Calcium Supplements

When most people think about a dietary supplement for bone health and bone building they automatically think of calcium and vitamin D supplements. The FDA has approved calcium and vitamin D to “reduce osteoporosis risk.”

What's the Evidence?

But does calcium reduce fractures? Several studies have looked at this question.

Secondary prevention of osteoporotic fracture (that is, prevention of another fracture once someone already has sustained one) was assessed in a trial of 5292 people aged 70 years or older (average age, 77 years).1 Volunteers (85% female) were randomized to receive 1 of 4 protocols: 800 IU vitamin D3, 1000 mg calcium carbonate, 800 IU vitamin D3 plus 1000 mg calcium carbonate, or placebo daily for up to 62 months (median duration, 45 months). In this trial no significant difference in fracture risk was detected between groups.

However, another study noted a 16% reduction in fracture risk (P < .025) over 3 years in 2532 community-dwelling residents (average age, 73 years; 59.8% female) who supplemented with 400 IU vitamin D3 and 1000 mg calcium as calcium carbonate daily.2 As well, in a randomized, open-label, 2-year sequential follow-up study of 43 healthy adult volunteers (14 men, average age 60.6 years; 29 postmenopausal women, average age 54.1 years), participants followed their usual diet for the first year and then were randomized to receive 500 IU vitamin D3 and 500 mg calcium (form of calcium not reported), or no supplementation, from October to March.3 During these winter months in which volunteers took vitamin D3 and calcium, their lumbar BMD was 0.8% greater than in controls (P=.04), while no significant differences between the groups were noted for femoral-neck BMD.

The bottom line for these research studies is that calcium supplements and vitamin D3 may reduce fractures by about 16%.

When Taking Calcium, Insist On the Best

When taking calcium supplements, people should take the best forms of calcium. There are two primary forms of calcium supplements that you will see in dietary supplements. One is calcium carbonate. This form of calcium is the form that is most frequently used in clinical research because it is less expensive than other forms and you need fewer capsules to obtain the same doses of calcium. However, it is also the least absorbable form. One molecule of calcium carbonate carries four calcium atoms with it. These atoms of calcium are tightly bound to the carbonate molecule. The calcium must be released from the carbonate to be absorbed by the body. To effectively liberate the calcium you need acid, which is provided for in the stomach.

The problem is that as people age they are at increased risk for decreased stomach acid production, thereby lowering the amount of calcium from calcium carbonate that they can absorb. Many people produce less stomach acid as they age, and it’s been estimated that 10–21% of people sixty to sixty-nine years old, 31% of those seventy to seventy-nine years old, and 37% of those above the age of eighty have low stomach acid or no stomach acid at all, and this rate may be higher in people with autoimmune conditions.4,5

To understand if you might not be producing enough stomach acid, ask yourself the following questions: “Do you feel fuller sooner than you used to and stay full longer than you used to when you eat?” Or, “Do you feel fuller sooner than you used to and stay full longer than you used to when you eat?” If the answer to either of these questions is yes, it may be that you have low stomach acid since decreased stomach acid increases the amount of time food sits in the stomach before passing into the small intestines.

When stomach acid is low, vitamins and minerals may not be efficiently released from the food that contains them. This may result in decreased availability of nutrients for absorption and nutritional deficiencies. People with low stomach acid have been shown to be at increased risk for vitamin and mineral deficiencies.6,7,8,9

Symptoms of low stomach acid production include bloating or distension after eating, diarrhea or constipation, flatulence after a meal, hair loss in women, heartburn, indigestion, malaise, and prolonged sense of fullness after eating.10 Additionally, the risk of hip fracture increases by 22% after one year and nearly 60% after four years in people taking acid-blocking medications as compared to people not taking them.11

In contrast to calcium carbonate, calcium citrate is the best absorbed calcium supplement form. It does not require extra stomach acid for absorption, hence you may take it anytime in a day, even on an empty stomach. Calcium citrate though provides less elemental calcium per pill than calcium carbonate, so you may need to take more pills per day to meet your nutritional needs.

It has been estimated that people consume about 600 mg per day of calcium in the diet. Therefore, to get the recommended amount of daily calcium of 1200-1600 mg per day, you should take a highly-absorbable form of calcium, such as calcium citrate, in the amount of about 800-1000 mg daily.

Learn more

Why Osteo-K clobbers the competition: click to view a chart comparing Osteo-K to other leading calcium supplements, such as Viactiv, Citracal, Bone-Up, Os-Cal and Caltrate.