This episode explores what can give brains a boost. In America, Angela tries out a new treatment that's proven to help memory and concentration. In Japan, a remarkable 100-year-old reveals the colourful foods that keep minds more active. Plus Chris discovers the best exercise we can do for our brains. At the cutting-edge of science, discover how injections of young people's blood may help beat dementia.

'The Coldest War': With the polar ice caps shrinking due to global warming, new trade routes are being exposed, along with billions of dollars' worth of natural-resource reserves. The five nations bordering the Arctic are readying themselves to fight for it. The problem is that there's one non-NATO country that already considers itself rightful owner of the region: Russia. With Vladimir Putin's recent military annexation of Crimea, there's a definite possibility its aggressions will boil over, returning the international community to precarious Cold War footing. We will head north to witness NATO forces participating in the largest polar military exercise in history. 'Heroin Warfare': Since the U.S. occupation of Afghanistan, heroin production in the region has skyrocketed, making the country the number-one producer by a large margin. Though Iran, Afghanistan's neighbor, is an ultraconservative country, Afghan heroin flowing across the border has actually caused Iran to have the worst heroin use problem in the world. Suroosh Alvi gets a rare look inside Iran to meet the suffering heroin addicts, and see how the country is coping with the illegal drug trade.

The world is affected by an obesity epidemic, but why is it that not everyone is succumbing? Medical science has been obsessed with this subject and is coming up with some unexpected answers. As it turns out, it is not all about exercise and diet. At the centre of this programme is a controversial overeating experiment that aims to identify exactly what it is about some people that makes it hard for them to bulk up.