Calcium is an essential mineral found in foods and dietary supplements. Its best-known benefit is building and maintaining strong bones, and slowing bone loss. But it plays a critical role in heart health, nerve transmission, and muscle contraction.

Which calcium supplements are the best, most effective, and budget-friendly?

A new review published by ConsumerLab.com — a leading provider of consumer information and independent evaluations of products that affect health and nutrition — aims to answer those questions by ranking the best available supplements on the market.

The organization’s Calcium Supplements Review rates 27 products evaluated by the group.

Among the findings:

• All 27 products contained the listed amount of calcium. But one product was not approved because it did not contain the listed amount of magnesium and also was contaminated with lead. A second product – labeled as “fast dissolving” – was not approved because it did not dissolve quickly enough.
• The other 25 products all had consistently high quality.
• Prices varied widely, ranging from 4-80 cents for a 500 mg dose of calcium.

Based on the organization’s research findings, the review’s authors identified a Top Pick for each of nine categories. To be a Top Pick, a supplement had to pass ConsumerLab’s tests of quality, provide calcium at a reasonable price, contain a reasonable dose, and offer a convenient formulation.

Two of the Top Picks are:

Overall Top Pick. GNC Calcium Citrate, which provides 500 mg of calcium per two-caplet serving at a cost of 9 cents. This supplement is also the Top Pick in the “Calcium Only” category.

Calcium and Vitamin D. Bayer Citracal Petites, which provide 400 mg of calcium and 500 IU of vitamin D per two-capsule serving for 11 cents.

Most adults need 1,000-1,200 mg of calcium per day, from all sources. These include food, supplements, and an often overlooked source: calcium-containing antacids.

Because you may already be getting that amount from food alone, supplementation may be unnecessary. Rich dietary sources of calcium include dairy products, beans, and green-leafy vegetables. For example, just one cup of milk or yogurt provides a whopping 300-400 mg of calcium.

If you’re not getting the recommended amount of calcium from your diet, supplements can help. Multiple studies show that 1,000-2,000 mg per day of calcium (usually as calcium citrate) in combination with 400-800 IU per of vitamin D can slow bone loss in postmenopausal women. Research shows that supplementation may be especially useful in in postmenopausal women who have been prescribed hormonal therapy after undergoing a hysterectomy.

The official tolerable upper limits for calcium are 2,500 mg per day for children ages 1-8, 3,000 mg for those ages 8-18, which falls to 2,000 mg for those over 50. But much lower amounts, usually from supplements, have been associated with risks for adults.

It’s rare to get toxic amounts of calcium from food alone. In fact, a high dietary intake of calcium is associated with many good effects. But excess calcium from supplements is associated with a wide range of ill effects.

“Be careful!” the authors write. “Calcium from supplements may increase the risk of cardiovascular disease if you get too much from supplements [over 1,000 mg per day] or if you already get enough calcium from your diet.”

A high calcium intake from supplements also may increase the risk of:

• Prostate cancer.
• Kidney stones.
• Dementia.

Calcium supplements also may impair the absorption of thyroid hormone and antibiotics in the fluoroquinolone class.

If you take calcium supplements, the researchers offer these tips.

• Since your body can’t absorb more than 500 mg of calcium at a time, it’s best to take only a few hundred milligrams at a time, and no more than 1,000 mg total per day.
• If your supplement includes vitamin D and/or vitamin K, taking it with the meal that includes the most fats and oils may enhance absorption.
• Avoid taking calcium supplements and other mineral supplements together because the calcium may reduce their absorption.