Researchers from Vanderbilt University found that low ratios of the minerals were associated with reduced risk of colorectal cancer, according to findings presented at the Seventh Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research.
The potential implications of the results include accounting for the status of both nutrients in individuals before recommending supplementation with one or the other alone.
Colorectal cancer accounts for nine per cent of new cancer cases every year worldwide. The highest incidence rates are in the developed world, while Asia and Africa have the lowest incidence rates.
It remains one of the most curable cancers if diagnosis is made early.
Both high magnesium and calcium levels have been linked to reduced risks of the disease, but studies have also shown that high calcium levels inhibit the absorption of magnesium.
According to Qi Dai, MD, PhD, and co-workers, Americans have high calcium intake, but also a high incidence of colorectal cancer. "If calcium levels were involved alone, you'd expect the opposite direction. There may be something about these two factors combined – the ratio of one to the other – that might be at play," said Dai.
At the AACR conference, the researchers report results from a large clinical trial that found indeed that supplementation of calcium only reduced the risk of cancer recurrence if the ratio of calcium to magnesium was low, and remained low during the intervention period.
"The risk of colorectal cancer adenoma recurrence was reduced by 32 per cent among those with baseline calcium to magnesium ratio below the median in comparison to no reduction for those above the median," said Dai.
Further research is clearly needed to explore these findings, but they do appear to add to the body of knowledge of how dietary factors affect the risk of colorectal cancer.
A role for vitamin D?
Studies have also reported that a combination of calcium and vitamin D may also have potential benefits in relation to colorectal cancer. However, this area is somewhat controversial, with some studies reporting benefits while others report null results.
Researchers from Emory University in Atlanta and the University of Minnesota reported earlier this year that epidemiological studies supporting vitamin D and calcium for protection against colorectal cancer may be biochemically and biologically plausible.
Studies presented at the American Association for Cancer Research annual meeting in San Diego in April reported that the vitamin-mineral combination may increase levels of a protein called Bax, which plays a role in the controlling programmed cell death (apoptosis) in the colon. Moreover, high levels of calcium and vitamin D together are were also linked to higher levels of E-cadherin, which reportedly plays a role in the movement and proliferation of colon cells
Taken together, the studies add to a small but ever-growing body of research supporting the anti-cancer benefits of vitamin D plus calcium.
Source: Seventh Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention ResearchAbstract A62“Magnesium, calcium, and colorectal adenoma recurrence: Results from a randomized trial”Authors: Q. Dai, J. Baron.