The Source - Nutrition Note: The Bare Bone Facts on Calcium and Phosphorous

The Source - Unbiased and Understandable Life Science Information by Dr Theresa M. Craig

Nutrition Note: The Bare Bone Facts on Calcium and Phosphorous

When we think of the nutritional needs for calcium and phosphorous, we automatically think of our bones and their intimate association with these two minerals. It is true that our bones are the major reservoir of calcium and phosphorous in the body. In fact, 99% of the body’s calcium can be found in the 206 bones of the body, as is 85% of the body’s phosphorous. Adequate consumption of calcium earlier in one’s life is paramount to allow for peak bone mass formation. Peak bone formation is thought to occur near a person’s mid 20’s and further bone mineralization accumulation can occur into a person’s 30’s. Enhancing peak bone mass mineralization is thought to help later in life in preventing osteoporosis (see insert box for important information on osteoporosis).

The remaining 1% calcium is very tightly controlled by the body. When this calcium level falls, bones act as a source of calcium allowing levels to remain stable. As a result, blood calcium levels are not a good indicator of overall calcium status in the body. In addition, only over time can a change in bone calcium levels be seen. These two facts have resulted in great variation in recommended levels of calcium by various countries. For example in Thailand, the recommendation for persons over 75 years old is 400 mg/day compared to 1,000 mg/day in the Netherlands⁷. Table 1 ^{7 8} shows the Recommended Dietary Allowances (RDA) as recommended by the United States and the Recommended Dietary Intakes (RDI) as recommended by Australia ^{7 8}. As these two countries divide requirements on different ages, some averaging has been used in Table 1 for comparison purposes. Note how the two recommendations are very similar.

Table 1
Recommended Dietary Allowance (RDA) and Recommended Dietary Intakes (RDI) for Calcium and Phosphorous

.	Calcium mg/day		Phosphorous mg/day
.	RDA	RDI	RDA	RDA
0 – 6 months	400	500	300	150
6 months – 1 year	600	550	500	300
1 – 10 years	800	770	800	670
11 – 24 years*	1200	957 males 864 females	1200	1064
25 – 50 years	800	800	800	1000
50 + years	800	1000	800	1000
Pregnancy/lactating	1200	1350	1200	1200

* greatest discrepancy between RDI and RDA levels

The remaining 1% calcium in the body is very important. Every time a muscle in the body moves, calcium is being used. Nerve transmission, blood clotting, and the transport of material across the body’s various membranes are related to this small but important level of calcium.

The remaining 15% of the phosphorous is found in soft tissues like muscle, organs, blood, and other fluids⁹. Phosphorous and its associated chemical bonds are essential for changing food energy into metabolic energy that can be used by the body. Phosphorous is also found in the bonds that hold DNA and RNA (ribonucleosides) together and give them stability. Phosphorous is found in many enzymes that control the chemical reactions in the body.

Typically, women do not meet their calcium requirements. This is due to many factors including the perception that all dairy products are fattening². By choosing low fat dairy products, the required calcium is obtained without additional fat. Not all leafy green vegetables are high in available calcium. For example, spinach which has a calcium level of 28 mg/serving of calcium has only a 5% absorption rate after ingestion. This is because the calcium is bound to oxalate¹. Dark green vegetables such as broccoli, kale, turnip greens, mustard greens, and collard are good sources of calcium ^{7 9}. Skipping breakfast and the lack of low fat dairy products at fast food outlets is also thought to contribute to the low intake of calcium². Table 2 below illustrates sources of Calcium and Phosphorous.

Table 2
Sources of Calcium and Phosphorous ^{4 7}

Calcium			Phosphorous
Dairy Products Legumes Nuts (i.e. almonds) Seeds (i.e. sesame seeds) Dark green vegetables Soft bones of fish (salmon, sardines, herring) Limed pressed tortillas Calcium precipitated tofu			Dairy Products Legumes Nuts Eggs Meats Fish

For most people, obtaining adequate amounts of phosphorous is easily achieved with normal diets. However, groups at risk of phosphorous deficiency are preterm infants, recovering alcoholics, diabetics recovering from ketoacidosis, recovery phase of renal failure, and starving people when first re-fed⁸.

The need for both calcium and phosphorous can not be under estimated. Their roles in the body are very important to maintaining proper health and cannot be all covered in this short article. Your lifetime calcium intake has long-term consequences on your health, and this need must be addressed everyday of your life.

Osteoporosis

Osteoporosis is defined as the loss of bone density and structural integrity, which leads to weak and fragile bones that easily break. The loss of bone is gradual with no warning signs given until the disease is advanced. It is known as the "silent disease". People do not realize they have the disease until a fall or bump causes a fracture, or severe back pain indicates a collapsed vertebra. Worldwide within a woman’s lifetime, she will have a 30 – 40% chance for a fracture due to osteoporosis. Although more common in women, men also experience osteoporosis with a 13% chance of fractures within their lifetime⁶.

Osteoporosis is estimated to cost the United States $17 billion dollars in 2001 ($47 million per day) in hospital and nursing home direct expenditures³.

Prevention occurs best before the age of 35 through living a healthy lifestyle, and minimizing the risk factors within your control. Risk factors of osteoporosis are as follows ^{3 5}.

Postmenopausal women
Women with premature menopause
Family history of osteoporosis
Use of certain medications ( i.e., glucocorticoids or some anticonvulsants)
People with slim body build
People with anorexia
Lifetime diet poor in calcium and vitamin D
Inactive lifestyle
Low testosterone levels in men
Smoking
Excessive alcohol consumption
Age (increased risk with older age)

Treatment for osteoporosis consists of proper nutrition, exercise, and prevention of falls. A bone density test can predict osteoporosis prior to a fracture. Medication maybe indicated by your physician to slow or stop the progression of bone loss³.

Reference for Nutrition Note: The Bare Bone Facts on Calcium and Phosphorous

Brody, T. Nutritional Biochemistry. 1994. Academic Press, New York
Brown, J. E. 1999. Nutrition Now. 2^nd ed. West/Wadsworth Publishing. Ca
Fast Facts on Osteoporosis. 2002. National Institutes of Health Osteoporosis and Related Bone Disease ~ National Resource Centre.
Hamilton, E. M. N., Whitney, E. N., and Sizer F. S. 1979. Nutrition: Concepts and Controversies.3^rd ed. West Publishing, St. Paul
International Osteoporosis Foundation. 2003. The Facts about Osteoporosis and its Impact. www.osteofound.org/press_centre/fact_sheet.html
Melton. L. J., et al. 1992. Perspective. How many women have osteoporosis? J Bone Miner Res 7:1005- 1010.
RDA. Recommended Dietary Allowances. 1989. National Academy of Science, Washington, D. C.
RDI. Recommended Dietary Intakes for use in Australia. 1985 for Calcium. 1986 for Phosphorous. National health and Research Council. www.nhmrc.gov.au/publications/diet/n6p4.htm
Weigley E. S., Mueller, D. H and Robinson, C. H. 1993. Robinson’s Basic Nutrition and Diet Therapy. 8^th ed. Prentice Hall, Columbus, Ohio

Back to Newsletter Archive