Kept apart from the drug pages on purpose. Every drug here stands on a prescribing guideline that says what to do differently at a given genotype. Almost nothing sold as a supplement has that, and listing the two together would lend the second the authority of the first.
So the evidence is stated on every entry, and on most of them the useful answer is that no guideline exists. Nothing here recommends taking anything.
The most important thing on this page is not a genotype. It is that two large trials gave these to smokers and counted more cancers, not fewer.
A professional body says genetic variation may explain why the same coffee helps one person and keeps another awake. It stops short of telling anyone to test.
Genetics has run the experiment nobody could run deliberately — lifelong high milk intake, assigned at conception. It did not reduce hip fractures.
Sold almost entirely to one group of people — statin takers with aching muscles — on a mechanism that the trial which measured it directly could not find.
MTHFR is the most overstated gene on the internet. The variant is real, its effect on an enzyme is real, and almost everything sold on the back of it is not.
The one supplement on this page where a genotype changes what a doctor would say — and it changes it towards caution, not towards a purchase.
One of the clearest gene–nutrient links there is, and it works through the gut lining rather than through anything on the label. It still does not tell anyone to take a supplement.
Genotype explains part of why two people in the same sunlight end up with different blood levels. It does not tell either of them what to take.