Last week’s post on “nutritional dark matter” – the concept that food is more than the sum of its macronutrients and micronutrients, and its effects on health cannot be predicted from its composition – prompted me to look up how many Australians are taking calcium supplements. Remarkably, despite the fact that the Royal Australian College of General Practitioners and Healthy Bones Australia (formerly Osteoporosis Australia) recommend against routine calcium supplementation on the grounds that it’s of no benefit except in people with calcium deficiency (which is vanishingly rare in non-institutionalised individuals), one in ten community-dwelling women over 65 reports popping calcium pills.
Because calcium is a mineral found abundantly in our food supply, the conventional wisdom for many decades was that raising calcium intake, through either higher intake of dairy products or supplementation, was at worst harmless, and at best beneficial to our bones.
That conventional wisdom turned out to be very wrong. Here are some disturbing facts on calcium supplements:
#1 Calcium supplementation raises the risk of renal calculi (kidney stones) by about 20 per cent.
The pain caused by kidney stones is so excruciating, it is often described as one of the strongest pain sensations humans can experience – and the closest that men (who comprise 80 per cent of kidney stone cases) ever get to the pain of childbirth!
Taking calcium supplements was found to raise the risk of kidney stones by 20 per cent in the Nurses’ Health Study I cohort and by 17 per cent in the Women’s Health Initiative trial. On the other hand, a higher dietary intake of calcium was found to be protective against kidney stone development in Nurses Health Study participants.
#2 Calcium supplements substantially raise risk of heart attack.
A meta-analysis of 15 randomised, placebo-controlled trials of calcium supplementation, involving over 20 000 patients aged 40+ who were followed up for a year or more, found that patients allocated to calcium supplementation had around a 30 per cent greater risk of suffering a heart attack.
Patients with renal failure (who are often given calcium supplements to lower their blood phosphate level) are at even higher risk: calcium pills dramatically accelerate coronary artery calcification, contributing to the very high cardiovascular death rate in this population.
#3 Taking calcium supplements nearly doubles your risk of admission to hospital with an acute abdominal condition.
A review of adverse events from seven randomised clinical trials of calcium supplementation found that taking calcium supplements caused a plethora of gastrointestinal complaints. Constipation, excessive abdominal cramping, bloating, severe diarrhoea or abdominal pain, upper gastrointestinal events and gastrointestinal disease were over 40 per cent more likely to afflict people taking calcium pills than those taking placebo.
Most worryingly, those on calcium pills were 92 per cent more likely to require hospitalisation for an acute gastrointestinal condition, with many of these individuals being initially admitted to a coronary care unit because their symptoms mimicked a heart attack.
#4 Elderly people have a higher risk of dying when they take calcium supplements.
A randomised, controlled trial conducted on 602 elderly, frail, institutionalised Australians found that those given 600 mg of calcium per day plus daily sunshine exposure had a 47 per cent increase in total mortality and a 76 per cent increase in cardiovascular mortality compared to those receiving sunshine exposure alone.
#5 Taking calcium supplements does NOT reduce fracture risk.
This is the real kicker. The aggressive marketing activities of calcium pill manufacturers have managed to persuade almost the entire populace – including, sadly, most doctors – that boosting calcium intake is the most important step we can take to lower the risk of bone fractures. Yet a systematic review and meta-analysis of randomised controlled trials (RCTs) of combined calcium and vitamin D supplementation, involving eleven RCTs with 43,869 participants, found no reduction in the risk of clinical fractures (i.e. those that actually cause symptoms, as opposed to fractures that are only detected via screening x-rays). Calcium monotherapy (i.e. without vitamin D) is similarly unimpressive for fracture prevention.
What about dietary calcium intake?
Higher dietary intake of calcium doesn’t prevent fractures either. In fact, in a study of 61 433 Swedish women followed up for 19 years, those with the highest intake of calcium had a 19 per cent higher risk of suffering a fracture than those with a mid-range intake. Total dairy product intake is also not protective against fractures. While higher milk consumption is associated with an elevated risk of hip fracture, fermented dairy products – yoghurt and cheese – are associated with decreased risk… although it’s possible that these divergent results may be due to confounding by socioeconomic status (that is, yoghurt and cheese are more expensive than fluid milk, so wealthier people can afford to eat more of them, and wealthy people also have fewer hip fractures).
Vegetarians and vegans have been found to have higher fracture rates than omnivores, but only if they have an average daily calcium intake of less than 525 mg – which is an indicator of low dietary quality. And in the Nurses’ Health Study population, recent consumption of a high-quality plant-based diet was associated with 21 per cent lower risk of hip fracture in postmenopausal women, while an unhealthy plant-based diet was associated with 28 per cent higher risk. Junk food vegans, beware!
The bottom line
Calcium supplements are neither safe nor effective. They’re only indicated for people with a dietary deficiency of calcium, and if your diet is deficient in calcium, it’s by definition a low quality diet which is deficient in pretty much every other nutrient. It’s also almost certainly supplying excessive quantities of food components that you shouldn’t be eating, such as sugar, refined starch and food additives. The solution to this problem is not to pop a calcium pill, but to improve your overall dietary quality.
Calcium supplements are just another example of the nutritional reductionism that has rendered our population overfed, undernourished and chronically ill. While there is always a handful of edge cases in which calcium supplementation may be necessary because of extraordinary circumstances, the vast majority of people who are currently taking calcium supplements would be well advised to skip the pill, and eat real food instead.
There are proven, safe and effective ways to build your bone health and decrease fracture risk, without the scary side-effects of calcium supplements! To find out more, read my article The top 5 tips for building strong, healthy bones.
