Calcium is the most abundant mineral in your body. Most of it – 99 percent – is stored in your bones and teeth. The remaining one percent is in your blood, for the normal function of muscles, nerves, and blood vessels.
Calcium is clearly important to your health, but does that mean you should take indiscriminate amounts of calcium supplements? Not exactly.
Calcium is what I like to call a “Goldilocks nutrient”—it’s best for you when the amount is just right.
In fact, too much calcium or too little can be deadly to your cells. That’s why your body tightly regulates its calcium blood levels. It truly needs a “Goldilocks” level – not too little and not too much.
Too much calcium (especially as supplements) can overwork your kidneys and cause kidney stones, as discovered in the Woman’s Health Initiative study. Excess calcium is called hypercalcemia and can increase your risk for:
- High blood pressure and heart disease
- Kidney stones
- Colon and prostate cancers
- Abnormal brain function
- Poor bone health, ironically
Your body’s hidden calcium control center
The amount of calcium in your food, the other supplements you take, certain health conditions, and any prescription and over-the-counter drugs can all affect calcium absorption.
Four tiny glands called your parathyroid glands (not to be confused with your thyroid) control calcium levels in your blood. When you need calcium, your parathyroid glands secrete a hormone that signals:
- Your bones to release calcium into your blood
- Your kidneys to excrete less calcium into your urine
- Your kidneys to activate vitamin D, which helps your digestive tract to absorb more calcium
As you might guess, overactive parathyroid glands can disrupt your calcium balance and create an overabundance of this mineral. So does having cancer. And because high calcium levels due to cancer are not triggered by dietary calcium, consuming less calcium won’t lower those high levels.
Cancers most likely to trigger high calcium levels in your body include:
- Breast cancer
- Lung cancer
- Kidney cancer
- Digestive cancers
- Head and neck cancers
- Multiple myeloma
If you have or have had cancer of any kind, it’s a good idea to make sure your doctor is monitoring your calcium levels. And if they’re too high, work with your healthcare team to lower them.
So, how much calcium do you need, anyway?
In the U.S. the RDA for calcium is 1,000 mg per day for women under 50, and 1,200 mg per day for women over 50.
Which begs the question… Why is the World Health Organization’s level set at less than half of that—at 500 mg per day— and the U.K.’s at 700 mg per day?
Turns out that the U.S. 1,200 mg per day for women over 50 was based on a couple of short studies in the late 1970s that seemed to indicate that 1,200 mg per day could keep your bones from releasing its stored calcium.
So, the experts moved the RDA level of calcium from 800 to 1,200. And they might be on to something when it comes to cancer prevention.
While cancer can trigger high calcium levels, in turn high levels of calcium can prevent certain cancers.
How calcium stops colorectal cancer
A number of epidemiological studies have shown that high calcium intake can prevent colorectal cancer.
In a study by the American Cancer Society of 120,000 men and women, those with the highest calcium intakes had a modestly reduced risk of colorectal cancer, compared to those with the lowest intakes. But the benefits leveled off at 1,200 mg per day.
Another randomized, placebo-controlled research effort, the Calcium Polyp Prevention Study and European Cancer Prevention Organisation Intervention Study, found that supplementing with 1,200 to 2,000 mg of calcium per day reduced risk of recurrence of colorectal cancers in both men and women.
A study out of Iowa of 35,000 postmenopausal women uncovered similar results. Women taking 1,280 or more mg per day of calcium had a 41 percent reduction in colorectal cancer, compared to intakes of approximately 800 mg per day.
And a study in Sweden of more than 61,000 women found the risk of colorectal cancer was 28 percent lower among women with the highest calcium intakes (800 to 1,000 mg per day) versus those with just 400 to 500 mg per day.
Then, there was the Nurses’ Health Study and the Health Professionals Follow-up Study of 135,000 men and women. Researchers found that those with a calcium intake of more than 700 mg per day had a 35 percent to 45 percent reduced colon cancer risk than those with intakes of less than 500 mg per day.
But what about other cancers? While there’s not as many definitive studies on other cancers, The World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) published an authoritative review of all existing evidence about food, nutrition, and physical activity in relation to overall cancer risk. They concluded that calcium does have a protective effect against cancer.
From the research it appears that the sweet spot for calcium consumption is around 1,280 mg of calcium a day. But how can you track your consumption?
Five tips for monitoring your calcium levels
Here are five tips to help you know if you’re getting too much or too little calcium:
1. Keep a food diary for two weeks. It should give you a pretty good idea of how much calcium you’re getting. Here are a few common food products you may eat regularly. It’s possible you may get plenty of calcium just from food… especially if you consume foods fortified with calcium!
|Ricotta, part-skim||4 oz||335 mg|
|Sardines with bones (canned)||3 oz||325 mg|
|Mozzarella, part-skim||1 oz||210 mg|
|Cheddar||1 oz||205 mg|
|Yogurt, plain, low-fat||6 oz||310 mg|
|Greek yogurt||6 oz||200 mg|
|Fresh broccoli, cooked||8 oz||60 mg|
|Bok choy, cooked/boiled||8 oz||160 mg|
|Almond, rice, or soy milk||8 oz||300 mg|
|Orange juice||4 oz||150 mg|
|Cereal||8 oz||100 – 1,000 mg|
Keep in mind that if you already consume many calcium-rich foods, you may not need to get any more through a supplement. However, if you follow a vegan diet, or are lactose intolerant and consume no dairy, you may need to supplement.
2. Check your medications. Ask your doctor or pharmacist whether any drugs you take promote or deplete calcium… and adjust accordingly.
3. Take care with antacids. If you take over-the-counter drugs such as antacids, find out if they contain or promote the absorption of calcium.
4. Don’t take calcium alone. If you take calcium supplements, be sure you also get vitamins D3 and K2. They all work as a team, and none of them work optimally without the others. In fact, supplementing with calcium alone has been linked with heart attacks.
5. Check the type of calcium you’re taking and when you’re taking it. Timing of calcium supplements is important… take calcium carbonate with meals for absorption, or calcium citrate any time.
Calcium has always been discussed in relation to bone health but is very rarely taken into consideration when it comes to discussions on cancer prevention or treatment. That’s a mistake. I encourage you to ensure you’re getting adequate intake of calcium—not too much, not too little—as part of your daily anti-cancer protocol. And if you have cancer, work with your medical team to manage out of control calcium levels during your treatment.