Fast Fact: Osteoporosis and Men
* * *
Osteoporosis is usually portrayed as a woman’s disease, but it also affects men. They make up about 2 million of the 10 million Americans with osteoporosis.
Men enter adulthood with stronger, denser bones than women, and they never face the sudden bone-draining loss of estrogen that occurs with menopause. This gives men a five- to ten-year hedge against osteoporosis, but not lifetime protection.
A fundamental problem is that studies lasting just a few weeks or, at most, one or two years observe only what is happening in the remodeling space—not what is really happening in the big picture of overall bone strength.
What these short-term studies fail to capture is the body’s remarkable capacity to adapt. A unique study of Scandinavian prisoners, all men, shows that their bodies were still adapting after several years on a low-calcium diet (500 milligrams a day), mainly by excreting less calcium and using calcium more efficiently. In another study, conducted more than sixty years ago in Peru, prisoners who had been fed diets that gave them less than 500 milligrams of calcium a day for many years had achieved a sustainable calcium balance.
Not surprisingly, when my colleagues and I used data from a large national survey of many thousands of women and men, we saw no connection between usual calcium intake and the calcium content of bones.2 A similar lack of association has been reported in children.
FOCUS ON BROKEN BONES
In real life, broken bones are a better measure of desirable calcium levels than the short-term flow of calcium in and out of the body or measurements of bone density.
Here’s a long-recognized paradox: rates of hip fractures—the most serious type of broken bone—tend to be high in countries with high dietary calcium intake and low in countries with low calcium consumption (see Figure 19).3
While such country-to-country studies can’t prove cause and effect, they do raise questions about the protective effects of high calcium intake. They also clearly demonstrate that a low calcium intake doesn’t necessarily doom you to a broken hip.
Figure 19. Calcium and Fractures. Hip fractures tend to be more common in countries with high average calcium intake, such as the United States and New Zealand, than in those with low calcium intake, such as Hong Kong and Singapore.
Some prospective cohort studies show that getting extra calcium protects against fractures, others show no benefit of getting extra calcium, and some show an increase in fracture risk with more calcium. The combined results from seven long-term prospective studies done in the United States, England, and Sweden that have followed large groups of people for a long time don’t show any important reduction in risk of broken bones with increasing calcium intake.4
The findings from randomized trials are muddled, in part because some tested the effect of vitamin D in addition to calcium and others didn’t. A meta-analysis of mostly small trials comparing calcium supplements without extra vitamin D to a placebo showed no real effect of extra calcium on overall risk of fractures; in fact, the risk of hip fracture was actually higher among those taking calcium supplements. In the few small trials that suggested a benefit of calcium supplements on fracture risk, the participants were also taking vitamin D, making it impossible to know whether the lower risk of broken bones was due to vitamin D, to calcium, to the combination, or maybe just to chance.
The largest randomized trial to evaluate the effect of calcium supplements on bone health was conducted by the National Institutes of Health. In the calcium and vitamin D trial, which was part of the Women’s Health Initiative, more than 35,000 women between the ages of fifty and seventy-nine took daily supplements containing either a placebo or 1,000 milligrams of calcium plus 400 IU of vitamin D for an average of seven years. At the end of the trial, women taking the extra calcium and vitamin D had slightly better hip bone density. But they did not have fewer broken hips and were more likely to have developed kidney stones.5
The U.S. Preventive Services Task Force is an independent group of experts that assesses the evidence for screening and prevention interventions. It recommends against the use of calcium supplements to prevent broken bones among postmenopausal women and says the evidence is “inconclusive” for gauging the balance of benefit and harms of calcium and vitamin D supplements among men and premenopausal women.6
Fast Fact: Calcium Recommendations Around the World
* * *
Based on essentially the same body of evidence, different countries have set different recommendations for how much calcium to take in each day. The World Health Organization says 400 to 500 milligrams of calcium a day are needed to prevent osteoporosis and fractures. The United Kingdom set the bar at 700 milligrams a day for everyone over age nineteen. Guidelines in Canada and the United States recommend that adults get between 1,000 and 1,200 milligrams a day, depending on age and gender.
BEYOND BONE
Although dietary calcium is mainly linked to bone strength, it plays other roles in maintaining good health.
• Colon cancer. Over the past two decades, studies of different types and sizes have indicated that getting more calcium from milk or supplements offers modest protection against colorectal cancer. Megadoses aren’t necessary: most of the benefit comes with intakes seen in a reasonable diet, around 700 to 800 milligrams of calcium a day.
• Blood pressure. A calcium-rich diet or taking calcium supplements may slightly lower blood pressure, although the evidence has been inconsistent and any benefit of supplements probably applies mainly to individuals who get relatively little calcium from food.
• Weight loss. Drinking milk has been touted as one way to lose body fat while maintaining muscle mass. That’s misleading. Scientific studies in rats and people link consuming dairy products with weight loss—but only if calories are scaled back too. It’s the eating less, not the calcium, that’s important. Not surprisingly, calcium supplements don’t affect weight.7
THE DARK SIDE OF CALCIUM
As I described in chapter nine, drinking a lot of milk has downsides. These include consuming extra saturated fat, calories, and unneeded hormones; a likely increase in the risk of fracture later on in life when consumed during childhood and adolescence; a likely increase in the risk of prostate cancer; a possible increase in endometrial cancer; and environmental problems. Some of these findings are probably due to factors in milk other than calcium, but this is hard to determine because milk is the main source of calcium among individuals in Western countries.
How much calcium you take in matters. For example, in a 2013 meta-analysis, higher calcium intake was associated with lower risk of stroke in populations with low calcium intake, particularly in Asia, where consumption of dairy foods is low. But in populations with calcium intakes of more than 700 milligrams a day, higher intake of calcium was linked with a slightly higher risk of broken bones.8 In Sweden, where consumption of milk and dairy foods is high, the risk of premature death was more than double among women with calcium intakes over 1,400 milligrams per day who also took calcium supplements.9
Calcium is essential for many biological functions. Humans have adapted to regulate this mineral over a wide range of intakes: If calcium intake is low, we absorb most of what we consume and excrete little in our urine. If calcium intake is high, we let much of it pass through our intestines and excrete more in urine. Aiming for 600 to 1,000 milligrams a day—a bit under the U.S recommendations—is a good target for overall health. Getting more calcium than this appears to have little or no benefit and may cause harm. I don’t recommend religiously counting your milligrams of calcium each day. Later I describe how to land in this safe zone without counting.
IF NOT CALCIUM, WHAT?
Complex processes like bone health are influenced by many different factors. There’s no doubt that we need some calcium to keep bones healthy. Bone health is also affected by exercise, sex hormones, and nutrients such as vitamin A, vitamin D, and vitamin K.
Exercise. A bone bend
s when some force is applied to it. Apply a large force and the bend turns into a break. Apply a small one and the bend is minuscule but physiologically important, especially if it is repeated again and again. That’s what happens when you walk or do other exercise. Cells inside bone sense physical strain or stress and orchestrate a silent flurry of activity that remodels the bone to make it more dense and stronger. Among children and young adults, vigorous physical activity lays the foundation for a strong and healthy skeleton. The more activity and healthy stress on bones, the more bone is built. During adulthood, exercise helps maintain the balance between bone-building and bone-dissolving processes. During old age, physical activity limits bone loss.
Keep in mind that physical activity doesn’t build or strengthen all bones, just those that are stressed. So you need a variety of exercises or activities to keep all your bones healthy.
There’s no question that exercise strengthens bones and reduces risk of fractures. That has been seen consistently in study after study. What we still aren’t sure of is the best combination of exercise to maintain strong bones. Some mix of weight-bearing exercises like brisk walking plus muscle-strengthening exercises like weight lifting will almost certainly turn out to be best. Not only would that combination continually stimulate bone growth, it would also strengthen muscles and improve balance and so help prevent bone-breaking falls.
Hormones. Estrogen and testosterone affect bone health. Estrogen is sometimes called the female hormone and testosterone the male hormone, even though women and men make both of them. Numerous studies have shown that these two hormones are important for building new bone early in life and for keeping it strong over the next seventy years or so. That can be a problem, because production of sex hormones plummets after menopause in women and falls off more gradually in men.
In older women, hormone therapy—usually estrogen plus a progestin—was once the first-line treatment for preventing osteoporosis and heart disease. That ended when the federally funded Women’s Health Initiative showed a large increase in breast cancer, an increase in stroke, and transient elevations in heart disease with long-term use of estrogen plus progestin among postmenopausal women. Hormone therapy is still helpful in the short term for treating the symptoms of menopause, ideally without the progestin when possible. These adverse effects were not seen with estrogen alone, and estrogen alone will reduce the development of osteoporosis.
In men, the slowdown in sex hormone production isn’t as abrupt or as predictable as it is in women. If there are warning signs of osteoporosis, such as an unexpected broken bone, a testosterone check is a good idea for men over age sixty-five. If the level of this hormone is low, a daily testosterone-delivering gel or patch or regular testosterone injections can bring it back up.
Don’t decide to take hormones without carefully weighing the benefits and risks and sorting through the options. This is best done with a trusted health care provider.
Medications. A number of medications have been developed to shore up bone. These include bisphosphonates such as alendronate (Fosamax), etidronate (Didronel), ibandronate (Boniva), risedronate (Actonel), and zoledronic acid (Reclast); selective estrogen receptor modulators such as raloxifene (Evista); calcitonin (Fortical); a monoclonal antibody, denosumab (Prolia); and a synthetic form of parathyroid hormone, teriparatide (Forteo). None of these work magic, restoring healthy, youthful bones, and all have their own sets of side effects. Talk with your health care provider before deciding to start taking a bone-building medication.
Limiting preformed vitamin A. You need some vitamin A for good vision, especially night vision. It’s best to get it from food, not supplements.
As I describe in chapter eleven, high doses of preformed vitamin A, the kind found in many supplements, stimulate the activity of cells that break down bone. Several studies have shown that intakes of preformed vitamin A above 5,000 international units (IU)—the equivalent of 1,500 micrograms—increase the chances of losing bone density, the risk of breaking a hip or other bone, or the risk of cancer. Current guidelines recommend that men get 3,000 IU of vitamin A per day and that women get 2,333 IU.
Vitamin D. The best-known function of this fat-soluble vitamin is helping the digestive system efficiently absorb calcium and phosphorus. Vitamin D helps build and maintain healthy bones in other ways too.
Several studies have shown that vitamin D deficiencies are more common among older people with broken bones than those without them. In the Nurses’ Health Study, older women who got at least 500 IU of vitamin D a day were one-third less likely to have broken a hip than women who got under 200 IU a day.10 Results from randomized trials of vitamin D and fractures have been mixed, but trials that used 700 IU or more per day showed a benefit, while those using lower daily doses did not.11
The current official daily target for vitamin D intake is 600 IU (15 micrograms) between the ages of nineteen and seventy, and 800 IU (20 micrograms) after that.
Few foods naturally contain vitamin D, so you need to get most of yours from the sun or supplements. A tablespoon of cod-liver oil delivers more than 1,200 IU of vitamin D. Many multivitamins carry 1,000 IU. Some calcium supplements come with added vitamin D, which is a good idea, since there is actually better evidence for benefits from vitamin D supplements than for calcium.
Can extra vitamin D help prevent osteoporosis-related fractures? Although the evidence isn’t totally consistent, extra vitamin D may be an effective way to prevent bone loss. I certainly agree with an editorial in the New England Journal of Medicine that succinctly concluded, “A widespread increase in vitamin D intake is likely to have a greater effect on osteoporosis and fractures than many other interventions.12 For most people, the easiest way to do this is to take a supplement that contains vitamin D. More on this in chapter eleven.
Vitamin K. This vitamin was long thought to be needed only for the formation of proteins that regulate blood clotting. It turns out, though, that vitamin K also plays one or more roles in the regulation of calcium and the formation and stabilization of bone.13 It is found mainly in green vegetables such as dark green lettuce, broccoli, spinach, Brussels sprouts, and kale.
Results from the Nurses’ Health Study show that too little vitamin K may help set the stage for osteoporosis. Women who got slightly more than the current recommended daily intake of vitamin K each day were 30 percent less likely to break a hip than women who got less than that amount.14
The current recommended daily intake for vitamin K is 90 micrograms for women and 120 micrograms for men. Eating one or more servings a day of foods rich in vitamin K should give you enough of this vitamin. If you take warfarin (Coumadin) or another medication to prevent blood clots, talk with your doctor first before boosting your daily intake of vitamin K.
PUTTING IT INTO PRACTICE
The ideal prevention strategy is one that stops something bad from happening without causing other bad things to happen. Consuming plenty of calcium, mainly from milk and dairy foods, has been portrayed as a key way to prevent osteoporosis and broken bones. Not only does this fail to fit the bill as a proven prevention strategy, it doesn’t even come close. The totality of evidence doesn’t support the claim that getting more calcium prevents fractures over the long term, and there is plenty of evidence that drinking two or three glasses of milk a day does little to reduce the chances of breaking a bone. What’s more, dairy foods pose several proven and potential problems. So if you are worried about osteoporosis, other prevention strategies make better sense than drinking more milk.
Exactly how much calcium we need for optimal health isn’t completely settled. But as I described earlier, a range of 600 to 1,000 milligrams of calcium a day is a good target. Healthy people who exercise, get enough vitamin D, and have a healthy overall diet need less calcium than those on the other end of the spectrum.
Here’s how to get yourself into a healthy calcium range without meticulously counting milligrams of calcium. First, almost every food you eat contains some ca
lcium (see “Calcium in Foods” on page 194). Of course, some foods, like greens and whole grains, have more than others. A reasonable diet without milk or other dairy foods can give you about 300 milligrams of calcium a day without thinking about it. Consciously including nondairy high-calcium foods can get you into the target range. (And there are many other added benefits of eating these foods apart from their calcium content.)
Dairy is in a class by itself, with about 300 milligrams of calcium per glass of milk or the equivalent amount of cheese or yogurt. Adding one serving of milk, yogurt, or other dairy food a day will almost certainly ensure you get the calcium you need. Adding two servings a day will send you to the high end of the range, and three servings a day will put you well above the healthy range. It’s one reason I don’t advise drinking this much milk, along with taking in extra calories.
If you don’t drink milk or eat other dairy foods, which is fine, and you worry that you aren’t getting enough calcium from your diet, I suggest taking a daily calcium supplement of 500 milligrams. You don’t need more than that. Keep in mind that many foods are now fortified with calcium, including breakfast cereals, orange juice, soy milk, and more. These can easily send your calcium intake above 2,000 milligrams a day. That isn’t good: the National Academy of Medicine has set that as the upper limit for anyone over age fifty.
Eat, Drink, and Be Healthy Page 26