Spoiler alert: You don't need to worry about most of your SNPs, but some of them do matter, and few of them matter a lot.
What is a SNP?
The acronym SNP stands for Single Nucleotide Polymorphism. A SNP is a TINY change in one copy of one of your genes. Some SNPs matter and some don’t. Some only matter some of the time. How can this be? Picturing how this all works gets a little complicated, so bear with me.
Genes are both mind-bendingly small and mind-bendingly big at the same time. For example, the gene for the enzyme that makes serotonin has 29,000+ base pairs. A SNP is a small change in ONE of those 29,000 base pairs. Yeah, what does that even mean? IMHO, it is pretty hard to understand SNPs without a visual aid, so I made this short animation to help. (Yes, it was hard, you're welcome)
Video Summary
Humans have 23 pairs of chromosomes. Each chromosome is made out of an absurdly long strand of DNA. A DNA strand is a double helix structure, which looks like a twisted ladder. Each rung on the ladder is made up of 2 parts, these couples are called "base pairs". There are only 4 possible molecules that can make up a base pair, and they are called "nucleotides".
A gene is a section of the DNA string. Genes range in size from 75 to 2 million base pairs long (with an average of about 54,000). Genes are the template used to 3D print molecules needed by your body (enzymes, proteins, messenger molecules). The number of base pairs determines how big the printed molecule is. The order of the base pairs (and what nucleotides make them up) determines the contents of the molecule, which in turn determines its shape and function.
A SNP is a change in ONE nucleotide of ONE base pair at ONE location of ONE gene.
Single (one) Nucleotide Polymorphism (swap-out).
It is a tiny, tiny change.
Can a SNP affect my health?
Some SNPs have huge health impacts, some don't have any at all, and some only matter sometimes. It all comes down to the molecules that are getting 3D printed off of your genes, and where on the gene the SNP is located.
The proteins, enzymes and chemical messengers in our bodies are all really big molecules. The function of these molecules depends on them having an exact shape. These molecules have "functional" areas (I like to call it the business end) where that particular molecule does its work. A fair amount of the rest of the molecule is structure to support the business end. A SNP that changes the functional area can have a bigger effect on the function of that protein or enzyme. Changes in the structure area might not have as much impact.
To build the best version of an enzyme or protein requires a precise genetic code. The perfect code (found in the majority of people) is called the "wild type". A SNP is a single small change in that code. This change will mean that the 3D printed molecule will be slightly different, a variant. Again, depending on where that variation is, it might or might not change how the printed molecule functions.
Changes to the functional area of an enzyme, like MTHFR, may make the enzyme work a little slower or a little faster than the "wild type". It is important understand that in this case the enzyme is still being produced and it still functions, it just functions a little differently. What this means is that metabolic pathways depending on that enzyme might run at a slightly different speed. This can cause imbalances and "functional" symptoms (fatigue, inflammation, mood changes, etc). Especially when the system is under stress. In the example below, we see a SNP in the right part of the ApoE gene (associated with lipid metabolism and Alzheimer's) changes its shape, and that changes its function. The ApoE2 works better. The ApoE4 is "closed" so the molecules it should be acting on can't fit into the space.
Is having a SNP the same thing as having a genetic disease?
Most of the gene SNPs you see on consumer tests, or "genomic" screens done through functional practitioners do not cause "genetic disease". Genetic diseases are really big departures from the normal range of structure and function. Most major genetic diseases are discovered in childhood.
The term genetic disease refers to a wide variety of possible changes in the genome. Some genetic diseases are due to the deletion of a whole chromosome (Turner syndrome) or the addition of a whole chromosome (Down syndrome). Some genetic diseases are due to missing entire genes or major changes in a gene - like one section of the gene being repeated multiple times (Cystic fibrosis, Sickle Cell, Hemochromatosis). Others are due to a confluence of changes to multiple genes (Ehler's Danlos). Some genetic diseases ARE due to SNPs in critical locations of specific genes. Many (but not all) genetic disease related to single SNPs also have environmental components or triggers (Parkinsons, Alzheimer, Diabetes). In these cases, SNPs can increase the risk of developing certain diseases in the future, but don't guarantee that the disease will happen.
Other SNPs can produce slower or faster than average enzyme systems that can affect mood, memory, detoxification, gut health and more. These would not be considered "genetic disease" but perhaps could be considered "metabolic challenges when under stress". Many other SNPs have no effect on health at all.
How can some SNPs matter only sometimes?
We have many redundant genes for every molecule our body needs to make.
For example, there are about 10 different locations on your DNA that have a gene to make the MTHFR enzyme, and there are 34 known variants (SNPs in different locations). Which one is being used as the "reference" code at any given time depends on environmental factors. Many of the SNPs that cause "metabolic challenges" are vulnerable to stress. These will only produce symptoms when the body is under stress of some sort. Examples:
nutrient deficiencies or imbalances
stress chemistry (how your body reacts to life stress)
infections
toxin exposures (chemical, biotoxins)
Help! I got my genome mapped and I have SNPs! Am I doomed?
Don't panic.
Everyone has SNPs, lots of them. Most normal, healthy people have 1000 SNPs or more.
Having looked at hundreds of genome maps, one thing I have noticed is that SNPs tend to balance each other out if you scroll back and look at the big picture.
Just remember:
There are many copies of most genes, each with the potential to have a SNP or be perfect (aka "wild"). One day you might have the gene with the unfavorable SNP turned on, the next you might have one of the "wild type" genes turned on. So even if you have a SNP it does not mean it is active.
Most SNPs either cause no problem at all, or cause minor changes in metabolism
Many SNPs can be supported (when symptomatic) with nutrients or herbs
Closing thoughts
SNP research is ongoing and progressing at an astonishing speed. Millions of SNPs have been mapped at this point, and we are learning what the implications of various SNPs and SNP combinations are. New tests and support services are popping up every few months. What we know today may be really different that what we know in 5 more years.
Watch this space!
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