Science Interviews

Sizzling Science - The Science of Food

Meera - I'm here in the biology zone at the Cambridge Science Festival. There seems to be an emphasis this year on eating healthily and the importance of a healthy diet to have a healthy body. With me is Gail Goldberg from the Human Nutrition Research Unit at the Medical Research Council. Gail, your stand here is looking at the importance of a healthy diet, particularly for healthy bone. Which components of the diet are important for having healthy bone?

Gail - A number of components are important. The ones that are particularly important are calcium and vitamin D. 99% of the mineral in our skeleton is calcium. We're born with about 25g as a new born baby. When we've finished growing as an adult we have over a kilo of bone mineral in our skeletons. Vitamin D is important because that's a key to helping calcium form healthy bones. Firstly, by making sure that we take up enough from our stomachs. It also plays a role in helping to make sure that mineral goes into bone and stays there. We do get some vitamin D from a few foods but most of the vitamin D that we have in our bodies comes because of the action of sunlight on our skin which means that we make the vitamin D that we need.

Meera - What about calcium?

Gail - Particularly in countries like the UK we get most of our calcium from dairy products, milk and cheese and so on. That's because traditionally we eat a lot of those foods and the calcium that's in them is very easily absorbed by our bodies.

Meera - What are the health effects if we don't have enough calcium and vitamin D?

Gail - Well there's a number of consequences in children and young people. They might not grow as much as they should. Calcium is important in adulthood to make sure we've still got functioning bones. In pregnancy and breastfeeding women because the developing baby gets its calcium from the mother. In old age calcium stays important. One of the health consequences in old age is osteoporosis.

Meera - Another one of your stands over there seems to have an exercise bike that children are riding. I think I'm going to head over in that direction.

Gail - Exercise is important for bones as well.

Martin - What you want to do, estimate how much energy it takes to pump the water from the bottom of the tube to the top of the tube.

Meera - I'm in a section that looks at energy and where it comes from, I.e. the fact that it comes from our food. I'm here with Martin King. What's going on in this section?

Martin - Basically we're demonstrating here how much energy we burn of in everyday tasks, for example cycling.

Meera - In order to show this you seem to have an exercise bike with a tall tube in front of it. What's going on here?

Martin - Basically the idea is, as you bike water is pumped from the bottom of the tube up to the top of the tube. We're getting the participants to estimate how much energy in the form of Maltesers it takes to pump the water to the top of the tube. Estimates have varied from 10-500.

Meera - And what is the answer?

Martin - The answer is 1.

Meera - Only one malteser?

Martin - That's right. Only one Malteser. This is shocking to most people.

Meera - I've just seen a child on this bike cycling for quite a while.

Martin - The average time it take is about 2-5 minutes, depending on the child. Another interesting fact is that you have to pump the water up the tube fifty times to burn off the energy found in a typical pizza.

Meera - So you say the children have been cycling for 2-5 minutes. Say the average was about 3 minutes and they have to do that 50 times. That's 150 minutes. That's over two hours of exercise on this bike just to burn off a pizza.

Martin - Yes. This is neglecting the fact that we all have what we call a basal metabolic rate. Basically the energy that you use without doing any work. This doesn't take that into account.

Meera - I've learned the importance of eating healthily for the strength of our bones as well as how much exercise we need to do to burn off something as small as one Malteser. Now I'm off to actually make healthy meals at the sizzling science lecture.

I'm now here with Dr Susan Jebb from the Medical Research Council who's been leading today's sizzling science talk and been explaining some of the science behind cooking. Hello, Susan. What have you been talking about in today's lecture?

Susan - We've been trying to show people that science is all around us, in everything we do and that cooking – there's a huge amount of science in there as well. Of course, we've also bee trying to give people some important messages about how the food we eat really can impact on our health.

Meera - how have you been getting the science of cooking across today?

Susan - We've had a couple of little tricks of the trade. We've been using a water bath to cook the meat in. In that way we can hold the meat at a very particular temperature. If you cook meat at a higher temperature actually you begin to break down some of the muscle fibres and you really lose the texture. A water bath allows us to control the temperature far better than you could in a conventional oven.

Meera - During today's talk you were mentioning about the glycaemic index. What is this and why is it important when it comes to understanding about parts of the diet?

Susan - The glycaemic index is a measure of how rapidly the energy in food is absorbed into the blood stream. Some of the research suggests that people who tend to choose foods with a lower glycaemic index, meaning the energy;s released very slowly, have a reduced risk of developing things like diabetes and heart disease.

Meera - You also mentioned that if people don't necessarily have access to fresh vegetables all the time it's good to have frozen vegetables in the home, just as a backup. Are these still just as good for you as fresh vegetables?

Susan - Frozen vegetables are a fantastic alternative to fresh. These days they're picked and frozen so very quickly it really preserves al the nutritional value. Some veg don't freeze as well as others and so the texture is not quite as good. Some vegetables, like peas, like sweetcorn and even to some extent green beans, freeze really well. They actually make for a very cheap and convenient option.

Meera - What would you say the emphasis of today's sizzling science is?

Susan - I really want people to see food as something as something which is incredibly interesting and important and a really valuable bit of their lives. I think if they value food they start to think a little bit more about what they're consuming. That can only be good for health.

March 2009