Genetics
Genes influence not only how we look but also our nutritional needs. A complete genome sequencing reveals that your genetic inheritance determines whether certain dietary approaches work for you—and how much your lifestyle can override that.
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Genes have plenty to tell us.
To understand what genetic analysis can do for us, you need at least a basic grasp of genetics: We inherit every gene twice—once from mom and once from dad. Each gene is—to oversimplify—a blueprint for a protein. Proteins, in turn, control the biochemistry of the human body and ultimately determine who we are.
Genetic analysis focuses primarily on the smallest variations within our genes. A single change at just one specific position in a gene can cause the resulting protein to function slightly—or significantly—differently. These tiny variations are enough to explain why humans, despite sharing 99.9% of their DNA, are so remarkably different.
Changes at a single position in a gene are called Single Nucleotide Polymorphisms (SNPs), pronounced "snip." Each SNP gets its own specific name, allowing researchers to precisely identify it. You inherit each SNP either once (from mom or dad) or twice (from mom and dad).
This is how services like 23andme and AncestryDNA estimate ethnic or population ancestry. They analyze the specific mix of SNPs in a population. The sum of SNPs in a given population acts like a fingerprint—unique to that group. Different populations have slightly different SNP patterns and frequencies.
That's why 23andme can tell you that you're "very likely" to have ancestry from Poland, England, Italy, or Asia. They only need a tiny fraction of your DNA—just 0.1%—to do this. That's nowhere near a complete decoding of your genome.
I—Chris—have had a full genome sequencing done. You get genuinely enormous amounts of data—your entire genome completely decoded. An incredibly long sequence of DNA information. And all the SNPs in every gene that science has so far described.
Once you've done this, you stop daydreaming about certain dietary approaches. For example:
These nutrients are found primarily—or exclusively—in animal products. That's why I know that veganism only works long-term for most people with a great deal of luck. The guessing stops. Most of us simply aren't born to be vegans.
Here's how it works: Provitamin A—beta-carotin—is converted to vitamin A by a protein called BCO1. Most versions of the BCO1 gene found in our population unfortunately cause the protein to lose function.
In other words, in most people, the enzyme that's supposed to convert beta-carotin to vitamin A doesn't work at all. Why did evolution make this enzyme obsolete? Because our ancestors always had a good dietary source of vitamin A—like liver or cod liver oil—and didn't rely on plant provitamin A.
But SNPs can do much more. Using SNPs, scientists can calculate what's called a Polygenic Score for disease risk. That's because many diseases are well-researched—some SNPs show strong associations with specific diseases.
Some studies identify 50–100 SNPs from various genes, each with different strengths of association with a disease. These are compared against your own genetic variants. Then those data are compared across all the people who've had their genomes analyzed.
Then you read: "You are in the 95th percentile for Disease X." That means: Compared to other people, you unfortunately have a high genetic risk for Disease X. Or sometimes you land in the low-risk percentile, which happens too ;-)
What you do with that information is up to you. The good news: genetics is usually overridden by epigenetics—your lifestyle. Whether genes make us sick or healthy often depends decisively on how we live.
Example: BCO1 (see above). If you have genes that can't make vitamin A from beta-carotin, you'd only get sick if you didn't consume vitamin A—that is, if you ate purely plant-based. Your lifestyle—getting enough vitamin A in your diet—overrides this gene's effects. Relatively simple.
Speaking of genes: In 2012, researchers discovered a gene—choline dehydrogenase—that appears to play a major role in how fit sperm are. A specific SNP that up to 10% of people inherit from both mom and dad causes a massive energy drop in sperm.
The researchers concluded: This gene—specifically this SNP—is a major determinant of male fertility. Incredible!
Why lifestyle matters here too, and what people can do if they carry this SNP twice, is the topic of [source no longer available]. Super fascinating, wide-reaching—definitely worth checking out. ;-)
