Health Effects of Wine - Heavy Metals in Wine Controversy

Heavy Metals in Wine Controversy

In 2008, researchers from Kingston University in London discovered red wine to contain high levels of toxic metals relative to other beverages in the sample. Although the metal ions, which included chromium, copper, iron, manganese, nickel, vanadium and zinc, were also present in other plant-based beverages, the sample wine tested significantly higher for all metal ions, especially vanadium. Risk assessment was calculated using "target hazard quotients" (THQ), a method of quantifying health concerns associated with lifetime exposure to chemical pollutants. Developed by the Environmental Protection Agency in the US and used mainly to examine seafood, a THQ of less than 1 represents no concern while, for example, mercury levels in fish calculated to have THQs of between 1 and 5 would represent cause for concern.

The researchers stressed that a single glass of wine would not lead to metal poisoning, pointing out that their THQ calculations were based on the average person drinking one-third of a bottle of wine (250 ml) every day between the ages of 18 and 80. However the "combined THQ values" for metal ions in the red wine they analyzed were reported to be as high as 125. A subsequent study by the same university using a meta analysis of data based on wine samples from a selection of mostly European countries found equally high levels of vanadium in many red wines, showing combined THQ values in the range of 50 to 200, with some as high as 350.

The findings sparked immediate controversy due to several issues: the study's reliance on secondary data; the assumption that all wines contributing to that data were representative of the countries stated; and the grouping together of poorly-understood high-concentration ions, such as vanadium, with relatively low-level, common ions such as copper and manganese. While some publications printed lists of countries showing the "worst offenders" and reported that wine from other countries did not pose a health risk, others pointed out that the lack of identifiable wines and grape varieties, specific producers or even wine regions, provided only misleading generalizations that should not be relied upon in choosing wines.

In a news bulletin following the widespread reporting of the findings, the UK's National Health Service (NHS) were also concerned that "the way the researchers added together hazards from different metals to produce a final score for individual wines may not be particularly meaningful". Commentators in the US questioned the relevance of seafood-based THQ assessments to agricultural produce, with the TTB, responsible for testing imports for metal ion contamination, have not detected an increased risk. George Solas, quality assessor for the Canadian Liquor Control Board of Ontario (LCBO) claimed that the levels of heavy metal contamination reported were within the permitted levels for drinking water in tested reservoirs.

Whereas the NHS also described calls for improved wine labeling as an "extreme response" to research which provided "few solid answers", they acknowledged the authors call for further research to investigate wine production, including the influence that grape variety, soil type, geographical region, insecticides, containment vessels and seasonal variations may have on metal ion uptake.