Nutrigenetics is not a diagnostic nor a predictor of disease. It makes no attempt to determine relative risks and odds ratios of complex diseases such as type 2 diabetes, cardiovascular disease, etc. The focus of attention of nutrigenetics is generally not the final disease but the many intermediate surrogate health markers such as homocysteine, LDL cholesterol, hypertension etc. Cardiovascular disease for example has many possible causes (hypertension, high cholesterol, inflammation, etc) and each gene-diet interaction focuses on just one area.
For example the knowledge of the MTHFR genotype is not used to predict the risk of heart disease or stroke but to define the daily requirement for folic acid, vitamins B6 and B12. It has been demonstrated many times that individuals with the 677TT version of the enzyme WILL have raised homocysteine if there is not adequate folic acid in the diet. Therefore the nutrigenetic test advice will be to consume an adequate amount of folic acid (600-800 µg / day) – and this WILL keep homocysteine levels lower. Most doctors who find a patient has high homocysteine levels will treat it with folic acid, B6 and B12, the aim of the nutrigenetic test is to ensure adequate amounts of these vitamins are in the diet BEFORE the levels become raised.