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Diet and mental health

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We are what we eat; how diet influences behavior in young people:

Recent research suggests that we really are what we eat.

Many of us know that a healthy diet reduces our risk in later life of problems such as heart disease, stroke, diabetes and cancer. However, it seems that food also influences our mental health and behaviour, including mood, concentration, impulsivity and even how we react to stress. This is not really surprising when you consider that food supplies the energy for our brain to function, along with the raw materials needed to make the brain cells and the chemicals that allow communication between them. Amazingly the brain accounts for only 2 percent of body weight but it uses about 20 per cent of the calories we need each day. The main fuel used is carbohydrate which comes mainly from eating enough starchy foods in the diet.

Recent studies show that eating breakfast helps improve mood, concentration and our ability to deal with stress. A recent study on over 800 nurses carried out in Wales showed that those who ate breakfast (which for most was breakfast cereal) had lower stress levels, fewer problems thinking and concentrating and surprisingly fewer injuries and accidents at work(1). In contrast, snacking on crisps, chocolate and biscuits was associated with higher stress and more injuries outside of work. Further research is needed to find out why this might be but it illustrates the potential importance of diet on behaviour.

Some interesting research has also been done recently on young offenders. This has shown that they often choose poor diets low in fruit and vegetables and fish, both in prison and on the outside, despite the availability of healthy alternatives(2). This in turn is believed to have an effect on behavior.

Two major scientific studies inside prisons have looked at the effect of supplementing prisoners' diets with key vitamins, minerals and essential omega 3 fatty acids (normally found in oily fish) to replace those which may be missing from a poor diet(3-4). Prisoners taking the nutritional supplements showed large reductions in violent, aggressive and antisocial behaviour, compared with those taking placebo or dummy pills. The first study at Aylesbury Young Offenders' Institute involving 231 volunteers showed that inmates receiving supplements committed a third fewer offences. The positive effects of an enhanced diet on antisocial behaviour have also been recently reported in the USA and Netherlands.

This suggests the potential of improved diet, as a complement to other approaches, to influence both the environment within prison and possibly reduce re-offending rates. Further work on this area is being led by scientists at Oxford University involving 1000 inmates at three UK prisons (Hindley in Wigan, Lancaster Farms in Lancaster, and Polmont in Falkirk) to see if better nutrition can improve behaviour. The findings will be reported in 2012. Watch this space for more information.

The results could have wide implications for the way we think about how our diet affects mental health and behaviour and the way we feed young people in a range of settings other than prison.

For easy value-for-money recipes using these foods which supply these valuable nutrients please see FOOD INSIDE OUT, RECIPES section.

1.Chaplin K , Smith AP (2011) Breakfast and snacks: associations with cognitive failures, minor injuries, accidents and stress.Nutrients. 3:515-28.
2. Eves A & Gesch CB (2003) Food provision and the nutritional implications of food choices made by young adult males in a young offender’s institution. Journal of Human Nutrition and Dietetics 16:167-179.
3. Gesch, C.B., Hammond, S.M., Hampson, S.E., Eves, A., Crowder, M.J. (2002) Influence of supplementary vitamins, minerals and essential fatty acids on the antisocial behaviour of young adult prisoners. Randomised, placebo-controlled trial. British Journal of Psychiatry 181 22-8.
4. Zaalberg AP, et al (2010) Effects of nutritional supplements on aggression, rule breaking and psychopathology among young adult prisoners. Aggressive Behavior 36: 117-126.

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Facts behind the headlines: the word on water.

Water is often overlooked but it is one of the main nutrients needed by the body - you could even argue it's the main one. We can only survive for a few days without water (only a few hours in a hot climate) and unlike many other nutrients, we don't store much of it so we need a daily supply.

What does water do?

Water plays a range of essential roles in the body. As blood plasma it transports nutrients and oxygen to all cells and takes away waste. It is crucial for excreting the waste products of metabolism as urine. Water is also important for temperature control - sweat produced by the exocrine glands of the body is largely water. When we are active or in a hot climate this evaporates, cooling the skin. Blood in contact with the cooled skin then circulates back to the core of the body and helps cool it down. The hotter we are the more we sweat. Without adequate water we cannot sweat and we risk heat exhaustion. Body water loss above about 10% usually requires medical intervention, and circulatory collapse, even death, are risks.

An average adult is about 60% water, for a 70kg man that's 42 litres! A young infant can be as much 75% water but for an older woman the level falls to about 50%. The difference is related to the amount of lean muscle tissue in the body. Older adults and women generally have a lower proportion of muscle and more fat hence the lower body water content. Most of it, about ⅔, is within your cells, the so-called "intra cellular" fluid. The rest is "extra cellular" fluid and is found bathing cells in body fluids like blood and urine.

Fluid balance

We take it in water not only from beverages, but also from food. About 20% (or 500ml of our daily water intake) comes from what we eat rather than what we drink. Fruit and vegetables can be as much as 80 - 90% water and even foods like cooked pasta and potatoes contain about 70% water.

Daily fluid turnover in an adult in a temperate climate is about 2,800 ml/day. Some is passed out in our breath and faeces. About half the water lost each day is in our urine. It is also evaporated in sweat but the amount varies considerably between individuals from as little as 500 ml/day up to 2 litres an hour in some sports. The amount is very much related to both climate and physical activity level.

Fluid balance is kept under close control by a process of homeostasis which ensures just the right amount of water inside and outside the cells. It relies on a clever feedback system involving osmoreceptors in the brain which detect the concentration of the blood. Hormones also regulate reabsorption of water in the kidney and so reduce urine production.


It's not always easy to know when you are short of fluid. Anyone can get dehydrated but those at increased risk include:

  • infants and children who have a larger potential body surface area for evaporation of water
  • people with increased needs for fluid such as breastfeeding mothers, those ill with fever or diarrhoea, or on diuretics
  • elderly people who may have a poor thirst mechanism, reduced absorption or swallowing problems (dysphagia).

Possible short-term symptoms of dehydration are shown in table 1. The physical symptoms may be familiar but the effects on mental ability less so. Interestingly, lack of fluid has been shown to increase the levels of a circulating hormone, cortisol, which can impair both learning and memory.

Table 1 Symptoms of dehydration

Physical symptoms

Mental symptoms




Reduced decision making ability


Poor concentration

Reduced muscular strength

Impaired mental arithmetic

Impaired physical endurance

Lack of alertness & accuracy

Impaired co ordination

Impaired short term memory

Reduced skin elasticity – the "lasting skinfold" when pinched

Delayed response reactions

Evidence is also starting to build for long term problems related to chronic dehydration. These include constipation, kidney stones and urinary tract infections as well as an increased risk of both bowel and bladder cancer.

Thirst is a relatively insensitive indictor of dehydration. By the time you feel thirsty you've probably already lost 1-2% of your total body water. It takes time for the osmoreceptors in the brain to recognise an increase in concentration of the blood. Some studies show that by the time participants rate themselves as thirsty they are already quite dehydrated. Thirst is a better mechanism for correcting long-term deficits and can continue to stimulate drinking in the 24 hours following dehydration.

The colour of your urine can be a good indicator of your hydration status. Dark yellowish brown coloured urine can reflect quite severe dehydration. Pale yellow straw coloured usually means you have lost less than 1% of your total body water. Pee charts (rather like paint charts) can be a practical and helpful tool, especially for sports people, but urine colour is not a precise measure of hydration status.

How much fluid do we need to drink?

Since around 500ml fluid a day comes from food, the recommended intake of fluid from drinks for an adult (with temperate climate and moderate activity levels) is around 2 litres per day. This equates to about 8 glasses or cups of 250 ml each- spread evenly throughout day but what should we drink?

Tap water is probably the easiest and cheapest source of fluid if safety is assured. This includes most of Europe where microbiological and chemical standards are very high and rigorously enforced. More than 1 billion people worldwide do not have access to safe drinking water, and many more spend a large part of their working day collecting a supply. We are very lucky to have low cost safe source of tap water delivered directly to our homes. In the UK the Drinking Water Inspectorate carefully monitors the chemical and microbiological safety along with the aesthetic quality of our water. Some consumers dislike the smell or even the hardness of tap water provided by minerals such as calcium and magnesium. For them jug or mains water filters are a great idea. These work by carbon filtration or ion exchange swapping sodium ions for the calcium. The extra sodium is small compared with that in the rest if our diet and of little concern except for those on a very strict low sodium diet.

Other types of water

Bottled water – table or mineral, still or sparkling - is a good alternative where standards of tap water are dubious. Intakes continue to soar in the UK, despite our safe water. Bottled water offers no nutritional advantages over tap water. Mineral water can contain minerals such as calcium, magnesium or sodium, leached from underground rocks on their journey to the surface. Some brands are a reasonable source of calcium but in many cases the levels are no higher than that in tap water and often only about 10% of that found in milk.

Bottled water is expensive, costing up to 100 times as much as tap water weight-for-weight. There's also the environmental costs of plastic bottles. Although providing no confirmed health risk, the fuel costs associated with moving them around the country (and even from country to country) is considerable. Who could have predicted 15 years UK ago that one day whole aisles of the supermarket would be given over to bottled water?

Many European countries, where water safety was until recently more of an issue, have relied on bottled water. However it's interesting to note that the tables are turning and many French consumers are now using tap water in preference in protest against the escalating cost.

Recently some companies have started to produce "not for profit" bottled water aiming to supply bottled water in a socially responsible and ecologically sound way using recyclable plastic and local spring water. The profits (up to 60p in the £) are donated to clean water projects around the world.

So much for water – what about other drinks?

Surprisingly some studies show that only about a third of our beverages are taken as water. The rest is provided as tea, coffee, cocoa, juice or sweetened beverages like squash and fizzy drinks. It's a common misconception that caffeinated drinks don't count towards fluid intake. However careful fluid balance studies show that if you are a regular tea or coffee drinker, the diuretic effect of caffeine is far out weighed by the fluid content. In other words, they count as " net hydrators " contributing to fluid in just the same way as other beverages. One study by Grandjean et al (2000) showed that consumption of up to 75% of the daily fluid intake from tea and coffee did not adversely affect hydration.

Isotonic drinks provide quickly absorbed fluid, along with a source of fuel as sugar and sodium to help with fluid absorption. They can be useful in sporting events lasting longer than about an hour but can be expensive to buy in the amounts you need to fully rehydrate. Homemade versions are cheaper and equally palatable. See table 2

Table 2 Recipes For Homemade Isotonic Drinks

Recipe 1

Measure out 250ml pure unsweetened fruit juice (any flavour)

Add 250ml water to make a total volume of 500ml

Add a pinch of salt (about 1/5 teaspoon)

Mix together and stir or shake well. Chill in the fridge.

Recipe 2

Measure out 100ml squash (any flavour – full sugar)

Add 400ml water to make a total volume of 500ml

Add a pinch of salt (about 1/5 teaspoon)

Mix together and stir or shake well. Chill in the fridge.

Squash and fizzy drinks contain fluid but along with it comes sugar. This can be broken down by bacteria in the mouth to form plaque acid which in turn can corrodes and causes decay in the teeth. The more frequently the teeth are bathed in sugary solution the more likely decay is to occur.

Sugar in drinks also provide calories and given the problems of childhood obesity it's easy to overdo energy intake. It seems appetite regulation does not compensate for calories in drinks the same way it can do with food. Unsweetened fruit juice will count towards fluid intake and provides one of the 5 portions of fruit and vegetables per day. However it is also a source of sugar providing calories and potential to cause tooth decay. Try diluting with water it especially for children. Sugar free or diet drinks are an alternative although they do contain acid with potential to damage the teeth.

Grandjean et al (2003) showed it was feasible in the short term to survive on fluids entirely from sources other than plain water. However for various reasons including cost, tooth health and energy intake it's not a strategy which is advisable in the longer term.

Is it possible to overdo fluid intake?

It is rare but cases of "water intoxication" leading to dangerously low body sodium levels (hyponatraemia) have occurred. This has been documented in people with psychiatric problems and active sports people who have drunk much more than they need. In the past few years at least 5 marathon runners around the world have died from water overloading after taking in excess fluid in an event.


Water is an essential nutrient for life. Dehydration can often go undetected with both short and long term health consequences. Drinking enough water, either on it's own or in a mix of drinks, is vital but often overlooked strategy for maintaining good health.


Grandjean AC, Reimers KJ, Bannick KE and Haven MC (2000) The effect of caffeinated, non caffeinated, caloric and non caloric beverages on hydration. Journal of the American College of Nutrition 19:591-600

Grandjean AC, Reimers KJ, Haven MC and Curtis GL (2003) The effect on Hydration of Two diets, One with and one without Plain water. Journal of the American College of Nutrition 22 165-173

Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2004) http://darwin.nap.edu/books/0309091691/html/73.html.

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Olive oil


Facts behind the headlines: Health conscious shoppers in the UK strike olive oil.

Olives have been cultivated in the Mediterranean for over 4000 years but only recently have they begun to feature as a major player in the diet anywhere outside of Southern Europe. Amazingly in the UK sales of olive oil have risen by almost 40% over the past 5 years.

Olive oil is obtained by crushing fresh olives and over 80 varieties of olive are used in the process. The final product can classified in several ways. Extra virgin oil is the juice from the first mechanical or cold pressing of the olives. It is generally considered to be the most flavourful and best quality oil. Virgin is the next best quality. Neither extra virgin nor virgin olive oil contain any refined olive oil. Refined olive oil is sometimes called 100% pure but is a blend of virgin and refined oil, often lacking in flavour and colour.

Olive oil is believed to be a significant factor in the health properties of the so-called Mediterranean diet. This diet seems to protect against both heart disease and stroke, as well as certain forms of cancer and some inflammatory illnesses. However nutritionists are not sure quite how or why this is so.

The fat in olive oil is monounsaturated, a type of good fat. This helps keep blood cholesterol low unlike saturated animal fats which will increase it. However this doesn't fully explain the wide range of health benefits

Recently a team of Spanish researchers showed that these health benefits may be the result of a group of chemicals in olive oil called polyphenols. They have a range of powerful effects in the human body including anti inflammatory, antioxidant and anti clotting properties.

The researchers fed a test group of people olive oil high in phenols or the same oil with the phenols removed. They then looked at the elasticity of their artery linings. Usually a dose of fat would impair artery flexibility but the high phenol group did not show this. Instead the lining of their arteries remained elastic and healthy blood circulation was maintained. This was the first study to show a health benefit of polyphenols in humans which would be expected to lower heart disease and stroke

Polyphenols include oleuropectin, lignans and catechols which are also found in tea, dark chocolate, vegetables and some fruits such as pomegranates. They are particularly plentiful in extra virgin olive oil giving it a pungent flavour and colour. They are found at much lower levels in refined olive oils and seed oils such as rapeseed and sunflower where they are lost as part of the processing.

Extra virgin olive oil, like wine, varies hugely in price but there's no need to spend a fortune. I found several good imported brands and some supermarket own brand extra virgin oils for between £4 and £6 a litre compared to the more familiar, upmarket brands at £7 and £10 a litre.

Olive oil is still high in calories - one tablespoon has 120 calories, the same as a slice of bread and butter. Use it in moderation if you are watching your weight. Lite on the bottle refers usually to a refined oil where the phenols along with colour and flavour have been removed - not to a lower calorie product. The daily amount of olive oil used in the Mediterranean is around 20ml, or 2 tablespoonsfull, a day so try not to exceed that - you can buy a drizzler or spray can to help regulate use. Olive oil based spreads are a good alternative to butter and margarine.

Finally it's worth remembering that there are other aspects of the Mediterranean diet responsible for the multiple health benefits including regular intakes of oily fish, poultry, fruit and vegetables, low fat dairy products, wholegrains nuts and low intakes of full fat red meat and dairy produce.

Ruano, J et al (2005) Phenolic content of virgin olive oil improves ischemic reactive hyperemia in hypercholesterolemic patients, Journal of the American College of Cardiology. 46(10):1864-8.

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Sea Salt
Picture  ©http://www.dlc.fi/~marianna/gourmet/i_salt.htm

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What's the story?

Recent market research has shown that sales of ordinary household salt dropped by 10% last year. Conversely sales of rock and sea salt are escalating as people seek out alternatives. But are they any better for you and why does it matter?

The background

High blood pressure or hypertension is very common in the UK; 1 in 4 adults suffer from it. It usually occurs as we get older and the walls of our blood vessels lose some of their elasticity and become rigid. Several aspects of your diet can cause this to happen more quickly. Untreated hypertension increases the risk of heart attacks and stroke as well as kidney and eye damage. The good news is that changes to your diet, especially the amount of salt eaten, can be a very effective part of both treatment and prevention of high blood pressure.

Find out more at: http://www.salt.gov.uk/salt_and_your_health.shtml.

Types of salt

All forms of salt, including sea salt and rock salt are basically sodium chloride and it's the sodium that is the problem in relation to blood pressure. Sea salt and rock salt contain a few more minerals than ordinary table salt but not enough to be of any real benefit. It's good that the message is getting through to consumers that too much salt can raise blood pressure. However it's a mistaken belief that switching to one will have a beneficial effect on your blood pressure.

Cutting down on salt

We all eat on average 9.5 g salt per day that's 1 and a half teaspoons. Recommendations for health suggest we keep below 6g per day (1 teaspoon). About a quarter of our daily salt comes from that at table and in cooking so cutting down on these can help. For help with this see: http://www.salt.gov.uk/cooking_without_salt.shtml.

The good news is that it only takes a few weeks to get used to eating less salt. That's about the same length of time it takes to start seeing a benefit on your blood pressure. Some people like to use a salt substitute, made from potassium chloride, where a dish really needs it. However this doesn't allow to get used to eating meals with a less salty taste

Hidden salt

However, surprisingly, around three-quarters of the salt we eat is hidden in processed foods including sauces, ready meals and takeaways. Reducing your intake of these and choosing lower salt options is vital to reducing overall salt intake.

Check the label for lower salt varieties when you do need to use processed foods.

Salt is often listed as sodium on food labels.
Salt = sodium x 2.5.

1g salt = 0.4g ( 400mg) sodium

Use the following as a guide to what is a lot and what is a little salt (or sodium) per 100g food.

This is A LOT of salt
1.25g salt or more per 100g
0.5g sodium or more per 100g

This is A LITTLE salt
0.25g salt or less per 100g
0.1g sodium or less per 100g

If a food contains between 0.25g and 1.25g salt (or between 0.1g and 0.5g sodium) per 100g, this is a moderate amount.

Try to avoid eating lots of foods that are high in salt (1.25g salt or more per 100g). If you eat lots of these foods, it can be very easy to have more than 6g. This is why it's important to choose foods that are lower in salt, when you can.

For more information on understanding food labels see: http://www.salt.gov.uk/understanding_labels.shtml.

Other ways to help reduce high blood pressure

If you have high blood pressure the other dietary changes you might find helpful are:

  • Keeping to a moderate intake of alcohol no more than 2-3 units per day for a man and 1-2 units for a woman (lower if advised by your doctor). A unit is half a pint of normal strength beer, a small (125ml) glass of wine or a pub measure of spirits (25ml).
  • Losing weight - even as little as 5-10% of your starting weight – if you are overweight. This is especially true if the weight is carried centrally i.e. around your waist.
  • Eating a low fat diet, rich in essential minerals and including:

  • Fruit and vegetables- Aim to eat at least 5 portions per day. Fresh, frozen, dried and canned all count. If you are using canned vegetables look for lower salt varieties.

  • Low fat options of dairy foods such as semi skimmed milk, low fat yoghurts and low fat cheese. Include 2-3 servings per day.

  • Wholegrains including breakfast cereals, brown pasta and wholegrain bread . Aim for 2-3 servings per day

  • Oily fish. Include at least 1-2 portions per week. Examples include salmon, pilchards, sardines, mackerel, herring and trout. Fresh, frozen or canned are all good but avoid fish canned in brine. (See previous article, below.)

Changing your diet along with keeping active will lead to a significant drop in your blood pressure levels, whether or not you are taking tablets. The effects can often be seen quite quickly- usually within weeks of starting. For some more useful tips see: http://www.eatwell.gov.uk/healthydiet/8tips/.

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Oily fish

"Eating fish may cut risk of heart problems" (Reuters, August 2005).

What was the story?

A relatively low level of fish consumption may reduce the risk of having a heart attack and heart-related chest pain by over 30%, according to researchers in Greece. The researchers analysed fish consumption among 848 patients who had experienced either a heart attack or heart-related chest pain and 1078 similar subjects who had not. Further analysis showed that fish consumption was tied to an 11 % reduced risk of these symptoms among smokers and a 24% reduced risk among diabetics.  The results are published in the latest issue of International Journal of Cardiology."

What are the facts behind the headlines?

This isn’t completely new information as nutritionists have known for several years that eating oily fish is good for you. After all, the Inuit and Japanese people who eat a lot of fish rarely get heart attacks!

The omega 3 fats found in oily fish can help lower your blood pressure, reduce blood clotting and help your heart beat in a normal rhythm- all of which help reduce the risk of heart attacks especially in people at high risk.

Recent evidence also suggests oily fish have a role in preventing mental health problems such as depression, dementia including Alzheimer’s and even learning and behaviour in children. For more information see: Food and Behaviour Research.

A variety of tasty fish whether canned frozen fresh or smoked all count including:

  • salmon
  • trout
  • herring
  • mackerel
  • sardines
  • pilchards
  • kippers

Fresh or frozen tuna also counts but canned tuna is not very rich in omega 3.

For clear-cut health benefits aim to eat oily fish at least once a week. A serving is about 100g or one small can. Oily fish can be used as filings for sandwiches or jacket potatoes, in stir-fries or with pasta and rice dishes. You could also try fish cakes or fish pie made with oily fish.

Some people are worried about possible environmental pollutants in oily fish but recent studies have shown that the health benefits outweigh the risks . However there are limits to the amount we should eat and some long lived fish such as shark, swordfish and marlin should also be avoided by certain groups in the population including girls and women who might have a baby one day. They also shouldn’t eat more than two portions of oily fish a week. In general, this advice also applies to women who are pregnant or breastfeeding.

Women who aren’t going to get pregnant in the future, boys and men there is no risk in eating up to 4 portions per week. For more information please see: Food Standards Agency - Your guide to oily fish.

Vegetarians can get omega 3 from "omega 3 enriched" eggs or spreads (check the label). Organic milk is also a reasonable source. Oils and seeds such as flaxseeds or linseeds, rapeseed and some nuts such as peanuts pecans, almonds and walnuts as well as green leafy vegetables also contain omega 3 although at much lower levels .

Omega 3 capsules (not the same as cod liver oil) are also available. Aim for around 0.5-1g omega 3 fat per day. Do stick to amount on label and choose especially formulated for children for this age group.

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