Ask A Food Scientist:
Questions Answered 11th August
11th August 2011
Q1 What is the best sugar, and what is the difference between cane and other sugars?
Q2 Does refined sugar give you more energy more quickly?
Sugar is a widely-used term describing edible crystalline carbohydrates, mainly sucrose (free sugar), lactose (milk sugar) and fructose (fruit sugar), which taste sweet. In food, the term sugar almost exclusively refers to sucrose regardless of whether it is refined (pure free sugar) from sugar cane or sugar beet or food sugars.
For more information visit http://www.britishsugar.co.uk/Sugar.aspx
Carbohydrates are an important part of our diet; ultimately sugars are broken down to glucose, fructose or galactose, and used to make energy (ATP) or stored in our muscles and liver as glycogen for future use. No one sugar is better or worse than another, and refined sugars such as sucrose still need to be digested to provide energy. Generally, we eat too much sugar, and too little starch and fibre. We should be eating between 200-300g of carbohydrate daily of which only 10% (20-30g) is recommended to be sugar, and this includes naturally-occurring sugars (e.g. milk and fruit/ fruit juice) as well as all the sugar added to sweets, cakes, biscuits, chocolate and some drinks. For more information visit http://www.nhs.uk/livewell/goodfood/pages/sugars.aspx
Q3 What are healthy foods and drinks for children?
Our dietary needs depend on our age, size, and activity levels. Current advice suggests we should base our meals on starchy foods (e.g. wholegrain bread, pasta and rice) and eat lots of fruit and vegetables, at least five portions every day, whether fresh, frozen, tinned in juice or water (without salt or added sugar) or dried. We need to eat more oily fish and cut down on saturated fat and sugar as well as salt (not more than 6g a day), and try to be more active to ensure we are a healthy weight. We also need to drink plenty of water and to eat breakfast; people who eat breakfast are less likely to be overweight. Based on the Department of Health Report on Health and Social Subjects No 41 (Dietary Reference Values for Food Energy and Nutrients for the United Kingdom London: HMSO 1991), guideline daily amounts for children (5-10 years) are typically: 1,800 kcal, 24g protein, 220g carbohydrate (not more than 85g sugar), 70g fat (not more than 20g saturated), 15g fibre, and not more than 4g salt. For more information, visit http://www.nhs.uk/Change4Life/Pages/change-for-life-adults.aspx, http://www.nhs.uk/livewell/Pages/Livewellhub.aspx, http://www.gdalabel.org.uk/gda/home.aspx and http://www.nhs.uk/Livewell/Goodfood/Pages/food-labelling.aspx#Tr
We need about six to eight glasses of liquid a day, some of which comes from our food. Drinks that contain a lot of sugar or sugar substitutes (e.g. aspartame) have few beneficial nutrients, and there are alternatives.
Fussy eaters – for more information and advice visit http://www.childrenfirst.nhs.uk/families/az_child_health/f/fussy_eaters.html
Q4 How do you work out portion sizes?
An adult portion of fruit or vegetables is about 80g or 3 oz (e.g. one whole apple or orange, a handful of grapes or cherries, tablespoonful of raisins, a bowl of salad or three heaped tablespoons of peas). An adult portion of meat is also about 80g/3 oz, which is about the size of a deck of cards … and a medium potato (a portion of carbohydrates, ca. 16.3g starch and 1g sugar) is about the size of a computer mouse! For more information visit http://www.nhs.uk/Livewell/5ADAY/Pages/Portionsizes.aspx and http://www.nhs.uk/Change4Life/Pages/adult-portion-sizes.aspx
Children are not small adults; they need child-sized portions. For more information visit http://www.nhs.uk/change4life/pages/kids-portion-size-tips.aspx
Q5 Are GM foods sold in the UK?
GM foods may only be authorised for sale if they are judged not to present a risk to health, not to mislead consumers and not to be of less nutritional value than the foods they are intended to replace. Each application is reviewed on a case-by-case basis including a detailed consideration of the potential for toxic, nutritional and allergenic effects. In the EU, if a food contains or consists of genetically modified organisms (GMOs) or contains ingredients produced from GMOs, this must be shown on the label. This means products such as flour, oils and glucose syrups have to be labelled as GM if they are from a GM source. For products sold loose, information must be displayed immediately next to the food to indicate that it is GM. Foods produced with GM technology (cheese produced with GM enzymes, for example) do not have to be labelled. Products such as meat, milk and eggs from animals fed on GM animal feed also do not need to be labelled. For more information visit http://www.food.gov.uk/gmfoods/gm/gm_labelling and http://ec.europa.eu/food/dyna/gm_register/index_en.cfm and http://www.bionetonline.org/english/content/ff_leg2.htm#Q1
Q6 How does fruit make you healthy?
Fruit provides vitamins and minerals and fibre but they also contain many other beneficial compounds (e.g. polyphenols), which are not nutrients but significantly reduce our risk of cancer and cardiovascular disease. Those who eat a diet rich in fruits and vegetables are less likely to be over-weight and have less tooth-decay. For more information about including fruit in your diet visit http://www.nhs.uk/Change4Life/Pages/change-for-life.aspx
Q7 How do you make tomato ketchup?
Commercial tomato ketchup generally contains tomatoes (132g per 100g), vinegar, sugar, salt, spice and herbs. The tomatoes are cooked during manufacture to concentrate the flavour and, as a result, 100g ketchup contains the equivalent of 132g of fresh tomatoes (in case you were worried about the maths). You can also make ketchup at home – try searching for recipes online.
Q8 Which apples are best; red or green?
The colour of the skin is simply different amongst the hundreds of varieties; neither is better than the other. Do not peel them because the skin is a source of fibre amongst other things.
Q9 Why is an orange called an orange?
Strictly, what we call an orange is called Citrus sinensis, which accounts for about 70% of the commercial crop. There are other oranges such as Citrus aurantium, also known as Seville orange, which are used for making marmalade, tea (Citrus bergamia Risso) or other orange fruit crops (e.g. Citrus reticulate – mandarin oranges). Like many of our words, orange comes via a long and complex inheritance of languages; whether it was applied to the fruit or the colour first is hotly debated but it is useful to be able to point and ask for the orange thing ...
Q10 How big can bananas grow?
Q17 Are bananas good for you? How many is too many?
Bananas contain per 100g flesh – 75.1g water, 1.2g protein, 0.3g fat, 23.2g carbohydrate, 95 Kcal., 2.3g starch, 20.9g sugar, 1.1g fibre, 1mg sodium, 400mg potassium, 6mg calcium, 34mg magnesium, 28mg phosphorous, 0.3mg iron, 0.1mg copper, 0.2mg zinc, 0.79mg chloride, 0.4mg manganese, 1mg selenium, 8mg iodine, 21mg carotene, 0.27mg vitamin E, 0.04mg thiamine, 0.06mg riboflavin, 0.7mg niacin, 0.2mg tryptophan, 0.29mg B6, 14mg folate, 0.36mg pantothenate, 2.6mg biotin and 11mg vitamin C
A medium-sized banana is about 100g (4 oz). Guinness World Records does not record the largest banana but a host of resources suggest the largest is typically 60 cm (24 inches).
Bananas do not count toward five-a-day; neither do potatoes because they are starchy foods. Bananas are a good source of potassium, starch and fructose (fruit sugar), which is why so many athletes are seen eating them whilst training or competing. Eating bananas regularly is fine, eating one a day is probably sufficient since even healthy foods have calories (95 Kcal per banana). For more information about five-a-day visit http://www.nhs.uk/LiveWell/5ADAY/Pages/5ADAYhome.aspx
Q11 Should newly diagnosed asthmatics cut out dairy and sugar?
We should all cut down on sugar (see Q1) and saturated fat (e.g. full fat milk) but dairy is a good source of vitamin D and calcium. Unless you have specifically been diagnosed with a milk allergy or intolerance, or sugar intolerance, however, there is no reason why an asthmatic should exclude these from their diet.
Milk allergy and intolerance can trigger asthma and eczema in some adults (less than 2%) and children (less than 10%). Consult your general practitioner if you believe dairy products are contributing to the problem to discuss whether a referral to an allergy specialist would be helpful. Although most children grow out of their milk allergy by school age, there is no cure of milk allergies that continue into adulthood or milk (lactose) intolerance. The only option is to exclude milk entirely from the diet and this is best achieved with the help of a community dietician, for example, since milk and milk products appear in many forms, under many guises (e.g. casein), in all sorts of manufactured products (e.g. wine). For more information visit http://www.anaphylaxis.org.uk
Q12 Do strawberries have seeds? And are they a fruit?
We call strawberries a fruit. Botanically, they are false-fruits because we do not eat the seed-producing part of the strawberry plant, and the seeds on the outside are in fact achenes containing individual seeds.
Q13 Is a tomato a fruit or vegetable?
Broadly, a fruit is a structure of a plant that contains its seeds and under this definition tomatoes are fruit.
Q14 Do apples have seeds in them?
Yes and they are a fruit. For a few more facts about apples visit http://www.ifr.ac.uk/info/society/spotlight/apples.htm
Q15 Why are fruits and vegetables coloured?
Fruits are often coloured to attract insects and animals, and encourage scattering of seeds. The colours are derived from naturally-occurring, brightly-coloured compounds such as the carotenoids (e.g. beta-cryptoxanthin which makes oranges orange) and anthocyanins (red-blue colours in, for example, blackcurrants). These natural colours also occur in many vegetables, but are masked by chlorophyll (green, e.g. cabbage). Carotenoids are also responsible for the colour of autumn leaves, revealed only when chlorophyll is no longer produced, and the pink of flamingos (which eat crustaceans containing carotenoids).
Q16 Can children absorb bovine insulin from milk?
Wow! Do not be put off by the science…
Insulin is a protein, also classified as a hormone, which is central in regulating carbohydrate (sugar) and fat metabolism. Insulin causes cells in the liver, muscle and fat to take glucose from the blood and store it as glycogen for future use. Diabetes mellitus occurs when we stop producing or responding to insulin.
There are two forms of diabetes. Type 1 occurs when the body produces no insulin. It is also called insulin-dependent diabetes, juvenile diabetes or early-onset diabetes, and the immune system destroys cells in the pancreas that are responsible for producing insulin. For more information visit http://www.nhs.uk/conditions/diabetes-type1/pages/introduction.aspx
Type 2 diabetes occurs when not enough insulin is produced or when cells in muscles and the liver do not react to the insulin (insulin resistance). For more information visit http://www.nhs.uk/conditions/diabetes-type2/pages/introduction.aspx
Proteins in our diet including insulin are digested, broken down to their constituent amino acids and absorbed via the small intestine. Very rarely, for a number of complex reasons, our immune system is exposed wrongly to whole or part proteins in food, which leads to an inappropriate response; this is how we become food allergic.
A study in Finland, published in July 2011, determined some cases of Type 1 diabetes might be explained by an enterovirus infection in the presence of a dietary antigen (antibody stimulant). The strongest candidate observed in this study was bovine insulin. The authors noted that the increasing incidence and decreasing age at diagnosis will mean more patients will have with the disease for longer and, eventually, an increased frequency of macro- and micro-vascular complications if the trend cannot be counteracted by improved metabolic control. They did not suggest, however, that children should not drink milk or that bovine insulin is absorbed by the body under normal circumstances. As with many studies, more work needs to be done to understand the mechanism(s) and the implications for human health.
Q18 Is peanut butter fattening?
Peanut butter contains per 100g – 606 Kcal, 51.8g fat (12.8g saturated, 19.9g monounsaturated, 16.8g polyunsaturated), 13.1g carbohydrate (6.4g starch and 6.7g sugar)
Butter contains per 100g – 744 Kcal, 82.2g fat (52.1g saturated, 20.9g monounsaturated, 2.8g polyunsaturated), 0.6g carbohydrate (all sugar)
Jam contains per 100g – 261 Kcal, no fat, 69g carbohydrate (all sugar)
Peanut butter is probably healthier than butter because it is slightly lower in fat, the majority of which is mono-unsaturated rather saturates. Gram for gram, although high in sugar, jam is much lower in calories than either butter or peanut butter and has no fat. Any food consumed in excess means unnecessary calories, which will make controlling your weight that much more difficult…
Q19 Why do tomatoes and pears make me sick?
If specific foods consistently make you unwell, you may be intolerant or have developed a food allergy. Contrary to public perception, however, food allergy is uncommon; 1-2% adults and 5-8% children. In either case, you may need to exclude specific foods from your diet but this is best achieved with professional advice because (1) food ingredients appear in many forms, under many guises (e.g. lecithin in ingredients is egg) in all sorts of manufactured products (e.g. chocolate) and (2) it is not always immediately obvious what is making you ill (e.g. strawberry yoghurt - allergic to dairy or strawberries or lactose intolerant). For more information visit http://www.anaphylaxis.org.uk
Symptoms of food allergy differ greatly between individuals and may differ in the same person, depending on the route and duration of exposure. For example, blistering and swelling of the lips and tongue may occur immediately on eating a peanut but nausea and vomiting might occur after eating chocolate, which contains a small amount of peanut from a production line but is otherwise peanut-free. Common symptoms of food allergy include skin irritation (e.g. rashes, hives and eczema) and gastrointestinal symptoms (e.g. nausea, diarrhoea and vomiting). However, sneezing, a runny nose (rhinitis) and shortness of breath (e.g. wheezing and asthma) also crop up. Some individuals may go on to experience a more severe reaction called anaphylaxis. Anaphylaxis is a severe and rapid body-wide allergic reaction, which is potentially fatal.
EuroPrevall, an EU-funded project led by Clare Mills from IFR, brought together a multidisciplinary partnership to address food allergies in infants, school-age children and adults across Europe. As a result of their work, for the first time, we are able to describe the prevalence of food allergies and rank allergenic foods (food groups) as a function of the number of reactions they provoke in the population as a whole as well as specific age and geographic groups. For more information visit http://www.europrevall.org and www.foodallergens.info
Foodallergens.info is a collection of critically assessed webpages about food allergy hosted by IFR. The information is available in 12 different European languages (Danish, Dutch, English, Finnish, French, German, Hungarian, Italian, Norwegian, Polish, Spanish and Swedish). Information can be searched for by language or audience; adults, young people, the scientific community including healthcare professionals and researchers, and food safety specialists. On 1st August 2009, Andrew Watson (IFR) made the front cover of New Scientist with his article ‘If the nuts don’t get you, the apple will’. The article considered the latest evidence from EuroPrevall that demonstrates the regional differences in foods causing allergic reactions, and offered a current perspective on testing for allergies, treatment and the use of cautionary statements whether those typically found on packaging or in response to the presence of an allergic person on an aeroplane! If the nuts don’t get you… http://www.newscientist.com/issue/2719
For more information about living with all allergies visit http://www.anaphylaxis.org.uk