Ask the Prof!

Professor Foodsmart

Professor Foodsmart here!

Is there something you would like to know about food? I'll answer as many questions as I can on this page.

Food gives us energy, but why do we need energy?

from James of Guildford

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You need energy to do all the things you love to do – from jumping, running and dancing to reading, eating and sleeping! While you are a child, your body also needs energy to grow. Energy is measured in calories and you can get it from food you eat. Foods containing carbohydrates are very good for giving you energy. The starchy ones like bread, pasta, potatoes and rice (especially wholegrain ones) are the best. Your body needs a good mix of lots of different foods to make sure it gets all the goodness it needs to stay healthy. It also needs water and air. Spare energy from the food we eat is stored by our bodies as fat. Exercise helps us use up the spare energy.

Learn more about foods that are good for you and give you more energy with our healthy plate game.

Why do we have to eat five different fruits and vegetables a day?

from Veera of Preston

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There isn't a magic fruit or vegetable that contains all the goodness your body needs to stay healthy - so eating five different ones every day is an excellent way to make sure you are getting a good variety of vitamins and minerals. And while eating five portions is great, eating more than this is even better! Try to have at least three portions of vegetables and two portions of fruit and try not to eat exactly the same ones every day. Also, try to eat a colourful mixture of vegetables and fruits as this is a good sign that you are getting a good mixture of nutrients.

Keep track of how many portions of vegetables and fruit you are eating, with this handy 5 A DAY wall chart.

Is a child's portion of fruit and veg the same size as an adult's?

from Harriet of Dorchester

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Well, Harriet, I always say that a child's portion of fruits or vegetables is roughly what can fit into their cupped hand. This means that a child's portion is actually less than an adult's because children's hands are smaller! Here are some examples of what might fit into a child's hand as one portion: an apple, orange, chopped banana, plum or satsuma; a handful of smaller fruits like grapes or berries; a small slice of large fruit like melon or pineapple; a handful of dried fruit; a handful of beans and pulses; a handful of vegetables like carrots or broccoli (raw, cooked, frozen or canned). Remember that both adults and children should try to eat at least five portions of fruits and vegetables each day to stay healthy.

Why can't we eat treats all the time?

from Layaan of Blackburn

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Foods that you might call treats are ones like take-away burgers and pizzas, chips, crisps, sweets, chocolate bars, ice-cream, cake and doughnuts. Most of these foods are high in either fat, sugar or salt - and some are high in all these things! Other 'treats' are fizzy drinks like lemonade and cola, which are also usually high in added sugar. Healthy foods (including fruits, vegetables and milk) have some natural sugar in them, but they have a lot of goodness in them too. The 'treat' foods containing added sugar often have no goodness at all. This doesn't mean you can't ever eat any of the 'treat' foods - but they shouldn't be eaten too often. After all, a treat is something to have occasionally.

Why not try this healthier treat? Our tasty berry mess recipe is easy to make.

Is water healthy?

from Athiya of Lancashire

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Well, water is certainly good for us – in fact we need water to stay alive and grow. It helps the nutrients in our foods to move around our bodies. We should drink plenty of water every day to make sure that our bodies get enough. In hot weather, or when we exercise, we should drink even more. This is because our bodies lose water when we sweat. We can get water from food and other drinks, like fruit juice or squash, but it is good to drink plain water because it has no sugar in it. Sugary drinks, especially fizzy ones like cola, can be bad for our teeth so we shouldn't drink too many of these.

To record how much you drink every day, download our Am I drinking enough? wall chart.

Why is salt bad for you?

from Grace of Swansea

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Your body only needs a small amount of salt. Salt contains something called sodium and too much of this is bad for your blood pressure. Salt is also bad for your stomach. Lots of foods you find in the shops contain salt, even ones you might not expect to have it – like some breakfast cereals and bread. Home cooking can help us cut down on the salt we eat as we can choose how much salt to put in the food we cook – or not put any in at all.

Instead of salt, try these spectacular spices to add some extra flavour to your food!

Where do bananas grow?

from Alexander of Wirral

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Bananas grow in bunches (called clusters) on tall plants that look like palm trees. They are grown in more than 100 countries in the world but grow best in tropical countries like Mexico, Colombia, Ecuador and Costa Rica. To begin with, banana skin is green. Then, as the starch in the fruit turns to sugar it turns yellow. This is when the banana is ripe and ready to eat. Bananas give us plenty of energy and contain lots of vitamins. Have you tried mashed banana on wholegrain toast? It's delicious!

Why do carrots grow in mud?

from Heidi of Hampshire

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Carrots grow in mud (or soil) because they are root vegetables - so you are eating the root of the plant, which grows underground. Parsnips, turnips and swedes are also root vegetables. Some other fruits and vegetables you might eat - like beans, sweetcorn, pumpkin and strawberries - grow above the ground. All these plant foods need the nutrients in the soil, as well as water and sunshine, to help them grow. Carrots contain lots of beta-carotene which helps keep your body healthy. Ask your mum or dad if you can try them boiled and mashed together with other root vegetables. This makes a tasty change from ordinary mashed potato and it is much healthier than chips!

Grow your own root islands using root vegetables. They will grow to look like trees on islands.

Why do onions make your eyes water?

from Taran of Coventry

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Well Taran, you're right there – chopping or slicing onions can make your eyes water. This is because when you chop or slice an onion (with an adult), a very small amount of harmless gas is made and let off. The gas travels in the air around the onion – up to your nose and eyes. Eyes are sensitive so the gas can sting, which makes them water to try to clear it away. Sometimes, opening a window can help blow away the gas – give it a try!

Play our fun online game, Where does it grow? and learn where onions and other vegetables and fruit grow.

Where does rice come from and why are there so many different types?

from Pippa of East Sussex

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There are lots of different types of rice, like basmati, arborio, long grain and short grain. Rice is a grain that grows on rice plants in fields. They grow all over the world. You can also buy brown or white rice, but this isn't to do with where or how the rice was grown. The different colours depend on how it has been treated after it has been harvested. Brown rice has had more nutrients (like fibre) left in it than white rice. This means that brown rice is better for you.

Is it true that carrots help you see in the dark?

from Leona by email

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What a good question! Carrots contain a nutrient called beta-carotene, which our bodies turn into vitamin A. Vitamin A helps keep our eyes healthy. Eating lots of carrots won't help us to see better in the dark, but will help us to have enough vitamin A in our bodies. Vitamin A also helps to keep our skin healthy. Other bright orange fruits and vegetables, like butternut squash, apricots and sweet potatoes, contain beta-carotene too.

Why not try our rainbow salad recipe, which has lots of carrots in it?

What can you grow if you haven't got a garden?

from Ruqayyah of London

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You can grow all sorts of herbs, salads and vegetables in window boxes, hanging baskets or pots, and in decorated containers like margarine tubs or yoghurt pots. Grow herbs like chives, mint and basil in pots on a window sill, and sprouts like alfalfa sprouts and mung beans in a germinator jar – you can get one of these from a good garden centre or health shop. If you have a balcony or a large outside window ledge you can grow tomatoes, peppers, courgettes, leafy salads and spring onions in big pots. Maybe you could keep some pots in a friend's garden or you might be able to grow something at school.

We have lots of ideas for things you can grow at home. Visit our Grow it page and find out more.

Which food is good for the immune system?

from Shamrez of Birmingham

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The immune system is the body's way of fighting germs. By eating healthy foods you can have a healthy immune system that helps to protect your body. Some examples of these foods are: Wholegrains – wholemeal pasta and bread, brown rice, oats, barley and other wholegrains. They are a good source of the vitamins, minerals and fibre that you need to keep the immune system healthy. Vegetables and fruits – different vegetables and fruits contain different vitamins and minerals. The best way to make sure you are getting all the goodness you need is to eat a colourful mixture – think of a rainbow and try to eat foods that come in all its different colours! Here are some ideas: Green – apple, grape, kiwi fruit. Red – raspberry, rhubarb, strawberry. Orange – mango, papaya, peach. Yellow – lemon, pineapple, banana. Purple – blackberry, plum, blueberry.

Why not download our Taste the rainbow wall chart and have fun drawing the different vegetables and fruit you eat everyday?

Why is sugar unhealthy?

from Indigo Lily of Salisbury

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What a good question! Your body turns the foods that you eat and drink into the energy it needs to grow and move. Different types of food give you different amounts of energy. The amount of energy in food and drink is measured in 'calories'. When you eat more calories than your body needs, the extra energy is stored in your body as fat. A lot of the foods and drinks that have added sugar - such as sweets, cakes and fizzy drinks - contain lots of calories. They are also bad for your teeth. We should try not to have these types of foods and drinks too often. This doesn't mean you can't ever have them - but you should try not to have them too often. After all, a treat is something to have only once in a while. There is also sugar in foods such as fruits and vegetables, but these foods contain lots of vitamins and minerals your body needs to stay healthy so they are good for you. So, next time you fancy something sweet, why not try a piece of fruit instead?

Which are the most popular fruits?

from Christy of Oldham

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To answer this question you could simply check what fruits you have at home. The chances are that the fruits you have in your kitchen are the most popular fruits eaten in the UK. Let's see if you have guessed right: Most popular: Bananas - they give you plenty of energy and contain lots of vitamins and minerals. You can eat them raw, baked or dried. Why don't you try mashing a banana and having it on brown toast? Tasty! Second place: Apples - they give you vitamin A and vitamin C. Try making dried apple rings at home - ask an adult to help you take out the core, thinly slice the apple and bake the rings in the oven at a low heat. Yummy! Third place: Oranges - they are high in vitamin C. Orange zest (the outer layer of the skin) can be grated into lots of dishes to give them a tangy taste.

Check out our A-Z of fruit and veg to discover lots of fun food facts. How many from the A-Z list have you tried?

I would like to grow very tall. Which fruits or vegetables should I be eating?

from Rebecca of London

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Wouldn't it be nice if there was a magic fruit or vegetable that would make you as tall as a tree or even as small as a mouse? Unfortunately there isn't, but fruits and vegetables, as well as other foods, do have a little magic in them called nutrients, which help you grow big and strong. It's important to eat at least five portions every day. And there's more. It doesn't matter if you eat fresh, tinned, dried or frozen fruits and vegetables, they all count towards your 5 A DAY! To make sure you are getting what your body needs to stay healthy don't forget to eat a range of foods from all of the different food groups – fruits and vegetables, starchy foods like bread, rice, potatoes and pasta, dairy foods like milk and yoghurt, and protein foods like chicken, fish, eggs, lentils and beans.

What is the difference between oranges, clementines and tangerines?

from Rukaiya of London

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What an interesting question! Oranges, clementines and tangerines are all citrus fruits. They count towards your 5 A DAY and are also a source of vitamin C which is good for your skin. Oranges are usually much bigger than clementines and taste sweeter too. Satsumas, clementines and tangerines are all different names for types of mandarins. The juiciest ones are the heaviest ones. Did you know that oranges are green before they ripen in the sun and turn orange? Oranges are really famous - they are one of the most popular fruits in the world! Try cutting an orange into quarters and freezing it to make a healthy icy treat. 

Have some fruity fun! Play our funny food figures game, and create your own cartoon characters.

Is it true that green vegetables and fruits are good for your eyes?

from Rukaya of London

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The vitamin that helps to keep our eyes healthy is called vitamin A. You find this vitamin in dark green leafy vegetables such as broccoli and cabbage, but also in orange vegetables and fruits like carrots and dried apricots and even in cheese, milk, yoghurt, eggs and oily fish. So, as you can see, it's not just green vegetables and fruits that are good for our eyes. All vegetables and fruits are good for you, what's important is that you try to eat as many different coloured vegetables and fruits as possible to help you get all the different nutrients you need to stay healthy. Can you name five green vegetables and fruits? How about five red, orange, yellow and purple ones? With so many delicious vegetables and fruits to choose from it couldn't be easier to get your 5 A DAY every day.

Why not try making these fun shaped sandwiches? They are a great way to help you get your 5 A DAY!

Why do coconuts have hair?

from Shakil of London

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A coconut is a very interesting food. It's a large round nut that grows on palm trees. It needs lots of sunshine and warm, wet weather to grow. That's why you only find coconut palm trees in tropical countries like the Philippines, India, Brazil and the Caribbean. Coconuts have many layers. When they grow on trees they have an outer layer which is usually a green colour.When you buy them from a grocery store or supermarket, this outer shell has already been removed and the coconuts look brown and hairy, which is what you might be familiar with. The hair of a coconut shell is called coir. People use it to make things like ropes, mats or brushes.The hair is waterproof and protects the coconut from getting soggy. This is very handy as coconuts often fall into the sea and float for days. The hair protects it from the sea water when the outer layer breaks. When the coconut finally reaches land, it sprouts and grows into a palm tree. Very clever! As well as the delicious flesh we all love to eat, coconuts also contain a milky juice which is very tasty. People in different countries use it as an ingredient when cooking sweet and savoury dishes and as a refreshing drink.

What is more unhealthy: sweets or chocolate?

from Octopus and Squid Classes, Fairlight Primary School, Brighton

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To answer your question, there isn’t one that is more healthy or unhealthy than the other. Sweets and chocolate are both foods that you might call 'junk foods'. They contain lots of sugar or fat and little nutrients. These are fine as a treat but you shouldn't eat them every day. If you fancy eating something sweet why not try these healthy options instead? Strawberries - sweet fruits that taste delicious on their own. Try them with some low-fat yoghurt too. Did you know strawberries are the only fruit to have their seeds on the outside? Kiwi fruit - this juicy fruit makes a great snack. You can scoop out the green flesh with a spoon just like a boiled egg! Mango - this tasty fruit comes in different shapes and sizes. You have to peel off the skin to eat the soft, juicy flesh inside.

Help the Grub Gang Kids to catch the fruits and vegetables. Leave the junk food to rot with our fun online game, Dump the junk.

Is all fat bad for you?

from Rami Taylor of Birmingham

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No. Lots of foods have fat in them and that’s a good thing because your body needs some fat for energy. But if you eat more fat than your body can use, you will store this fat in a layer around your body. The fat in some foods is better for you than the fat in others. The fat in nuts, avocados, oily fish and olive oil helps to keep you healthy, but eating too many fatty foods like doughnuts, bacon, crisps and chips is bad for you.

Have fun choosing healthy meal ideas with our interactive packed lunch planning game.

Why do some vegetables grow underground?

from Rhianna of Ilford

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Most vegetables have parts that grow underground – their roots. These suck water and nutrients from the soil and fix the plant to the soil. Some plants have underground parts that we can eat. We call these root vegetables. For example: potato, carrot, radish, beetroot, turnip and parsnip. But the parts we eat are not usually true roots. They are underground parts that grow thick to store food for the plant. Root vegetables are full of goodness like fibre, vitamins and minerals. Other vegetables you might eat - like beans, sweetcorn and pumpkin – have roots, but we eat the part that grows above the ground. So to answer your question, I don't know why some vegetables grow underground, but I know they are delicious and good for you too.

Parsnips grow underground. They’re a healthy root vegetable you can turn into tasty wedges with this simple recipe.

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