A weekly programme featuring a mix of sound-rich stories about science, the environment and medical research, recorded around New Zealand in laboratories and in the field. Our Changing World is broadcast nationwide on Thursday nights on Radio New Zealand National, during Nights with Bryan Crump. It is preceded in this recording by a news and sports bulletin, and weather forecast. In today's programme:
1. Childhood Obesity:
We hear a lot about rising rates of obesity in adults, but in New Zealand, childhood obesity is an even more worrying issue. Obesity in young children and teenagers is increasingly recognised as a precursor to major adult diseases such as diabetes and heart disease, even if the weight problem itself does not continue into adulthood.
According to Ministry of Health figures, one in every three children in New Zealand is either overweight (22%) or obese (11%), and the rate of childhood obesity has increased from 8% in 2006 to 11% in 2013.
Paul Hofman, a paediatrician at the Liggins Institute, tells Veronika Meduna that he sees some of the worst cases, including teenagers who weigh between 150 and 200kg. As a consequence of their weight, these young people are already pre-diabetic or diabetic and suffer from fatty livers, sleep apnoea and heart problems.
Research at the Liggins Institute has shown that many aspects of a child’s physiology are programmed before birth and influenced by the mother’s diet, and Paul says the same applies to childhood obesity. This is also supported by the statistics of obesity, which show that adults (in the US) were becoming more obese from the 1960s, while American children only started to show weight issues from the late 1980s. “So there’s a delay of about a generation.”
Paul Hofman says research also shows that maternal weight before conception is a major predictor of a baby’s birthweight, suggesting that “somehow the excess nutrition [the babies] get from the mother sets them up to be more likely to become obese”.
‘So you get into this situation of obesity begetting obesity, and it’s not genetic, it’s environmental. If we can break that down, if we can reduce the amount of nutrients getting to the child during pregnancy, perhaps, just perhaps, we can modify that obesity risk and reduce the risk for the next generation.’
Childhood obesity tracks, says Paul Hofman, and an obese youth has a six to seven times higher risk of becoming an obese adult.
In order to break the obesity cycle, his team has been conducting trials that target pregnant women (of normal or access weight) to see if regular, supervised exercise can reduce the birth weight of their children. In one trial, normal-sized pregnant women who exercised up to 40 minutes each day had babies who were 250g lighter on average. These children are now eight years old and the team is in the process of analysing their risk of obesity. In another trial underway at the moment, obese pregnant women are exercising to see if this can modify the outcome for their children in the long term.
Earlier this year, Our Changing World featured an interview with University of Otago neuroscientist Christine Jasoni, who is investigating how maternal obesity affects the formation of the baby's brain.
2. Fun with Fermented Food and Drinks:
From bread and cheese, to kimchi and sauerkraut, beer and wine, fermentation is a key process in the creation of many foods and drinks. The process of fermentation is not just of interest to chefs and brewers – there’s even an area of science known as zymology, or zymurgy, which is the science of fermentation.
And at the recent International Science Festival in Dunedin there was an event titled Great Fermentations, which was billed as ‘zymurgy + communication = fun! an evening of beer, science and food.’
Alison Ballance went along to the evening to find out how a chef, a brewer and two food scientists had collaborated to create a five-course menu comprising a wide range of fermented foods, that were then matched to nine different and complimentary Emerson’s beers.
Mark Lane, executive chef at Otago Polytechnic, worked with students to develop the menu, which included items as varied as sauerkraut, clams pickled in a beer-based vinegar, sourdough bread, kimchi, pickles and salami. Richard Emerson, owner and brewer at Emerson’s Brewing Company was responsible for the beers.
Alison also went along to the Food Science Department at the University of Otago to talk with flavour scientist Graham Eyres and food scientist Phil Bremer.
Phil explained that fermented foods had a long history, going back about 4000 years.
“There’s a whole lot of science in something like salami,” he says. “If it’s done right the way the microbes interact, the way the nitrate works, and the anaerobic conditions mean that you get a product that’s safe, has a long shelf life and of course tastes fantastic.”
Fermentation depends on microbes such as bacteria, fungi or yeast. “The beauty of fermentation is that once it’s happened the bacteria or the yeast convert the lactose, the sugar in the milk, to lactic acid,” says Phil. “That drops the pH, and that makes the product more stable and importantly safer, as a lot of the pathogenic bacteria are killed.”
“Throughout history there’s been no technique that I can think of that’s been more important for providing a source of safe food,” comments Phil.
Graham works in the field of flavour science. He says that “an aspect of our research is to understand what the flavour and aroma characters in hops are.” Graham explains that a lot of the flavour in food comes from the volatile compounds that make up the aroma profile of a food or drink, and the ‘trained noses’ of human testers are used alongside gas chromatographs and mass spectrometers to quantify the compounds that make up each food’s unique flavour signature.
3. Littlest Hadron Collider:
The Large Hadron Collider at CERN is one of the world’s most expensive and most complex experimental facilities to date. It is a particle accelerator which lies in a 27 kilometre circular tunnel built under the ground on the Franco-Swiss border.
Here in New Zealand, at the University of Otago, a team of physicists led by Niels Kjaergaard, have created what they call the Littlest Hadron Collider.
“So where at CERN particles are travelling essentially at the speed of light, here we are colliding particles at pedestrian speeds. So that would be a metre per second,” says Niels.
To slow down the rubidium atoms used in the laboratory, a large table is set up with a complex array of optical devices enabling the atoms to be cooled to temperatures of less than a millionth of a degree above absolute zero.
“We have two stages of magnetic trapping…and then I can take these very, very cold atoms and then I can load them into the focus of a very strong laser beam,” says Neils.
This is a process called optical tweezers, which uses two laser beams, one horizontal and the other vertical. The cloud of atoms sit where these laser beams cross and the atoms can be steered and manipulated using the tweezers. Our Changing World has previously featured a story on optical tweezers.
“By taking the vertical and then dividing that into two laser beams which we move progressively from each other, we can then split this atomic cloud into two,” Niels tells Ruth Beran.
By splitting these daughter clouds sequentially, a total of 32 equally sized clouds can be created in the Littlest Hadron Collider.
“What I naively expected was all the atoms would go into one of the tweezers but we are actually able to split them apart and then we can progressively move them further from each other,” says Niels.
While potential applications for this work include sensors that can map minute variations in magnetic fields, and new tools for probing microscropic structures, it is the fundamental science that Niels is particularly interested in.
For example, two clouds of atoms can also be smashed together to study the scattering and how they interact with each other.
“We can learn about how these atoms interact at an atomic level,” says Niels
4. Great Whites, Big Shark Experts and Small Shark Fans:
Electronic satellite tags have revolutionised the study of marine creatures such as whales and sharks, allowing scientists to study their movements across long distances.
Great white sharks have been the focus of a joint NIWA-Department of Conservation research programme for the past 10 years. For most of that time Malcolm Francis from NIWA and Clinton Duffy from DoC have focused their tagging efforts at Stewart Island, and what they’re finding is throwing up as many questions as answers.
“In the last couple of years we’ve been putting what we called SPOT tags on the dorsal fin of sharks, and that gives you a really accurate fix every time they come to the surface,” says Malcolm. “And we’re starting to find out now that some of them make direct migrations to the tropics, but we’ve got a couple this last year that have been meandering around a bit and making diversions from their straight line course, and we’ve realise we have no idea what they’re up to.”
The titi islands near Halfmoon Bay, where the researchers tag their sharks, are a known aggregation site, where sharks congregrate each summer near seal rookeries around the time young fur seals are taking to the water. The tagging research has revealed that great white sharks from New Zealand undertake long migrations up to the tropical Pacific, spending up to 9 months there each year. Sharks have been tracked to Tonga, Fiji, New Caledonia and Australia’s Great Barrier Reef. As well as spending a lot of time at the surface as they travel, they also make frequent deep dives, to depths of 1000 metres or more.
Ex-pat Kiwi Ryan Johnson has been studying white sharks in South Africa since 1998, and he co-founded Oceans Research as well as appearing in many shark documentaries. Over the last two years he has been involved in a large project with Ocearch in which more than 30 great white sharks were fitted with satellite positioning tags on the dorsal fin which send back the shark’s location every time the fin breaks the surface.
“We found the South Africa population of great white sharks shares its time between South Africa and Mozambique,” says Ryan, “Which is massive, as in Mozambique they’re not protected and that has a direct consequence on South Africa's protection for the species.”
“They seem to stay around the seal islands of South Africa during the winter, and then when the warmer temperatures come over the summer that’s when we see these migrations up to Mozambique, Madagascar and a little offshore into the Indian Ocean.”
“It was really exciting to get four or five mature or nearly sexually mature females as those are the ones that are really important …. The big females are pretty much the only ones of the South Africa [white shark] population that explore far offshore,” says Ryan. “We’ve also found that there’s different aggregation sites that we didn’t know about that appear to be related to reproduction.”
Malcolm Francis says understanding what large mature female white sharks do – where they go to mate, feed and give birth - is ‘the missing piece of the puzzle” in New Zealand as well.
Most of the sharks that the researchers see at Stewart Island are sub-adults, with more males seen than females. Larger mature sharks are believed to spend most of their time out in the open ocean, while juvenile sharks are occasionally seen in warmer waters around northern North Island, and in harbours such as the Manukau.
Ryan Johnson and Malcolm Francis were both involved in the Fish and Ships marine science day, run in Dunedin earlier this month as part of the International Science Festival. As well as giving talks about their research they ran a public shark dissection, which attracted many young shark fans keen to learn more about their favourite animals.
You can see where Ryan’s sharks have been travelling on the Ocearch shark tracker web site, and Our Changing World joined Malcolm Francis and Clinton Duffy on a white shark tagging trip to Stewart Island two years ago.