Tuesday, August 25, 2009

Organic food has same nutrients as conventionally grown

The last time I was the messenger on this topic, three people unsubscribed in protest. Once, when I spoke about organically grown food on the radio, a lady from Tasmania kindly took the time to ring and abuse me. It is a very emotional area. Let me see if I can get the message across clearly.

A report published this month in the American Journal of Clinical Nutrition came to the conclusion that organically grown produce and livestock had a similar nutrient offering to conventionally grown food. The reviewers trawled all the research for the past 50 years and found only 55 good quality research studies comparing organic and conventionally grown food, many conducted this century. The comparison did not include pesticide residue or the environmental impact.

The price is not right
In many cases, it won’t matter how you dress up organic produce because most people won’t be prepared to pay the premium price. I once inadvertently paid four times the price for organic onions. Most organic produce is at least 50% dearer that the regular type. I’m not suggesting that anyone is getting ripped-off as organic farming will be more labour intensive and therefore command a higher price. On the other hand there will only be a small number of suburbs where organic produce will sell well.

What else is relevant?
The other critical factor is that less than one in ten adults eat enough fruit and vegetables to be good for them. Most adults need to double their vegetable intake to get the benefits they provide, before they start to wonder whether they should go organic or not.

Fresh produce in Australia is tested for pesticide residues. Most farmers will ensure that they meet the withholding times to ensure they are below the Maximum Residue Limits for pesticides, which are set by international scientific agreement. At lot of fresh produce has no detectable pesticide or herbicide residue at the point of sale. All the same, this will not appease many people who prefer no pesticides to be used in the first place (and if they weren’t used then fruit and vegetables will be a lot more expensive than they are now).

What does it all mean?
If you can afford it, and you eat plenty of organic produce, then keep buying it. Many of you already are as the organic market is rapidly growing. It sends a message that you prefer food that is a little more gentle on the environment. For those of us with plenty of mouths to feed and a modest budget, then feel comfortable eating good quality conventionally grown food, as the nutrient levels are very similar to organic produce. Remember that how you look after fresh produce after it has been bought will have the greatest impact on its nutrient content. Eat fresh food as soon as you can after purchase to get the most nutrients from your meal.

References: American Journal of Clinical Nutrition 2009; doi 10.3945/ajcn.2009.28041

Tuesday, August 11, 2009

A myth that will never die

At a recent presentation someone told the group that caffeinated drinks dehydrate people. It is always difficult to gently correct a long held belief. I explained that caffeine causes a very small increase in urinary production at most, however, drinking cola soft drinks, tea and coffee do not cause excess urine production or dehydration. Even the more enlightened sports physicians and dietitians now tell athletes that drinking tea and coffee after training helps rehydrate the body.

Nearly a decade ago, Dr Ann Grandjean from the University of Nebraska gave people equal amounts of water and caffeinated beverages and measured their pee output for 24 hours. There was no difference between water and caffeine containing drinks. All subsequent research has shown that caffeinated drinks can be part of your fluid intake.

It is not clear who first said: “The plural of anecdote is not data”. The quote seems to suit many myths. An anecdote or observation is always worth investigating because it can lead to greater understanding. The anecdote that caffeinated drinks cause dehydration has been investigated and proven to be not correct. I might also add that “repetition without understanding slows progress”.

Water for the brain

You might have a bottle or glass of water handy as you read this. We were designed to drink water, so it makes sense that we should make it our main beverage. Does it make you think better? There doesn’t appear to be many studies on water’s ability to improve brain function under our normal daily living conditions. Now, two research papers on kids hints that a water bottle on the school desk could improve cognition.

Very few studies are conducted on children for ethical reasons, so it’s no surprise that, until these two studies were done, only one other research paper had been done on kids, dehydration and thinking skills.

Water improves memory
Forty children aged 8-9 years were selected from two schools in Wales. The kids were tested mid-afternoon on two different days, one when they were given a 300 mL drink of water and one where they weren’t given water. Cognitive testing, lasting for about eight minutes, was scheduled for 30 mins later. The classroom temperature was around 20ºC (68ºF), quite pleasant, although chilly outside. Those that were given water, and observed to drink it, had a better memory (word recall) than those that weren’t given water.

A second study was of 58 children, aged 7-8 years, with half of them receiving 250 mL of additional water. Twenty minutes later they were given a range of cognitive tests. The water drinkers again did better in the tests, such as answering questions after a short story and “spot the difference” between similar cartoon pictures.

Drinks break
Water consumption during sport and hot weather has been encouraged for many decades. Coaches call for a drinks break during training because they know kids and adults function better physically when they are well hydrated. Adult cognitive function begins to decline when they are 1% or more dehydrated (that’s a 70kg adult losing 700 mL of sweat). Less is known about children because they are rarely subjects in dehydration studies. These two studies may be the trigger to start further research to find out how fluid affects young thinking.

What does it all mean?
Both studies were done in the UK when the ambient temperature was less than 10ºC (50ºC) so the kids weren’t likely to be dehydrated after playing outside as they might be during an Australian summer. As young children have an immature thirst mechanism they may become mildly dehydrated when distracted by play and classroom activities and “forget” to drink water. The studies do suggest that the practise of having water bottles in classrooms could well be having educational dividends. Just to think how much smarter I could have been with a water bottle by my side during the physics and chemistry classes. I might have at least remembered Boyle’s Law.

References: Appetite 2009; 52: 776-779; Appetite 2009; 53: 143-146