Danielle Pavliv and Brandel France de Bravo, MPH. Updated August 2014.
As a child, you were probably told to “drink your milk so you’ll have strong bones.” You may have seen television commercials and magazine ads with celebrities sporting milk mustaches and the words “Got Milk?” printed next to them. Walking through the grocery store, you may have noticed the phrases “Fortified with Calcium and Vitamin D” (vitamin D helps us absorb calcium), or “A Good Source of Calcium!” on cartons of juice, boxes of cereal, and even boxes of chocolate pudding mix. Calcium helps prevent broken bones, and many women take it to prevent hip fractures, which can take away a person’s independence and even be deadly. Clearly, calcium and vitamin D, which is found naturally in a small number of foods, are important, but do you know what these nutrients do and how much you need every day to keep your bones healthy? And if you’re not getting the recommended daily allowance through food, should you take supplements?
What the Most Recent Studies on Calcium and Vitamin D Supplements Tell Us
In 2012, calcium and vitamin D made headlines in the health world, with many new studies raising more questions than they answered. What’s worse, some of the findings seem to conflict with one another or suggest that these supplements could even harm your health. A closer look at the research, however, shows that there are some clear do’s and don’ts when it comes to taking calcium and vitamin D supplements. It also tells us who is most likely to benefit from taking them, and at what doses.
Calcium and Vitamin D Supplements to Prevent Cancer and Bone Fractures in Older Adults
In June 2012, the United States Preventive Services Task Force (USPSTF) released a draft Recommendation Statement concluding
- There is not enough evidence to determine whether the benefits of vitamin D supplements, with or without calcium, outweigh the harms if taken to prevent cancer in adults.
- There is not enough evidence to determine whether the benefits of the combination of vitamin D and calcium supplements outweigh the harms, if taken to prevent fractures in pre-menopausal women or in men.
- There is not enough evidence to determine whether the benefits of taking more than 400 IU of vitamin D3 together with 1,000 mg of calcium outweigh the risks, if taken to prevent fractures among post-menopausal women who don’t live in an assisted living facility or nursing home.
- Post-menopausal women who don’t live in assisted living or nursing homes should not take 400 IU or less of vitamin D3 and 1,000 mg of calcium to prevent fractures, because it does not work.
- In at least one major study (the Women’s Health Initiative), there was a small but statistically significant increase in kidney stones among the women taking calcium and vitamin D supplements as compared to the women who took nothing.
The cancer-related recommendation was based on only 3 studies, the most important of which was the Women’s Health Initiative (WHI). The WHI included more than 36,000 post-menopausal women. Half were given 400 IU of vitamin D3 and 1,000 mg of calcium carbonate daily, and the other half were not. Over seven years, women developed cancer at about the same rate regardless of whether they were taking the supplements or not. In the past, several research studies have found an association between taking calcium and vitamin D supplements and a lower risk of common cancers, especially colorectal and prostate cancers. Why did the WHI and the other two studies find nothing? Could it be that the doses studied were too low to make a difference among people with a deficiency? The Institute of Medicine, for instance, recommends 600 IU of vitamin D for men and women 51 to 70, and 800 IU for people over 70. Would higher levels of vitamin D have showed different results? More research is necessary to find out. The recommendations about fracture prevention were based on 16 studies, but the studies were difficult to compare. The kind of vitamin D varied, as did the dose (from 300 IU to 1,370 IU). In addition, some studies compared vitamin D to placebo or no treatment, some compared vitamin D and calcium to placebo or no treatment or to vitamin D alone, and others compared vitamin D to calcium. No women of childbearing age or men younger than 50 were included in any of the studies-the majority of people in the study were white, post-menopausal women. The WHI study was the largest, but the US Task Force pointed out that the dose of vitamin D (400 IU) “would not be considered sufficient today, and that nearly 30% of study participants were already taking calcium supplements of 500 mg or more prior to the start of the trial.”
In July 2012, a meta-analysis (combining the results of several studies) was published in the prestigious New England Journal of Medicine showing that vitamin D, if taken in high enough doses along with calcium, does help reduce fractures. This study, led by Dr. Bess Dawson-Hughes of the Department of Agriculture, included over 31,000 participants (91% of these were women). The researchers concluded that vitamin D doses of around 800 IU and higher (792 to 2000 IU), taken with a calcium supplement, can reduce hip fractures in people over 65 by 30%, as well as reduce the risk of fracturing other bones by 14%. Doses of vitamin D lower than 792 IU made no significant difference in preventing fractures. The study, which had many authors from around the world and was funded by the Swiss National Foundations, the European Commission Framework 7 Program, and a Swiss maker of supplements, combined data from patients in 11 double-blind randomized, controlled trials, which are the “gold standard” for research. The researchers measured each participant’s actual intake of vitamin D, not just the dose of vitamin D assigned. In 7 of the 11 trials, the researchers had checked how much vitamin D each patient had actually taken, and in the other 4 trials where that information was not available, a calculation was made by Dr. Bess Dawson-Hughes and her colleagues to account for people taking lower than the dose assigned. One drawback of this meta-analysis was that in 8 out of the 11 studies, the participants taking high levels of vitamin D were also taking a calcium supplement of some kind. It was therefore impossible to study the impact of Vitamin D supplements alone. The people who took calcium supplements lowered their risk of fracture only if they also took the highest amounts of vitamin D (792 to 2000 IU). The authors say that their findings support previous research showing that people taking that amount of vitamin D have fewer fractures if they take 1,000 mg or less of calcium rather than higher amounts., The authors caution that taking calcium supplements without vitamin D is associated with a higher risk of fracture. 
Bottom Line on Cancer and Fracture Prevention:
There is no clear evidence of whether vitamin D prevents cancer. If you are going to take vitamin D and calcium to prevent fractures, take at least 800 IU of vitamin D and take 1,000 mg or less of calcium.
Calcium Supplements and the Risk of Heart Attacks
In May 2012, a study of 24,000 people by Sabine Rohrmann from the University of Zurich was released in the medical journal Heart, showing that the people who took calcium supplements were more likely to have a heart attack during the 11 years that researchers kept in contact with them than those who didn’t take calcium supplements. The researchers add that consuming calcium through food is different than taking supplements, and there is no evidence that getting your daily intake from calcium-rich foods is harmful for your heart. When you take a supplement, though, the level of calcium in your blood spikes much faster than when you eat foods that contain calcium. However, this study did not focus on adults taking calcium and vitamin D supplements together. Although some of the subjects did take both supplements, and the researchers did mention that people taking calcium supplements were more likely to take vitamin D supplements as well, calcium was the primary concern of the researchers. Therefore, it is unclear what effect, if any, vitamin D supplements have on heart health.
Reduced Risk of Death Among the Elderly Taking Vitamin D and Calcium
In May 2012, a study was published by Danish researcher Lars Rejnmark and colleagues from many different countries, showing that elderly people taking vitamin D with calcium live longer. The researchers pooled results from various studies for a total of over 8,000 patients-mostly women aged 62 to 77. Patients who received both of these supplements daily were significantly less likely to die (9%) within the next 3 years than people not taking the daily supplements. When they restricted their analysis to the 4 studies with Vitamin D alone, they found no difference in the risk of death between those who took vitamin D and those who took no supplements.
Vitamin D Deficiency May Cause Weight Gain
A 2012 study by Erin LeBlanc and colleagues from Kaiser Permanente suggests that vitamin D deficiency may be associated with weight gain in elderly women. The study followed more than 4,600 women aged 65 and older for four and a half years. The researchers measured levels of vitamin D in the body and weight for all the women at the beginning and at the end of the study. They separated the women into three groups: women who gained at least 5% of their body weight, women who lost more than 5% of their body weight, and women whose weight remained relatively stable over 4.5 years. The researchers found that of the women who gained weight, the ones who had lower levels of vitamin D in their body gained more than those who had sufficient levels of vitamin D. Among the women who lost or maintained their weight, vitamin D levels did not play a significant role. As interesting as this study is, it does not tell us whether taking vitamin D supplements can help elderly women avoid or minimize weight gain.
Bottom Line on Vitamin D and Calcium Supplements
Vitamin D, which is hard to get through food alone and easier to get from the sun (but not if you’ve applied a high SPF sunscreen to prevent skin cancer), is generally considered safe in doses as high as 4,000 units per day. Calcium, on the other hand, may not be as safe either when taken alone or in doses higher than 1,000 mg, because it increases the risk of kidney stones and possibly heart attack. If you are at high risk for vitamin D deficiency, because you are over 65 or are African American, it may be a good idea to take at least 800 IU a day of Vitamin D-with or without calcium. Regardless of whether or not you take these two supplements, try to eat a diet rich in calcium and vitamin D because our body absorbs nutrients best when they are delivered through food.
What Does Calcium Do For Your Body?
Calcium can be found naturally in many foods, including dairy products such as milk, yogurt and cheese; dark green leafy vegetables like kale and broccoli; and some nuts and seeds such as pistachios, almonds and sesame seeds. There are also many calcium-fortified foods available, such as orange juice, soy products, oatmeal, and other cereals. It is important for people of all ages to consume a lot of calcium because it helps children reach their full potential height and develop strong bones and it helps adults prevent weak and broken bones. Osteoporosis is a disease caused by the loss of bone density and thinning of bone tissue. People with osteoporosis have very fragile bones and are more likely to fracture their bones than are healthy people. The National Institutes of Health estimates that more than 40 million Americans either have osteoporosis or are at high risk of developing it due to low bone mass. Although osteoporosis can affect men, most people with this disease are post-menopausal women. To read more about the risks and benefits of frequently prescribed treatments, check out this article.
How Bone is Made and Lost
We know that calcium and vitamin D help maintain strong bones, but how does that happen? Over the course of a person’s life, bones are constantly changing due to resorption and formation. Resorption is the process of bones breaking down and releasing minerals into the body. Formation refers to making new bone from calcium deposits in the body. During childhood, you are making more new bone than you are losing. Later in life, however, resorption or breakdown of the bone exceeds formation. This leads to bone loss and an increased risk of osteoporosis. While many foods are good sources of calcium, they may not provide enough to prevent osteoporosis. For example, individuals who are lactose intolerant and have trouble digesting dairy products, and vegans who eat nothing made from animals (no meat, eggs, or dairy) may be at higher risk for calcium deficiency. Calcium supplements are a way to prevent these problems. There are two main types of calcium supplements. Calcium carbonate is often less expensive and more widely available than calcium citrate. However, it is not as easily digested as calcium citrate, so it should always be taken with food. There are few side effects of calcium supplements, but they can include gas, bloating and constipation.
What Does Vitamin D Do?
Vitamin D is also very important for bone health because it helps us absorb calcium. It is found naturally in only a small number of foods like fish, egg yolk, and fortified foods like milk and juice. However, sunlight is a good source of vitamin D. Although ultraviolet rays can be harmful and cause skin cancer, spending 10-20 minutes in the sun a few times a week allows your body to produce a sufficient amount of vitamin D. The peak vitamin D hours are 10:00 a.m. to 4:00 p.m., which are also the hours you are advised to wear sunscreen. While sunscreen reduces vitamin D production, it doesn’t prevent it completely, mainly because few people apply it correctly, regularly or in sufficient quantities. You will absorb less vitamin D during winter months, and cloud cover and smog reduce vitamin D throughout the year. The darker your skin, the less vitamin D you will absorb from the sun. Lack of vitamin D can cause rickets, a condition which can cause weak bones and teeth, stunted growth, and a misshapen skull or body, such as a curved spine, in children. In adults, it can cause muscular weakness and weak bones. Some types of people are more likely to lack vitamin D than others:
- The elderly-Over time, the skin loses its ability to produce vitamin D as efficiently as in the past. In addition, elderly individuals tend to spend less time outside.
- The obese-Having more fat alters the release of vitamin D, meaning that less will be circulating in the body.
- Individuals who wear more or heavier clothing for religious or other reasons are less likely to get enough vitamin D.
- Breastfed infants-There is not enough vitamin D in human milk, unless women take a vitamin D supplement while they are breastfeeding.
- People with darker skin-The more melanin you have, the darker your skin, and that reduces your ability to produce vitamin D from sunlight.
Another way to avoid hip fractures is to preventing falling. In fact, there is no better way to prevent hip fractures. Two effective strategies include getting rid of area rugs and other things in the house that can cause a fall, and avoiding medications that tend to increase your chances of falling.
 U.S. Preventive Services Task Force. Vitamin D and Calcium Supplementation to Prevent Cancer and Osteoporotic Fractures in Adults: Draft Recommendation Statement. AHRQ Publication No. 12-05163-EF-2. Available at: http://www.uspreventiveservicestaskforce.org/draftrec3.htm.  Wactawski-Wende J, Kotchen JM, Anderson GL, Assaf AR, Brunner RL, O’Sullivan MJ… Manson JE. Calcium plus vitamin D supplementation and the risk of colorectal cancer. Women’s Health Initiative Investigators. New England Journal of Medicine. Feb 2006;354(7):684-96.  Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: Results of a randomized trial. American Journal of Clinical Nutrition. 2007; 85(6):1586-1591.  Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M…Holick MF. Vitamin D and prevention of colorectal cancer. Journal of Steroid Biochemistry and Molecular Biology. 2005;97(1-2):179-194.  Ahonen MH, Tenkanen L, Teppo L, Hakama M, Tuohimaa P. Prostate cancer risk and prediagnostic serum 25-hydroxyvitamin D levels (Finland). Cancer Causes and Control. 2000;11(9):847-852.  U.S. Preventive Services Task Force. Vitamin D and Calcium Supplementation to Prevent Cancer and Osteoporotic Fractures in Adults: Draft Recommendation Statement. AHRQ Publication No. 12-05163-EF-2. Available at: http://www.uspreventiveservicestaskforce.org/draftrec3.htm.  Bischoff-Ferrari HA, Willett WC, Orav EJ, Lips P, Meunier PJ, Lyons RA… Dawson-Hughes B. A pooled analysis of vitamin D dose requirements for fracture prevention. New England Journal of Medicine. 2012;367(1):40-49.  Steingrimsdottir L, Gunnarsson O, Indridason OS, Franzson L, Sigurdsson G. Relationship between serum parathyroid hormone levels, vitamin D sufficiency, and calcium intake. JAMA 2005;294:2336-41.  Bischoff-Ferrari HA, Kiel DP, Dawson-Hughes B, et al. Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S. adults. J Bone Miner Res 2009;24:935-42.  Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, et al. Calcium intake and hip fracture risk in men and women: a metaanalysis of prospective cohort studies and randomized controlled trials. Am J Clin Nutr 2007;86:1780-90.  Li K, Kaaks R, Linseisen J, Rohrmann S. Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg). Heart. 2012;98:920-925.  Rejnmark L, Avenell A, Masud T, Anderson F, Meyer HE, Sanders KM… Abrahamsen B. Vitamin D with calcium reduces mortality: Patient level pooled analysis of 70,528 patients from eight major vitamin D trials. Journal of Clinical Endocrinology and Metabolism. 2012; DOI: 10.1210/jc.2011-3328.  LeBlanc ES, Rizzo JH, Pedula KL, Ensrud KE, Cauley J, Hochberg M, Hillier TA. Associations between 25-hydroxyvitamin D and weight gain in elderly women. Journal of Women’s Health. Online ahead of print. Doi:10.1089/jwh.2012.3506.  Vitamin D. Medline Plus. National Institutes of Health. June 7, 2012. Available at: http://www.nlm.nih.gov/medlineplus/druginfo/natural/929.html#Safety.  National Institutes of Health Osteoporosis and Related Bone Diseases National Research Center. Osteoporosis overview. October 2010. Available at: http://www.niams.nih.gov/Health_Info/Bone/Osteoporosis/overview.asp.  Dietary Supplement Fact Sheet: Calcium. Office of Dietary Supplements, National Institutes of Health. 2011. Available at: http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/.  Dietary Supplement Fact Sheet: Vitamin D. Office of Dietary Supplements, National Institutes of Health. 2011. Available at: http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.