For many years, a popular chorus of wisdom about calcium and bone health has been playing. Its refrain exclaims calcium is essential to bone health. Variations on this theme are also heard. “Drink your milk for healthy bones.” “Take a calcium-based antacid, and it will help your bones while it soothes your stomach.” “Look, this food is fortified with calcium for healthier bones!” In the well-known “Got Milk?” campaign, one ad even has Superman promising “bones of steel” if you drink milk.
In our society, where calcium is widely available and its benefits widely known, bone disorders such as osteoporosis (fragile bones) and osteopenia (reduced bone mineral density) are still prevalent. Why is this? The reasons for this paradox fly in the face of popular understanding: Bone loss is not caused by low calcium intake alone.
Calcium’s Role in Bone Health
Calcium is the most abundant mineral in the human body and serves several important functions. Two percent of our total body weight is made of calcium, and more than 99 percent of total body calcium is stored in bones and teeth, where it supports their structure. The body gets the calcium it needs for everyday, minute-to-minute physiological functioning in two ways. One way is from the intake of calcium-rich foods. These include dairy products, which have a high concentration per serving of highly absorbable calcium, but also many other foods, including dark leafy greens, nuts, seeds and beans.
The body can also obtain calcium by extracting it from the bones when blood levels of calcium drop too low and dietary calcium intake is insufficient. Ideally, calcium taken from the bones will be replaced when calcium levels are replenished. But before you reach for that glass of milk, realize that replacing the calcium in our bones is an intricate process involving not only intake, but also metabolism and utilization.
This is the crux of the myth—while calcium is clearly important, there are at least 19 other key nutrients that each play a vital role in the structural integrity and overall health of our bones. (Visit Better Bones for a full list of these nutrients.) Think of bone as a brick wall, where the bricks are made of calcium and the other key nutrients make up the mortar. Just like a brick wall without mortar is unstable, bone without vitamin D, vitamin K and magnesium will lose its calcium.
Calcium and Vitamin D
The last few years have witnessed a virtual explosion of research on vitamin D. This “sunshine vitamin” has been linked with the prevention of many chronic diseases, including cancer, heart disease, diabetes, autoimmune disease and osteoporosis. When it comes to bone health, vitamin D is the key to calcium absorption. To paraphrase vitamin D researcher and doctor Michael Holick, you can swim in calcium and it will do no good unless you have adequate vitamin D. Specifically, without vitamin D our bodies can only absorb 10 to 15 percent of dietary calcium—even if calcium is present, the body can’t use it. When vitamin D is added, the absorption of dietary calcium increases to 30 to 40 percent. Both calcium and vitamin D are necessary to prevent osteoporosis, including postmenopausal osteoporosis.
Calcium and Vitamin K
Vitamin K is critical for calcium use and regulation. It helps proteins bind to calcium and transports them to where they are needed in bones, organs and other tissues. Vitamin K is also needed in the bone to produce a protein called osteocalcin, which, as the name suggests, helps bind calcium to the bone. Low vitamin K status is associated with higher levels of bone turnover (the process of the body removing old bone) and increased fracture risk, while adequate levels of vitamin K have been shown to protect from a loss of calcium in the urine. French researchers have noted in their studies that low vitamin K status predicts the subsequent risk of hip fracture. Without adequate vitamin K, more bone is lost and fracture risk increases.
Calcium and Magnesium
Through many mechanisms, magnesium is needed for calcium absorption and bone formation. Magnesium is an essential cofactor in 80 percent of all cellular enzymes, including the thyroid hormone calcitonin, which regulates bone turnover. Magnesium is also needed by the liver enzymes that convert vitamin D into its active form, known as calcitriol. Recall that vitamin D is needed for proper calcium absorption, and magnesium deficiency can lead to a syndrome known as vitamin D resistance. The activity of another critical enzyme for bone formation, alkaline phosphatase, also depends on magnesium. This enzyme is required to solidify calcium and other soluble factors into bone. Much of the body’s magnesium (60 percent) is stored in bone and is released into the blood when needed by other tissues. Magnesium deficiency is known to impair parathyroid hormone secretion and action, and contributes to the development of osteopenia and bone fragility.
The Dairy Dilemma
In America, the popular solution to our calcium needs is to eat lots of dairy products, including milk, yogurt, cheese and ice cream. But there are problems with this logic. First, many people are lactose-intolerant or otherwise sensitive to proteins in milk. Second, dairy products are generally acid-forming foods, meaning that—when taken in excess, and without counterbalancing alkalizing foods—they tend to promote a pH imbalance in the body that leads to further calcium loss from the bones. So while dairy products do contain a great deal of calcium, dairy alone doesn’t provide the “quick fix” to bone health many Americans assume it does.
Try This: Stronger Bones Through Exercise
Like muscle, bones are living tissue that respond to the demands we place on them—people who regularly exercise generally achieve greater bone density than those who don’t, according to the National Institutes of Health.
Most forms of exercise can help halt bone loss by building muscle, but studies show that strength-training (lifting weights) and weight-bearing (walking, jogging and dancing) exercises may outperform the rest.
While strength-training and weight-bearing exercises show the biggest effects, don’t limit yourself. A 2005 study of adult female athletes found that high- and odd-impact sports such as volleyball, hurdling and soccer lead to denser bones than weight-lifting. In contrast, repetitive low-impact sports such as bicycling and swimming showed no benefit to bone density. Leisurely walks may also help build bone: In the Nurses’ Health Study of more than 60,000 postmenopausal women, those who engaged in moderate activity, including walking, were associated with a lower risk of hip fracture.
For the best bones, aim to perform weight-bearing exercise for 30 minutes on most days, and a series of strength-training exercises two to three days a week, according to the National Osteoporosis Foundation. You could also take walks, enroll in a yoga class or meet with a personal trainer.
The first step toward better bone health is following an alkaline diet high in vegetables, fruits, nuts and seeds. (Read more about an alkaline diet.) The second step involves the use of nutritional supplements. If the diet doesn’t include sufficient amounts, nutrients such as magnesium, zinc, boron and even omega-3 fatty acids often need to be supplemented, especially if the person is experiencing suboptimal bone health.
When supplementing with calcium, choose an alkalizing form such as calcium citrate, and aim for a total daily intake (from diet and supplements combined) of 1200 mg. Doctor Andrew Weil recommends women take 500 to 700 mg of calcium citrate twice daily with meals; men shouldn’t exceed 600 mg daily, and probably don’t need to supplement, as higher amounts have been linked to prostate cancer. Calcium should never be taken alone; it’s best taken with magnesium, vitamin D and the remaining 20 key bone nutrients from author and doctor Susan Brown’s Better Bones, Better Body Program. Visit Better Bones for more information about bone-enhancing nutrients. —Gina DeBacker
Dietary Sources of Bone-Promoting Nutrients
• Whole-wheat products
• Vegetables from the Brassica family such as broccoli, kale, cabbage, bok choy
• Dark leafy greens such as collards, kale, turnip greens, dandelion greens, mustard greens, beet greens
• Canned fish and crustaceans with bones such as sardines, pink salmon, shrimp
• Beans and legumes such as edamame, tofu, tempeh, black-eyed peas, black beans, dried beans
• Nuts and seeds such as almonds, sesame seeds
• Mineral water
• Herbal teas and infusions such as oatstraw, nettle, red clover
• Fatty fish such as salmon, tuna, mackerel
• Organ meats such as beef, pork, lamb liver
• Eggs (research has found that eggs from free-range hens contain more vitamin D)
• Dark leafy greens such as kale, collard greens, spinach
• Cruciferous vegetables such as Brussels sprouts, broccoli, cauliflower
• Fish such as shrimp, mackerel, herring
• Meat such as beef, chicken breast (free-range meat contains more nutrients)
• Nuts such as almonds, cashews, pistachios
• Fruits or vegetables such as bananas, dried apricots, avocado, carrots, spinach, Swiss chard
• Beans and seeds
• Whole grains
Susan E. Brown is a medical anthropologist, a New York State-certified nutritionist, and the author of Better Bones, Better Body. Learn more about the Better Bones, Better Body Program, and subscribe to her weekly blog, by visiting her online.