Dietitian Dish: Are You Getting Enough Calcium in your Diet?

May 03, 2018

By Saba Zahid,  RD, LDN
Patient Experience Manager, Unidine Corporation

Calcium is an important mineral our bodies need. Calcium is needed for muscle function, nerve transmission, hormonal secretion, and contraction and dilation of our arteries. All these functions require less than one percent of the body’s calcium; the remaining calcium supply is stored in the bones and teeth, where it supports their structure and function.

How Much do You Need?
How much calcium you need varies by age and gender. For adults between 19 and 50 years of age, both male and female, you need 1000 mg of calcium per day. Milk, yogurt, and cheese are rich natural sources of calcium. Eight ounces of plain, low-fat yogurt contains around 400 mg of calcium. Vegetables such as broccoli and kale are some non-dairy sources of calcium, although they don’t provide nearly as much calcium per serving. One half a cup of raw broccoli only provides 24 mg of calcium. Other sources of calcium include foods fortified with calcium such as fruit juices, tofu, and cereals. Six ounces of calcium-fortified orange juice contains 261 mg of calcium.

The Absorption Factor
Aside from including calcium-containing foods in our diet, the tricky thing about getting the calcium our bodies need is that there are many factors that affect how much or how well our body absorbs calcium from what we eat. For instance, calcium is absorbed less efficiently as the intake increases. So while a breakfast that includes yogurt, toast with peanut butter, and orange juice packs a whopping 734 mg of calcium, you would only absorb a fraction of that amount. Additionally, other components in food can inhibit absorption. Phytic acid and oxalic acid bind to calcium and inhibit absorption. Foods high in phytic acid include fiber-containing whole-grain products and wheat bran, beans, seeds, nuts, and soy isolates. Foods high in oxalic acid include spinach, collard greens, sweet potatoes, rhubarb and beans. The extent to which these compounds affect calcium absorption varies.

Some of the calcium that is absorbed in our body is eliminated from the body. Certain factors can impact the amount that is eliminated. High sodium intake increases the amount of calcium in our urine. Caffeine too can modestly increase calcium excretion and reduce absorption. One cup of regular brewed coffee can cause a loss of 2-3 mg of calcium. Alcohol impacts calcium status by reducing its absorption. Alcohol also inhibits enzymes in the liver that help convert vitamin D to its active form. Vitamin D is important for calcium absorption.

The Dangers of Calcium Deficiency
Not getting enough calcium in your diet does not produce any obvious symptoms in the short term. This is because there is a constant exchange between the calcium stored in our bones and the calcium in our blood stream. To maintain the calcium levels in our blood, our bodies take it from the calcium in our bones. Over the long-term, calcium intake below the recommended levels has health consequences, most notably osteopenia (low bone mass) and increased risk for osteoporosis.

Learn More
With May being National Osteoporosis Awareness and Prevention month, Shore is hosting a free community breakfast event focusing on Osteoporosis Awareness and Prevention on Wednesday, May 9 at Greate Bay Country Club in Somers Point. Guests will enjoy a continental breakfast while hearing from Rheumatologist Dr. Linda Brecher of Shore Physicians Group and experts from Shore Medical Center. To RSVP, contact Katie Byrnes at 609.653.3435 or via email kbyrnes@shorephysiciansgroup.com.


References:

  1. Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
  2. U.S. Department of Agriculture, Agricultural Research Service. 2011. USDA National Nutrient Database for Standard Reference, Release 24. Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/ba/bhnrc/ndl.
  3. Weaver CM, Heaney RP. Isotopic exchange of ingested calcium between labeled sources: evidence that ingested calcium does not form a common absorptive pool. Calcif Tissue Int 1991;49:244-7. [PubMed abstract]
  4. Weaver CM, Heaney RP, Martin BR, Fitzsimmons ML. Human calcium absorption from whole-wheat products. J Nutr 1991;121:1769-75. [PubMed abstract]
  5. Weaver CM, Proulx WR, Heaney RP. Choices for achieving adequate dietary calcium with a vegetarian diet. Am J Clin Nutr 1999;70:543S-8S. [PubMed abstract]
  6. Heaney RP. Bone mass, nutrition, and other lifestyle factors. Nutr Rev 1996;54:S3-S10. [PubMed abstract]