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Can blueberries and red wine boost immunity?

“Red wine and blueberries could protect the body…by boosting the immune system,” The Daily Telegraph reports. Laboratory research suggests that a combination of substances found in berries and wine enhances the activity of a ‘germ-fighting’ gene.

This was a laboratory study in which scientists analysed 446 different compounds for their effect on the activity (gene expression) of a gene called cathelicidin antimicrobial peptide (CAMP), which produces proteins that can help defend against bacterial infection.

It found that two compounds in particular – resveratrol, which is found in red grapes, and pterostilbene, found in blueberries – appear to increase expression of the CAMP gene.

Individually the effect was modest, but when used in combination with vitamin D3 there was a statistically significant increase in gene expression.

The findings of this study are therefore of interest – but it should be noted that the research was undertaken not in humans (or even mice or rats) but in laboratory cell cultures. The study does not prove that consuming foods high in these compounds will boost the human immune system. 

Whether this research will lead to specific treatments to boost immune function is not clear. What is clear is that fruit is an important part of a healthy balanced diet.

Where did the story come from?

The study was carried out by researchers from the Linus Pauling Institute, Oregon State University in the US and was funded by the National Institutes of Health.

The study was published in the peer-reviewed journal Molecular Nutrition and Food Research.

The results of this laboratory study were perhaps overplayed by the papers, as the research did not involve humans or even animals, but cell cultures.

What kind of research was this?

This was a laboratory experiment in which researchers aimed to identify new compounds which might be involved in regulating the expression of one gene which is involved in protecting the body against microbes such as bacteria.

The gene in question is the cathelicidin antimicrobial peptide (CAMP) gene. The protein produced by this gene is, say the researchers, effective at killing a wide range of bacteria, and is produced by immune system cells and the cells that line the cavities and structures of the body. 

CAMP gene expression is known to be regulated by several compounds, including vitamin D3, which the body makes from sunlight. Read more about the so-called sunlight vitamin.

Scientists wanted to identify additional molecules that can lead to the CAMP gene expression (the gene being “switched on” to produce the CAMP protein).

The researchers hope that identifying such compounds could increase knowledge of the biological pathways involved in regulating CAMP gene expression and lead to better understanding of how diet and nutrition affect immune function. It may also help in the development of compounds to boost the immune response, they say.

What did the research involve?

For this experiment, the researchers tested a panel of 446 compounds currently being used in clinical trials to see if they were capable of “switching on” the CAMP gene in human cells in the laboratory.

For their first set of experiments they used one type of human immune system cell. The researchers inserted special pieces of DNA into the cells that meant that when the CAMP gene was switched on, the cell also started to produce a light emitting protein. This allowed the researchers to easily monitor whether the CAMP gene had been ‘switched on’ in the cells by the compounds.

The researchers treated the cells with various combinations of 446 compounds, at differing concentrations and intervals. The researchers then monitored the cells to see which compounds or combinations of compounds caused the cells to emit light – meaning that they were also switching on the CAMP gene.

The compounds that were being tested included reservatrol and pterostilbene, from a class of compound known as stilbenoids. Both of these compounds are naturally produced by plants. Resveratrol is probably best known for being found in the skins of red grapes, and therefore in wine. Pterostilbene is found in blueberries and grapes.

Once they identified compounds which switched on the CAMP gene, they went on to do other tests on cells in the laboratory to confirm their results and look at how the compounds were having an effect.

What were the basic results?

The researchers found that two compounds, reservatrol and pterostilbene, caused the CAMP gene to be switched on. When cells were treated with a combination of either of these compounds plus a form of vitamin D, this caused the gene to produce even more protein than if the cells were treated with any of the compounds individually.

The researchers’ other experiments suggested that stilbenoids might affect some of the signalling pathways that allow vitamin D to do its job in switching on the CAMP gene.

How did the researchers interpret the results?

The researchers say their findings demonstrate for the first time that stilbenoid compounds may have the potential to boost the immune response by increasing CAMP gene expression, particularly in combination with vitamin D. They say that this might have applications for humans, but note that this will need to be tested.

Conclusion

This study suggests that two plant compounds can increase expression of one gene that produces an antimicrobial protein in human cells in the laboratory. They had an even greater effect if the cells were also treated with vitamin D.

However, this was an experiment on cells cultured in the laboratory, on one particular gene. Many genes and proteins are involved in regulating human immune system function and fighting infection. Also, as the researchers point out, the two compounds were applied directly to the cells in this study, but whether they will have the same effect if eaten is far from clear, as both are processed to form different compounds by the digestive system and liver. Because of this, they think that these compounds might have more promise if applied to the skin to improve “barrier” defences against micro-organisms. However, this will have to be tested.
 
We know that fruit is good for us – but far more work is required before scientists can say whether dietary intake of these two compounds can boost the immune function by increasing the expression of this one gene. Like any alcoholic drink, red wine should be consumed in moderation.

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