Carbohydrates and the Glycemic Index

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    Carbohydrates and the Glycemic Index

    Carbohydrates and the Glycemic Index


    Carbohydrates are the body's preferred fuel source. Once, nutritionists classified carbohydrates as either 'simple' or 'complex', depending on their chemical configuration of carbon, hydrogen and oxygen atoms, and the presence of fibre. All the lay person needed to know was that simple carbohydrates were the sugars and complex carbohydrates were the starches. It was recommended that we limit our intake of simple carbohydrates and get most of our fuel requirements from the starches, such as pasta, rice, bread and potatoes. Paying strict attention to simple and complex carbohydrate intakes was particularly important for those with diabetes. However, current research indicates that these old theories are inadequate. Foods are now rated on a scale called the glycaemic index, or GI.
    Digestion and absorption of carbohydrates
    The digestive system breaks down carbohydrates into simple sugars, predominantly glucose. This simple sugar is then transported to each cell via the bloodstream. A gland of the endocrine system, called the pancreas, secretes a hormone called insulin, which helps the glucose to migrate from the blood into the cells. Once inside a cell, the glucose is 'burned' along with oxygen to produce energy. The body converts any excess of glucose into another form called 'glycogen'. Glycogen is then stored inside muscle tissue and the liver, ready to supplement blood sugar levels should they drop between meals or during physical activity.

    Diabetes and glucose
    People with diabetes either don't produce enough insulin (Type I diabetes) or their insulin is ineffective (Type II diabetes), which means the amount of glucose in their bloodstream (their blood sugar levels) remain too high. Symptoms include weight loss, abnormally high levels of sugar in the urine and an unquenchable thirst. It is important for people with diabetes to carefully monitor their diet to ensure a slow, steady absorption of glucose. All people with Type I diabetes and some people with Type II diabetes need to inject themselves with insulin to make sure that their blood sugar levels are adequately controlled. For most people who suffer from Type II diabetes, exercise and weight loss can improve sensitivity and response to the body's insulin.

    'Simple' versus 'complex' carbohydrates
    It was once recommended that people with diabetes should limit their carbohydrate intake to complex carbohydrates, because it was believed that the glucose was released much more slowly from the gut into the bloodstream. On the other hand, simple carbohydrates were thought be absorbed rapidly, giving the body a glucose 'hit' and provoking a more severe response from the pancreas. In fact, it turns out that many simple carbohydrates are absorbed much more slowly than complex ones. Several carbohydrate-rich foods, which mainly contain sugars (for example, fruit and flavoured yoghurt), produce less of a glucose 'hit', or glycaemic response, when eaten than foods high in 'complex' carbohydrates like bread and potatoes.

    The glycaemic index
    The terms 'simple' and 'complex' for classifying carbohydrates are becoming obsolete. The glycaemic index - GI - is a newer and more commonly used method to rate carbohydrates. The GI measures the rise in blood sugar levels caused by a measured quantity of a particular food. Foods are given a score out of 100, where white bread (GI of 70) is used as a reference food and all foods are compared to it. Those which take longer to be absorbed are called 'low GI' (GI less than 55). Carbohydrates which offer a quick hit are called 'high GI' (GI greater than 70). It is recommended that all people, and especially people with diabetes, choose to eat low GI foods most of the time. Some studies have shown that diets leaning towards low GI carbohydrates can:

    Lower blood cholesterol levels
    Lower the risks of heart disease and diabetes
    Help with weight loss and weight maintenance, as the slow absorption of glucose may help to sustain a feeling of fullness.

    High GI foods are influenced by low GI foods
    The absorption of glucose from the small intestine into the bloodstream is influenced by other foods eaten at the same time. Generally, eating low GI foods slows down the absorption of glucose from any high GI foods eaten along with them. This is important as most foods are not eaten singularly but as a meal and this affects the GI value of foods.

    People with Type II diabetes benefit from consuming a diet that contains predominantly low GI foods. It is recommended that they consume at least one low GI food at each meal. A little sugar (equivalent of 2 tablespoons or 50g over a day) added to otherwise healthy and lower GI foods, such as spreading honey on wholegrain bread, is generally acceptable and will not adversely affect blood sugar levels.

    Foods with a high glycaemic index can help to manage blood glucose levels, especially when blood glucose falls below normal levels. High glycaemic foods can quickly deliver glucose to the blood stream to restore blood glucose to normal levels.

    GI scale examples
    Some examples of the GI rating of various carbohydrates include:
    Low GI (less than 55) - soy products, beans, fruit, milk, grainy bread
    Medium GI (55 to 70) - sugar, orange juice and oats
    High GI (greater than 70) - potatoes, wholemeal and white bread, and rice.

    Factors which affect the glycaemic index of a food
    Factors such as the size, texture, viscosity and ripeness of a food affect its glycaemic index. For instance, an unripe banana may have a glycaemic index of 30 but a ripe banana may have a glycaemic index of 52. The presence of fat, protein, soluble fibre, fructose (a carbohydrate found in fruit), and lactose (the carbohydrate in milk) also generally lowers a food's glycaemic response. Other factors present in food, such as phytates in wholegrain breads and cereals, may also delay a food's absorption and thus lower its glycaemic index.

    The presence of dietary fibre does not always seem to delay absorption, as blood glucose responses to wholemeal bread are similar to those following the consumption of white bread.

    Better Health Channel

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    this ones a keeper.

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    In other words, foods such as potatoes that were once considered complex actually have a high GI and, if consumed in excess, can make you fat?

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    Well, anything can make you fat if consumed in excess. What's important is to know when to take a high GI food....post workout & at breakfast. Low GI foods at other times will ensure minimal fat gain from your meals. Insulin helps to shuttle nutrients into the muscles. that's why a high GI carb w/ protein after a workout is a must. Also why a GI carb w/ fat isn't ever a good idea.

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    you always post such great info!! Thanks a lot

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    I think the important thing to remember is that we need to calcualte the GI of the whole meal not just the individual food.
    Potatoes are fine when consumed with fat and protein sources as this will drastically reduce the effect of the high GI of the potatoes.

    GI of the whole meal is the most important factor.

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    Originally posted by Dorian
    I think the important thing to remember is that we need to calcualte the GI of the whole meal not just the individual food.
    Potatoes are fine when consumed with fat and protein sources as this will drastically reduce the effect of the high GI of the potatoes.

    GI of the whole meal is the most important factor.
    Yes But..........(and don't forget fiber)

    You want to look at the insulin index of the entire meal, the glycogenic nature of the composition of the meal, and the individual eating that meal (4 out of 5 are IR, insulin resistant)

    For most, potatoes are NEVER an acceptable choice!

    DP

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    Good post w8....great info from all angles!

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    Originally posted by Dr. Pain

    (4 out of 5 are IR, insulin resistant)

    DP

    Is there a source for this stat DP?

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    Found a quote from Phil Kaplan...

    "It appears, based on clinical research, that 10-25% of Americans do have some level of insulin resistance (carb sensitivity)"

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    That's cause 10-25% of americans are fat.

    The fatter you get, the more insulin resistant you get.

    Why?

    It's an adaptive mechanism to try and maintain homeostasis. The body has a setpoint of where it likes to be and it tries to maintain this. So lean people can stay lean because they have a fast metabolism which can rev up to burn off a lot of calories under periods of overfeeding, and usually after a few days of overfeeding, these type of people notice a drop in hunger so they subconsciously don't eat as much. End result, they maintain their leaneancy. And these type of people are usually more leptin sensitive, so their bodies are happy being a leaner state. They don't have the associated hunger pangs or sugar cravings that come with hovering too far below your setpoint.

    Anyhoo, since the body is maintaining this homeostasis, it doesn't actually like getting too fat, just as it doesn't like getting too lean. So if there's a lot of calories constantly coming in, it adapts - one way by increasing insulin resistance. If a cell is more insulin resistant, then insulin can't do it's job to the cell - storing nutrients and shutting off lipolysis. Which is why fatter people have piss-poor blood profiles, and (one of the reasons) why fatter people can lose fat and gain muscle at the same time - because fat is more readily available, so the body happily burns more of it to fuel metabolic processes.

    So a simple way of increasing insulin sensitivity (IS) is merely by getting leaner. The leaner you are (and the closer to the under side of your setpoint) the higher your insulin sensitivity, because the body is in a state more readily to accept storage to maintain homeostasis.

    So fatter people simply need to get leaner to improve their insulin sensitivity. It is when IS improves where low GI carbs and all that jazz becomes more important re: hunger pains and cravings goes, since lower leptin will be screwing with your system.

    So Fatter people (20+%) don't really need to bother with the whole low carbs, low GI stuff. Providing they're in calorie deficit, they can eat pretty much what they want and lose fat, providing any poor food choices don't spur on any binges (fat people are like that) that would result in more calories being consumed.

    Which is sorta why the low fat diets work for a short period. It's partly that, and partly something to do with the 'nutrient balance', which is basically a fat balance of fat intake - fat burned.

    There's some other stuff i could mention but ill save it for a rainy day.

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    This may sound stupid, but I thought brown rice was NOT HIGH GI? Do they mean white rice??

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    What about glazed sourdough doughnut holes?

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    Brown Rice is moderate to high GI.

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