Welcome back to the discussion on bone health! In the previous issue of Food Insight, the article, "Spring for Stronger Bones" addressed the role that physical activity plays in keeping bones healthy and strong. This issue continues the discussion as it pertains to nutrition. Many people know that adequate calcium intake is a crucial building block of strong bone tissue, but would it surprise anyone to know that the large majority of Americans (both men and women) consume insufficient calcium on a daily basis? In addition, nutrients other than calcium are also responsible for bone health.

May is National Osteoporosis Awareness and Prevention Month in the United States. Following up on that event, there is no better time to increase awareness of the risks associated with the development of osteoporosis so that you can prevent it from happening to you. Let’s take a closer look at what nutrients we need to keep our skeletons strong for all seasons.

More Bone Basics

Calcium and vitamin D are the two key nutrients involved in building and maintaining strong bones. Calcium receives the most media attention, but vitamin D is equally important because Vitamin D and calcium work together.

Calcium

Calcium circulates in the blood and is important in a number of bodily reactions, such as blood clotting, heart beat consistency, and nerve transmission. To carry out these functions, our bodies prefer to use the calcium that we consume from our diets. If we do not consume enough calcium, it will be taken from storage in our bones. Even small reductions in blood calcium concentrations can trigger calcium loss from bone. One of the most effective ways to protect our bones is to get plenty of calcium in the foods and beverages that we consume daily.

Vitamin D

Vitamin D plays a supporting but essential role in bone building: it helps the body absorb and deposit calcium in bones and teeth. Without vitamin D we cannot use the calcium that we get from our foods and supplements. Our skin makes vitamin D, provided we receive adequate exposure to sunlight. However, experts now caution against relying just on sun exposure because the source of vitamin D is dependent on the variability of nature as well as the variability of our bodies. The use of sunscreen also inhibits the skin’s ability to manufacture vitamin D.

Experts worldwide have focused anew on vitamin D in the 21st century, partly because there appears to be increases in the rates of vitamin D deficiency and vitamin D deficiency-related rickets. (Rickets is a vitamin D deficiency disease that affects the young during skeleton growth and is caused by failure to assimilate and use calcium and phosphorus usually because of inadequate levels of exposure to sunlight or inadequate vitamin D intake.)

"The groups most likely to be vitamin D deficient are the elderly and dark-skinned people," explains Connie M. Weaver, Ph.D., professor and head of the Food and Nutrition Department at Purdue University. "The elderly cannot synthesize as much vitamin D and are frequently not spending time outdoors. Dark-skinned people also cannot synthesize the required amount of vitamin D in their skin," adds Weaver. Similarly, individuals who live where the winters are long, or where cloudy days are the norm, may also need to rely on dietary sources of vitamin D.

In the United States, fortified foods and dietary supplements provide most of the vitamin D in our diets, since the foods that are naturally high in vitamin D (e.g., sardines, herring, liver, and egg yolks) are not usually consumed in adequate amounts. Fortified milk and dairy products, breakfast cereals, and recently, calcium-fortified fruit juices are the foods most commonly enhanced with vitamin D.

Strong Bones at Every Age

Children and Teens: The easiest way to prevent osteoporosis later in life is to ensure adequate calcium and vitamin D intake throughout childhood, adolescence, and early adulthood.

In 2003 the American Academy of Pediatrics (AAP) began recommending that all infants and children receive 200 international units (IU) per day of vitamin D, starting in the second month of life, to help prevent deficiencies that might arise from exclusive breastfeeding. Although breastfeeding remains the preferred type of feeding for infants, the low vitamin D content of human breast milk in combination with low levels of sun exposure may predispose infants to vitamin D deficiencies. For infants who receive formula feedings of at least 17 ounces per day, supplements are not necessary, as all infant formulas sold in the United States contain adequate amounts of vitamin D.

According to data presented at the 2001 National Institutes of Health Consensus Development Panel on Osteoporosis Prevention, Diagnosis and Therapy, only 25 percent of boys aged 9 to 17 years were found to consume the recommended amount of calcium, and only 10 percent of girls this age meet the recommendation. Older children can be given chewable multivitamins that contain 200 IU of vitamin D, and infants can be given liquid vitamin drops.

Calcium deficiency is a particular concern among growing teenagers because teens tend to stop consuming dairy products. Research also shows that many teens do not get enough vitamin D, and AAP suggests supplements for individuals in this group.

Encouraging children and teens to drink milk with their meals is one of the best ways to help ensure that they obtain adequate amounts of calcium and vitamin D. However, milk is not the only beverage option that can be used to ensure consumption of adequate amounts of calcium. For example, some brands of orange juice are fortified with calcium and vitamin D. Other calcium-rich foods like cheese, yogurt, and fortified snacks also add variety to the diet. Fortified and flavored milk beverages as well as powdered beverages prepared with milk are also good sources of dietary calcium.

Twenties, Thirties, and Forties: In the United States, 9 out of 10 women and nearly two-thirds of the men do not get sufficient calcium. Be sure to eat enough calcium and vitamin D-rich foods throughout your 20s because the ideal is to build up optimal bone mass by the time you are 30 years of age. After that, bone mass generally does not increase. However, there’s still plenty of time left to make changes that will help maintain your bone mass, reduce bone loss, and reduce your risk of osteoporosis. Consider taking a multivitamin. Be sure to check that it contains some vitamin D and calcium. Calcium chews also provide a quick and tasty way to obtain calcium and vitamin D. Consult your healthcare provider with any questions or concerns.

Fifty Plus: If you have done a good job of taking care of your bones so far, then you’ve won half the battle already. If not, it’s still not too late to make amends. Ask your healthcare provider about supplements. Your calcium and vitamin D requirements are somewhat higher after age 50, and your body does not absorb calcium as efficiently as it did when you were younger. Continue to eat a diet rich in both calcium and vitamin D, but don’t be surprised if you need supplements to make up the difference.

Use the chart below to see whether you and your loved ones are getting adequate amounts of calcium and vitamin D on a daily basis.

For Calcium Dietary Reference Intakes:
http://www.iom.edu/Object.File/Master/7/294/0.pdf

For Vitamin D Dietary Reference Intakes:
http://www.iom.edu/Object.File/Master/7/296/0.pdf

For Additional Information:

Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, National Bone Health Campaign
http://www.cdc.gov/nccdphp/dnpa/bonehealth/index.htm

National Osteoporosis Foundation
http://www.nof.org

National Institutes of Health, Osteoporosis and Other Related Bone Diseases
National Resource Center
http://www.osteo.org/

Physical Activity, Nutrition, and Bone Health,
International Food Information Council Foundation
http://ific.org/publications/reviews/bonehealthir.cfm

Eat for Strong Bones

Got Dairy? Dairy products are by far the most common food sources of calcium. Milk, cheese, yogurt, even pudding made with milk—are good sources of calcium, and products made from fluid milk also contain vitamin D. Milk, which has 300 milligrams (mg) of calcium per 8-fluid-ounce serving, and other dairy products are the primary sources of calcium that can be well-absorbed by the human body. In the United States fluid milk is also fortified with vitamin D, which makes dairy products doubly nutritious for bones.

Veggies Too! In addition to certain vegetables (such as broccoli, kale, and collard greens), tofu, almonds, and fish with bones (such as salmon and sardines) are sources of calcium. Be aware, however, that it can take large quantities of these foods to equal the amount of calcium you would get in eight fluid ounces (1 cup) of milk. For example, it takes about four cups of cooked broccoli to equal the amount of calcium you would get in a cup of milk. But, when it comes to obtaining sufficient calcium, every little bit helps.

Don’t Do Dairy? Fortified milk alternatives are a good choice for some people who don’t consume dairy products. Juices, breads, cereals, and snack foods are just some of the calcium-fortified foods you can find in a typical supermarket. In addition, increasing numbers of foods and beverages are fortified with vitamin D. Read the food labels to check whether the product you are buying is fortified with calcium and vitamin D because not all brands are enhanced. Incorporate some of these products into your diet, especially if you "don’t do dairy."