Likely, one of the most important roles of a pediatrician is to maximize health in childhood and positively impact health in adulthood. Bone density is one of the few things that can be maximized in adolescence. By maximizing bone density, we can directly slow and reduce the osteopenia that occurs later in life and the osteoporosis that 10 million Americans struggle with annually.
The physiology of calcium absorption changes throughout life. In early adolescence, the absorption is greater than the elimination. Between 30 and 50 years of age, absorption and elimination are about equal, but as we enter into the sixth decade of life, there is significant bone loss. Studies have shown that bone density is maximized by age 30 years, and little change is made later in life despite supplementation (Eur. J. Clin. Nutr. 1993;47:617-22). The greatest amount of bone loss occurs after the age of 65 years, and fractures after this age are predominantly at cortical sites.
Consumption of the appropriate amounts of calcium can be difficult given the inadequacies of most adolescents’ diet. The recommended daily intake is 1,200-1,500 mg of elemental calcium. But, absorption of calcium is quite variable and is dependent on other factors to be in place for it to be maximized.
The two most common form of calcium are calcium carbonate and calcium citrate malate. Calcium carbonate requires a higher pH of the stomach, and therefore needs to be taken with food. Calcium carbonate is more cost effective but is also associated with more side effects such as gas and bloating. Calcium citrate malate is found in many juices that are fortified with calcium, can be taken with or without food, is better absorbed with chronic conditions, and is thought to be protective against stone formation (J. Am. Coll. Nutr. 1996;15:313-6; Adv. Food. Nutr. Res. 2008;54:219-346).
Common sources of calcium include milk, yogurt, cheese, Chinese cabbage, kale, broccoli, and spinach. Appropriate levels of vitamin D are important to maximize the absorption of calcium, and recent studies have shown that 40% of adolescents are deficient in vitamin D (Arch. Pediatr. Adolesc. Med. 2004;158:531-7; Arch. Pediatr. Adolesc. Med. 2008;162:513-9). Many other adolescents are lactose intolerant or have a milk protein allergy, which also limit the calcium sources. Soymilk has similar levels of calcium, compared with whole milk. Almond-coconut milk has double the amount of calcium, compared with whole milk, so it is a great substitute for those who are lactose intolerant.
Oxalic acids are found in food such as spinach, collard greens, and sweet potatoes, all of which are rich in calcium, but the oxalic acid reduces the absorption of the calcium. Consumption of large amounts of tea and coffee also can reduce calcium absorption, so despite consuming appropriate amounts of calcium, limited amounts become bioavailable.
If using calcium supplements, ingesting less than or equal to 500 mg is better than taking 1,000 mg at once because it is better absorbed (Adv. Food Nutr. Res. 2008;54:219-346). Orange juice, apple juice, and cereals are fortified with calcium so these also are great sources that usually are accepted by adolescents.
Calcium is a critical dietary supplement that is needed for strong bones, metabolic functions, nerve transmission, and vascular contraction and vasodilation. Long-term deficiency will result in disease, and fragility of the bones. Early supplementation and calcium rich diets can ensure maximum bone development, but if parents are not educated on the appropriate delivery, this opportunity could be missed.
An excellent resource is the National Institutes of Health, Office of Dietary Supplements website. This site gives a wealth of information for sources and consumption of calcium. Another excellent resource for parents to use to guide them to make healthier choices is the U.S. Department of Agriculture site, www.choosemyplate.gov. Parents are looking for quick simple ways to maximize their children’s diet and ensure they are getting everything they need to be healthy adults. Becoming familiar with the basics will allow you to give informed advice that will significantly affect their children’s future.
Dr. Pearce is a pediatrician in Frankfort, Ill. E-mail her at pdnews@frontlinemedcom.com.