That said, there are several supplements that are commonly recommended by conventional doctors and healthcare practitioners that are unnecessary at best, and potentially harmful at worst. Perhaps the best example of this is calcium.
Calcium has become extremely popular to supplement with, especially amongst older women, in the hope that it will prevent osteoporosis. We've all seen the products on the market aimed at the "worried-well", such as Viactiv and Caltrate, suggesting that supplementing with calcium can help maintain bone health and prevent osteoporosis, a serious condition affecting at least 10% of American women. (1) Yet the evidence that calcium supplementation strengthens the bones and teeth was never strong to begin with, and has grown weaker with new research published in the past few years. A 2012 analysis of NHANES data found that consuming a high intake of calcium beyond the recommended dietary allowance, typically from supplementation, provided no benefit for hip or lumbar vertebral bone mineral density in older adults. (2) And a 2007 study published in the American Journal of Clinical Nutrition found that calcium supplements don't reduce fracture rates in older women, and may even increase the rate of hip fractures. (3)
Beyond being ineffective for bone health, calcium supplements are associated with some pretty serious health risks. Studies on the relationship between calcium and cardiovascular disease (CVD) suggest that dietary intake of calcium protects against heart disease, but supplemental calcium may increase the risk. A large study of 24,000 men and women aged 35 - 64 years published in the British Medical Journal (BMJ) in 2012 found that those who used calcium supplements had a 139% greater risk of heart attack during the 11-year study period, while intake of calcium from food did not increase the risk. (4) A meta-analysis of studies involving more than 12,000 participants also published in BMJ found that calcium supplementation increases the risk of heart attack by 31%, stroke by 20% and death from all causes by 9%. (5)
An analysis involving 12,000 men published in JAMA Internal Medicine found that intakes of over 1,000 mg of supplemental calcium per day (from multivitamins or individual supplements) were associated with a 20% increase in the risk of death from CVD. (6) Researchers suspect that the large burst of calcium in the blood that occurs after supplementation may facilitate the calcification of arteries, whereas calcium obtained from food is absorbed at slower rates and in smaller quantities than from supplements. (7) It is also suspected that extra calcium intake above one's requirements is not absorbed by bones, but rather excreted in the urine, increasing the risk of calcium kidney stones, or circulated in the blood, where it might attach to atherosclerotic plaques in arteries or heart valves. (8)
The Office of Dietary Supplements at the National Institutes of Health has compiled a comprehensive review of the health risks associated with excess calcium, particularly from supplementation. (9) For example, daily supplementation of calcium at 1000 milligrams is associated with increased prostate cancer risk and an increase in kidney stones. (10) Additionally, a recent Swedish study reported a 40% higher risk of death among women with high calcium intakes (1400 mg and above), and a 157% higher risk of death if those women were taking a 500 mg calcium supplement daily, compared to women with moderate daily calcium intakes (600-1000 mg). (11) A Consumer Lab analysis found that many of the calcium supplements they analyzed failed quality testing, including lead contamination and mislabeled contents. (12)
Even if you're not popping a calcium supplement every morning, that doesn't mean you're not consuming supplemental calcium. Many commonly consumed foods in the United States are fortified with supplemental forms of calcium, including orange juice, breakfast cereals, non-dairy milks, breads, instant oatmeal, graham crackers, and other staples of the standard American diet. While these foods are typically eliminated on a whole foods or Paleo diet, it's important to pay attention to whether some of your fridge staples, such as commercial almond, coconut, or other non-dairy milks, are fortified with calcium. You may be consuming more supplemental calcium than you realize. In addition, many multivitamins contain significant amounts of calcium - so be sure to check the label if you're taking one. (This is one reason I advise against multivitamins in most cases: they contain too little of the right nutrients and too much of the wrong ones.)
If you're concerned about maintaining healthy bones, you're better off ensuring adequate calcium intake from foods like dairy products, sardines, salmon, dark leafy greens and bone broth. 600 milligrams per day from food (approximately two servings of dairy products or bone-in fish) is plenty to maintain adequate levels of calcium in the body. Healthy bone formation also depends on vitamin D and vitamin K2, both of which regulate calcium metabolism. There are also other minerals besides calcium involved in supporting bone health, such as silica and magnesium. If you have adequate levels of these nutrients, and regularly perform weight-bearing exercise, there is no need for calcium supplementation, which will likely do more harm than good.
Well as with everything there's Yin and there's Yang. If Calcium is Yin then Magnesium is Yang. Too much of Calcium will have severe consequences for bones and knees. It's imperrative to balance out Calcium with Magnesium, if you find yourself having to have a higher dosage of Calcium than people most.