Should Calcium and Iron Supplements Be Taken Together?

Two minerals are important to your health — calcium, to maintain the density of your bones, and iron, for the production of red blood cells to prevent anemia. When you can't get enough iron and calcium from your diet, you may need to take supplements. It's important to know how much of these essential minerals you need, what is a safe dosage and the possible interactions.

Calcium and iron supplements help strengthen your bones. (Image: yorkfoto/iStock/GettyImages)

Tip

Iron pills taken with high doses of calcium may inhibit the absorption of iron, so it's often advised that you take the supplements separately.

Why You Need Calcium

Calcium is one of the most important nutritional elements for optimal bone and dental health and muscle performance. The skeleton contains 99 percent of your body's calcium supply. When you don't get the calcium your body needs, it is taken from your bones. Many women take calcium supplements in an attempt to boost bone strength, especially after menopause, to help prevent osteoporosis.

Due to the increased risk of bone loss and fracture from rheumatoid arthritis and other forms of inflammatory disease, calcium supplements are often prescribed, especially in people who also have a milk allergy.

Why You Need Iron

Iron is essential for proper growth and development. Your body uses iron to support many biological functions including energy production, oxygen transport and synthesis of hormones. When the body does not get enough iron, it is unable to produce normal amounts of red blood cells, and iron deficiency anemia may result. A deficiency in iron is the most common deficiency of vitamins or minerals worldwide.

Children, women of childbearing age, pregnant women, frequent blood donors and individuals with certain medical conditions are particularly prone to having low iron levels. Iron is especially important during pregnancy, so for healthy fetal growth, iron supplements are usually recommended.

How Much Calcium You Need

Dairy products, such as milk, yogurt and cheese, are the best natural sources of calcium. Some vegetables contain calcium, such as cabbage, kale and broccoli. Unless they are fortified, most grains contain only a small amount of calcium.

The National Institutes of Health has developed recommendations for how much calcium is needed for bone health and adequate retention of calcium, dependent on age and gender. The daily amounts from food and calcium supplements are:

  • Ages 14 to 18 years of age: 1,300 milligrams
  • Ages 19 to 50 years of age: 1,000 milligrams
  • Ages 51 to 70 years of age: males, 1,000 milligrams; females, 1,200 milligrams
  • Ages 71 years of age and older: 1,200 milligrams
  • Pregnant and Lactating women: 1,000 to 1,300 milligrams

How Much Iron You Need

Lean meat and seafood provide the richest sources of dietary iron. You can also get iron from nuts, beans, vegetables and fortified grain products, such as breads and cereals.

The recommended daily amount of iron you need differs if you are a vegetarian. People who don't eat meat require 1.8 times more iron because plant-based foods contain a form of iron that is not as bioavailable as animal-based sources, according to the NIH. The RDA for iron from food and iron supplements for nonvegetarians is:

  • Ages 14 to 18 years of age: males, 11 milligrams; females, 15 milligrams
  • Ages 19 to 50 years of age: males, 8 milligrams; females, 18 milligrams
  • Ages 51 years and older: 8 milligrams
  • Pregnant and lactating women: 9 to 27 milligrams

Causes of Calcium Deficiency

Although food is the best way to get calcium, supplements may be an option if your diet falls short or if you have difficulty getting enough calcium as a result of certain conditions, including:

  • Vegetarian or vegan diet
  • Lactose intolerance
  • Certain medical conditions that decrease the ability to absorb calcium, such as celiac or inflammatory bowel disease
  • Osteoporosis
  • Long-term treatment with corticosteroids

Causes of Iron Deficiency

Some conditions may make it harder for you to get sufficient dietary iron from food alone. The Mayo Clinic reports that some of the reasons you may be deficient include:

  • Blood loss, such as with heavy periods, peptic ulcers, hiatal hernia or colorectal cancer
  • Vegetarian or vegan diet
  • Certain medical conditions that decrease vitamin absorption, such as celiac disease or gastric bypass surgery
  • Pregnancy

About Calcium Supplements

According to NIH, about 43 percent of Americans, including almost 70 percent of older women, take dietary supplements containing calcium.

Calcium supplements generally do not have significant side effects but can occasionally cause gas, constipation and bloating. You can take calcium supplements in oral tablets, capsules, chewables, liquids and powders.

Supplements may contain different kinds of calcium salts with varying amounts of elemental calcium. NIH reports that the two forms of calcium supplements are carbonate and citrate. You should take calcium carbonate with food because stomach acid is required for absorption. When choosing a calcium supplement, look for one that also contains vitamin D, which can help with efficient absorption.

High calcium intakes can cause constipation and may be associated with an increased risk of kidney stones. If you exceed the total Tolerable Upper Intake levels for calcium of 2,000 to 2,500 milligrams for adults, NIH reports that calcium supplements may interfere with the absorption of iron. Johns Hopkins recommends that you take calcium and iron supplements, or multivitamins containing iron, two hours apart.

About Iron Supplements

Iron supplements are available in several forms, including capsules, tablets, chewable tablets and liquids.

Although it's unlikely you will experience iron overload from food, taking too high a dosage of iron pills — more than 20 milligrams per kilogram — can cause constipation, nausea, faintness, abdominal pain and vomiting, especially if food is not taken at the same time.

MedlinePlus advises that you should not take iron supplements at the same time as milk, calcium and antacids. To increase iron absorption, drinking orange juice or taking a vitamin C supplement with your iron pills will help.

Calcium’s Effect on Iron Absorption

Clinical studies sometimes report conflicting results when it comes to calcium's inhibitory effect on iron and vitamin absorption. A study published in the Journal of Food Science Technology in April 2016 examined the diets of 60 rural farm women to determine the role of dietary factors on the bioavailability of iron in their diets.

Although the study was small and therefore may not be completely applicable to all populations, its findings are of interest, as it identified calcium, as well as zinc, as negatively affecting iron absorption.

Findings were that low intake of iron-rich foods, such as meat, and high consumption of calcium foods cause iron and zinc deficiencies. The researchers noted that the addition of 150 milligrams of calcium to a hamburger meal reduced iron absorption by 50 percent. The authors suggested increasing iron intake or avoiding taking calcium and iron-rich foods at the same time as a practical solution for the competition of calcium with iron.

Another study published in Advances in Nutrition in March 2016 reviewed the administration of calcium carbonate to pregnant women for the prevention of preeclampsia. It reported that the effect of calcium-inhibiting iron absorption had a minimal effect and recommended that doctors should not counsel patients to take calcium and iron pills separately in order to make it easier to adhere to a regular regimen.

Because conclusions from studies vary on whether it's OK to take calcium and iron supplements together, follow the advice of your healthcare provider to help you determine what is best for you.

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