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Monday, December 26, 2011

Eating up the food miles

I recently heard a radio interview with Dr I. Eatwell (I can’t remember her real name but she was a Californian food-head) who told us about her weekly cycle jaunt out of the small town of Davis in California to pick wild herbs.  We were, of course, all supposed to gasp in admiration at her zeal to seek and eat local. In a sense, she was emulating the famous French aristocrat who suggested that, in view of the shortage of bread: "Qu'ils mangent de la brioche" or “Let them eat cake”. Quite simply, there are not sufficient wild herbs to meet the gastronomic needs of the firm and courageous citizens of even a small town such as Davis. Moreover, since Dr I. Eatwell harvested the herbs before the seeding period, she selfishly pulled the plug on food chain sustainability. The concept of local food is elitist and unworkable for the general population. So let’s do the sums. According to Sustainable Table, we should confine our food choice to 100 km radius. Lets extend that to 120 km to allow for the area of a large city. That translates into about 4524 hectares which if farmed for wheat would yield 38,798,324 kg of wheat, translating into 27,158,826 kg of flour or 108,635,307,000 calories. Assuming a daily energy need of just 2,000 calories, we would have enough to feed about 150 persons a year.  So the theory works for towns with a population up to 150,000 and of course the nearest other town must be 240 km away, otherwise there would be territorial battles where their circles overlap. It just doesn’t work for today’s demography. Of course a few privileged elite can easily achieve this but its cake for the rest of us.

One of the smart things mad did which no other species achieved was the division of labour: “I’ll buy the peas you grow on your farm and you can buy tractor insurance from me”.  The chore of being responsible for the provision of our own food was passed on to farmers who in turn passed on responsibility for education, power and so forth. Many centuries ago, those farmers were local but as modern transport evolved, we bought food that was grown far away, often continents away. And so the high priests of healthy eating introduced the concept of “food miles” and “eating in season”. I will surely eat a strawberry this Christmas or find one on my champagne glass and I’m not in the least bit bothered that it might come from Spain or Greece. And I might concede that if I were to pluck a fresh strawberry in season in County Wexford it would taste better than the imported and out-of-season variety. But that imported and out-of-season variety still is unmistakably strawberry in every olfactory sense if you’ll excuse the pun (did I just punnet!). Not only does it taste and smell of strawberry, but it has the exact nutritional composition that the in-season County Wexford strawberry has and I can vary my diet to include imported and out-of-season fish, fruit, vegetables, yams and so on. The overall health of the nation would improve if we were to eat more fruit and more vegetables. Any implication that these foods have to be sourced locally and in-season is utterly unhelpful.

Food miles are another obsession with the high priests of health eating. The implication of counting food miles is that local is best and the greater the food mile the greater the sin. As ever, when put under the microscope, things are not so straightforward. An apple, grown locally and sold at the end of the season just before a new harvest, carries little mileage but it has consumed a significant quantity of energy keeping it nice and juicy through autumn and into spring. Without that energy consuming technological intervention, the apples would rot.   In contrast, a New Zealand apple, just harvested in that beautiful country and consumed in Dublin carries huge mileage but has used relatively little energy. Locally grown low mileage tomatoes require a glasshouse and yet more energy while imported ones are grown where the sun shines all day, yielding high mileage and low energy.  And of course, one of the biggest contributors to the energy cost of food occurs when it leaves the supermarket shelf. Driving there and back, freezing, chilling and cooking food all gobbles up energy. And of course, there is food waste. Sin scĂ©al eile, which, for the Sassenachs among you, translates into: “That’s another story”

Monday, December 19, 2011

Dying for Christmas

According to the experts and politicos in public health nutrition, the greatest food-related condition on the planet is obesity.  That is not so. The fat and overweight all over the world will enjoy hearty feasts this Christmas or at their equivalent major holiday. It is hunger that is the greatest food-related condition facing mankind. One billion of the globe’s citizens will go to bed hungry on Christmas night, as they do every night. That is one in 6 of our fellow humans.  They live mostly in South Asia and in sub-Saharan Africa. By 2050, over 95% of the growth in the global population to 9 billion will be in these two regions. So too will be the worst effects of climate change in reducing agricultural output. Aside from the de-humanizing effect of hunger, there follows in its food steps a whole slew of diseases, mostly infectious diseases, caused by a greatly impaired immune system.  The consequent daily death rate from hunger is equivalent to 30 fully laden jumbo jets crashing each and every day with all lives on board lost. Never forget that statistic.

The hungry are not forgotten of course. They are constantly in our thoughts and most importantly in the thoughts of our political leaders and our major global agencies. They have been in their thoughts for the last 50 years as the following quotes show:

We have the ability, we have the means, and we have the capacity to eliminate hunger from the face of the earth. We need only the will.
President John F. Kennedy, 1963

Within one decade no child will go to bed hungry, no family will fear for its next day’s bread, and no human being’s future and capacities will be stunted by malnutrition. Every man, woman and child has the inalienable right to be free from malnutrition and hunger
World Food Conference, Rome, 1974

As a basis for the Plan of Action for Nutrition . . . we pledge to make all efforts to eliminate before the end of this decade: famine and famine-related deaths; starvation and nutritional deficiency diseases in communities affected by natural and man-made disasters; iodine and vitamin A deficiencies.
World Declaration and Plan of Action for Nutrition, Rome, December 1992

The Rome Declaration calls upon us to reduce by half the number of chronically undernourished people on the Earth by the year 2015 . . . If each of us gives his or her best I believe that we can meet and even exceed the target we have set for ourselves.
World Food Summit 1996

Goal 1: Eradicate extreme poverty and hunger; Target 2. Halve, between 1990 and 2015, the proportion of people who suffer from hunger.
 UN Millennium Development Goals 2002

We have seen in the present crisis among the states of the euro zone a generally selfish attitude of individual member states. On a global basis, a similarly selfish attitude has impeded progress with regard to climate change. In each case, the individual member states have a strategic interest, which is influenced by its business community and by many non-governmental organisations.  What hope has hunger got? The various quotations above show that we are kidding ourselves and paying lip service to the problem. In his book ‘Common wealth: Economics of a crowded planet’ the distinguished leader in development studies Jeffrey Sachs points out the need for a global solution to the problem. But how can we persuade the business and NGO communities in Ireland and elsewhere that global hunger is an issue of major importance and of sufficient importance to merit significantly more investment than we give at present? “We are in a recession” might be the general response. For the hungry, there is no recession since you can only recess from what has been progressed and, in their case, there has been no progression. Africa can help itself but not without our help. So, right now, take out the credit card and in multiples of 6 make a donation now to your favourite aid agency. If you don’t know of one immediately, try my favourite:

Monday, December 12, 2011

The inherent flaws of food intake data

The inherent flaws of food intake data

Measuring our dietary patterns and linking it to patterns of disease is at the core of modern nutritional epidemiology and such data drive national and global food and nutrition policy. There is, however, a serious and inherent flaw in the measurement of food intake which modern nutritional epidemiology tends to forget. That flaw is energy under-reporting. Our energy requirements are composed of several factors, the most important of which is resting metabolism which accounts for about 85% of energy needs in a normal adult following a typical sedentary western lifestyle. These energy needs are to keep our hearts beating, our lungs breathing, our kidneys filtering, our brains remembering and so on. We can directly measure this as a person’s resting metabolic rate (RMR) using a calorimeter and there are also a number of ways of doing so indirectly, some of which are  extremely accurate. We can also calculate our RMR using a number of equations and you’ll find plenty of calculators on the internet. My RMR is 2,030 calories. Because I’m sedentary, except for golf on a Saturday morning, I need to up that figure by about 15% to 2,335 calories to take account of my daily ohysical activity. A very sporty person would have a higher multiplier of RMR.  If I was a volunteer in a dietary survey and I reported an energy intake of 1,900 calories, then ocviously I must be dieting. If I say I’m not dieting and that this is a typical dietary intake, then I’m under-reporting. There never has been and there probably never will be a large survey, large enough to be of value to epidemiology, which does not have some element of under-reporting. And the level of under-reporting is huge - anywhere from 30% to 50%. We know this to be so using both simple equations to measure RMR and also using very sophisticated stable isotopes.

Why do people under-report? We know it is higher among females amd we know it increases with increasing body weight. My explanation, which is not based on any experimental data but on supposition is as follows. Most people with a western sedentary lifestyle, have at some time sought to lose weight. They inevitably start on Monday morning. Come Thursday, something happens, good or bad and the dieting pattern is gone. Its back to normal to start all over again next Monday morning. This cyclical pattern is familiar to many people. So, when asked to take part in a dietary survey and when pressed to be truthful in every way to report their habitual intake, which days do they deem to be “typical?. I’m afraid that 30-50% of people deem the dietary restrictive days of Monday, Tuesday and Wednesday to be normal. Thus they don’t deliberately lie but they do under-report their food intake. In effect, food intake data are flawed and we have to live with that for now until we come up with some smart way of overcoming this problem.

Because under-reporting is higher among the over-weight and obese, many assume that the foods that are under-reported tend to be the so called “guilty” ones: foods high in sugar and fats such as fast food, soft drinks, savoury snacks and so on. This assumption is of course false since obesity is associated with ALL foods (see blog of November 6th: “Taxing the fat and sweet”). Not surprisingly, when we examine food intake data in those with plausible energy intakes against those under-reporting food intake, we find all food categories under-reported.

This issue of energy under-reporting is dismissed by nutritional epidemiology on the grounds that all their propsed statistical associations of diet and disease are adjusted for all of those factors of importance in under-reporting (body weight, energy intake, gender, age etc). However, there is an increasing number of researchers who are showing that this statistical adjustment is flawed when it comes to under-reporting food intake. Basciaclly, an average daily intake of a food is composed of three elements. Firstly, the population average embraces  both consumers and non-consumers of the food in question. Some people who under-report energy intake may simply deny eating one or more foods. That is the first route of under-reporting. The second is that they admit reporting but under-report the frequency of consumption. The third is that they admit eating the food, are truthful about the frequency of intake but are untruthful with the portion size they report. Of course any combination of these is possible. There is simply no way in which statistical jiggery-pokery can unravel this web of deceit. So we have only one option. We create a cut off point (RMR + 15% of RMR) for energy requirement and anyone falling below this is excluded from the analysis. Its painful to lose subjects in this way when statistical power is dependet on adequate numbers.

Without doubt the area of greatest concern over the distorting impact of energy under-reporting is in relation to obesity. Firstly, the scale of under-reporting rises considerably with rising body weight. Secondly, obesity is such a hot topic as regards candidate foods for taxation or labeling. How can we be so confident in shaping public health nutrition policy in obesity when (a) we know that food under-reporting is generally a problem but particularly a problem in obesity and (b) when there is no hope of any statistical trick separating out the three lines of mis-reporting: denying ever eating the food in question, not accurately reporting frequency of the intake of a target food and finally, under-reporting portion size. It bothers me a lot but its a mere nuisance to the high priests of public health nutrition who know both  the problem and the solution. 

Monday, December 5, 2011

The epidemic of obesity ~ as fat as it gets

The epidemic of obesity ~ as fat as it gets

John Minnoch (1941-1983) lived in Seattle and is credited in the Guinness Book of Records as being the heaviest male in history. At 6 feet 1 inch tall, he weighed 442kg, equivalent to a BMI of 128. That equates to the biomass of just 4.5 Irish adult males! Now when we talk about the epidemic of obesity, there is a possibility that some people might think that a significant fraction of the population would reach the weight of John Minnoch. That is not how it works. Several years ago Steve O’Rahilly, Professor of Medicine at Addenbrooke’s Hospital Cambridge and a world authority on the genetics of obesity, raised the possibility that the epidemic of obesity was beginning to level off in the UK. Thus, faced with an obesogenic environment, the population variation in genetic predisposition to obesity is such that those who can cope with this environment will remain within the normal weight range while those susceptible to an obesogenic environment will attain a level of over weight or obesity up to their genetic potential. Two recent papers now put flesh on O’Rahilly’s speculation.

The first of these papers gathered data on time trends in obesity over the period 1999 to 2010.  The authors of the paper[1], from the Institute of Preventative Medicine at Copenhagen, set out a total of 7 criteria, which had to be met if a published study was to be included in their analysis. For example, the sample size had to be greater than 5,000 and data on weight and height had to be measured directly and not self reported. Thus out of 52 studies, only 44 met the 7 inclusion criteria. They also graded the studies into very high, high, medium or low quality. Of the 6 studies graded very high quality data, 5 showed that obesity rates were stable during the period 1999 to 2010. These 5 were from France, Sweden, England, Greece and Australia and only in China did a very high quality study show an in crease in obesity. Among children and adolescents, there was a clear trend toward a stabilization of obesity across continents and while the pattern among adults was less clear-cut, nonetheless, stabilization was generally evident.

The second study comes from Australia, actually from a rather distinguished WHO Collaborating Centre for Obesity Prevention, and it looked at obesity trends in preschool children over the period 1999 to 2007[2]. They studied two cohorts, one aged 2 years old in 1999 (130,000) and the other 3.5 years old in 1999 (96,000), each of which was followed annually to the year 2007. Weight, height (and length for younger age groups) were measured annually. Whereas in 1999, some 2.5 % of 2 year olds were obese, in 2007, this fell to 1.7%. For three year olds in 1999, the comparable figures were 4.5% and 2.9%. Similar trends were seen when obese children were combined with over weight children (from 13.5% to 12.4% in the 2 year old cohort and from 18.5% to 15.4% in the 3.5 year old group over the period 1999-2007). Although the overall rate of obesity and overweight was higher in the lower socioeconomic groups, the rate of decline in fatness was highest in these groups.

The first study would suggest that, as expected, the variation in the genetic potential to develop obesity would ultimately be met and that the prevalence rate would stabilize. It doesn’t mean the problem has gone away since obesity will continue to be a major drain on the economics of our health care systems. What it will do is to increase the focus on the management of the physiological disadvantages of obesity and overweight and in that regard, a greater emphasis on the promotion of physical must emerge, since nothing compares with physical activity as an antidote to the adverse effects of obesity. In the case of the Australian study of preschool children, the data suggests that there is a greater awareness of the problem of obesity among parents, particularly those who are socially disadvantaged. Preschool children do not make their own food choices so this reflects a mind change of mums and dads. Whether this all translates into fewer obese adolescents remains to be seen.

[1] Rokholm R et al Obesity Reviews (2010) 11, 835
[2] Nichols MS (2011) International Journal of Obesity 35, 916-024