Calcium Requirements and Dietary Sources

Calcium is the most abundant mineral in the human body. The majority is stored in our bones and teeth (about 99%). The remaining 1% is found in our blood, muscles, and extracellular fluid.

Calcium is necessary for more than just healthy bones. It also plays a significant role in blood clotting, muscle contraction, hormonal secretion, and normal nervous system function. We get calcium from dairy products, green vegetables, fortified foods, and dietary supplements. Here's a closer look at how much calcium we need and what happens if we don't get enough.

How Much Calcium Do I Need?

Dietary calcium recommendations vary slightly by age and sex. Certain health conditions make it more difficult to absorb calcium. Furthermore, various lifestyle and eating habits can cause a greater excretion of calcium (for instance, the amount of protein, sodium, phosphorus, and caffeine we consume).

The Recommended Dietary Allowance (RDA) offers a general guideline of how much daily calcium we should aim for to cover our basic needs:

• Ages 1 to 3: 700 mg
• Ages 4 to 8: 1,000 mg
• Ages 9 to 18 ( including pregnant and lactating for ages 14-18): 1,300 mg
• Ages 19 to 50 (including pregnant and lactating): 1,000 mg
• Men ages 51 to 70: 1,000 mg
• Women ages 51 to 70: 1,200 mg
• All adults ages 71 and older: 1,200 mg

The Adequate Intake of calcium for babies up to 6 months old is 200 mg and for 7 to 12 months, 260 mg. For food labels described as the "Daily Values (DV)", which is regulated by the FDA, has a recommendation of 1,300 mg per day for adults and children ages 4 and older.

Sources of Dietary Calcium

Dairy products are naturally high in calcium, but it's also available in certain plant foods and fortified products. If you don't eat cheese and yogurt or drink cow's milk, be sure to include plenty of kale, bok choy (Chinese cabbage) chia seeds, and broccoli in your meal plan. Another natural source of calcium is the small bones in fish. Canned sockeye salmon or whole sardines contain soft bones that are chewable and rich in calcium.

Milk substitutes, including rice milk, almond milk, and soymilk are often fortified with calcium, but check the food label to be sure. In addition, you should shake the bottle or carton because the calcium may end up on the bottom and you may not get the calcium you thought you were getting. Fortified tofu, cereals, and orange juice are additional ways to get non-dairy calcium.

Taking Calcium Supplements

At least 1000 mg of calcium supplementation with 400 IU of vitamin D are often recommended for post-menopausal women to prevent osteoporosis. Menopause causes bone loss because the decrease in estrogen production causes increased breakdown of calcium from the bones, while decreasing the absorption of calcium into the body. In the first years of menopause, there is a rate of bone loss of about 3-5% per year and then about less than 1% after the age of 65. 

If you decide to take calcium and vitamin D supplements, you should tell your doctor or consult with a registered dietitian nutritionist to ensure they won't interfere with any medications or impact other health conditions you may have. Some drugs used for osteoporosis, antibiotics, thyroid disease, convulsions, and diuresis may interact with calcium.

Calcium supplements can be found in two forms: calcium citrate or calcium carbonate. If you've ever taken over-the-counter antacids, you're familiar with the chalky taste of calcium carbonate. While either form can contribute to your total calcium intake, calcium citrate is more easily absorbed. Calcium supplements are often combined with vitamin D to enhance absorption.

The upper limit of calcium intake is as follows:

• Ages 0–6 months: 1,000 mg
• Ages 7–12 month: 1,500 mg
• Ages 1–8 years: 2,500 mg
• Ages 9–18 years: 3,000 mg
• Ages 19–50 years: 2,500 mg
• Ages 51+ years: 2,000 mg

Exceeding these limits can cause high calcium in the blood, kidney insufficiency, kidney stones, calcifications in your veins or arteries, constipation, and interfere with iron and zinc absorption.

Calcium Deficiency Signs and Symptoms

You may be at risk for a calcium deficiency if you avoid dairy products, have a history of an eating disorder or multiple pregnancies, or suffer from malabsorptive conditions, like lactose intolerance. Long-term use of certain medications, such as proton pump inhibitors, can also lead to a calcium deficiency.

Symptoms of low blood calcium (hypocalcemia) may include muscle cramps, lethargy, numbness, and tingling in the fingers, and problems with heart rhythm. However, because blood calcium levels are highly regulated, hypocalcemia is more often the result of an underlying medical condition or medication side effect, rather than a poor intake of dietary calcium.

You're unlikely to notice the symptoms of long-term calcium deficiency in everyday life, but fractured bones or a low score on a bone density test can clue you into an issue. Over time, calcium deficiency can lead to osteopenia, which is a loss of bone density. Osteopenia may progress into osteoporosis, where bones become weak and brittle.

Strengthening your muscles with weight-bearing exercise can improve bone density and reduce your risk of fractures. Certain medications also may be prescribed to improve bone density. Getting enough calcium, vitamin D, and physical activity (especially as a teenager and young adult) are some of the best ways to prevent issues with bone density later in life.