Scientists have known about it for decades but didn’t think much of it. It was Venn-Watson who established that it is an essential nutrient, which improves liver function, reduces inflammation, lowers cholesterol and repairs mitochondria. Yet it is difficult to get it through diet alone. Venn-Watson and her team reckon one in three people are C15:0 deficient, with higher numbers among vegans. The 1970s are partly to blame, when nutritional guidance came out against saturated fats. We now know that there are good fats and bad ones, and whole milk and butter are having something of a renaissance, which is good news for our C15:0 levels. But it is still not bioavailable in many food sources, which is why Venn-Watson and her husband Eric spent five years manufacturing a vegan C15:0 supplement.