Calcium Q&A
with Dr. Duffy MacKay


What is calcium?
Calcium is a mineral that is necessary for life and can be found throughout the body and in many foods.

Why is calcium important?
Calcium is important to build stronger, denser bones early in life and to keep bones strong and healthy later in life. Unfortunately many Americans do not get the amount of calcium they need every day.

About 99 percent of the calcium in our bodies is in our bones and teeth, supporting their structure and stability. In addition to building bones and keeping them strong and healthy, calcium helps blood clot, nerves send messages, muscles contract, and other body functions.

Our bodies cannot produce calcium on their own, which is why it’s important to try to get enough calcium through diet or through supplementation. When we don’t get enough calcium for our body’s needs, calcium is taken from our bones.

How can calcium help make me healthy?
At any age, you can benefit greatly from calcium. During childhood and adolescence, a proper intake of calcium plus vitamin D helps build optimum bone mass. Throughout adulthood, calcium will slow the rate of bone loss that naturally occurs with aging.

Substantial research has demonstrated supplementing with calcium and vitamin D to be effective in maintaining or increasing bone density, preventing osteoporosis, and potentially in protecting health in other ways as well. 

What foods contain calcium?
Dairy products, such milk, yogurt and cheese, are high in calcium. Certain green vegetables, such as kale, broccoli, and Chinese cabbage, and other foods, such as fish, contain calcium in smaller amounts. Calcium-fortified foods and calcium supplements are helpful for people who are unable to or simply cannot get enough calcium in their diets. Calcium supplements are available in various delivery methods, from liquid to tablets to soft chews.

Should I take calcium supplements? And how much should I take?
Substantial research has shown calcium supplements to be effective in maintaining or increasing bone density. The amount of calcium needed from a supplement depends on your age and dietary intake of calcium. Talk with your doctor, nurse practitioner, registered dietitian or other healthcare practitioner to determine what is right for you.

According to the U.S. National Academy of Sciences, Institute of Medicine (IOM), here are the Recommended Dietary Allowances (RDAs)* for calcium:

Life Stage Group

Dietary Allowance (mg/day)

1 – 3 years old


4 – 8 years old


9 – 18 years old


19 – 50 years old


51 – 70 year old males


51 – 70 year old females


>70 years old


*RDAs are quantities of nutrients in the diet that are required to maintain good health.

How much is too much calcium?
The IOM has set a Tolerable Upper Intake Level (UL), depending on your age, of between 2,000 – 3,000 mg/day—from all sources, including food, supplements and water. The UL is not a daily intake recommendation. It is considered the maximum level of daily intake that poses no known risk of adverse health effects for the general population. Going above the UL does not necessarily pose a safety risk; however, it is not recommended that you exceed the UL on a regular basis unless your healthcare practitioner has specifically directed you to do so. 

Are there safety concerns with calcium?  
There are no safety concerns for long-term calcium intake at or below the Tolerable Upper Intake Level (UL). Calcification of blood vessels has been reported with very high calcium intake; however, the reports are based on individuals with already compromised kidney function. No link has been clearly established for the general population.

Calcium is present in approximately 80 percent of kidney stones however the role of calcium and other nutrients, acting alone or together as risk factors for kidney stones, is not completely understood. There are various dietary and non-dietary factors that are associated with stone formation, making data difficult to interpret. Taking calcium supplements with meals should reduce the potential formation of kidney stones. Talk to your healthcare practitioner about how much calcium is right for you.

Duffy Dr. Duffy MacKay is a licensed Naturopathic Doctor, who works for the Council for Responsible Nutrition (CRN) as the Vice President of Scientific and Regulatory Affairs. Formerly co-owner and practitioner in a family-owned New Hampshire complementary and alternative medicine private practice, he currently resides in the Washington, D.C. area, seeing patients part-time in a retail pharmacy setting. In addition to his hands-on experience as a practitioner in the field of integrative medicine and his work with CRN, he previously spent eight years working as a medical consultant for two companies in the dietary supplement industry, where he served as an advisor on clinical research. Professionally and personally, he approaches the path to good health as a journey, taking small steps forward, and not letting detours get in the way of the ultimate goal. He currently blogs on the Life…supplemented website:


What's new

U.S. Preventive Services Task Force (USPSTF) Recommendations
CRN responds to the USPSTF's recommendations

Did you know?
  • About 99 percent of the calcium in our bodies is in our bones and teeth and must be obtained from the diet.

  • Even after a body has stopped growing, a generous calcium intake must continue to be provided to reduce or stop age-related bone loss, reduce the rate of bone fractures, or both.

  • Calcium is important for maintaining strong bone. Vitamin D is another critical component as it helps our bodies absorb calcium.
  • Vitamin D is the only vitamin that can be produced by your body.

  • Very few foods have vitamin D naturally. So, supplementation with vitamin D is important to avoid shortfalls.

For Healthcare Professionals
Recent scientific studies supporting vitamin D and calcium:

Additional Resources on Calcium and Vitamin D