Do peanuts cause cancer to spread faster?

alt="Peanut cartoon" Peanuts have been implicated in cancer metastasis. (Image: Sandhya Raghavan)

There’s some disconcerting news about everyone’s favourite nut snack (I said snack… not.. never mind). The humble peanut, known for its functional compounds like proteins, fibres, polyphenols, antioxidants, vitamins and minerals may be hiding a terrible secret. A team of researchers at the University of Liverpool unearthed the link between the legume and cancer metastasis. Frequent consumption of peanuts could increase the risk of cancer spread or metastasis.

The findings of the study are published in the journal Carcinogenesis.

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How do peanuts cause the spread of cancer?

Peanuts contain a carbohydrate-binding protein called Peanut agglutinin (PNA). When one eats peanuts, PNA rapidly enters into the bloodstream, interacts with the walls of the blood vessels and produces molecules known as cytokines.

Cytokines are small proteins that control the growth and activity of other immune cells. PNA results in the production of two types of cytokines IL-6 and MCP-1 which are known to promote cancer spread.

The uptick in cytokine production causes other cells in the blood vessel lining to express more cell surface adhesion molecules, which help cells stick to each other and their surroundings.

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These adhesion molecules attract circulating tumour cells, leading to the spread of cancer.

In an earlier study, Professor Lu-Gang Yu and colleagues found that PNA in the bloodstream binds to a special sugar in pre-cancerous and cancer cells. It interacts with a larger protein on the surface of the tumour cells, causing changes within the protein.

These changes expose the adhesion molecules on the surface of cancer cells. This increases their ability to stick more easily to blood vessels.

Cancer cells can also form clumps. Clumping not only strengthens them but also increases their chances of surviving in the body’s bloodstream.

These cells travel through the bloodstream unharmed to other organs, causing the spread of cancer.

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How many peanuts can one eat safely?

Findings point to a link between frequent peanut consumption by cancer patients and the risk of cancer spread, but further research is still needed, said Dr Yu.

However, a rather large study saw no serious impact of peanut consumption on cancer deaths. Another study on men with prostate cancer also yielded similar results.

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In the group’s previous study, they found that PNA levels in the blood were high only when the subject consumed a large dose of peanuts (250g). So “normal” peanut consumption which resulted in lower PNA levels may be harmless, said the researchers. That means, eating peanuts in moderation is fine.