In a previous post, I wrote about epigenetics, the exciting new science that’s illuminating how our daily lifestyle choices affect the expression of our genes, and what this means for our health.
In this article, I’m going to focus on epigenetic influences on cancer.
People who have a family history of cancer are often afraid that it might be ‘in their genes’. The fear of a cancer that is genetically programmed to attack, no matter how they live their lives, even drives some women to undergo so-called prophylactic mastectomy: surgical removal of their breasts, or their teenage daughters’ breasts, in hopes of preventing a cancer that there’s currently no sign of.
Fortunately, breakthroughs in research on histone deacetylases, enzymes which influence how the DNA code is ‘read’ by a cell, provide hard evidence that dietary prevention of cancer is a genuine option even for those at increased risk.
First, a short primer on genes and how they work, for those who happily forgot their high school biology as soon as they left school!
- DNA is the long-term storage vessel for the genetic information required for our development and functioning. It is contained in the nucleus of each of our cells.
- Genes are segments of DNA. Genes contain the ‘instruction manual’ needed to construct proteins that play structural and functional roles in our bodies, and RNA molecules. The genetic code specifies the sequence of the amino acids within proteins.
- To organise and compact the large volume of DNA, proteins called histones act as ‘spools’ around which the DNA winds.
- Histones package and order the DNA into structural units called nucleosomes, and – through the activity of histone deacetylases (HDACs) – play a role in gene regulation by controlling which parts of the DNA are ‘transcribed’, or copied to RNA to make proteins.
People (along with other animals, and plants too) start their lives with a certain genetic code, which is determined at conception. However, we have a multitude of genes that hold the codes for production of an astonishing variety of proteins, with widely divergent effects.
The choice of which genes are ‘expressed’, or activated, at any given time or indeed over time, is strongly affected by what scientists call environmental factors – that is, factors in the environment of the cell itself, such as hormones, neurotransmitters, nutrients and toxins.
These environmental factors can change the expression of some genes very rapidly (in fact, within minutes); can cause very persistent changes in the expression of other genes; and can even cause certain changes in gene expression that are passed on to our children.
Cancer is known to have its origins in aberrant gene expression, and scientists are now learning that this doesn’t just mean mutations, or errors in the DNA sequence of the cell.
Many cancer cells, for example, show ‘silencing’ of genes that code for tumour suppressor proteins such as p53 and p21, which ordinarily act to keep cell division within normal limits.
On the other hand, genes that code for cell survival proteins such as Bcl-2 are ‘upregulated’, or more active, allowing cancer cells to proliferate rapidly and form a tumour.
There has been an explosion of research in the last 10 years, into how HDAC dysregulation contributes to these abnormalities. Excessive HDAC switches off the tumour suppressor genes, allowing cells to replicate themselves without restraint – one of the fundamental characteristics of cancer – even without mutations in the DNA sequence of the cell.
And now for the good news: a variety of compounds, found in everyday foods or produced in our bodies when we eat certain foods, act as HDAC inhibitors, limiting the harmful overproduction of HDAC. HDAC inhibitors can turn on the tumour suppressors that have been silenced, causing cancer cells to ‘commit suicide’ via a process called apoptosis.
These HDAC inhibitors include:
- Sulforaphane in broccoli;
- Indole-3-carbinol in Brassica/cruciferous vegetables including broccoli, cabbage, bok choy, kale, cauliflower, Brussels sprouts, radish and turnip;
- Organosulphur compounds in allium vegetables including garlic, onions, leeks and chives
- Organoselenium compounds in garlic; and
- Butyrate, a compound produced in the intestine when probiotic bacteria ferment dietary fiber from vegetables, legumes, fruits and whole grains.
As you can see, there is no single ‘silver bullet’ when it comes to preventing cancer. No high-priced pill or supplement contains all the known and and as yet unknown dietary HDACs.
But the diet I recommend to my clients for health, longevity and cancer prevention, and teach to my cooking class students, incorporates all of these foods, to ensure you obtain the full symphony of protective nutrients.
Best of all, meals based on these foods taste great – see my Recipe Pages for inspiration!
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