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Calcium Supplements — Too Much of a Good Thing?

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a blog by Breea Johnson, MS, RD, Pulling Down the Moon, October 22, 2010

A recent meta-analysis showed that people who take calcium supplements (about 500 mg per day) have a 30 percent increased risk of myocardial infarction, otherwise known as a heart attack. While some people may be shocked (What? We need calcium and lots of it!), some are skeptical, and many medical practitioners who know a lot about bone health are not surprised.

Bone health requires many nutrients beyond calcium, specifically vitamin K, vitamin D, boron, strontium, magnesium, vanadium and even omega-3 fatty acids. While calcium is a key component in bone health, taking it without its accompanying nutrients may cause mineral imbalances and inadequate mineral absorption — conditions that could lead to calcification of the arteries — and an increased risk of heart attacks.

While these recent findings are not completely conclusive, they may be causing some people to re-examine their use of calcium supplements. Here at Pulling Down the Moon, we wanted to take it a step farther and look into the relationship between calcium supplements and fertility.

Too Much Calcium

A high intake of calcium (without accompanying nutrients) can interfere with the absorption of other nutrients, such as:

  • iron,
  • magnesium, and
  • vitamin D.

All of these nutrients are critical for fertility.

High levels of calcium are known to prevent iron absorption, and iron is critical in blood development, oxygenation and circulation. Iron is also a crucial nutrient for thyroid function, which we know is essential for fertility, and high doses of calcium can interfere with thyroid function.

Magnesium is known to help with estrogen metabolism, and high intakes of calcium without adequate magnesium may cause critical mineral imbalances.

Vitamin D is essential for bone health because it helps retain calcium in the bones. We know that Vitamin D is also important for fertility, with studies showing that women with higher levels of Vitamin D in follicular fluid have increased IVF outcomes. Taking calcium without vitamin D may suppress levels of this vitamin.

Examining Calcium Intake

A lack of calcium in the diet is a concern among women, especially those with a family history of osteoporosis or bone diseases. In addition, recent research linking low-fat dairy with ovulatory infertility has many women who are trying to conceive limiting their intake of low fat milk, yogurt and cheese. For this reason, women may wonder how they will get enough calcium in their diet while they are trying to conceive.

Dairy can be a great source of calcium, but it is not the only source. There are plenty of non-dairy calcium sources — such as green leafy vegetables, nuts, and seeds — that give you ample calcium if eaten daily.

At the Moon, we are seeing a new trend of women decreasing their intake of dairy and adding a calcium supplement on top of their prenatal vitamin instead. For reasons mentioned earlier, this “calcium blast”may not be the best strategy for fertility. If a woman is limiting dairy, educating her about alternative sources of dietary calcium is key. A good prenatal vitamin will also have a balanced vitamin and mineral profile (including calcium) for optimal bone health.

At the Moon, we carefully assess our patients’ calcium intake from dietary sources AND their prenatal vitamins before considering any additional supplementation. Upon achieving pregnancy, we assess calcium intake again to ensure it is adequate for mom and baby.

For more information about nutrition and fertility or to maximize nutrients for optimal fertility and bone health, please contact Pulling Down the Moon at (312) 321-0004 or visit

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