Your Clubcard may say more about you than your DNA, so should it be considered more private? When it comes to understanding patterns in health and illness, examining our data may be even more powerful than examining our bodies. This data comes from medical or social care records, but also supermarket loyalty cards and internet browsing history. Mhairi Aitken asks: Would you rather researchers were looking at your Clubcard data or your DNA? Is this information personal and private, or a public asset to be used in the "public interest"?