Companies like 23andMe, which produce DNA report based on your genes, give you a lot of data and point out some important genetic markers, but they are not allowed to give any health advice. They do give some reports on potentially inherited conditions, but genetic potential is only part of the picture.
Your genes are not your destiny
"Genetics loads the gun, but the environment pulls the trigger" is a famous quote by Dr Judith Stern.
What that means in a nutshell is that, even though we may have the genetic potential to develop a certain illness or condition, our environment (diet, lifestyle, stress, toxic exposures etc) influence how this potential develops. DNA is a molecular code containing the “recipes” that tell your body how to make proteins – the molecular workhorses that do the heavy lifting inside your cells. Your unique DNA code shapes who you are and how you grow. A section of DNA that contains a complete recipe for a particular protein is known as a gene. But… Not all of your genes are read all of the time. Different genes may be “expressed” (turned on) or “silent” (turned off). Sure, genes which code for things like your eye colour or hair colour are not going to change, but what about the genes which tell your body how to run its various biochemical pathways and how to replicate your cells, or how your immune system should behave? These genes must be “expressing” – that is turned “on”. Or conversely, genes which might predispose us to say, cancer, need to be turned “off”.
Some helpful terminology
Diet and lifestyle factors can impact the expression of the genes greatly. This is known as 'epigenetics'. The branch of genetic research of how foods affect our genes and how, in return, genetic variations affect the way we react to nutrients in foods is called 'nutrigenomics'. In nutrigenomic testing we look at things called 'SNPs' (aka Single Nucleotide Polymorphisms) which are variations of portions of genes .
A little background
DNA consists of long strings of four component molecules, called bases: A, C, G and T. adenine (A) and thymine (T) and cytosine(C) and guanine. The order, or sequence, of these bases along the DNA string serves as our genetic code. This includes things like eye colour, hair colour, etc but it also codes for protein synthesis and the enzymes, hormones, and neurotransmitters – all the chemical signallers and controllers of our bodies. We are not talking here about mutations where the gene is abnormal or non-functioning but we focus on SNPs which have variations which affect function on-going. If one of those 4 base molecules we mentioned gets changed slightly in the sequence, then the function of an enzyme can be changed ever so slightly. It still functions normally but not necessarily optimally. SNPs are usually listed with a 3-6 alphanumeric acronym or short name and variations are typically listed as:
“-/-“ or wild type - this is the version which typically occurs in a species in nature - and in most cases is considered the “normal” or fully functioning version
“+/-“ or heterozygous - this is a version of a wild type from one parent and a slight mutation from the other parent
“+/+” or homozygous - this is a version of a mutation from both parents
A typical genetic test will give a number of SNPs, their variations, and an indication of whether that particular variant is considered helpful/neutral/detrimental, typical/slow/slower, etc. In most cases wild type is considered neutral or no detrimental effect, heterozygous might indicate that an enzyme express at 60-70% of the level of the wild type and the homozygous type might indicate expression at only 30-40% the level of wild type for the same SNP. There are exceptions to this for some SNPs, which is why it is a good idea to work with someone trained in this area instead of trying to figure it all out yourself!
What can you learn from a nutrigenomic DNA test?
Do you have extra need for B6, B12, folate or Vitamin D?
Do you have a lessened ability to convert beta-carotene to Vitamin A? (which is an important thing to know for anyone who is a vegetarian or vegan)
Food intolerances and sensitivities
Do you have a higher risk for coeliac disease?
Could you be predisposed to lactose intolerance?
Are you more sensitive to salt, caffeine, or alcohol?
Food cravings, preferences and satiety
The MC4R variant known as the “death by buffet” SNP tends to cause overeating and a lack of awareness of being full. People with this variant may need to practice more mindful eating.
Are you a “super taster”? more sensitive to bitter foods so with a tendency to avoid healthy vegetables like broccoli and brussels sprouts?
Or does coriander taste strange to you?
Are you more prone to mood disorders such as anxiety, depression, bipolar disorder or schizophrenia?
Would you possibly have a higher disposition to addiction?
Might you have a greater risk of developing dementia?
Do you process toxins (both those created in the body as by-products of metabolism and those from outside the body) efficiently?
Do you process your hormones to the “good” type of oestrogen?
Are some medications more or less suitable for you?
No one SNP controls each of those functions. Usually there are multiple SNPs related to a function and in some cases one SNP can be relevant to health on multiple levels.
One of the most well-known SNPs is MTHFR (methylenetetrahydrofolate reductase). This codes for an enzyme used in something called the methylation cycle. It is estimated that about 40% of the population carry some variant of MTHFR and research indicates that this variant can be linked to higher incidence of heart disease, diabetes, stroke, depression, cancer, and dementia. This does not mean that person is doomed! It means they need to be aware of the diet and lifestyle modifications they need to make to countermand its potential effects. Or the APOE3/4 or APOE4/4 variants - these predispose someone both to higher heart disease and dementia risk. These people are advised to follow a Mediterranean style diet and keep alcohol intake low.
What can you do with this information?
The point is not to be afraid of this information – but to use it to protect and improve your health to the best of your ability. Knowledge is power. And remember no one SNP or gene works in isolation and it is better to look at the whole than to focus on a “bad” SNP. We always say, don’t treat the SNP, treat the person. Working with a qualified nutrition practitioner who has training in nutrigenomics can help you make sense of this information and to develop a truly personalised approach to your health. Work with Sharon