This story and its sidebar raise important concerns about the potentially toxic effects of too much zinc, but provides insufficient detail to allow consumers to accurately gauge the risks. It fails to discuss the limitations of animal studies and a small case series suggesting neurological impairment from excessive zinc, and makes vague references to studies suggesting links between zinc and health problems. Finally, in a story whose main point was to discuss the harm that can result from too much zinc, it was strange to see no mention of a strongly worded FDA advisory warning consumers not to take the zinc-based nasal spray Zicam.
We often hear the claim that we consume too little or too much of certain foods and nutrients, and that changing our habits may lead to better health. Good reporting can help consumers focus on changes that are most likely to be beneficial. Articles such as this pointing out potential for harm are also critically important for consumers.
While it probably can be assumed that the zinc-containing products discussed in the story are relatively inexpensive, the story contained no direct discussion of costs. Readers would have benefited from this information, for example, when evaluating the value of zinc-based cold remedies. The story mentions that zinc lozenges "may help and probably won’t hurt" when it comes to colds, but how much will the reader have to pay for a shot at this benefit? Readers’ perceptions would no doubt differ if the product costs $2 vs. $20.
The sidebar to this story notes that zinc lozenges have been tested in patients with colds or the flu in 14 studies over 25 years. It noted that benefits were seen in about half of the studies, but no benefits and potential harms were observed in other studies. It quantified the benefits found in one study, where colds, coughs and runny noses were of shorter duration in the zinc group compared with the group that received a placebo lozenge. While it would have been nice to see a description of the studies that found no benefit and/or harm (Were they more or less rigorous than the studies reporting benefits?), the story does enough to fulfill this criterion.
While the story suggests a number of potential harms associated with zinc, it makes no mention of the recent FDA warning on the zinc-based nasal spray, Zicam. In June, agency warned in no uncertain terms that consumers should stop taking and discard any Zicam nasal spray or gel that they have in their medicine cabinets. The agency had received more than 130 reports of consumers losing their sense of smell after taking Zicam. The story says merely that "researchers recommend avoiding nasal sprays containing zinc." This message is insufficient to convey the serious known risks associated with the use of this product.
The story does not adequately describe the design and limitations of many of the studies discussed. For example:
For the most part, the story struck a reasonable tone in discussing the risks of excessive zinc consumption. It stated that adverse effects were found among certain small groups and noted that too little zinc also could cause problems. When discussing the potential adverse effects of denture creams that contain zinc, the author was careful to include a reassuring quote that puts the risks in an appropriate context.
The story quotes four sources who are knowledgeable about zinc. However, it did not disclose that a key source, Dr. Imre Lengyel, receives funding from PRANA Biotechnology, a company which is developing a zinc chelation therapy for the treatment of Alzheimer’s disease. Given that the extent of this relationship is unknown and the article does not appear overtly biased, we’ll give the benefit of the doubt and award a satisfactory for this criterion–but barely.
Since the primary thrust of the story was the potential toxic effects of zinc (not the benefits), it would be inappropriate to criticize the reporting for not discussing alternatives to zinc.
The story states that consumers are receiving zinc through supplements, cold medicines that contain zinc, and in fortified foods. It also mentions foods that are naturally rich in zinc such as oysters and beef, as well as unintentional sources of intake such as denture cream.
The story suggests that a recent paper by Flinn and colleagues was "one of the first pointing to zinc’s potential dangers," but research as far back as the 1930s has suggested that zinc applied to the nose was associated with loss of the sense of smell. Papers in the 1960s and 70s demonstrated other negative effects, such as induction of copper deficiency. It is inaccurate to suggest that excessive zinc intake is a relatively new concern.
Because the story quotes multiple experts, the reader can assume the story did not rely on a press release as the sole source of information.