Some people have an objectively better metabolism than others when it comes to longevity - perhaps better mitochondrial DNA, perhaps less LDL cholesterol, for example: "Coronary atherosclerosis - a hardening of the arteries due to a build-up of fat and cholesterol - can lead to heart attacks and other forms of coronary heart disease (CHD). Lowering low-density lipoprotein (LDL), or 'bad' cholesterol, reduces the risk of CHD ... By the time most people begin treatment to lower LDL, CHD has often been quietly developing for decades. Because coronary atherosclerosis begins early in life, lowering LDL at a younger age may produce even greater reductions in the risk of CHD. Researchers sought to test this hypothesis by using genetic data to conduct a series of 'natural' randomized controlled trials involving over one million study participants. ... researchers used a novel study design called a Mendelian randomized controlled trial (mRCT) to study the effect of nine single-nucleotide polymorphisms (SNPs), or single-letter changes in DNA sequence, each of which is associated with lower levels of LDL cholesterol. Because each of these SNPs is allocated randomly at the time of conception, inheriting one of these SNPs is like being randomly allocated to a treatment that lowers LDL cholesterol beginning at birth. The researchers found that all nine SNPs were associated with a consistent 50-60 percent reduction in the risk of CHD for each 1 mmol/L (38.67 mg/dl) lower lifetime exposure to LDL cholesterol. "