Fortification, Bioavailability, Supplementation: Mastering a Calcium Diet

Can a high-calcium diet cause kidney stones?

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

Calcium plays several significant roles for your health, such as building bone, contributing to normal heart rhythm, and sending messages throughout the nervous system. Professor Anding answers your questions about how to incorporate calcium into your diet.

Calcium rich foods
Good sources of calcium are dairy, some fruits, certain fish, whole grains, and dark leafy vegetables. Photo By Tatjana Baibakova / Shutterstock

High-Calcium Diet and Kidney Stones

First, you may be wondering if a high-calcium diet increases the likelihood of kidney stones. According to Professor Anding, the science suggests that calcium in the diet is not the predominant cause, but the dissolved minerals within the blood system must be maintained within a normal range. 

For example, three cups of yogurt contain about 900 milligrams (mg) of calcium. The entire amount of 900 mg will not go into your blood system. Some calcium will be directed to bone, some will be stored in tissues, and a consistent amount will be maintained in your blood supply. And, calcium will be excreted in your urine after the kidneys filter the blood, removing wastes and extra water, making urine. One of the dietary variables that increase the risk of kidney stones, however, is dehydration from a lack of drinking water. Remaining hydrated is a sure way to avoid the creation of kidney stones. 

Kidney stones are hard deposits of minerals and acid salts that form into small pebble-sized structures within concentrated urine. Thus, if you are prone to kidney stones, consult with your doctor, but, in general, a high-calcium diet is not the predominant cause. Causes might stem from your genetics as well as whether you are sufficiently hydrated. 

Bioavailability

You may also be wondering if the calcium in fortified foods is bioavailable. The evidence is mixed, but it mostly depends on the form of calcium, as well as whether it is a liquid or solid food. 

Research has been conducted on the calcium fortification of orange juice, which is in the form of calcium citrate malate, a biologically available form of calcium. There are subtle differences, depending on the form of the calcium; there can be calcium citrate malate in orange juice and perhaps calcium carbonate in a different food. 

Can we as a consumer look at a food package and figure out the bioavailability? No, you really can’t. It is best to get your calcium intake from a wide variety of fortified foods.

Calcium and Magnesium

Calcium does need magnesium to function. Most minerals have a delicate, interwoven balance and work hand-in-hand with one another. 

Thus, calcium and magnesium work together for bone formation. They really do depend on one another. 

“This is why I will tell my clients over and over again, don’t rely on supplementation of a singular vitamin or a singular mineral to optimize your health,” Professor Anding said. “What you’re really looking for, first and foremost, is dietary balance.” 

Sources

Look for forms of calcium that you like in your diet. Maybe you’re not a milk drinker, but you like yogurt, or maybe you don’t like yogurt, but you can drink calcium-fortified orange juice. 

Additionally, incorporate whole grains into your diet. Instead of having a processed breakfast cereal, choose oatmeal, which is a whole grain. Look for a way to partner these two together with a whole food approach. Whole grain sources of calcium include amaranth at 135 mg, calcium fortified bread at 150 mg, brown rice at 50 mg, and oatmeal at 100 mg to 150 mg. 

Besides dairy and grains, other good sources of calcium are green leafy vegetables such as kale, okra, and spinach. You can also get calcium from fish, where you eat the bones, such as sardines and pilchards.

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.

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.
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.