Please don’t eat the daisies

daisiesBy: Christopher Labos MD CM FRCPC

Like most people I get most of my news by scanning the headlines and picking a few choice articles to read in depth. In general, political scandals get a pass and world events get a second look. But one day I awoke to find this headline in my Twitter feed: Eating flowers ‘could help reduce cancer risk.’

I really couldn’t let this slide.

I had to read this article if only to find out why “could help reduce cancer risk” was in quotation marks.

The article was published in the British newspaper The Telegraph and opened with this paragraph: “Eating flowers grown in British gardens could help to reduce the risk of heart disease and cancer, according to a new study.”

It made me wonder whether the chipmunks that harass my garden all summer might be on to something.

The article itself was sparse on details, so I went back to the original study, which was published in the Journal of Food Science. This is hardly a high-end medical journal, with an impact factor (how we measure the quality of medical journals) of 1.775, which is pretty underwhelming.

Already skeptical, I read on. Essentially a group of researchers measured the levels of phenols in various species of flowers and reported their antioxidant effects using a variety of chemical tests. Nowhere did the report mention cancer or heart disease, nor did they do any tests on human subjects. Clearly, the Telegraph reporter decided to editorialize a bit.

The big leap was that antioxidants must be good for you because everyone is talking about them. In fact, the clinical evidence for antioxidants is very poor.

It is true that antioxidants can neutralize free radicals. It also true that free radicals have been implicated in a number of diseases, including heart disease and cancer. But clinical trials of antioxidants have come back negative.

Vitamin A, vitamin C, vitamin E and carotenoids (all antioxidants) have been studied in large trials like the Physician’s Health study and the Women’s Health Initiative and have been found to have no benefit in preventing heart disease or cancer.

A recent Cochrane Review came to the same conclusion. Certain supplements like beta carotene have actually been seen to increase cancer risk in certain subgroups like smokers. Will phenols, the latest class of antioxidants to gain popularity, have better outcomes? We shall see; but so far the track record for antioxidants is not stellar.

Clearly, the conclusions of the newspaper account went beyond what the scientific study had reported. The danger of these types of stories is that, firstly, the public becomes misinformed. Although some flowers are edible and can be part of very appetizing dishes, some can be poisonous when ingested. Lilies, azaleas and poinsettias can cause health problems if eaten, although serious health consequences are fairly rare.

What happened here is that a study with very limited clinical applicability was given undue prominence by a British newspaper that capped it off with an eye-catching title that had little evidence to back it up.

Fortunately, most North American media outlets didn’t pick up the flower story and the National Health Service in Britain did a fairly good job of exposing the flimsy evidence behind the headline.

Although I recognize that most people are not going to start reading obscure medical journals, it is worthwhile to go beyond the headlines and read news reports all the way to the bottom. It is especially important to do so if the headline contains the word “miracle cure” or “breakthrough,” because by the end of the article you will probably realize that it is neither.

So my advice to you is not to go eat the flowers in your garden, not to go buy something simply because it has the name antioxidant on the label, and always read health related articles all the way to the bottom. For those of you who made it to the end of this article: well done.

 

Christopher Labos MD CM FRCPC

Division of Epidemiology, Biostatistics and Occupational Health

McGill University

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