Osteoporosis is a disease in which the density and quality of the bone are reduced, making it weak and brittle. A variety of supplements offer potential benefit, although in limited situations. (Use the links below for details.)
Adequate intakes of calcium (and vitamin D) during youth are important for building strong bone, and it's important to get adequate calcium throughout life to help maintain bone. However, in postmenopausal women, calcium supplements (with vitamin D) may only modestly protect against osteoporosis. Most adults currently get enough calcium for bone health, and some postmenopausal women who take supplements may be getting too much calcium, which can increase the risk of kidney stones and stroke.
Vitamin D may help to increase bone density, but only in people with low blood levels of vitamin D (below 20 ng/mL) and with adequate calcium intake. It may also help to reduce the risk of fractures and falls. However, getting too much vitamin D could be detrimental to bone health.
Magnesium deficiency can increase the risk of osteoporosis. In people with inadequate intake, supplementing with magnesium can increase bone mineral density.
At doses higher than nutritional needs, vitamin K supplements have been found to increase bone density in healthy postmenopausal women, and higher intakes of vitamin K from foods has been associated with reduced risk of fractures in elderly men and women.
In postmenopausal women, soy isoflavones may increase bone density, although higher doses are required than those typically used to reduce hot flashes.
A form of strontium (strontium ranelate), previously available by prescription in Europe and Australia but not in the U.S., showed promise in reducing the risk of developing osteoporosis as well as increasing bone density and reducing the occurrence fractures in postmenopausal women with osteoporosis. However, due to increased risk of heart-related adverse events, use of prescription strontium ranelate became restricted in 2014 to only people with severe osteoporosis for whom other treatments were not possible and who had no history or pre-existing heart or circulatory problems (Protelos Product Information 2014). Due to the decreased number of prescriptions for strontium ranelate following the implementation of these restrictions, strontium ranelate production ceased in August 2017. Strontium supplements in the U.S. typically contain strontium citrate and, while it is absorbed into bone (Moise, Bone 2014), there is no research showing it to be effective against osteoporosis. Also, be aware that too much strontium may weaken bones. In some studies, up to 680 mg of elemental strontium from either strontium ranelate or strontium citrate has been taken for between 3 to 4 years without serious adverse effects (Meunier, N Engl J Med 2004; Moise, Bone 2014); however, Health Canada has warned that an increased risk of cardiovascular events has been reported in some people who have a history of, or risk factors for cardiovascular disease who took a daily dose of 680 mg of strontium ranelate. The agency advises those with risk factors for cardiovascular disease should not take strontium supplements, and that those taking strontium for longer than 6 months consult their healthcare provider (See the Warning for more information). Extremely large doses (1.5 - 3% of dietary intake) have been reported to decrease bone calcium in animals (Brandi, Am J Med 1993). If you decide to take any form of strontium, make sure to tell your healthcare provider. Since strontium has a higher atomic weight than calcium, it can artificially inflate bone density measurements using dual energy X-ray absorptiometry (DEXA). In cases where 680 mg of strontium (from strontium citrate) was taken daily for more than one year, bone mineral density from DEXA scans was shown to be overestimated by 8% or more, and it can take months to years after discontinuation of strontium to substantially reverse this effect (Mirza, J Nutr Health Food Sci 2016).
Very preliminary research also suggests that boron might be beneficial for osteoporosis, although this has not been studied in clinical trials.
Research suggest that long-term use of melatonin may help increase bone density but, unfortunately, it may also make bone more susceptible to fracture.
Be aware that excessive vitamin A as retinol (but not beta-carotene) may increase the risk of osteoporosis and hip fractures.