Grape's Compounds in Cancer Prevention

The global burden of cancer is rapidly increasing as the years go by, with cancer now contributing to one in eight deaths worldwide.¹ The number of new cancer cases that were diagnosed in 2020 around the world was 19 million², and this number of new annual cases is expected to rise to around 30 million by 2040.³ Given this rising incidence of cancer, coupled with the expensive cost and side effects of most treatments, it is imperative to try to identify new strategies to prevent cancer from happening. A particularly effective way in which we can each play a part in reducing our chances of developing cancer is through a healthy diet.⁴ 

A particular sweet and juicy fruit that is included within this healthy diet, and which contains compounds and nutrients that have shown promise in preventing cancer, is the grape.⁵ 

This article will outline which particular compounds found within grapes help us fight off the risk of developing cancer, and how they do so. 

Which grape compounds help prevent cancer? 

Polyphenols

The main group of compounds found within grapes that help contribute to the prevention of cancer is called polyphenols. Polyphenols are a large group of nutrients which are naturally found in plants and plant-based foods, such as grapes. Whilst a plant is growing, polyphenols have the role of making sure the plant is absorbing sunlight for it to grow, as well as protecting the plant from potential diseases. When we eat food which has grown on such plants, like grapes, polyphenols perform the same roles in our food as they did in the growing plants - protecting us from diseases, such as cancer, and keeping us healthy.⁶ 

These polyphenols are considered one of the most important compounds within grapes, and there are various types of polyphenols found within the fruit. The most important examples are given below.

Resveratrol

Resveratrol belongs to the subfamily of polyphenols known as stilbenes. This compound is mostly found within the skins of grapes, particularly the red variety.⁷ 

This nutrient is the most studied individual polyphenol of grapes - as grapes are one of the few major food sources of resveratrol. Scientists have studied this particular compound for over 3 decades, as it has been found to help prevent a variety of cancers - breast, brain, lung, blood, kidney, liver, bone, eye…the list goes on.⁸

Flavonoids

An important subfamily of polyphenols, which are known to be very beneficial for our health, include flavonoids. Flavonoids are mostly found in the skin and edible seeds of grapes, and are considered the most important components of grapes in preventing cancer.⁹

The most well-studied and known examples of flavonoids include the following:

• Anthocyanins - These anti-cancer compounds are the ones primarily responsible for the colour of red grapes¹⁰
• Proanthocyanidins - The most common anti-cancer flavonoid compounds found in grape seeds and skin¹¹ 
• Flavonols - These anti-cancer flavonoid compounds are mostly found in the white variety of grapes. Famous examples of flavonols include catechins and quercetin¹² 

How do these grape compounds prevent cancer?

The grape compounds mentioned above help in a variety of ways in the prevention of cancer. The following are the most prominent mechanisms these compounds use. 

Anti-oxidative effects 

All grape polyphenols mentioned above are known to be strong antioxidants.¹³ Antioxidants are compounds which have the role of hunting down molecules called free radicals.¹⁴

Free radicals are highly reactive molecules, which are created as a result of normal bodily processes, as well as a result of external sources such as X-rays, cigarette smoke and industrial chemicals.¹⁴ These free radicals are created when a molecule either gains or loses an electron -  a tiny particle which makes up a portion of a molecule. Essentially, we can look at free radicals like jigsaw puzzles: a free radical is a puzzle that is either missing a piece (when an electron has been taken away from the molecule) or has an extra piece which has no place to fit (when an extra electron has been added to the molecule). These missing and/or extra pieces make the free radical highly reactive to any and every other molecule in the body, as they aim to either try to get rid of their extra electron or fill their missing space - their goal is to become a complete puzzle with no extra pieces.¹⁴ Small doses of these free radicals are beneficial for us. However, too many free radicals can lead to too many interactions and disruptions to our normal bodily functions and processes, and in turn, affect our overall health - this is called oxidative stress.¹⁴

A particularly important example of oxidative stress that commonly leads to cancer is when free radicals damage areas of our DNA that code for tumour suppressor genes. These genes hold important instructions to make proteins that are involved in making sure that cells do not turn cancerous. How they do so includes the following:

• They tell a cell when to stop growing or dividing into more cells.
• They repair any DNA damage within a cell.
• They start a process called apoptosis in damaged, dying cells - this process consists of a programmed and controlled death of these cells. Apoptosis is essential in making sure these dying cells do not cause harm to surround healthy cells, as well as to give space and resources to newer, growing cells

When free radicals interact with and damage tumour suppressor genes, these important proteins are not produced or do not function properly, meaning that there is a lack of regulation of cell growth (cells grow and divide in an uncontrolled, constant manner) and there is no repairment of DNA damage within the body - both of which are characteristics of cancer.¹⁵

As mentioned previously, antioxidants, like the polyphenols found in grapes, can interact with and “neutralise” these free radicals, preventing damage done to normal bodily processes. Within the context of cancer prevention, these antioxidants can prevent free radicals from damaging essential parts of DNA, such as tumour suppressor genes, which in turn helps these tumour suppressor proteins continue their function of protecting the body from the potential formation of cancer.¹³  

Anti-inflammatory effects

Inflammation is a normal bodily response that occurs when our body experiences any sort of harm - including injuries and infections. Inflammation informs our immune system, which is a whole network of cells which act as our natural self-defence system, about the harm we are experiencing, signalling to the immune cells where to go in the body to get rid of the harm. Hence, inflammation is incredibly important, as it helps us defeat any virus or bacteria that comes into our body, as well as it helps repair any damaged tissue or organ.¹⁶ However, it is also equally important for inflammation to go away after it has performed its role of informing our immune system. If inflammation persists in the body, it can cause trouble - this is called chronic inflammation. Such type of inflammation, in turn, can prepare the body for cancer formation. Moreover, inflammation helps cancer progress: from its initial stages of growing, to metastasis (where the cancer spreads to other organs).¹⁶

The polyphenols within grapes help reduce unnecessary inflammation. They do so by promoting anti-inflammatory genes, which in turn produce anti-inflammatory proteins whose role is to regulate inflammation within the body and prevent chronic inflammation from occurring, in turn preventing a cancer-friendly environment from forming.¹⁷ 

Anti-mutagenic effects

Cancer commonly occurs due to random changes in our DNA and genes, termed mutations. These mutations can lead to the formation of proteins that do not function properly, or whose important function has been altered completely, which in turn can affect overall health and promote cancer. This altering and/or deleting of important functions can benefit cancer growth. Moreover, if you have mutations in genes such as tumour suppressor genes (as mentioned above), then this can make your cells replicate quicker and in an uncontrolled manner, leading to the formation of tumours.¹⁸ 

Polyphenols in grapes, particularly resveratrol, can prevent mutations from occurring and hence can stop the cascade of events that occur after harmful mutations happen, thus reducing the risk of developing cancer.¹⁹  

Induction of apoptosis

As mentioned previously, apoptosis is the programmed and controlled death of cells which are damaged and/or dying. This is a necessary, natural process that occurs in our bodies to ensure that cells do not continue to grow uncontrollably, as well as to make sure damaged cells do not affect surrounding healthy cells and do not take up essential resources.²⁰  

However, as cancer is characterised by the unregulated growth of cells, apoptosis tends to not occur. The polyphenols in grapes can address such issues, as they can identify any abnormal cells which are growing and replicating uncontrollably, and they can initiate their apoptosis. This leads to the elimination of any potential cancer cells, resulting in the prevention of tumour formation.⁵    

Inhibition of angiogenesis

Angiogenesis is the growth of blood vessels from already-existing vessels. This process occurs throughout life and is essential in making sure all parts of the body have close access to a supply of blood. However, angiogenesis also occurs in cancers. As a cancer continues to grow bigger, certain parts of the cancer may not have access to the closest blood supply from which the tumour first originated. Hence, most growing cancers stimulate our blood vessels to undergo angiogenesis, to make sure the whole tumour is supplied with blood, allowing easy access to nutrients to help the cancer continue to grow.²¹ 

Polyphenols in grapes are known anti-angiogenic compounds. This means they prevent the process of angiogenesis from happening. This characteristic of theirs would help prevent the formation of new blood vessels in potentially growing cancers, in turn leading to the death of any part of the tumour that has no close access to a blood supply, hence halting the development of cancer.²² 

Summary

As a response to the rapidly rising incidence of cancer worldwide, an effective solution is to look at how we can prevent it from happening in the first place. One of the simplest things each of us can do is eat healthy foods which have shown promise in fighting off the risk of cancer. Grapes are one of the fruits which contain a multitude of compounds which help in the prevention of cancer. These compounds include resveratrol and flavonoids, both of which fall under the wider category of polyphenols. These nutrients have been shown to help reduce the risk of developing cancer through a variety of mechanisms - the most prominent examples include stopping the uncontrollable growth of abnormal cells and killing any suspicious cells via their antioxidant, anti-inflammatory and anti-mutagenic properties. Hence, adding grapes as one of your 5-a-day would benefit you greatly.