Why we need adequate calcium intake

Melissa Southern-Garcia, Dietitian, Jakarta, SouthernDietitian@yahoo.com

In many of my previous articles I have mentioned the importance of calcium. I have also received several follow-up questions on the subject so this week I would like to focus on some of the benefits and common questions associated with calcium and calcium supplementation.

Calcium is the most abundant mineral in the body by weight, and it is also one of the most diverse. It plays a key role in a broad range of chemical processes and, as is commonly known, it is essential to healthy teeth and bones.

Some of the most abundant food sources of calcium are dairy products such as milk, cheese, and yogurt. It is important to remember that most adults should choose skim or low-fat dairy options to avoid the saturated fat content. The only difference between skim milk and full cream is the amount of fat and calories. The calcium and protein content of both types of milk is the same.

For those who are unable to tolerate dairy products, soy may be a good alternative. Although soy milk is not naturally a good source of calcium, many packaged versions are enriched with up to 30 percent of the average daily recommended allowance of calcium. Read your label to make sure the soy milk you are purchasing is enriched with calcium. Tofu is another soy-based product that is a source of dietary calcium.

Other non-dairy sources of calcium include green leafy vegetables such as spinach, bok choy or kangkung (water spinach).

Broccoli and other cruciferous vegetables are also good sources. When choosing these foods, it is important to think about substances called "oxalates". Oxalates actually bind or stick to the calcium in foods making it unusable by the body. Many green leafy vegetables such as spinach are high in oxalates so although they may be a source of calcium, the oxalate in the food blocks the absorption of calcium found in these vegetables. This means that although green-leafy vegetables are a source of calcium -- and many other beneficial vitamins and minerals -- they should probably not be the only source in your diet.

Other foods, including rhubarbs, chocolate and tea, contain oxalates and may inhibit the body's absorption of calcium. It is wise to avoid combining calcium rich foods with oxalate rich foods. Also, if you choose to take a calcium supplement, it should be taken at least two hours after eating a food containing oxalate. That said, calcium generally tends to be better absorbed by the body in the presence of food. Therefore, if you are taking a calcium supplement, you should not do so on an empty stomach.

So what is so important about calcium and why do we need to make sure we are getting enough?

One of the most important issues related to calcium is the disease Osteoporosis, which affects a significant percentage of people around the world, particularly women. Our bones are constantly in the process of being built and broken-down (resorbed). When the body needs calcium for a specific chemical process, if it is not available from our dietary intake, it will be pulled from reserves in our bones. The natural aging process and hormonal changes also lead to a net bone loss. Over time as bones weaken further, thin fracture-prone bones and a hunched- over appearance can develop as a result of osteoporosis.

Achieving a proper intake of calcium early on in life to help minimize future bone loss can prevent this long-term process.

Newer research also indicates an important relationship between calcium and body fat. In the early 1980's a study on blood pressure and obese men indicated that those who consumed two cups of non-fat yogurt per day lost 4.9 kg (11 pounds) of body fat over the course of the one year study without otherwise altering their diets. Since then, researchers have conducted further studies to identify the mechanism by which calcium might impact body weight.

The results have indicated that as calcium intake increases in the diet, fat metabolism increases as well. In simple terms, as calcium increases, fat cells are burned. As has been the case with many other studies comparing supplements to actual consumption of food, the greatest benefits were derived from people who had adequate intake of calcium in their normal diets as opposed to those who took supplements.

Studies on this subject continue, and it is important to remember that all foods should be consumed in moderation and any supplements taken should not exceed the recommended daily allowance of a mineral or vitamin unless specifically recommended by your doctor or dietitian.