The fact that calcium is the most abundant mineral in the body, and that 99 percent of it is housed within the bones and teeth, underlines the importance of dietary calcium to bone health. During the bone-building process, the osteoblast cells secrete bone mineral consisting of calcium and phosphorus, which strengthens the bone. By providing structural integrity to bones, dietary calcium plays a critical role in preventing osteoporosis.
The remaining 1 percent of your body’s calcium circulates in your bloodstream and is vital to your heart, nervous system and muscles. Your body keeps this circulating pool of calcium at a constant level. If your diet lacks calcium and your blood calcium level drops, your parathyroid gland releases parathyroid hormone (PTH), which returns calcium to your blood by taking it from the bones. So when you shortchange your diet, you short-change your bones, too.
To see how much calcium you and your female family members need, see the RDA table on page 16 in chapter 1. Many calcium-rich foods provide other important bone-building nutrients like vitamin D, magnesium and potassium. Use the list of calcium-rich foods on page 17 in chapter 1 to help you boost your intake.
Your body does not absorb calcium from all foods equally well. While many plant foods contribute calcium to the diet, some natural compounds in vegetables prevent some of this calcium from being absorbed. Studies show that dairy products contain the most absorbable form of calcium. To enhance the amount of calcium your body absorbs, you should also avoid taking iron supplements with calcium-rich foods. Factors in your diet that hamper your body’s ability to absorb calcium include
• large amount of phytates in fiber-rich foods, which can bind with calcium and limit its absorption
• oxalic acid in spinach and some other vegetables (cooking green vegetables boosts their calcium content by releasing some calcium that’s bound to oxalic acid)
• too much phosphorus in the diet
• taking iron with calcium-rich foods (iron competes with calcium for absorption)
• drinking tea with a meal rich in calcium (natural compounds in tea, known as tannins, inhibit calcium absorption)
• a lack of vitamin D (as you’ve read above, vitamin D stimulates the intestine to absorb dietary calcium)
Studies do support using calcium supplements to lower your risk of osteoporosis. Researchers at the University of Texas Southwestern Medical Center in Dallas found that a 400-milligram calcium citrate supplement taken twice daily increased bone density in healthy postmenopausal women.8 In contrast, women in the placebo group experienced a 2.38 percent bone reduction in the lower spine.
Scientists at the University of Massachusetts studied 98 premenopausal women (average age 39 years) and found that those who received 500 milligrams of calcium carbonate increased bone density by 0.3 percent per year.9 The women in the placebo group lost bone at a rate of 0.4 percent per year in the hip and 0.7 percent in the neck. A number of studies have also shown that older women (and men) who take calcium and vitamin D supplements have a lower incidence of nonvertebral fractures.
If you’re thinking you had better take a calcium supplement, you’re probably right. Recent surveys have found that many Americans do not get the recommended two to three dairy servings per day. Sure, there’s calcium in broccoli and almonds and tofu. But let’s be truthful—do you really eat tofu on a daily basis? Are you willing to eat five cups of broccoli to make up for your missing 500 milligrams of calcium? Many women I see in my private practice are not meeting their daily calcium needs and should be taking a calcium supplement. Women may find it difficult to meet their calcium goals if they are lactose intolerant, if they are following a vegetarian diet or if they have poor eating habits. In these cases, supplements are often the only way that I can ensure a client is meeting her calcium needs.
To help you decide if you need a calcium supplement, use my 300 Milligram Rule. One milk serving gives you 300 milligrams of calcium. For every serving you’re missing and not replacing with other calcium-rich foods, you need to get 300 milligrams of elemental calcium through a supplement. Here’s how to choose a high-quality supplement:
1. Look at the source of calcium. There are many types of calcium supplements on the shelf. Some of the more common types include these:
• Calcium carbonate is only about 10 to 30 percent absorbed by the body. The amount you absorb depends on how much stomach acid is present. As people age, their stomach produces less hydrochloric acid. Because of this, calcium carbonate is not the best choice for older adults or for people on medications that block acid production. If you do take this form of calcium, take it with meals to increase absorption. Do not take calcium carbonate at bedtime unless you take it with a snack. On the plus side, this is the most inexpensive type of calcium supplement.
• Calcium citrate is about 30 percent absorbed by the body, so it is a better choice for anyone over the age of 50. Calcium citrate malate is one of the most highly absorbable (and expensive) forms of calcium. Calcium citrate supplements are well absorbed either with meals or on an empty stomach.
• Calcium chelates (HVP chelate) are supplements that contain calcium bound to an amino acid. In the case of HVP chelate, the amino acid is from vegetable protein. Some manufacturers claim that up to 75 percent of calcium in the chelate form is absorbed by the body.
• Effervescent calcium supplements contain calcium carbonate and often other forms of more absorbable calcium. Because they get a head start on disintegrating, they may be absorbed in the intestinal tract more quickly. Dissolve these in water or orange juice.
• Bone meal or dolomite or oyster shell are not recommended, because some products have been found to contain trace amounts of contaminants such as lead and mercury.
2. Know how much elemental calcium each pill gives you. Look on the list of ingredients for this information. The amount of elemental calcium is what you use to calculate your daily intake. Calcium carbonate or calcium chelates may not be 100 percent elemental calcium. The front label may state 500 milligrams, but when you look carefully at the ingredient list you may find the product contains only 350 milligrams of elemental calcium. This will determine how many tablets you need to take to get your recommended dose.
3. Choose a formula with vitamin D and magnesium. These nutrients work in tandem with calcium to promote optimal bone health. For instance, vitamin D increases calcium absorption in your intestine by as much as 30 to 80 percent.
4. Spread larger doses throughout the day. Since all calcium sources (including food sources) are not 100 percent absorbed, it makes sense to split a higher dose over two or three meals. If you’ve been advised to take 600 milligrams of calcium a day, take a 300-milligram tablet with breakfast and another one at dinner.
5. Take your calcium supplements with a large glass of water.
The daily upper limit for calcium intake is 2500 milligrams from food and supplements. In most healthy people, this amount will not cause any side effects. The major risks from getting too much calcium include kidney stones in people with a history of stones, constipation and gas.
Calcium for Osteoporosis Photo Gallery
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