May 14, 2007

Calcium is a nutrient that is essential for life - where would your teeth, bones, hair and skin be without it? The impact of calcium on bone health is well-established, but did you know that calcium plays a role in managing high blood pressure (hypertension) and weight control? Calcium, as well as essential minerals, magnesium and potassium are believed to be to the basis for the success of the DASH diet (Dietary Approaches to Stop Hypertension - see below for more information on this) in reducing blood pressure as well as making weight control easier.

The dietary calcium intake of many Asians is below recommended levels, often amongst the groups that need it most - infants, adolescents, pregnant and lactating women and the elderly  The traditional Asian diet contains some good sources of calcium but research is indicating that additional calcium-rich foods and/or supplements may be a wise regular addition to the diet, to achieve optimal intake levels. This is applicable both for the younger generation, laying the foundation for good health, and for older generations to slow some aspects of the ageing process. In other words, achieving adequate dietary calcium intake is a goal to be sustained throughout your life.

What is Calcium?

Calcium is the most plentiful mineral found in the human body, accounting for 1.5-2% of an adult's total body weight. The teeth and bones contain the majority of the body's calcium, about 99%. Calcium in these tissues is concentrated in the form of calcium phosphate salts. Nerve cells, body tissues, blood, and other body fluids contain the remaining calcium.

What Does Calcium Do for You?

It is essential for the formation and maintenance of healthy teeth and bones. The bones incorporate calcium into their structure as they are formed. Like other tissues in the body, bone tissue is continuously being reabsorbed and re-formed, and a constant supply of calcium is needed to maintain this cycle. This is especially the case during periods in life when growth of bones and teeth is occurring. The most critical times are during pregnancy and breast feeding, closely followed by the adolescent years when boys and girls typically 'shoot up' in height and bones are increasing in size at a very fast rate. The third most important age group is younger children, whose bones and teeth are also growing at a rapid rate.

Calcium is needed for many other functions including blood coagulation, transmission of nerve impulses, muscle activity, normal heartbeat, stimulation of hormone secretion, and activation of enzyme reactions.

Calcium and Your Health

Your body needs a balanced diet containing both macronutrients (energy, protein, fat and carbohydrate) and micronutrients (vitamins and minerals) for its normal development and function. Calcium is an essential mineral needed in greater amounts than any other micronutrient, and plays a key role in three important functions:

Improving Bone Health

Calcium is a major structural component of bone tissue, and the skeleton also acts as a reservoir of calcium for maintaining calcium levels in the blood. The link between calcium and bone health has been demonstrated in studies across almost all age groups: Adequate dietary calcium in childhood and adolescence has been repeatedly proven to improve bone density; a three-year study in healthy young women aged 30 - 42 years showed that enriching the diet with dairy foods which are rich sources of calcium, prevented bone loss in the spine, compared with control subjects who did not increase their dietary calcium intake; finally, research has also demonstrated that boosting calcium and vitamin D intake reduces rates of bone loss and fracture rates in older male and female adults.

Of very great relevance to the Asia region is the mounting evidence that Asians are not genetically shorter than Caucasians and that Asian children whose diet through childhood contains optimal quantities of all essential nutrients, including calcium (which historically was often deficient), will grow to similar heights by adulthood as their western counterparts.

Managing Weight

It has also been found that increasing dietary calcium intake, especially in the form of dairy foods, can play a role in weight management. It is not yet clear how including more calcium-rich in the diet can help in weight management, but studies to date indicate that including more high calcium foods in your diet can make a very positive as well as tasty change to your regular diet. Because overweight puts you at greater risk of developing high blood pressure and many other serious health risks such as heart disease and stroke, including low fat calcium-rich foods 2-3 times a day in your diet, as part of your personal weight management strategy, will also indirectly help to reduce these risks.

Controlling High Blood Pressure

Regularly including low fat calcium-rich foods in your diet can also directly improve management of high blood pressure. Increased calcium intake though all routes appears to have this effect, and perhaps unsurprisingly the benefits gained are greatest for those with the lowest calcium intakes before treatment.

For those who prefer to think in terms of foods, rather than nutrients, the DASH Diet has been demonstrated to be very effective in treating and preventing high blood pressure. The DASH diet emphasizes plenty of whole grains, fruits, vegetables and low-fat dairy foods; advises limiting salt, sodium and alcohol intake; and encourages regular physical activity. Additionally, DASH can also help in maintaining a healthy weight since the diet is low in fat and high in calcium. 

How Much Calcium Do You Need?

Calcium requirements are determined primarily by the balance between the amount that is absorbed from the diet by the body, and the amount that is lost from the body through normal excretion and tissue repair and replacement. In adults, total calcium absorption needs to match the rate of all losses from the body if bone mass is to be preserved and the risks of disease and fracture minimized. In children and adolescents, extra is needed to cover the requirements of skeletal growth. Increased amounts are necessary during specific periods such as pregnancy, breastfeeding and after menopause, when the body is undergoing demanding changes. United Nations Food and Agriculture Organisztion and the World Health Organisation (2002) Recommendations for Daily Calcium Intake are outlined below:  

Source: International Osteoporosis Foundation website, www.iof.com

Which Foods Should You Eat?

Dairy products are one of the most concentrated sources of calcium. Milk and milk products, including yogurt, buttermilk, milk curds such as paneer and cheese are rich sources of calcium and are also very well absorbed. 2 or 3 servings of dairy foods, (a 200 ml glass of milk would be equivalent to one serving), would ensure that virtually all children and adults would achieve their daily required calcium intake.

Leafy, green vegetables such as broccoli, spinach, kale, mustard greens, bok choy or Chinese cabbage are typical sources of calcium in the Asian diet, well absorbed by the body. Fish eaten whole such as anchovies or ikan bilis, as well as canned sardines or salmon are also excellent sources in the traditional Asian diet. In addition, legumes such as soy, nuts, beans can provide useful contributions, even though calcium in these is a little less well absorbed than from other foods.

Processed soy products are common in the Asian diet, ranging from the Indonesian tempeh, the Chinese dried bean curd sticks and the Japanese natto or fermented soy beans. Calcium-enriched tofu in its many shapes and forms, miso and soy bean curd and soy milk are rich sources of calcium,  but be sure to check on the packet that the brand you are choosing is one of the high calcium ones. You can now also find many newly developed calcium-fortified soy products such as ice cream and desserts, to further increase your calcium intake.

An increasing range of high calcium foods are now becoming readily available in Asia. As well as dairy and soy products, a wider variety of produce, such as nuts and vegetables, calcium-fortified products such as orange juice and cereal bars are also convenient, tasty sources that can help to boost calcium content of Asian diets 

Source: USDA Agricultural Research Service, Nutrient Data Laboratory

Your Health in the Long Term

Having sufficient calcium in your diet is necessary to your overall good health now and in the future. A balanced, varied diet is also highly recommended, because this will enable your body to make the best use of the calcium in the foods eaten. Thus the very familiar but tried, tested and proven advice to eat a diet rich in fruits, vegetables and whole grains, as well as low fat dairy products or calcium-enriched soy products, with reduced levels of saturated fats and added sugars, plus moderate quantities of lean meat and fish and eggs will also contribute to optimal calcium nutrition. 

References:

1. International Osteoporosis Foundation website: www.osteofound.org

2. USDA Agricultural Research Service, Nutrient Data Laboratory: http://www.nal.usda.gov/fnic/foodcomp/Data/

3. Zemel, B. Michael, Calcium Modulation of Hypertension and Obesity: Mechanisms and Implications, Journal of the American College of Nutrition, Vol. 20, No. 5, 428S - 435S (2001)

4. WHO Child and Adolescent Health and Development: http://www.who.int/child-adolescent-health/

5. McCarron & Reusser (1999) Finding Consensus in the Dietary Calcium-Blood Pressure Debate: Journal of the American College of Nutrition, Vol. 18, No. 90005, 398S-405S (1999)