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  CALCIUM and MAJOR DISEASE

Abstract: Calcium is confirmed to reduce risk of Colorectal Cancer and Stroke.  Although it does increase risk of Prostate Cancer for men somewhat, most health-interested men and women should aim for a Calcium  intake of 1,000 mg per day in a combination of diet and supplements.  Calcium may provide benefit from shorter durations of use than those needed for best benefit from antioxidants.  A separate paper provides evidence on the effect of Calcium in benefiting osteoporosis.

Background:  Calcium intake in foods and especially its content in dairy products has been a much studied area of research.  Although Calcium has usually been thought of as a factor in bone health, it appears to be a factor that more importantly can affect the progress of the major diseases, and especially the progress of cancer.

Calcium and Colorectal Cancer:  Most research on Calcium has been for its effect on Colon and Rectal or Colorectal cancer.  Table C1 first lists the 10 key studies of this found.  Nine of the ten show substantial benefits for Calcium in reducing risk of both Colon and Rectal Cancer.  This is an unusually consistent result from multiple studies, and confirms at high overall significance a reduction in cancer risk for maintaining an adequate intake of calcium.  These ten studies show an average risk ratio of Colorectal Cancer from 13 different included risk comparisons as a value of 0.61 from a usual difference of about 700 mg per day in Calcium intake. Similar benefits are indicated for men and women, and for Calcium in overall foods, in dairy foods, or in Calcium supplements.  A slightly more conservative risk ratio of 0.65 was selected for use in Life Ahead for a 800 mg/day difference in Calcium, with formula as:

      Risk Ratio for Colorectal Cancer = Exp  (- 0.00054 *calcium, mg/day)

A maximum amount of Calcium accepted for use in Life Ahead is 1000 mg/day as research does not now confirm values for much larger differences.  Thus a largest benefit computed for Colorectal Cancer is a risk factor benefit of 0.58 for any amount of Calcium. 

Calcium normally is closely related to Vitamin D, and much of the research shows similar relationships of Colorectal Cancer with Vitamin D and calcium.  Thus it is difficult to ascertain which of these is the true causal factor.  An active form of Vitamin D, [1,25(OH)2D], appears to inhibit carcinogenesis. But the estimation of Vitamin D is difficult as it is enhanced by sunlight as well as by foods and supplements.  Thus the health-interested person must consider Calcium as the related health factor to monitor.

No useful information was found relating the benefits of Calcium to its duration of use.  The semi-quantitative estimates for studies C1-C10 suggest that all involved long term duration of Calcium use.  Study C11 investigated the effect of a 1200 mg/day supplement on the progress of adenomas – a precursor of cancer – via a 1-4 year clinical study. A risk factor of 0.74 found suggested a benefit from the 1-2 year average duration measured.  This in turn suggests that Calcium may act to inhibit Cancer development near immediately, or at least over a few years of time.  With lack of any current and adequate Global analysis of Calcium, this factor is now included in Life Ahead as a direct statistical association.

Calcium and Prostate Cancer:  A quite different result is shown for the effect of Calcium on Prostate Cancer via Studies P1-P6. Allowing for the high amount of Calcium in study P2, an average overall risk is about 1.35, with an increase in risk for increasing amounts of Calcium. The mechanism noted above for Calcium and Colorectal Cancer involving a special form of Vitamin D has been cited here, but it is not clear how this could act differently on Colorectal and Prostate cancers.  Despite the variation in results for studies P1 - P6, the overall results suggest an increase in risk of about 1.3 times for 700 mg of Calcium per day.

This effect of calcium on Prostate Cancer risk is included in Life Ahead for men.  Men are cautioned that the benefit for Calcium in reducing Colorectal Cancer could be partly offset via a negative from Prostate Cancer.  This could become a consideration for men having either Prostate Cancer or a family history of this disease. And it warns against taking amounts of calcium higher than those confirmed to be beneficial.

Calcium and Other Cancers:  The only other useful research found relating Calcium use to risk of cancer was that for women for Breast and Endometrial Cancer, studies B1 and B2.  The Nurses study on a very large group of women found a significant risk ratio on Breast Cancer of 0.69, but this applied only to pre-menopausal women.  Because this was only a single study, and risks during this younger age period usually have only a small effect on ultimate Well-Days of life, this factor has not been included in Life Ahead now.

The large case control study B2 in Sweden showed that Calcium produced a substantial reduction in risk of Endometrial cancer.  This single study result does not meet that usual need for at least three confirming studies for inclusion of a factor in Life Ahead.  Yet this and study B1 suggest to health-interested women that they may have a somewhat larger benefit for including adequate calcium in their diets than that now is acknowledged in Life Ahead.

Calcium and Heart Disease:  The research on studies H1-H3 is clearly inadequate now for an inclusion in Life Ahead.  A further problem on Calcium and heart disease is that any benefits of Calcium might be obtained via its value as an antioxidant.  If so, more than the maximum needed antioxidant benefit can be obtained from the four antioxidants now included, and any further benefit here from Calcium could be duplicative.

Calcium and Stroke:  The consistent results from the three studies H4 - H6 citing benefits for Calcium intake on stroke are sufficiently convincing for this factor to be included in Life Ahead.  Studies H5 and H6 are large and important studies. Life Ahead uses a modest reduction in Stroke risk of 0.75 for a 800 mg/day increase in Calcium, again with a 1000 mg/day total limit on any benefit from this nutrient.

Conclusion:  A typical US diet includes about 550-600 mg/day of Calcium in foods.  Risk factors in Life Ahead are taken relative to this average value.  Thus a supplement of at least 500 mg/day would appear to be prudent for any health-interested person. Large men and those that do not much drink milk should consider a 1000 mg/day supplement.  Persons should monitor their intake of Calcium periodically with Life Ahead and be sure that their total intake from foods and supplements is at least 1000 mg/day. Life Ahead identifies amounts of Calcium in diets and desired health targets for each individual that are adjusted for gender and body weight.

Benefits to cancer from Antioxidants and Cardiofitness appear to apply to all or nearly all sites of the disease. Thus it is possible that despite of lack of research now, the benefits from Calcium may apply to other types of cancer not yet researched.   Benefits of adequate Calcium should be particularly useful for women.  Life Ahead now computes a net risk of Calcium on men for both Prostate and Colorectal Cancer.  The computed advantage for men usually will be for use of Calcium because the its benefit to Colorectal cancer will be larger than any debit from Prostate cancer. Also, Life Ahead now includes the modest potential reduction in Stroke obtained from Calcium.  But health-interested persons should recognize that Calcium many need accompanying amounts of Vitamin D for benefit.  Thus any Calcium supplements used should included accompanying amounts of Vitamin D.