Edible flowers not proven to prevent cancer

Behind the Headlines

Wednesday April 23 2014

Edible flowers have long been a staple of Chinese cuisine

Some flowers were found to have high levels of antioxidants

“Eating flowers grown in British gardens could help to reduce the risk of heart disease and cancer, according to a new study,” The Daily Telegraph reports.

However, the study the news is based on did not actually involve any humans.

So while the flowers may be edible, claims they prevent cancer are unproven.

The study in question measured the levels of one group of antioxidant chemicals called phenolics in 10 edible flowers. It found that there are high levels of these compounds in tree peony; a group of plants native to China. Tree peony extracts also had the highest levels of antioxidant activity.

As mentioned, the study did not assess the effects of the flowers on human health outcomes.

While antioxidants have been suggested to have various health benefits, a review of antioxidant supplements found no evidence of a beneficial effect on survival. In fact it found that some compounds might actually be harmful.

The review highlights the importance of not assuming that compounds will be beneficial just based on their antioxidant levels.

This doesn’t mean people can’t continue to enjoy edible flowers for their beauty and taste. However, some flowers are poisonous, so people should be careful not to eat flowers unless they are certain they are safe.

Current methods known to reduce the risk of cancer, such as not smoking, eating a healthy diet and regular exercise, may not be particularly newsworthy, but they are tried and tested.

 

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Remember, claims made for THR products are based on traditional usage and not on evidence of a product's effectiveness. Using them for more serious conditions could put you at risk, especially if you delay seeking advice from a medical practitioner.

 

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Where did the story come from?

The study was carried out by researchers from Zhejiang University and other research centres in China. It was funded by Foundation of Fuli Institute of Food Science, Zhejiang University, and the National Natural Science Foundation of China. The study was published in the peer-reviewed Journal of Food Science.

The Daily Telegraph reports on this story briefly and non-critically. The suggestion in their headline that edible flowers may reduce cancer risk is unproven by this study.

 

What kind of research was this?

This was laboratory research looking at the antioxidant chemicals in edible flowers found in China. The study measured the amount of a specific group of antioxidant compounds called phenolics, which includes flavonoids.

The authors say that increased consumption of phenolics has been associated with reduced risk of cardiovascular disease and certain cancers.

While this study can tell us how much of these compounds are present in the flowers, it cannot tell us what effect they have on human health.

 

What did the research involve?

The researchers measured the level of phenolic compounds in 10 edible flowers commonly found in China:

  • Paeonia suffruticosa (tree peony)
  • Lilium brownii var. viridulum (a type of lily)
  • Flos lonicerae (Japanese honeysuckle)
  • Rosa chinensis (China rose)
  • Lavandula pedunculata (French lavender)
  • Prunus persica (peach)
  • Hibiscus sabdariffa (a type of hibiscus)
  • Flos carthami (safflower)
  • Chrysanthemum morifolium (a type of chrysanthemum)
  • Flos rosae rugosae (a type of rose)

They also looked at exactly which phenolic compounds were found in the flowers, and measured their antioxidant activity.

 

What were the basic results?

Paeonia suffruticosa (tree peony) had the highest levels of phenolic compounds and Flos lonicerae (Japanese honeysuckle) had the highest levels of flavonoids. Paeonia suffruticosa and Rosa chinensis extracts had the high levels of antioxidant activity. Overall, higher levels of phenolic compounds in the flowers was associated with high levels of antioxidant activity.

 

How did the researchers interpret the results?

The researchers concluded that the 10 edible flowers tested were rich sources of phenolic compounds and antioxidant activity. They also suggest that the flower extracts have potential to be used as food additives to prevent chronic diseases and promote health.

 

Conclusion

The current study has identified the levels of phenolic compounds in certain edible flowers. These compounds have antioxidant compounds, and antioxidants have been suggested to have various health benefits, including fighting cancer and heart disease. However, the current study has not assessed whether eating these flowers could have effects on human health, or at what levels they would need to be consumed to have any effects.

A Cochrane systematic review pooled data on the effects of antioxidant supplements tested in clinical trials and found no evidence of beneficial effects on survival in healthy people or people with specific diseases.

Certain antioxidant supplements (beta-carotene and vitamin E) appeared to potentially slightly increase the risk of death during the trials.

While the trials in this review may not have tested edible flower extracts specifically, the review does highlight the importance of testing compounds to be sure of their effects, rather than assuming that simply because they have antioxidant properties they must be beneficial.

Just because a substance comes from a plant you should never assume that it is guaranteed to be safe. Some of the deadliest poisons are derived from plants.

Similarly, despite claims to the contrary, it is untrue that science looks down its nose at substances derived from plants. Many widely used drugs, including aspirin, warfarin and some chemotherapy drugs are based on plant chemicals.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links to the headlines

Eating flowers 'could help reduce cancer risk'. The Daily Telegraph, April 22 2014

Links to the science

Xiong L, Yang J, Jiang Y, et al. Phenolic Compounds and Antioxidant Capacities of 10 Common Edible Flowers from China. Journal of Food Science. Published online March 12 2014

Further reading

Bjelakovic G, Nikolova D, Gludd LL et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database of Systematic Reviews. June 2012

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Analysis by Bazian

Edited by NHS Choices

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