Calcium and bone health
The health and strength of our bones rely on a balanced diet and a steady stream of nutrients, most importantly, calcium and Vitamin D. Calcium is a mineral that people need to build and maintain strong bones and teeth. It is also very important for other physical functions, such as muscle control and blood circulation. Calcium is not made in the body — it must be absorbed from the foods we eat. To effectively absorb calcium from food, our bodies need Vitamin D. If we do not have enough calcium in our diets to keep our bodies functioning, calcium is removed from where it is stored in our bones. Over time, this causes our bones to grow weaker and may lead to osteoporosis — a disorder in which bones become very fragile.
Postmenopausal women are most vulnerable to osteoporosis. Although loss of estrogen is the primary reason for this, poor lifelong calcium and Vitamin D intake, as well as lack of exercise, play a role in the development of osteoporosis.
Note that men also are at risk for osteoporosis — typically later in life than women — and it is important for them to keep track of calcium intakes, as well.
Calcium needs vary with age. The Food and Nutrition Board (FNB) of the Institute of Medicine of the National Academies provides guidelines on the amount of calcium needed each day.
RECOMMENDED DAILY ALLOWANCE IN MILLIGRAMS (MG)
Life Stage GroupRecommended Daily Calcium Intake
Women and men 9 to 18 years1,300 mg
Women and men 19 to 50 years1,000 mg
Women 51 to 70 years1,200 mg
Men 51 to 70 years1,000 mg
Women and men > 70 years1,200 mg
Pregnant or nursing women 14 to 18 years1,300 mg
Pregnant or nursing women 19 to 50 years1,000 mg
Intakes for Calcium and Vitamin D, 2011 by the National Academy of Sciences, Courtesy of the National Academies Press, Washington, D.C.
Dietary Sources of Calcium
People can get the recommended daily amount of calcium by eating a healthy diet that includes a variety of calcium-rich foods. Milk, yogurt, cheese, and other dairy products are the biggest food sources of calcium.
Other high-calcium foods include:
Kale, broccoli, Chinese cabbage (bok-choy) and other green leafy vegetables
Sardines, salmon, and other soft-bone fish
Breads, pastas and grains
Calcium-fortified cereals, juices, and other beverages.
Good sources of calcium include milk, cheeses, leafy green vegetables, and almonds.
Some foods make it harder for the body to absorb calcium. In particular, sodas and carbonated beverages should be avoided, not just for bone health but also for many nutritional reasons, including preventing obesity. Sodas decrease calcium absorption in the intestines and contain empty calories. Milk, calcium-fortified juices, and water are better beverage alternatives for all age groups.
Although adequate calcium can be obtained through your diet, it is difficult for many people, particularly for those who avoid dairy products. People who are lactose-intolerant or vegetarians who do not eat dairy products have a harder time getting enough calcium from foods.
It is also hard to get enough calcium from the diet during certain times of our lives, such as in adolescence when our bodies require more calcium to build strong bones for life. Postmenopausal women and men older than age 70 also require more calcium to slow down bone loss.
Doctors recommend calcium supplements to those who do not get enough calcium from the foods they eat. Although calcium is sometimes found in multivitamins, it is typically not in significant amounts. Many people need to take separate calcium supplements to ensure they reach the Recommended Dietary Allowance for their life stage.
Not all the calcium consumed — whether through food or supplement — is actually absorbed in the intestines. Research shows that calcium is absorbed most efficiently when it is taken in doses less than 500 mg. Because many calcium supplements come in 500 mg doses, people who require 1,000 mg of supplementation each day should take their doses at separate times. Newer daily slow release formulations of calcium citrate that supply 1200 mg have recently become available.
Most calcium supplements also contain Vitamin D, which helps the body absorb calcium.
Without Vitamin D, our bodies cannot effectively absorb calcium, which is essential to good bone health. Children who lack Vitamin D develop the condition called rickets, which causes bone weakness, bowed legs, and other skeletal deformities, such as stooped posture. Adults with very low Vitamin D can develop a condition called osteomalacia (soft bone). Like rickets, osteomalacia can also cause bone pain and deformities of long bones.
Vitamin D Recommended Dietary Allowance
The FNB recommends 400 International Units (IU) of Vitamin D for infants during the first year of life. The RDA for everyone from age 1 through 70 years is 600 IU. Recent research, however, supports that the body needs at least 1000 IU per day for good bone health, starting at age 5 years.
Many foods contain some Vitamin D, however, few contain enough to meet the daily recommended levels for optimal bone health.
In the 19th and early 20th centuries, children were routinely given cod liver oil for a range of medicinal purposes. When cod liver oil was tied to the prevention and treatment of rickets, Vitamin D was discovered. Soon after, Vitamin D was added to milk — one glass of milk contains about 100 IU of Vitamin D. As a result, parents stopped using cod liver oil. Because today’s children do not drink as much milk as in the past, it is difficult for them to get enough Vitamin D from milk. In addition, other dairy products are not typically supplemented with Vitamin D. Getting enough Vitamin D from what we eat is very difficult.
Although our bodies can make Vitamin D in our skin when it is exposed to good sunlight, it is very important to protect our skin by using sunscreen when we are outdoors. This blocks the excessive UV radiation that can cause skin cancer. Sunscreen does, however, also block our skin’s ability to make Vitamin D. This is why doctors often recommend Vitamin D supplements for both adults and children. The American Academy of Paediatrics recommends that all children — from infancy through adolescence — take Vitamin D supplements.
OTHER KEY NUTRIENTS IN BONE HEALTH
Many other nutrients — most found naturally and at sufficient levels in a typical diet — contribute to bone health and growth.
Phosphorus. A major mineral in the body’s bone crystal, phosphorus is found in dairy products and meat. Vitamin D improves phosphorus absorption in the intestine and kidney.
Magnesium. Primarily found in bone crystals, magnesium improves bone strength. Older adults are more likely to be deficient in magnesium. Calcium supplements that contain magnesium can help.
Vitamin K. Necessary for bone formation and mineralization, Vitamin K also is important for blood clotting, and may assist in channelling calcium directly to the bone rather than the blood vessels.
Vitamin C. Collagen is the main protein in bone, and Vitamin C is necessary for collagen synthesis. Vitamin C is present in citrus fruits and tomatoes and in many vegetables.
Vitamin A. Vitamin A is necessary for cells to differentiate normally and for normal skeletal growth, and also is extremely important for eye health. Vitamin A is available in liver, eggs, butter, green leafy vegetables and carrots. Too little vitamin A is a major cause of blindness worldwide. In contrast, too much vitamin A can cause bone loss and increase the risk of hip fracture. The animal source supplements (retinols) may cause toxicity but plant sources (B carotene) do not. Daily intake of retinols should be less than 10,000 IU.
Source: National Institutes of Health (NIH) (Dietary Supplement Fact Sheet: Calcium): U.S. Department of Agriculture, Agricultural Research Service. 2011. USDA National Nutrient Database for Standard Reference, Release 24. Nutrient Data Laboratory Home Page; Institute of Medicine of the National Academies Dietary Reference Intakes for Calcium and Vitamin D.