In reply to Strachan:
> I'm sorry to be a pedant but a large amount of what you are saying about sugars I feel needs correction.
With this sort of subject matter, scientific knowledge is always useful
> For one thing, you say that 'refined sucrose' creates a 'spike', where 'natural fructose' does not. In fact sucrose must first be hydrolysed at the o-glycosidic bond, to give fructose and glucose monosaccharide units. Glucose is then metabolised, via the pathway we call glycolysis. Fructose enters fructolysis, which then converges with glycolysis when a common intermediate is formed. The point being, that fructose is able to be metabolised more rapidly when consumed in monosaccharide form, than when it is necessary to break down disaccharide sucrose first, and so the reverse holds true if anything. (Cleavage of the glycosidic bond is very fast, but regardless, it is certainly true to say that monosaccharides must pass through a shorter metabolic pathway).
The problem is though, that's a complex and in-depth explanation which takes time to assimilate, which is why a lot of people go for heuristics like natural/unnatural just to get them round the supermarket shelves when they're in a hurry. However, I always hated it at school when the science teachers simplified explanations because that often distorted things and confused me so I'm going to try to get my head around this. You're saying that monosaccharide fructose is quicker to convert to what - glucose? Or is it burned to create energy directly as fructose? And is the monosaccharide form of fructose the sort most commonly found in fruits?
> It is true that if you take in an equivalent amount of fructose as molecular fructose as opposed to in sucrose form, then the glucose component of sucrose is of course omitted. That is naturally going to lead to a smaller energy release, but of course this can be mitigated by eating half as much of a sucrose source instead.
So where does the concept of 'slow release' come in? - It's a claim that's often made for bananas for instance.
> I am also unsure of the issue with sulphur dioxide. I have not looked into it, but as a gas, I find it difficult to believe that it is present in foods in considerable quantity, though I am willing to be proven wrong.
Sulphur dioxide a fungicide and anti-discolourant used in drying fruit. I had a cold I couldn't shake off last December and was diagnosed with winter asthma - some inhalers cleared it up pretty fast but I've noticed that dried fruit seems to provoke it to come back. Whether that's a direct effect or whether it's psychological because I know it's there and have heard it triggers asthma is hard to say.
http://www.livestrong.com/article/317156-the-health-risks-of-sulfur-dioxide...
> That said, it just seems there are bigger health risks in every day life that could be avoided instead. It is like the debate about decaff drinks: caffeine can have undesirable physiological effects on some people, but decaffination often uses chlorinated solvents such as DCM, so really, is it worth trying to avoid these things, because there is always something else just as nasty that hasn't been considered?
I couldn't cope without copious amounts of tea
> Energy gels are essentially designed to get blood glucose levels to spike as hard and as high as possible in the minimum time. So they are definitely not what you are after. They contain fructose (exactly the same as in a piece of fruit, forget about this idea of 'refined' when comparing like for like; fructose and fructose are chemically and biochemically identical!), and maltodextrin. Maltodextrins are just oligosaccharides of glucose subunits, that are almost instantly converted to glucose by enzymes in the saliva. they are chosen over glucose itself purely to avoid an overpoweringly sweet taste. I am a big believer in energy gels whilst cycling, but they will certainly give a big blood sugar spike, think of them as emergency fuel. In terms of composition energy gels are essentially the same as the much-maligned high fructose corn syrup, or even sucrose, once the body splits it into glucose and fructose, although the ratios of glucose and fructose will likely vary.
I can feel a tendency to go all heuristic here and say 'gels = unnatural and I don't understand the biochemistry, so leave alone!'
> Fundamentally the thing to remember is that carbohydrates are the body's primary fuel source. It is possible to access the energy in proteins etc but via convoluted metabolic routes. I would stick to proteins for recovery, and tune the types of carbs used as fuel.
Just what I've been doing
> Don't think about refined/unrefined, natural/ unnatural, as these words are completely irrelevant so far as chemistry and physiology are concerned (in the same way that many people wrongly interpret the words man-made, or synthetic, as being synonymous with harm or toxicity where chemicals are concrned).
It is such a complex subject that the urge to adopt heuristics (rules of thumb) can be almost irresistible if you're a lay-person!
> Instead, consider that complex carbohydrates will need to enter a longer metabolic route, with the energy release accordingly slowed. So in order to fuel activity over a longer period, a range of carbs should be taken in, to cover a range of timescales. It is also worth eating carbs in advance of exercise, in order to store enough glycogen to fuel the first hour or so of work.
This makes perfect sense to me and matches what I've heard/ read and what I've been doing.
> Proteins can't be stored, after all, and fats can be stored, but not accessed in a hurry during exercise. Processed meats are also, beyond being extremely questionable as a fuel source, likely to be far more harmful in terms of carcinogenicity etc than taking in sugars of any kind.
I've heard there's a window of about an hour and a half, within which it's useful to take protein for repair after exercise. I've also been operating on the principle that protein immediately before or during exercise is good, just from the common-sense perspective that it must take a bit of time to work its way through. I eat almonds and drink skimmed milk during exercise and have an egg or a kipper or some mackerel just after if I can.
> I honestly wouldn't worry about a blood sugar spike during vigorous exercise, as your body will be crying out for the carbs anyway- they aren't going to hang around, especially once glycogen stores have been depleted.
Yeah, I understand, but then it's probably easy to overdo it and consume more sugary food than your body actually needs, which is why I've stopped taking cereal bars with me, except as iron rations for any major emergency that might happen outdoors.
> In case you hadn't guessed, I'm a chemist, not a dietician, but that's just my thoughts and hopefully some useful info.
Much appreciated, thanks!