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Calcium and Vitamin D Supplementation... the Jury is Still Out
Sorting through the conflicting evidence
My Friends, Bone health stands shoulder to shoulder with cardiovascular health in importance for maintaining quality of life, longevity and independance. There is a wealth of well-done, high-quality scientific study investigating the role of dietary and supplemental calcium and vitamin D in maintaining bone health and reducing fracture risk. However, the findings of these studies are conflicting. Today we objectively review both sides of this debate and help you make the best decisions for yourself! Enjoy! -Carla
Why We Care
Declining bone health has emerged as a very close “second” to cardiovascular disease in the major causes of loss of function, independence, quality of life, and mortality in women over age 50.
Beginning just before menopause onset, the average rate of bone loss is 2% per year. This rate of loss continues for 5 to 10 years, resulting in an average of 10% to 12% loss in bone mineral density (BMD) in the spine and hip, then leveling off to a loss of 0.5% per year. By age 80 years, women have lost an average of 30% of their peak bone mass.
When bone loss is extensive (technically defined as BMD 2.5 standard deviations below the average, Caucasian, young adult reference population), it can lead to osteoporosis, a disease characterized by low bone mineral density and disrupted bone architecture.
The most devastating potential consequence of osteoporosis is fracture, which can lead to a rapid decline in health, loss of mobility and independence, and even increased mortality. Among Caucasian adults in the USA aged 50 years and older, about 50% of women and 20% of men will experience an osteoporotic fracture in their remaining lifetime.
Note: Rates of bone loss and fracture differ among ethnic groups. Caucasians are cited here because current clinical reference ranges are based on the Caucasian population.
What We Know
Childhood and adolescence are critical periods for building bone mass, particularly for females, where 40-50% of their bone mass is achieved in the early teen years. Peak bone mass is achieved in the early 20s. High peak bone mass is a protective factor against the development of osteoporosis later in life.
Genetic factors appear to account for 60-80% of total adult bone mass. Substantial contributions are made by multiple factors that include nutrition, physical activity, smoking, chronic illness, and medications that can impact bone mass.
Adequate calcium and vitamin D intake are among many essential components for building peak bone mass earlier in life including protein, magnesium, phosphorous, potassium, and fluoride are required to support bone formation. Adequate calcium and vitamin D intake is also important during adult life for minimizing bone density loss after peak mass had been achieved.
Because of the importance of calcium and vitamin D for bone health across all age groups, a wealth of studies surrounding calcium and vitamin D intake as well as supplementation has emerged through the decades, particularly in the area of osteoporosis prevention and treatment in menopausal women.
Historically, calcium supplementation has been recommended for menopausal women with “inadequate intake from dietary sources alone”. Two of the leading authorities on bone health, the North American Menopause Society (NAMS) and the Bone Health and Osteoporosis Foundation issued position statements in 2021 and 2022, respectively. Both organizations are aligned in their recommendations based on the “review of the available evidence and expert opinion” that calcium supplementation is recommended in menopausal women “not meeting the daily targets” of 1200mg of elemental calcium daily through dietary sources alone. These recommendations are based on some compelling data from large, randomized control trials (RCTs), observational studies, and meta-analyses.
However, more recently, compelling evidence from additional randomized controlled trials and meta-analyses has shown conflicting results and has called these recommendations into question.
A recent review in Clinical Interventions and Aging by Kelvin Li et al at Tulane University very objectively summarizes the evidence on both sides of this controversy as it pertains to fracture risk, osteoporosis, cardiovascular disease, and kidney stones, among other conditions. Below are a few of the pertinent points:
Osteoporosis: Although many studies show a beneficial effect of calcium supplementation on bone mineral density and fracture risk, several other large studies have shown increases in fracture risk at doses in excess of 1100mg daily and doses <750 IU daily.
Cardiovascular Disease: There is some evidence that dietary calcium and supplementation <1000mg daily in Chinese and European populations has a protective effect on cardiovascular disease. However multiple large RCTs, meta-analyses, and prospective studies have demonstrated an increase in cardiovascular disease and events in individuals consuming >1000mg of calcium daily.
Kidney Stones: Calcium supplementation has been associated with an increased risk of kidney stones in many studies. However, other studies show that adequate dietary calcium intake has beneficial effects on kidney stone formation.
Why the Confusion?
Two major determinants of bone mineral density and fracture risk are genetic predisposition and peak bone mass. These are very difficult to quantify and thus difficult to incorporate into study analysis. This issue, in my opinion, could be the biggest reason for such disparity in the results of even the most well-done studies.
There may be a “therapeutic window” of calcium intake (dietary or supplemental) that has favorable effects with unfavorable effects living outside the therapeutic window.
It is important to be aware that just because calcium intake is important for bone health one cannot, therefore, conclude that taking calcium supplements will be beneficial. Dietary intake of calcium is different from supplemental intake in absorption and bioavailability. Claims that supplemental calcium is equivalent to dietary intake are simply wrong.
The published “target intake” may not be applicable to all populations. Do healthy athletic women who strength-train regularly require the same amount of calcium to maintain healthy bones as sedentary women with chronic disease? Does the use of MHT impact these recommendations? Questions such as these remain unanswered.
Deciding if Calcium Supplementation is Right for You
Assessing risks and benefits: When data are inconsistent, we are left with expert opinion on the interpretation of the data and the best way forward. You will see many compelling and valid arguments on both sides of the debate. This is healthy and a good thing!
Below are my suggestions based on my assessment of this data and how I approach this question for myself as an athletic 52-year-old menopausal woman.
Listen to all sides of the debate with an open mind. Choosing one “camp” over the other leaves out a valuable perspective.
Assess your risk/benefit equation. One tool that is available and well-studied is the FRAX tool for assessing 10-year risk of osteoporotic fracture. This tool is far from perfect as it does not take into account physical activity or nutritional calcium intake, but it is a start!
If you are menopausal with no fracture history, request a bone density scan (DEXA scan). Current guidelines recommend that all postmenopausal women have a DEXA scan at age 65. This recommendation has borne some criticism. The average age of menopause onset in America is 52. Bone loss rapidly declines at menopause onset. Waiting until age 65 leaves more than a decade of bone loss before the need for intervention is evaluated. If you have suffered a fracture at any age, consider bone density testing.
Discuss your risk/benefit profile with your healthcare provider. Given the wide range of physical systems (bone, cardiovascular, kidney, and gut health) that are involved, your healthcare provider is best suited for this discussion.
Assess your own calcium intake. This knowledge will be important for your personal decision-making and discussions with your provider.
If you decide to use supplementation, do not exceed the 1000-1200mg recommendations for combined daily intake from food and supplements. When studies have shown detrimental effects, many times higher intakes were used by the study subjects. More is NOT better!
If you do not get much sunlight, consider vitamin D supplementation. The best source of vitamin D is the sun and inadequate vitamin D levels have been associated with a variety of health risks. But if you live in areas of the world where sunlight is scarce during certain seasons, you may want to consider vitamin D during those times.
What do I do for myself? I do not take calcium supplements, but I take 1000 IU of Vitamin D daily in the winter months. I consume dairy products with a daily intake of 800-1000mg of dietary calcium. I have no other health issues, and perform a variety of weight-bearing exercises as part of my training. My mother has osteoporosis. However, at age 93, she has never sustained a fracture (despite defying my desparate pleas for her to stop shoveling snow!)
Navigating these decisions when there is no clear answer is difficult, but not uncommon - particularly in the area of menopausal medicine. But through self-awareness, education, and discussions with your healthcare provider, you will undoubtedly arrive at the decision that is right for you!