What happens when you lack calcium
About 99% of the calcium in your body is in your bones and teeth. The remaining 1% does vital work in the blood, muscles, and nerves: it is needed for your heartbeat, for blood vessels to tighten and relax, and for nerve signals. After menopause, and from about 65 onward, calcium leaves the bones faster, raising the risk of osteopenia and osteoporosis, so a steady intake matters.
How much calcium do you need after 65?
The 2020 Dietary Reference Intakes for Koreans recommend 700 mg a day for men and 800 mg a day for women aged 65 and older. US guidelines are higher: the NIH recommends 1,200 mg a day for women over 50 and men over 70. Surveys suggest many older adults fall short of these targets, so if your meals do not provide enough, a supplement is one option.
Keep it apart from iron and zinc supplements
Calcium can block the absorption of iron and zinc in the gut. For this reason, the NIH and MedlinePlus advise taking calcium (or dairy) and iron or zinc supplements at least 2 hours apart. Calcium is also absorbed less efficiently the more you take at once, so split supplements into doses of 500 mg or less (NIH). Calcium carbonate needs stomach acid and is best taken with food; calcium citrate is absorbed well even on an empty stomach. If you take an iron supplement for anemia, try one in the morning and the other in the evening.
Pair it with vitamin D
Vitamin D is the key that lets your gut absorb calcium. Without enough vitamin D, even a lot of calcium will not be absorbed well. For adults 65 and older, Korea recommends 15 µg (about 600 IU) of vitamin D a day, and some sources suggest 800–1,000 IU for preventing osteoporosis. Choosing a product that contains vitamin D, or getting some sunlight, can help. The often-quoted "15 to 30 minutes of sun a day" is a rough rule of thumb, not an official recommendation; how much vitamin D your skin makes varies widely with season, time of day, and how much skin is exposed.
The downside of too much
With calcium, more is not better. The upper limit for adults over 50 is 2,000 mg a day. Korea's KDCA health portal warns that going over this for a long time can cause constipation and indigestion and raise the risk of kidney stones. A meta-analysis (Bolland et al., BMJ 2010) found about a 30% higher risk of heart attack with calcium supplements, raising concern, but later analyses found no link, so the question remains open. Because this risk has not been seen with calcium from food, the usual advice is to get as much as you can from your diet and use supplements only to fill the gap. It is safest to stay within the recommended range rather than taking extra.
Calcium-rich foods
Good sources include dairy products such as milk, cheese, and yogurt; small fish and shrimp eaten with their bones or shells (such as dried anchovies); tofu; and leafy greens and seaweed. Processed foods such as ham, sausages, and instant noodles are high in phosphorus, which can interfere with calcium absorption, so it helps to cut back on them.
When to talk to a doctor or pharmacist
If you have been diagnosed with osteoporosis or have had a fracture, have a history of kidney disease or kidney stones, or take blood pressure medication, antibiotics, or osteoporosis drugs (bisphosphonates), check with your doctor or pharmacist before starting calcium. If you develop severe constipation, nausea, frequent urination, or extreme fatigue after starting, stop taking it and see a doctor.
Please keep in mind
- This article is based on information checked as of the date shown at the top. New research or changes in official guidelines may change the details, so please use it as a reference rather than taking it as definitive.
- For an accurate diagnosis and advice about your health, please see a doctor in person.