are and how much you weigh. The DRIs are lower for younger people, continuing to increase until they’re adults. When you’re an adult, they stabilize, but they may fluctuate during a person’s lifetime. 

A key point, however, is that these DRIs are designed to cover about 98% of a healthy population, not individuals with chronic disease. We have no DRIs for illness, so if, for example, you have a family member in the intensive care unit, you might see significant amounts of vitamins and minerals being administered. 

DRIs also may change if you are overtly deficient in a nutrient. A prenatal vitamin contains a lot of iron. If the pregnant woman has iron-deficiency anemia, the physician may prescribe a significantly larger amount of iron than even what is recommended for pregnant women. 

Additionally, for Crohn’s disease, which causes significant malabsorption, many individuals are given magnesium supplements to deal with the malabsorption. The magnesium level may be way above the upper limit of about 350 milligrams, but it’s appropriate for that individual.

Another example is with the prevalence of vitamin D deficiency going up. Often, physicians might prescribe as much as 50,000 International Units of vitamin D, way above that upper tolerable limit, attempting to correct a deficiency. 

As a further example, physicians might prescribe taking potassium chloride at amounts way above the upper DRI limit if a patient is on diuretic medication. Suppose your physician has prescribed a diuretic to help control your blood pressure. Some of the diuretics on the market can cause significant potassium loss, so you might be prescribed potassium chloride as a supplement, or as a pill, that’s above the daily reference intake of 4,700 milligrams.

In summary, although the daily reference intakes are designed for the majority of the population, the daily intake amount might need to be adjusted in order to correct for a vitamin or mineral deficiency, while managing a chronic illness that an individual may have.

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.