Good for your bottom and your bones
Reported February 24, 2009
We’ve long been told that getting enough calcium helps guard against osteoporosis, a disease that makes bones more likely to fracture. But study findings published this week in the Archives of Internal Medicine suggest that meeting your daily calcium requirements may also keep cancer at bay.
According to the report, women and men with higher calcium intakes have a lower risk of digestive cancers, in particular colorectal cancer.
Colorectal cancer is the second leading cause of death from cancer. It’s estimated that 21,500 Canadians were diagnosed with colorectal cancer last year. While previous research has explored the link between calcium and colorectal cancer, this is the first study to investigate dairy and calcium intakes in relation to total cancer and other digestive cancers.
In the study, researchers from the U.S.-based National Cancer Institute followed nearly 500,000 American men and women, aged 50 to 71, for seven years.
In both men and women, dairy food and calcium were protective of digestive-tract cancers including those of the head and neck, esophagus, stomach, colon, rectum and bladder. Men who consumed the most calcium from food and supplements (about 1,530 milligrams a day) had a 16 per cent lower risk of these cancers compared with those who consumed the least (526 milligrams a day).
For women, high daily calcium consumers (1,881 milligrams) were 23 per cent less likely to be diagnosed with a digestive tract cancer than their peers who consumed, on average, only 494 milligrams a day.
The protective effect of calcium was most evident for colorectal cancer. Dairy foods, dietary calcium and supplemental calcium were all associated with a significantly lower risk of colorectal cancer. Men with the highest total calcium intake had a 21-per-cent lower risk of colorectal cancer and their female counterparts were 28 per cent less likely to develop the disease.
This isn’t the first study to hint that calcium plays a role in colon-cancer prevention. A recent analysis of 10 studies conducted in five countries found that people who consumed the most calcium had a 20-per-cent lower risk of colorectal cancer than those who consumed little.
What’s more, randomized controlled trials have shown calcium supplementation to reduce the recurrence of colorectal adenomas, polyps that can develop into cancer.
A calcium-rich diet is thought to guard against colorectal cancer in a number of ways. Studies in the lab have demonstrated the ability of calcium to slow the growth of and kill certain cancer cells. It’s also thought that once consumed, calcium binds to certain compounds in the intestinal tract, preventing their toxic effects on colon cells. Furthermore, dairy products not only contain calcium but other potential cancer-fighting nutrients such as vitamin D and conjugated linoleic acid, a fatty acid.
To get enough calcium for your bones and possibly to lower your risk of colorectal cancer, adults aged 19 to 50 need 1,000 milligrams a day. The daily recommended amount increases to 1,500 milligrams after age 50.
For most of us, these numbers translate into three or four dairy servings a day. One cup (250 millilitres) of milk or yogurt delivers roughly 300 milligrams of calcium, as does 1.5 ounces (45 grams) of hard cheese. If you don’t consume dairy, calcium-enriched beverages such as soy or rice drinks and orange juice also provide about 300 milligrams a serving.
Cooked green vegetables, legumes, almonds, tofu and canned salmon with the bones are also calcium sources.
If you aren’t meeting your calcium needs from food which is the case for many Canadians reach for a supplement. If you need to take more than 500 milligrams from a supplement, split your dose over two or three meals.
Choose a calcium supplement with vitamin D since this nutrient is also thought to reduce cancer risk. The Canadian Cancer Society advises a daily intake of 1,000 international units (IU), an amount that can’t be obtained in the diet or from sunlight in the fall and winter.
Figure out how much vitamin D you’re getting from your calcium and multivitamin supplements. If necessary, make up the difference with a separate vitamin D pill. Choose a supplement than contains vitamin D3, a form that is more active in your body.
While it’s important to meet your daily calcium needs, more is not better, especially for men.
Some studies but not all hint that high calcium and dairy intakes increase the risk of prostate cancer. In the current study, a high intake of calcium was not associated with a greater risk of prostate cancer.
Among studies that have observed a link between calcium and prostate cancer, the risk only seems to rise with very high intakes of more than 2,000 milligrams a day. An excessive use of calcium supplements is generally needed to reach this amount.
A high calcium intake has been hypothesized to boost prostate-cancer risk by suppressing vitamin D production in the body, offsetting the vitamin’s potential anti-cancer effects.
Because of the possible increased risk of prostate cancer with high calcium intake, men should limit their intake to no more than 1,500 milligrams a day.
For women, as well as children older than 1, the safe upper daily limit for calcium is 2,500 milligrams. An excessive intake can cause elevated blood levels of calcium, impaired kidney function and decreased absorption of other minerals.