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Wednesday, December 22, 2010

Is Calcium Dangerous?

An article published earlier this year in the British Medical Journal concluded that taking calcium supplements is associated with an increased risk of having a heart attack.

However, there were several problems with this study. Among them:
  • It was a meta-analysis, a study of studies, but the studies selected excluded several trials that linked calcium supplements to a reduced risk of heart attack. 
  • Vitamin D helps our bodies absorb calcium, but the study excluded people who took calcium in combination with vitamin D.
  • According to the researchers, the increase in heart attacks was only "modest" and there was no increase in the number of deaths from heart attacks.
This isn't the first poorly designed trial to grab headlines while misleading and confusing the public, but it raised an important issue. Too many people take too much calcium.

Of course our bodies need calcium. Most of it is used to strengthen bones and teeth, but calcium has other important functions. It stabilizes cell membranes and aids the transport of compounds into and out of cells. Calcium regulates neurotransmitters, substances that transmit nerve impulses, and helps initiate blood clotting. And without calcium, muscles, including the heart, don't contract properly.

Bone Metabolism

Putting more calcium into your body doesn't necessarily mean putting more calcium into your bones. Bones are constantly remodeling themselves and this complex process is controlled by a complex system of hormones. It is not controlled by the amount of calcium you take in (although calcium must be present in the blood before it can be incorporated into bone matrix).

Many factors are involved in bone mass: bone cell growth, bone cell destruction, mineralization (adding more minerals like calcium to bone matrix) and resorption (removal of minerals like calcium from bone matrix).

In childhood, when bone cell growth exceeds bone cell destruction, our bones and our bodies become bigger. Once we're fully grown, bone growth balances bone destruction. After the age of 30, bone destruction slowly begins to exceed bone growth and we gradually lose bone mass as we age. After 50, declining levels of estrogen and testosterone can speed the process.

At any age, exercise can slow or even reverse bone loss. Simply put, our bones stay strong when we stay active. Weight-bearing exercises and activities that place forces on bones stimulate growth, ensuring that the body will be able to withstand future forces. When we become sedentary and forces that stimulate bone growth no longer exist, we lose bone mass. 

Osteoporosis

The number one reason that people take calcium supplements is to prevent bone loss and osteoporosis. But for most older people, osteoporosis is not a disease at all. It's a natural aging process.

The real danger is not weak bones. Falls and fractures have a much greater impact on quality of life. Only 1 in 4 elderly individuals who sustain such injuries are able to return to their pre-fracture activity level. 75 percent of older adults who survive falls require specialized long-term care in a rehabilitation facility or nursing home, and 25 percent die within one year.

Regular exercise not only keeps bones strong, it also improves balance and coordination, making falls and fractures less likely. Studies have shown that walking at least 2 hours each week can reduce the risk of hip fractures in elderly adults. For best results, I recommend participating in a variety of activities that apply forces to a variety of bones.  People who do not exercise regularly should talk to their doctor before they start.

To further reduce the risk of falls and fractures, older adults should live in clutter-free environments with good lighting, have their sight and hearing tested annually, wear rubber-soled shoes and use caution when walking on slippery or uneven surfaces.

Calcium Supplements

Getting enough calcium is important but more isn't necessarily better. Worldwide population studies have shown that people who consume the most calcium – like those in Scandinavian countries and the United States – also have the highest rates of fracture, while people who consume the least – like those in Asian and Mediterranean cultures – have the lowest fracture rates.

Ideally, calcium should come from our diet.  When it doesn't, it must be supplemented. Our bodies probably need about 1000 mg of calcium each day. But before you start taking supplements, evaluate your diet and estimate your true needs.

Each day, the average person usually consumes at least 300 mg of calcium from foods that are not especially rich in calcium. So assume a starting point of 300 mg and add what you get from these calcium-rich foods:
  • 1 cup of cooked spinach = 300 mg of calcium
  • 1 serving of dairy (1 cup of milk or yogurt, or 1.5 ounces of cheese) = 300 mg of calcium
  • 3 ounces of fish with soft bones that you eat like canned wild salmon and sardines = 400 mg of calcium
  • 1 cup of cooked collard or turnip greens = 400 mg calcium
Adults who eat, on average, at least one daily serving of dairy, dark green leafy vegetables or fish (with bones) already get 600 mg of calcium from food alone. So they only need to supplement 400 mg per day.

Adults who eat at least three servings of these foods have no need to supplement calcium at all. This is a good goal.

Calcium supplements come in many forms. Calcium carbonate is inexpensive to produce and widely available, but it is more difficult to digest and can cause constipation. Larger doses are required because a lower percentage is absorbed.

Better choices include calcium citrate, calcium malate and calcium aspartate. These forms are more costly to produce and take up more space inside capsules and tablets, but they are better tolerated and more easily digested and absorbed by the body.

Those who do take calcium supplements should supplement an equal amount magnesium. Get magnesium from foods too. Good sources include tofu, cherries, figs, beans and lentils, halibut, dark green leafy vegetables like Swiss chard and beet greens, and nuts like almonds and cashews.

Vitamins D and K are necessary for the absorption and utilization of calcium. Vitamin K should not be taken in supplement form unless your doctor recommends it, but you should include food forms in your diet. Turnip greens and broccoli are by far the best source of vitamin K, but other green leafy vegetables, cabbage, liver and green tea are also good sources. Make sure to eat these foods with some form of fat to ensure that the vitamin is well-absorbed. Vitamin K plays an important role in blood clotting, so individuals taking blood-thinning medications should get specific dietary recommendations from their doctor.

Sunlight stimulates the skin to produce vitamin D - which is why deficiencies are most common in winter and in areas furthest from the equator - but vitamin D can also be found in food. Good sources include cod liver oil, fish (especially sardines, which are also a good source of calcium when consumed with the bones), mushrooms, egg yolk, lamb and beef.

Vitamin D can also be found in supplements. Because it is fat-soluble, vitamin D should always be taken with food or fish oil.

However, taking too much vitamin D in supplement form can cause it to accumulate in the body and reach toxic levels. Small amounts are usually not worrisome, but larger amounts (1,000 IU per day or more) should only be taken if blood tests show that levels are low. If you aren't sure, ask your doctor for the test. It's worthwhile because low levels of vitamin D have been linked to an increased risk of osteoporosis, autoimmune disease, depression, heart disease and cancer.

Remember that supplements are no substitute for a healthy diet and that calcium output is as important as calcium intake. Excessive consumption of coffee or alcohol, and diets high in sodium, animal protein and grains can cause the kidneys to increase excretion of calcium. But plant-based diets high in vegetables and fruits and low in sodium additives cause the kidneys to increase calcium retention. It's a great reason to eat plenty of dark leafy greens and avoid processed foods.

References:

Bolland MJ et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010 Jul 29;341:c3691. doi: 10.1136/bmj.c3691.

Feskanich D et al. Walking and Leisure-Time Activity and Risk of Hip Fracture in Postmenopausal Women. Journal of the American Medical Association. 2002;288(18):2300-2306. doi: 10.1001/jama.288.18.2300

Koot VC et al. Functional results after treatment of hip fracture: a multicentre, prospective study in 215 patients. The European Journal of Surgery. 2000 Jun;166(6):480-5.

2 comments:

Anonymous said...

In terms of bone and teeth health, it's critical to factor in the effect of municipal water fluoridation. Sodium fluoride and it's variants have a significant effect on the body's ability to maintain proper health on a wide spectrum. Chief among these are the effects on bones.

If you want to negate or block positive results from consuming calcium, all one has to do is regularly ingest sodium fluoride.

Anonymous said...

Just left a comment earlier regarding sodium fluoride. Please amend with this:

Versus calcium supplements, sodium fluoride is found to greatly increase various bone fractures. While making them 'harder,' fluoride brittlizes bones and teeth and makes them prone to breakage.

Even the naturally occurring calcium fluoride can produce toxic effects in higher quantities.

Proper calcium supplementation may serve to stave this off.