A storm in a jam jar

Monday October 13 2008

“Scientists believe a chemical found in jam and jelly could help to combat cancer,” the Daily Express reported. It said research suggests that pectin – a natural gelling agent found in fruit and vegetables – can block cancer’s progress through the body. The Daily Mirror also covered the study and said that under the right conditions, pectin can “stick” to a protein which causes tumour growth and thereby stop the spread of cancer. BBC News gives the story a different angle, focusing instead on the presence of pectin in most fruit and vegetables, removing the need for people to eat “so-called superfoods”.

This is very early research. The fact that it was not carried out in living cells gives some idea of how preliminary it is in terms of its application to cancer prevention. Instead, the researchers explored whether components of pectin could bind to Gal3, a protein that has been implicated in cancer progression, and how they do this. At present, there is no good evidence that pectin prevents cancer in humans. By extension, it is also not known for sure if the pectin in jams and jellies has the same properties as the type of pectin used in this study. These foods are high in sugar, therefore a more conventional way of eating healthily would be to follow a balanced diet. 

Where did the story come from?

Dr A. Patrick Gunning and colleagues from the Institute of Food Research in Norwich carried out this study. The research was funded by the Biotechnology and Biological Sciences Research Council. The study was published in the peer-reviewed Journal of the Federation of American Societies for Experimental Biology: FASEB.

What kind of scientific study was this?

In this laboratory study, the researchers were interested in exploring some of the molecular properties of pectin. Pectin is a complex polysaccharide (a type of carbohydrate) found in the walls of plant cells. When pectin is treated with acid, certain components (arabinogalactans and galactans) are produced, which have been shown to inhibit the activity of another protein, galectin-3 (Gal3). Gal3 has been implicated in cancer progression and metastasis (the spread of cancer). Cancer cells use this protein to enable them to detach from tumours and reattach elsewhere. The researchers say that previous studies have suggested that only particular parts of pectin molecules might be able to bind to Gal3, namely the rhamnogalacturonan 1 units (RGI) – also called “hairy units”.

No live cells were used at all in these experiments. The researchers obtained hairy units derived from potato pectin. They used complex chemical processes to bind Gal3 (of human origin) to silica beads. A variety of processes including atomic force microscopy, scanning electron microscopy, fluorescent labelling, flow cytometry and force spectroscopy were then used to examine at molecular levels how the hairy regions of pectin bound to Gal3 on the beads.

What were the results of the study?

The researchers found that galactan from potato pectin binds specifically to Gal3. This binding was inhibited by adding lactose. They say that their finding that fragments of pectin can bind to Gal3 “is consistent with the molecular hypothesis for the observed anticancer action of modified pectin”. This means that their findings support the theory of how modified pectin might bind to Gal3 and have anticancer properties.

They note that the methods developed in this study provide a basis for further studies of optimal (the most effective) binding of molecules.

What interpretations did the researchers draw from these results?

The researchers say the results suggest that “bioactivity resides in the neutral sugar side chains of pectin polysaccharides, and that these components could be isolated and modified to optimize bioactivity”. They mean that through their research they have identified which components of pectin bind most effectively to Gal3 and that this knowledge might be used in future to enhance the activity of chemicals in the body.

What does the NHS Knowledge Service make of this study?

This laboratory study will be of interest to biochemists as it demonstrates that components of pectin molecules can bind to the Gal3 protein (which is implicated in cancer progression). From reading some of the news coverage, one may get the impression that eating jams and jellies would have some anti-cancer effect. However, this is very preliminary research, and such a conclusion would be premature. Jam and jellies have high sugar content, and people should not eat them in the hope that they will prevent cancer. A balanced diet and regular exercise are more accepted approaches to a healthy lifestyle and the possible prevention of diseases, including some cancers.

There are several relevant points to keep in mind when interpreting this study’s findings:

  • Modified pectin is already used by some people as an alternative therapy for prostate cancer and malignant melanoma. However, to date, research does not support its efficacy in humans. This study suggests which elements of pectin can bind to Gal3. It does not reveal whether pectin or its components actually have anticancer properties in humans.
  • This study found that the key components of pectin were the modified hairy regions – which the researchers found to be ideal candidates for binding to Gal3. These fragments are generated by sequential exposure to alkali and then acid treatment. The Daily Mail  quotes one of the lead researchers as suggesting that the modified pectin used in jam and jellies would have these anticancer properties. However, this needs to be investigated. It is not clear whether the pectin that occurs naturally in fruit and vegetables has the same properties as the simpler forms that were used in this experiment. While some previous studies have suggested that a diet high in fruit and vegetables can protect against some cancers, it is not known if this is due to their pectin content.

Cancer is a complex disease with many risk factors. There are a number of questions that remain unanswered about the effects of pectin. Firstly, whether or not pectin has any effect on cancer in humans and, secondly, what the best dietary sources of the right kinds of pectin are.

Analysis by Bazian
Edited by NHS Choices