The science

One page per trait. Each starts with a short answer, explains what a result does and does not mean, and lists its sources.

• Lactose and your genes

  How the LCT -13910 C>T variant (rs4988235) predicts whether you keep making lactase as an adult, what it can and cannot tell you, and how to eat dairy with low lactase.

• Gluten, celiac disease and HLA-DQ2/DQ8

  Almost everyone with celiac disease carries HLA-DQ2 or DQ8, yet most carriers never develop it. What a consumer DNA result can rule out, and why you should not drop gluten before testing.

• Alcohol flush and ALDH2

  The ALDH2*2 variant (rs671) slows the breakdown of acetaldehyde, causes facial flushing after alcohol and raises cancer risk for people who drink anyway.

• Caffeine and CYP1A2

  How a common CYP1A2 variant relates to caffeine clearance, what the coffee and heart attack study actually found, and how strong the evidence is.

• Iron and the HFE gene

  What the HFE C282Y and H63D variants mean for iron absorption, how often C282Y homozygotes actually develop iron overload, and which diet changes matter.

• What DNA can't tell you about diet

  Why GenomEats does not offer MTHFR panels or genotype-matched weight-loss diets, and what trials like DIETFITS found when they tested the idea.