In the last Currents we addressed the importance of vitamin D and its essential importance in calcium absorption. Since then I have received questions about calcium.
Q: How much calcium do I need and which calcium supplement is the best? Also, is there a reason why my pediatrician would want me to limit how much milk my toddler gets?
A: First, let’s talk about why ensuring adequate calcium intake is important. Calcium is the key element in building new bone. It is not produced in the body, although bone regeneration occurs continuously. If one doesn’t have adequate calcium intake, the balance between bone growth and bone degradation shifts to bone loss. This leads to bone weakness and ultimately bone softness in children and osteoporosis in adults. If bones are weak (soft) or fragile (osteoporosis), we are then susceptible to deformities and fractures. Just try to imagine how difficult it would be to walk around without our skeleton. Normally, with aging, humans begin to have bone loss in adulthood, and it accelerates after menopause in women and after 50 in all ages. Calcium is also important for many physiological processes. One is muscle contraction, especially, but not exclusively cardiac muscle.
So now to address how much and what kind of calcium: should a person consume. I will include a table at the end of this answer that addresses dosage recommendations for all ages. There are many excellent dietary sources of calcium, the main source is dairy products (milk, cheese, yogurt, etc.). Milk is an excellent source of calcium and protein; for adults it is recommended to drink low-fat or fat-free milk (to reduce fat intake and reduce cardiovascular risk). Children should, generally, drink whole milk unless there is a family history of obesity or cardiovascular disease. Many health and pediatric agencies recommend AGAINST giving cow’s milk to infants under 12 months due to allergy risk. Also, too much milk that contains lactose (a milk sugar) can increase the risk of tooth decay. Children should be offered milk after meals to promote a balanced intake of other foods. In the U.S. cereals are fortified with calcium and now orange juice is, as well. Other foods high in calcium are: poppy seeds (10gm=150mg calcium), seaweed, carob powder, sardines, almonds, crab meat, tofu and soy milk (calcium enriched).
Milk does NOT have iron, and excessive calcium intake can interfere with iron absorption, leading to anemia. Calcium and iron are both positively charged ions in the blood stream and they compete for binding molecules, so this can alter calcium absorption. Iron will bind more quickly. Adults should take calcium separately from any iron supplement to increase absorption. Also, if children get most of their protein from milk and not red meat, they run the risk of too little iron intake, and this results in anemia.
When considering calcium supplements, the most important factor is the amount of elemental calcium the tablet contains. The elemental calcium is what is actually available for the body to absorb. Please remember from the last issue how important Vitamin D3 is for calcium absorption. Calcium carbonate (TUMS, Vivactiv, etc.) has the most elemental calcium, is less expensive, needs to be taken with food or vitamin C to effectively be absorbed, but has a greater risk of constipation. Calcium citrate (Oscal, Citrical) is absorbed better and doesn’t require an acidic stomach to be absorbed, may be taken on an empty stomach, is less likely to cause constipation, but requires higher doses to get the same elemental calcium.
Genetic risk factors for the development of osteoporosis are: female (especially post-menopausal), white or Asian races (although recent evidence shows all races are at risk), thinness (slight frame) and a family history of fractures. Lifestyle risks include: smoking, excessive alcohol intake, excessive caffeine intake, and lack of regular weight-bearing activity.
Originally published in the May/June 2010 issue of Currents, Vol.XXVI No. 3 "Daily Routine"