The Duke and Duchess of Cambridge are visiting Denmark to learn more about the work of children's charity Unicef in East Africa.
An estimated 12 million people in the region are at risk of starvation because of food shortages, and famine has been declared in Somalia.
The royal couple are touring Unicef's emergency supply centre in Copenhagen.
The UK is giving £200m in aid to the affected region, £72m of which has been raised through public donations.
After their arrival at the supply centre, the couple were offered a taste of the special high-protein peanut paste which is sent to malnourished children in Africa.
The duke took a sample before passing it on to the duchess, who declined to taste it and passed it over to Denmark's Crown Prince Frederik and Crown Princess Mary, who accompanied them on the visit.
The crown prince and crown princess also tasted a multivitamin paste, but no-one tried the tray of muffins made with a corn soya blend.
They were given a briefing by Peter Hailey, senior nutritional manager at Unicef, on the crisis threatening the region and details on nutrition and food being provided for people in the area.
After the briefing the two royal couples were taken into the supply centre's warehouse, which is the size of three football pitches, where they helped to pack boxes.
Prince William said he hoped his visit would raise the profile of the charity's work in the region.
"I think what has touched me the most is probably the fact there's an incredible amount being done," he said. "Unicef are leading the way and they're doing a fantastic job.
"Sadly there's still a lot more to do and that's why we're here today, to try our best to put Unicef ahead of the system again and get as many people as possible realising the truly horrendous situation going on in East Africa."
The duchess said she wanted to remind people who may have forgotten about the crisis.
"I think it was initially a very big story," she said. "A lot of people did hear about it, but I think because it has been going on, people have perhaps lost track of this terrible situation.
"So I think this, hopefully, will put the light back on this crisis.
She added that she was "shocked by some of the statistics and I think other people would be if they'd lost track of the story".
After their tour of the site they attended a private reception at Unicef, which included Unicef ambassador Sir Roger Moore.
Speaking after their meeting, Sir Roger said: "We just discussed what they had seen and what their thoughts were and how glad they were that they came to support this extraordinary appeal.
"They are both very interested in east Africa, they were engaged in Kenya, it's so close to their hearts.
"It was just reiterating their passion for this cause and I think it must be a passion otherwise the royals wouldn't just give up a day of their very busy lives and the high demands there are on them for attending all sorts of functions - and that's apart from the RAF duties of the duke."
The royal couple then arrived at Copenhagen Airport to view a British Airways Boeing 747 before it left to make a relief flight carrying 45 tonnes of aid, including emergency medical supplies, to East Africa.
BA has lent the aircraft to Unicef for a flight to Nairobi in Kenya where the items will be distributed by the charity and other aid agencies.
The duke and duchess spoke to British Airways staff about the amount of aid being taken on board before being shown the interior of the aircraft and the overhead bins full of boxes of supplies.
David Bull, executive director of Unicef UK, said the supplies would help to save the lives of malnourished children.
The worst drought in East Africa in 60 years has resulted in severe food shortages across Somalia, Kenya, Ethiopia and Djibouti.
By going to the Unicef centre in the Danish capital, Prince William and Catherine are seeking to maintain a global focus on what is a long-term situation.
A spokesman for St James's Palace said the visit was instigated by the duke and duchess.
He said: "This visit has come about through a mutual meeting of minds between the two royal couples.
"The crown prince and crown princess have already shown a very keen interest in the terrible tragedy that's unfolding in East Africa and the crown princess has been to Kenya.
"The Duke and Duchess of Cambridge have personal links in Kenya - they have friends there, they got engaged there, they've visited many times and they've followed the tragedy unfolding not only on the news but also from people they know on the ground."
BBC royal correspondent Peter Hunt, in Copenhagen, says William and his wife attract intense attention wherever they go in the world.
William wants to exploit this interest and focus it on the plight of people living in East Africa, our correspondent adds.
This is the couple's first joint humanitarian mission and their third official engagement since their wedding in April. They flew out on Wednesday morning and will return on the evening of the same day.