I have blogged before on calcium and concluded we should supplement if we do not get enough calcium in our diet. Contrary to recent fears, the majority of studies show that the risk of cardiovascular disease appears to increase, not decrease, in those with inadequate calcium intake:
What about cancer and calcium intake? In particular, what about lung cancer?
Worldwide, lung cancer is the most common cancer and the most common cause of cancer deaths. In 2008, there were 1.6 million new cases, and 1.4 million deaths due to lung cancer. The highest rates are in Europe and North America. The population group most likely to get lung cancer is people over 50 who have a history of smoking. In contrast to the mortality rate in men, which began declining more than 20 years ago, women’s lung cancer mortality rates have been rising over the last decades. In the USA, the lifetime risk of developing lung cancer is a staggering 8% in men and 6% in women.
Dr. Yumie Takata and colleagues of the Vanderbilt University School of Medicine recently studied calcium and magnesium intakes and incidence of lung cancer in 71,000 Chinese women who were followed for an average of 11 years. During that time, 428 women got lung cancer.
The median intake of dietary calcium was 441 mg, while dietary magnesium was 266 mg. This calcium intake is low by USA standards, while the magnesium intake is about the same as an average American.
Takata Y, Shu XO, Yang G, Li H, Dai Q, Gao J, Cai Q, Gao YT, Zheng W. Calcium Intake and Lung Cancer Risk Among Female Nonsmokers: A Report from the Shanghai Women’s Health Study. Cancer Epidemiol Biomarkers Prev. 2013 Jan;22(1):50-7.
The authors found that Intakes of calcium and, interestingly, the calcium-to-magnesium ratio were inversely associated with lung cancer risk. Meaning, higher intake of calcium was associated with a lower risk of lung cancer. Higher dietary magnesium intakes were not associated with lower risk of lung cancer.
The corresponding risk for the highest quartile of calcium intake compared with the lowest quartile were lower (RR = 0.66) for calcium intakes, and lower (RR= 0.62) for higher calcium to magnesium ratio of dietary intake of the two minerals. In other words, the risk of lung cancer decreased when people had high calcium intakes and high calcium intakes combined with low magnesium intakes. Furthermore, no lower risk was found for the use of calcium supplements or vitamin D supplements, but the vitamin D dosages used were meaningless.
The authors point out their findings were for dietary calcium, not calcium supplements and stated,
“Unlike many North American and European countries, where the majority of previous studies have been conducted, the consumption of dairy foods in China is relatively uncommon (43% reported no intake of dairy foods in our study) and a considerable amount of calcium intake comes from nondairy foods such as rice and vegetables.”
This study adds continued mixed results in the study of calcium intake and health outcomes. It may be that higher calcium intakes, especially via dairy products, increase the risk of some adverse health outcomes, but as this study shows, research to date is mixed.
As far as the dietary calcium to magnesium ratio and risk of lung cancer, which showed an association with lung cancer (the higher the ratio, the lower the risk of lung cancer) while dietary magnesium did not, the authors had no explanation for the calcium to magnesium ratio, and nor do I. Readers, any ideas or theories?