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GI - what a load of...

GI. Joe.

Glycaemic index.  In scientific lingo what the glycaemic index is = the area under the blood glucose curve over a two hour period in response to consuming a test food providing 50g of glycaemic carbohydrate which is compared to a 50g sample of a reference food.  The reference food being glucose or white bread. These foods are expressed on a scale of 100. Or something like that.  In brick layer chat this means how much a food effects your blood sugar levels. Or does it?

The glycaemic effect of a food or how much it affects your blood sugar is influenced by the type of carbohydrate present, as well as the presence of fat, fibre or protein in the food or what other food is being eaten at the same time.  Add to this the acidity and temperature of the food item, how refined it is, it’s ripeness, it’s variety and how much you have chewed it and you may have a number of different factors affecting glycaemic responses.  Then throw in there the fact that this slice of brown bread was made with 50% white flour, but the one I had yesterday was 100% unrefined.  Or that today I boiled my potato but yesterday it was baked.  All of these factors give us absorbable carbohydrates at a different rate.

 

Why is this control of blood glucose important anyway? Well for general health we want to avoid highs and lows in our blood glucose levels to prevent a loss in insulin sensitivity.  Insulin is the hormone the controls glucose levels amongst other things, without it we are diabetic and that is not a great place to be. We also struggle to control body composition with these fluctuations and our hunger cues are linked to our glucose levels.  So too are hydration, heart rate and cognitive (brain) function.  For an athlete you want the right type of carbohydrate at the right time, either a quick or slow releasing carb.  With these goals in mind some spark decided to test a few foods on a few people and see how they fared compared to white bread or glucose.

First problem: there are two scales of GI, one uses white bread, the other uses glucose.  There are arguments to pros and cons of using a different reference food, but mainly confusion.  On the white bread scale all foods have a higher GI than on the glucose scale.

Next: not all foods that are given a GI rating are tested. They are merely estimates according to their ingredients.  And what about all the factors like ripeness, variety, cooking method etc etc..

Then only small samples of people are needed to provide a GI value for a food, the number is 10. This somehow provides us with a consensus on how 6 billion people would react to a food when compared to white bread..or glucose..

An example of a high glycaemic index food: watermelon has a GI of 96 (I don’t know which scale this is). You would think that watermelon would have so much sugar in it because it got an A+ in the GI exam.  You know how much you would have to eat for it to affect your sugar at all! Most of it is water, it is not called sugar melon. To provide the 50g of sugar necessary for the test you would have to eat about 900g of the stuff.

Anyway if we were to follow the GI route and believe its value then perhaps the slightly more relevant scale of glycaemic load (GL) is worthwhile.  This takes into account the GI of a food and the amount of carbs in a portion that you would actually eat. We don’t hear too much about GL though. 

I am not saying we should ignore the value of understanding how foods affect us but I dont agree this is the way.  Knowing which foods provide quick releasing, simple sugars is quite easy to figure without the mystical GI.  High fibre foods or those containing fats and protein are not quick releasing.  Foods with a lot of water or other non-carbohydrate ingredients can’t have too much available sugar in an average portion.  Sugary and sweetened foods and drinks, refined grains and a few fruits like bananas, grapes and peaches are quick releasing.

So for everyone out there choose the high fibre, slow releasing foods for most snacks and meals.  Wholegrains, vegetables, legumes and fruit should be predominant.  The quick releasing sugar foods are only really valuable before, during or after exercise or when you feel like a little treat.  A diet high in added sugars and refined carbohydrates are strongly linked to obesity, diabetes and cardiovascular disease.  There is no point in giving these foods an arbitrary number that means you might miss out on valuable food options because they have been wrongly classified.  Don’t fall for the gimmicky low GI labels, read the ingredients and make your own choices.  A fibre content of at least 5g per 100g is a guide and the ingredients list is in order of quantity, most to least. Learn what the labels on food mean!

G bye.

Carbohydrates

Carbohydrates.  An athlete’s best friend?

As discussed in an earlier post, carbohydrates are the single most important nutrient in an athlete’s diet.  Research also shows that carbohydrates are the most commonly deficient nutrient in the majority of athletes’ diets.  Carbohydrates give us both immediate energy and energy we can use later after we convert glucose from carbohydrates in glycogen that is subsequently stored in our muscles and liver.  When we need energy during exercise the first fuel we use is carbohydrate based (well this is not entirely true, the first few seconds of exercise actually uses creatine phosphate but this runs out very quickly and I am sure you get my point).  As an ergogenic aid carbohydrates consumed before or during exercise are the most successful in terms of performance enhancement when compared to other supplements and nutrients.

Our carbohydrate stores, however, only get us as far as about 60 minutes of exercise.  We can then top up and “pay-as-you-go” but nonetheless our bodies eventually switch to fat utilisation and protein breakdown.  Ensuring our stores are at their maximal before exercise is the point of a high carbohydrate diet and the well talked about carbo-loading regimens some athletes choose.  A high carbohydrate diet will provide sufficient glycogen in our muscles to push the 60 minutes a little further toward the 90 mark before we again increase the rate of burning other fuels.

Regularly active individuals may need somewhere in the region of 3-5g carbohydrate per kilogram body weight per day.  More strenuous exercise will up this to 6-8g/kg/day and endurance and ultra endurance may need 10-12g/kg/day.  This is a lot of carbohydrate but includes snacks and drinks taken pre/during/post exercise. Bear in mind these recommendations are tweaked according to the periodisation of your training (future post).

Your general meals and snacks consumed should provide a variety of carbohydrate foods and ideally be high in fibre.  Cereals, grain products, fruits, vegetables and legumes should be the basis of the carbohydrate portion of the diet.  Foods eaten around or during exercise should be quicker releasing carbohydrates and sugars, something like the high GI foods.  The glycaemic index is a post I will come to in time as I believe it to be a load of.... Anyway, sweetened foods or foods with sugars (sweets, chocolates, carbohydrate drinks) and processed grains (white bread, muffins, cereal bars) can be consumed around the exercise times mentioned earlier.  Certain fruits (bananas, grapes, peaches, dried fruit) provide sugar quickly too that may assist recovery or provide immediate energy during exercise.  Remember to add a little protein to post exercise snacks to get the most out of recovery, a good goal is a 50-60g carbohydrate portion with 20g protein.  A carb-protein recovery drink, a couple bananas and a yoghurt or 500ml of sweetened chocolate milk sound pretty good.

Eating regularly, 5-8 times a day, will help you get to the higher intake levels if this is needed.  More than that it will also assist in body composition management, control of insulin and blood glucose and increase the thermic effect of food.  This is the energy we spend digesting and using our food which helps with that energy balance and body composition thing. Regular eating will also ensure we are topped up before we train to get the most out of any session.

Below – a table of carbohydrate rich foods and how much we actually get from each.

Food item	Portion	Grams of carbohydrate
Bread	1 slice	15-20
Muesli	60g	40
Oats	60g	45
Weetbix	2 biscuits	30
Pasta	100g	35-70
Potato	Large (200g)	70
Sweet potato	Large (200g)	60
Beans/lentils	2 Tablespoons	15
Banana	1 medium	20
Grapes	Handful	12
Pear/orange/apple	1 medium	10
Dried fruit	Small handful (60g)	40
Yoghurt	175ml tub	30
Sweetened milk drinks	330ml	30
Energy/cereal bars	1 bar	20
Energade/Powerade	500ml	40

Over the next few days I will add posts on the glycaemic index vibe as well as the hot topic of very low carbohydrate diets.

Energy balance

Energy = carbs + protein + fat (+alcohol)

Energy balance.  Our food gives us energy (calories).  We spend energy to stay alive, to watch Rafa vs Rog on the HD TV, to trim the grass patch outside, to walk to the pub, to chase the dog, to do those 3km on the treadmill.  If energy in (from food) is more than energy out (from daily activity) we store energy and put on weight.  If the converse is true we lose weight.  The weight we put on or lose can be in the form of fat, protein or carbohydrate stores.  How we eat and how we train effects that.

Not all calories from food were made the same.  Each gram of protein, fat, carbohydrate or alcohol in our diet gives us a different amount of calories.  Finding the right ratio of all these in your diet will affect your body composition, your performance and your recovery.  Add to that the timing of eating these nutrients and you have another aspect to take note of. 

The man on the couch, the woman on the bike and the china on the squat machine all have different needs.  The energy they spend is all different, their goals are all different and so too their energy needs from their diet will be different.  Getting to grips with what your food is and what you are getting from it in order to reach your goals is the first step in successful nutrition.

Carbohyrates.  Carbs.  Starches.  Sugars.  These words are all used for the same group of things really and are the single most important nutrient to us all.  These puppies give us about 4 calories per gram.  We break down most of our carbohydrates into smaller sugars to be absorbed.  These sugars give us energy to use immediately or to store as glycogen for later use.  They should make up between 45% and 65% of our diet.  We can tweak this ratio in order to lose weight or to meet the demands of strenuous exercise.  That guy who is still on the couch might need only 3-4 grams per kg body weight* every day.  Our fine lady on the bike training for an ironman (ironwoman?) may need up to 3 times that amount!  Not only should carbohydrates be the backbone of meals, but pre/during/post exercise nutrition is based on carbohydrate intake.  The type and timing of which is very important.  Grains, cereals, fruit, sugar, dairy are all sources of carbohydrate.  The topics of simple and complex sugars, fibre, GI, low carb diets and nutrient timing are for another day I think.

* You will note I refer to recommendations quite a lot as grams per kilogram body weight.  Everyone’s needs are different and this allows for fine tuning of an individuals intake.  Research and documented guidelines often work on this basis too *

Protein.  This is the building blocks of a helluva lot in our bodies and another essential element to our diet.  Like our carbohydrates, Mr Protein gives us about 4 calories per gram too.  We break these down into amino acids which later get rebuilt to make muscle fibers, hormones, connective tissue (ligaments etc) and assist with any repair or immune function fighting that needs to go on. Usually 15-20% of our total dietary energy should be from protein.  Our friend is obviously still on the couch and he needs about 0.8g per kg (15% total energy) every day.  Endurance and strength athletes need a bit more depending on their training.  For weight loss we often choose to go higher at the expense of carbs.  Lean sources of protein should be plentiful in our diet.  Lean meat, legumes and dairy are common sources.  Many more posts will follow on this one!

Fat. Sounds evil doesn’t it? Not true.  We need fat; it is vitally important for proper functioning of our immune systems, hormones, enzymes and to physically protect our organs and provide a source of energy.  We get a whopping 9 calories per gram with these big boys.  A dense source of energy.  I am sure we have all heard of good fats and bad fats, a nice simple way of discriminating.  I fear that my views on this may be against the grain of that which many others believe and profess.  Please feel free to argue with me.  I feel too much attention is placed on pounding and criminalising fat.  My views are based on research, evidence and common sense which we will come across in future posts.  Obviously too much of anything is going to have a negative effect but tread wisely when choosing your sources of fat.  Widely available information describes bad fats as animal sources (meat, butter, dairy) or saturated fats. Also in this group of baddies are trans fats which are for the vast majority manufactured fats not naturally occurring.  We find these guys in baked products, processed foods, chips and cooking oils and on and on.  No qualms here with trans fats.  Avoid.  Our good fats are unsaturated fats from fish, nuts, seeds, avo, olives etc.  A bit of a blanket statement that we should also be careful about.  Once again the truism that too much of a good thing… Watch this space.

Alcohol.  An empty calorie they say.  About 7 calories per gram.  Not much nutritional benefit comes from these calories and the requirement of our bodies to process the alcohol is one we should keep to a moderate level.  The metabolism of alcohol takes preference over a lot of important processes.   The champ on the couch isn’t helping his blood pressure, cholesterol, blood glucose control or weight by knocking back 2 tinnies every day.  In balance with a healthy lifestyle I can’t mock it and I am sure along the way my love for wine will provide a post or two on the booze.  There are some beneficial nutrients in wine anyhow, plus some research evolving for the benefits of yeast (beer and wine) on recovery. This is likely to be alcohol free however.  For now exercise moderation and don’t indulge when you should be recovering, or if you are on medication.  Any complicated health issues are another sign to stay away.

Post…done