Study linking high intake of calcium rich foods and calcium supplements to low death risk

Saturday Nov 16, 2013 (foodconsumer.org) -- A new study of Chinese men and women in PLoS One suggests that eating calcium-rich foods or taking calcium supplements habitually can drastically reduce risk of premature death from all causes and cardiovascular disease.

The study led by R. Chan and colleagues from the Chinese University of Hong Kong in Hong Kong, SAR shows Chinese men and women who had the highest intake of calcium supplements and calcium rich foods were almost 40% and 30% less likely to die from all causes and cardiovascular disease respectively, compared with those who had the lowest intake.

Epidemiological studies of calcium intake and mortality risk are often conducted in populations with moderate to high calcium intake, according to the authors.  The current study focused on a small group of Chinese men and women with their mean habitual dietary calcium intake lower than 700 mg per day.

For the study, researchers surveyed 3,139 Chinese men and women aged 65 years or older who were enrolled in a population-based prospective cohort study and free of heart diseases or stroke at baseline for their intake of dietary calcium or calcium rich foods, and calcium supplements.  Then subjects were followed up for a median of 9.1 years during which, 529 all-cause deaths and 114 deaths from cardiovascular disease (heart attack and stroke) were recorded.

Dietary calcium intake from calcium rich foods was found inversely associated with mortality, meaning that high intake of dietary calcium was linked to low death risk.  Specifically, compared with those in the lowest quartile of dietary calcium intake (lower than 458 mg/d for men and lower than 417 mg/d for women), those Chinese men and women in the highest quartile of dietary calcium intake (greater than 762 mg/d for men and greater than 688 mg/d for women) had their risk of all-cause mortality reduced by 37%.  The risk of death from cardiovascular disease was also decreased by 30% among those in the highest intake of dietary calcium or calcium rich foods.

Similarly, the highest intake of supplemental calcium from calcium supplements was inversely correlated with risk of all-cause mortality and mortality from cardiovascular disease.

The researchers concluded "Higher intake of dietary calcium was associated with reduced risk of all-cause mortality and possibly cardiovascular mortality in Chinese older people with low habitual calcium intake."

Chan R, Leung J, Woo J. A prospective cohort study examining the associations of dietary calcium intake with all-cause and cardiovascular mortality in older Chinese community-dwelling people. PLoS One. 2013 Nov 5;8(11):e80895. doi: 10.1371/journal.pone.0080895.

Calcium rich foods

Calcium rich foods include milk, yogurt, Cheddar cheese, pinto beans, red beans, white beans, tofu, Bok Choy, kale, broccoli, spinach, rhubarb, and fruit punch with calcium supplements.

Factors that affect calcium absorption

Not all calcium rich foods are the same.  Absorption of calcium element is influenced by many factors and can be affected by the calcium sources per se.  Vitamin D is well known to promote calcium absorption.  High intake of sodium, phosphorus, protein and caffeine can cause calcium secretion and make it difficult for the body to absorb the important mineral.  Absorption of calcium element may be a problem for those who have high intake of protein rich foods such as meat and dairy products, salt and coffee.   For those people, calcium supplements may be beneficial.

Urinary pH and absorption of calcium element

Calcium at low pH can be precipitated along with other weak acids and deposited on arteries causing coronary heart disease or in the kidneys to form kidney stones.  Epidemiological studies have already associated high doses of calcium supplements with increased risk of heart disease.   But not all studies are consistent.   Theoretically, this is possible in some people whose body pH is acidic, which can vary depending upon the location.  Salivary pH, urinary pH and serum pH may not be the same.  It is certain that an acidic pH is harmful.  An acidic pH can caused by many things including drugs, diseases and inadequate diet.  It may be a good idea to check urinary pH from time to time to make sure to keep urinary pH normal.  Urinary pH ranges from 4.6 to 8 with neutral or pH 7 desired.  Kidney stones can be formed at a low pH.  Dietary supplements like potassium citrate and sodium bicarbonate can help to adjust the pH.  Studies have already found potassium citrate, which may be available at any local pharmacy, can help dissolve kidney stones.  (David Liu, PHD)