It is widely known that calcium is an important nutrient and a key factor in bone strength. From the “Got Milk” campaign to the large number of calcium supplements available, there is no shortage of information as to the importance in getting enough calcium but most of us do not know the many roles of calcium and the complexity of absorbing the nutrient into the bloodstream.
Calcium’s many roles include not only bone strength, but also blood clotting, nerve conduction, muscle contraction, enzyme regulation and membrane permeability.
Vitamin D is essential in helping the body absorb and use calcium. In fact, the body cannot absorb calcium at all without some vitamin D. Vitamin D comes from two sources. It is made in the skin through direct exposure to sunlight, and it comes from the diet.
The body’s ability to produce vitamin D from exposure to sunlight and to absorb calcium and vitamin D decreases with age. Getting enough vitamin D helps the body absorb calcium and also helps the kidneys break down and incorporate (resorb) calcium that would otherwise be excreted. Vitamin D is found in eggs, butter, fatty fish, liver, and fortified foods such as milk, orange juice, and cereal. Elderly individuals who are not exposed to sunlight and may not eat a variety of food containing vitamin D may need vitamin D supplements to maintain adequate levels to help calcium absorption. In addition to vitamin D, vitamin C, vitamin E, vitamin K, magnesium, and boron assist in absorbing calcium and also increasing bone mass. Exercise also helps the body absorb calcium.
When taking a supplement, more isn’t always better. The recommended daily dose should not be exceeded because exceeding the dose increases the risk of side effects.
Because the body has a hard time absorbing a large amount of calcium at once, spreading out the intake of calcium is recommended. Taking in about 500 mg or less of calcium throughout the day is best. See the link for recommended dosages of Calcium and Vitamin D.
Calcium carbonate and calcium citrate are the most commonly used calcium supplements, particularly because they contain more calcium per tablet and are less expensive per milligram of calcium than other supplements.
- Calcium carbonate supplies more elemental calcium per tablet than other forms and is therefore usually the best value; however, it is best to take this kind of calcium compound with food because stomach acid is needed to dissolve it.
- Calcium citrate has less elemental calcium in it, so more of it will need to be taken, but it is absorbed more easily than calcium carbonate.
Calcium absorption is not as simple as just drinking milk or taking a pill. Because the process is multistep, other foods and medications can get in the way. Without absorption, you’re better off pouring that milk or supplement down the drain.
A doctor or pharmacist knows whether a calcium supplement will interact with any prescription medications also being taken. For example, calcium chews, such as Viactiv, contain calcium and vitamin D but also contain vitamin K and should not be taken by individuals treated with anticoagulants, such as warfarin (Coumadin).
A balanced diet will generally aid in the absorption of calcium but excessive amounts of the following substances should be avoided, especially in those with low calcium intake.
- Excess protein: The body uses excess protein for energy. However, as protein is burned for energy, it produces sulfate. Excess protein creates excess sulfate. Sulfate increases the amount of calcium excreted in the urine, which decreases the amount of calcium in the body.
- Phosphoric acid, phosphate or phosphorous, which is in cola and many processed foods, can interfere with calcium absorption.
- Phytates (and phytic acid) are antioxidant compounds found in whole grains, legumes, nuts and seeds and when consumed in excess, can bind to calcium and decrease availability and subsequent absorption.
- Oxalates in foods such as spinach, swiss chard, rhubarb and beets, inhibit calcium absorption in the small intestine.
- Unabsorbed dietary fatty acids found in the intestinal tract can interfere with calcium absorption by forming insoluble calcium soaps.
- Insoluble fiber, such as the kind in wheat bran, reduces calcium absorption.
- Corticosteroid therapy, such as prednisone, taken for longer than six weeks can negatively impact absorption.
- Also of note is excess caffeine. This is particularly important as there are many people who get their only calcium of the day with their morning coffee. The good news is that if you keep your intake to less than 300 mg (about 12oz of coffee), you should be fine.
- Drinking excessive amounts of alcohol can interfere with the calcium balance by inhibiting the enzymes that convert inactive vitamin D to active vitamin D.
- Smoking, stress, and lack of exercise: These lifestyle factors contribute to the body not being able to absorb calcium as efficiently.