Calcium, vitamin D and heart disease. What’s the 4-11?

Posted by Liz on May 2, 2011 in bone health, heart disease | 5 comments

“Calcium supplements cause heart attacks in postmenopausal women.”

Whoa! What?!

If you saw the headlines last week, you may be wondering what’s up with calcium supplementation. Afterall, don’t medical professionals advise the use of supplements to stave off bone loss associated with osteoporosis? And as a result, the Centers for Disease Control reports that over 50% of adults currently use calcium supplements and more than 60% of women over age 60.

It’s important to get away from the sensational headline and take a closer look at what the research shows and what you need to know.

Previous studies have suggested that there may be a link between use of calcium supplements (without vitamin D) and heart attack; in fact, as Reuters‘ reported last year, calcium supplements were shown to increase the risk of heart attack by as much as 31%, possibly as a result of plaque formation in blood vessels. However, is the risk the same if calcium is used alone versus if it is used in conjunction with vitamin D?  In the Women’s Health Initiative study, the use of calcium and vitamin D did not appear to influence heart disease risk at all.

However, researchers decided to take another look at the data because they say that in this trial, more than half of participants were taking ‘personal calcium’ (i.e. not regulated or standardized to all trial participants) and almost half were also adding Vitamin D.

In this reanalysis, published just last week in the British Medical Journal, the researchers discounted the women who were characterized as personal users of calcium supplements and instead, limited their evaluation to a group of women who were not using personal calcium supplements at the study’s start and previously unpublished data from the trial. The findings? The use of calcium with or without vitamin D appeared to cause a 25% to 30% increase in the risk for heart attack and a 15% to 20% increased risk for stroke. However, the researchers say that even small increases in the incidence in heart disease may manifest substantially, especially in the elderly. They add that if you take a look at the risk-benefit ratio, it is unfavourable, meaning that taking calcium with or without vitamin D for five years would cause twice as many heart attacks or strokes than then numbers of fractures that would be prevented.  Additionally, the data analysis suggests that dosing is not a factor, and that the total amount of calcium taken daily is less important than the abrupt changes in blood calcium levels immediately following supplementation.

Although this research answers a few questions about potential risks about calcium supplementation, it also leaves a key question unanswered:  how does the addition of magnesium and vitamin K, which are often included in commercially-available calcium supplements, affect these findings? Data suggest that these minerals and vitamins are added to keep calcium in the bones where it belongs and out the arteries where it does not.

The best guideline, as always, is to visit a physician to assess your bone health and come up with a plan that works specifically for you. Although calcium supplementation appears to be risky, more data are needed before leading organizations start to change their tune about calcium and bone health. Meanwhile, stay ahead of the headlines and try to focus on increasing the amount of calcium-rich foods in your diet:

Table 2: Selected Food Sources of Calcium [Source: National Institutes of Health]

Food	Milligrams (mg) per serving	Percent DV*
Yogurt, plain, low fat, 8 ounces	415	42
Sardines, canned in oil, with bones, 3 ounces	324	32
Cheddar cheese, 1.5 ounces	306	31
Milk, nonfat, 8 ounces	302	30
Milk, reduced-fat (2% milk fat), 8 ounces	297	30
Milk, lactose-reduced, 8 ounces**	285–302	29–30
Milk, whole (3.25% milk fat), 8 ounces	291	29
Milk, buttermilk, 8 ounces	285	29
Mozzarella, part skim, 1.5 ounces	275	28
Yogurt, fruit, low fat, 8 ounces	245–384	25–38
Orange juice, calcium-fortified, 6 ounces	200–260	20–26
Tofu, firm, made with calcium sulfate, ½ cup***	204	20
Salmon, pink, canned, solids with bone, 3 ounces	181	18
Pudding, chocolate, instant, made with 2% milk, ½ cup	153	15
Cottage cheese, 1% milk fat, 1 cup unpacked	138	14
Tofu, soft, made with calcium sulfate, ½ cup***	138	14
Spinach, cooked, ½ cup	120	12
Ready-to-eat cereal, calcium-fortified, 1 cup	100–1,000	10–100
Instant breakfast drink, various flavors and brands, powder prepared with water, 8 ounces	105–250	10–25
Frozen yogurt, vanilla, soft serve, ½ cup	103	10
Turnip greens, boiled, ½ cup	99	10
Kale, cooked, 1 cup	94	9
Kale, raw, 1 cup	90	9
Ice cream, vanilla, ½ cup	85	8.5
Soy beverage, calcium-fortified, 8 ounces	80–500	8–50
Chinese cabbage, raw, 1 cup	74	7
Tortilla, corn, ready-to-bake/fry, 1 medium	42	4
Tortilla, flour, ready-to-bake/fry, one 6″ diameter	37	4
Sour cream, reduced fat, cultured, 2 tablespoons	32	3
Bread, white, 1 ounce	31	3
Broccoli, raw, ½ cup	21	2
Bread, whole-wheat, 1 slice	20	2
Cheese, cream, regular, 1 tablespoon	12	1

* DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents among products within the context of a total daily diet. The DV for calcium is 1,000 mg for adults and children aged 4 years and older. Foods providing 20% of more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet. The U.S. Department of Agriculture’s Nutrient Database Web site lists the nutrient content of many foods. It also provides a comprehensive list of foods containing calcium.
** Calcium content varies slightly by fat content; the more fat, the less calcium the food contains.
*** Calcium content is for tofu processed with a calcium salt. Tofu processed with other salts does not provide significant amounts of calcium.