Common Questions About Calcium – Its Association with Cancer

Calcium is the most abundant mineral in the body. It first brings to mind bone health and osteoporosis, but it is also critically important for functions such as nerve activity, cell signaling, hormone secretion and muscle contraction. Calcium requirements vary with age and sex (increasing during pregnancy or breastfeeding). Calcium is thought to have protective properties against some cancer types. Population-based observational studies suggest an association between calcium and colon (colorectal) and prostate cancer .

Why Do We Need Calcium?

Of the body’s calcium, %99 is located in bones and teeth, while the remaining %1 is in body fluids.

Functions of calcium:

• Calcium’s primary function is to support bone and tooth development and maintain their health.
• Blood calcium is necessary for blood clotting.
• It plays an active role in transmitting cell signals.
• Calcium is necessary for nerve conduction and regulation of the heartbeat.

Where Can We Obtain Calcium?

You can obtain the calcium you need without supplements by choosing calcium-rich foods. However, supplementation may be needed if a deficiency is diagnosed.

Calcium is abundant in dairy products but can also be obtained from other foods. However, you should consider how much calcium from your chosen food source is absorbed by the body. For example, fiber-rich foods reduce calcium absorption. Intestinal absorption is %32 for calcium in milk and dairy products, %21 for calcium in almonds and about % 5 for spinach.

The best calcium sources;

• milk and dairy products (2-3 drinking glasses: 600-700 mg calcium)
• molasses
• nuts (hazelnuts, peanuts, almonds)
• dried fruits
• dried legumes

Moderate calcium sources; green vegetables (1 portion: 60-70 mg), eggs, oranges, lemons, strawberries.

Poor calcium sources; leafy herbs (parsley, mint and so on, 1-2 bunches: 35-40 mg) and fruits.

How Much Calcium Do We Need Daily?

The daily calcium requirement of an adult is not known precisely and may vary individually. However, the amount needed to maintain an average calcium balance ranges from 200-800 mg daily.

Is There a Relationship Between Cancer and Calcium?

Calcium and Colorectal Cancer

In a multicenter, double-blind study, for 1-3 years, calcium carbonate (3 g or 1200 mg elemental calcium) or placebo (a product with no active ingredient) was given to patients with colorectal adenomas (colon polyps), with 930 patients followed endoscopically. Those receiving calcium supplements showed a significant reduction in new adenomas during follow-up compared with placebo.

Another analysis found this benefit particularly pronounced for hyperplastic polyps and tubular adenomas known to have the potential to cause cancer. Long-term follow-up showed that calcium’s protective effect continued 5 years after supplementation stopped.

However, studies also exist showing no reduction in colon polyp recurrence.

Another study of whether calcium reduced postoperative colon cancer recurrence included 220 patients who had undergone colorectal cancer surgery. Cancer recurrence risk was found to decrease significantly among those receiving calcium supplements.

Calcium and Prostate Cancer

Some studies suggest that high calcium intake may increase prostate cancer risk and that this may result from calcium suppressing vitamin D formation.

A case-control study involving 1062 men found that high calcium intake increased the risk of prostate cancer and metastatic prostate cancer.

These findings are supported by a study involving 65.321 older men in the United States. Participants completed questionnaires on diet and lifestyle, and prostate cancer status was documented during follow-up. Increased calcium intake, both dietary and supplemental, was found to significantly increase prostate cancer risk.

In addition, research involving 9.559 participants in the Prostate Cancer Prevention Trial found no significant association between calcium supplementation and prostate cancer risk. This study found a significant protective effect of high dietary calcium intake against high-grade prostate cancer, but no association with low-grade tumors.

What Is the Possible Mechanism by Which Calcium Reduces or Increases Cancer Risk?

Although it is uncertain whether calcium may help reduce colorectal cancer risk, we know it binds to bile acids and fatty acids in the gastrointestinal 8stomach-intestine) system. This reduces the ability of acids to damage cells in the intestinal lining. Calcium also plays a role in intracellular signaling and may affect cancer cells’ growth and proliferation pathways through this role.

Conclusion

Adequate calcium intake is unquestionably important for development in children and young people and for dental and bone health later in life. Balanced intake is suggested to reduce the risk of some cancers, particularly colorectal cancer. However, evidence regarding calcium’s effects on colon polyps is conflicting: some studies show protection, while others show no association.

Although calcium supplementation increased prostate and metastatic prostate cancer risk in population-based epidemiological studies, the findings were not confirmed in a randomized controlled clinical trial.

In conclusion, we do not support taking calcium “supplements” to prevent cancer. For other health conditions, such as pregnancy, breastfeeding, osteoporosis or kidney failure, decisions about calcium supplementation should be made together with the relevant specialist doctors.

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