Forum
calcium it carries could help
CARDIOVASCULAR HEALTH
reduce blood pressure, whereas
low serum magnesium concen-
Hard Data for Hard Water
trations common to people
Are people who drink  hard water containing higher levels of calci- living in soft-water areas
um and/or magnesium less likely to suffer cardiovascular disease? appear linked with arrhythmias.
This is the question that delegates who attended a World Health  Couple this with the fact that
Organization (WHO) meeting 21 22 January 2008 in Geneva, many of today s refined foods
Switzerland, are now trying to answer once and for all. are low in magnesium, that
The idea that hard water particularly that with higher magne- many people in developed
sium concentrations helps ward off cardiovascular problems has countries either do not cover or only barely cover their magnesium
been around for 50 years. However, due to the ecologic nature of needs, and that magnesium in drinking water is more bioavailable
most studies, uncontrolled confounding factors, and the different than that in food, and you can see how [even the relatively small]
variables and outcomes measured, no firm conclusions have ever extra supply of this mineral to people in hard-water areas could be
been drawn. The WHO is therefore coordinating worldwide efforts beneficial, says Frantisek Kozísek, head of the National Reference
to compare cardiovascular morbidity before and after changes in the Centre for Drinking Water in Prague, Czech Republic.  Cooking
calcium/magnesium content of water supplies. food in soft water also tends to remove magnesium, calcium, and
The aim of the Geneva meeting was to discuss how such a other essential elements from food, making matters worse.
study ultimately a composite of many smaller studies from differ- The results could lead to countries adopting legislation to supple-
ent nations should be performed.  A prospective, multi-country ment drinking water supplies in soft-water areas with calcium and
study following a single protocol would be the best way to ensure a magnesium. Kozísek has already proposed that levels of calcium and
sufficiently large sample for overall analysis . . . if we are to make magnesium in drinking water be set at 40 80 mg/L and 20 30
meaningful comparisons, says Paul Hunter, a professor of health mg/L, respectively.  The available evidence suggests these ranges
protection at the University of East Anglia, United Kingdom, whose could be beneficial, and . . . there is no evidence that harder water
group has been testing a possible protocol. causes any harm, he explains.
Hunter s work involved obtaining mortality and residence data Regu Regunathan, a consultant for the Water Quality
on individuals in areas where notable changes in water hardness had Association, says that any recommendations on magnesium or other
occurred through the introduction or cessation of softening practices, minerals must be based on absolutely solid data; otherwise, desalina-
allowing trends in cardiovascular mortality before and after the tion plants and industries providing water softeners and reverse
change in water hardness to be detected. osmosis devices could be needlessly affected. Indeed, soft water has
Controlling the confounding factors in a final meta-analysis palpable technical advantages over hard water, including reduced
involving populations from different countries could pose problems, scaling in appliances, pipes, and on surfaces, as well as better soap
but  the  before and after nature of the individual studies should cer- lathering. To this, Kozísek responds,  If health and technical aspects
tainly provide meaningful results at the population level, he says. of water are in contradiction, then cost benefit analyses of the con-
The mechanism by which hard water may provide protection sequences of both aspects should be made to decide what is more
against cardiovascular disease remains a matter of debate. The extra important for society.  Adrian Burton
according to the National Cancer Institute, 4,374 individuals were available for follow-
CANCER
about 630,000 deaths were expected to up between 1948 and 2005. Daily intake of
occur worldwide in 2007. Even moderate dairy products ranged from less than 0.5 cup
Dairy Paradox
changes in diet and lifestyle could prevent at at the lowest level to nearly 2 cups at the
The etiology of colorectal disease revolves least 70% of all colorectal cancer cases, highest; liquid milk constituted 94% of the
around genetic and environmental factors, according to a review in the December 2002 dairy intake.
particularly diet. A meta-analysis in the Gastroenterology Clinics of North America. Those individuals who grew up in fami-
7 July 2004 issue of the Journal of the The main culprits appear to be excessive lies reporting the highest levels of dairy con-
National Cancer Institute suggested that con- caloric intake, as well as frequent consump- sumption showed a nearly threefold increase
suming more dairy products and calcium tion of red meat, processed meats, alcohol, in the risk of colorectal cancer compared
may reduce colorectal cancer risk, but epi- and refined carbohydrates. with those from families reporting the lowest
demiologic studies on this link have yielded The historical cohort study employed intake. The elevated risk remained even after
inconsistent results. One explanation for data from the Carnegie Survey, conceptual- the researchers adjusted the data for potential
this inconsistency may be the timing of ized by Sir John Boyd Orr, which recorded confounders such as socioeconomic status
exposure: cancer develops over decades, and food consumption patterns in 1,343 English and meat, fruit, and vegetable intake. No
early-life exposures to carcinogens and and Scottish families from 1937 to 1939. other cancers were significantly affected by
growth factors could be a critical factor. A The survey was designed to investigate the higher dairy intakes.
new study designed to address this possibil- long-range impact of children s diet,  The mechanisms underlying these asso-
ity has found that adults who consumed growth, living conditions, and health on ciations remain unknown, but there is
more dairy during childhood may have a adult cardiovascular disease. increasing evidence that nutrition early in life
greater risk of developing colorectal cancer Dietary data were obtained using a 7- can have long-lasting programming effects,
in adulthood. The results appear in the day household inventory; also, weighed says lead author Jolieke C. van der Pols, an
December 2007 issue of the American inventories of all foods in the household epidemiologist at the University of Queens-
Journal of Clinical Nutrition. were conducted at the start and end of the land. For example, childhood dairy intake
Colorectal cancer is among the leading survey period. The average follow-up time appears to be inversely associated with adult-
causes of mortality in developed countries; for adults included in this study was 65 years; hood concentrations of insulin-like growth
A 114 VOLUME 116 | NUMBER 3 | March 2008 " Environmental Health Perspectives
Joseph Tart/EHP/istock