Advice
Advice :: Nutrition :: Carbohydrate
Carbohydrates are the prime source of glucose manufacture in the body. They
are also the only macronutrient we can live without and the prime source
of cholesterol and adipose tissue synthesis. Fact, there exists Essential
Amino Acids and Essential Fatty Acids; there is no Essential Carbohydrate.
When foods are ingested, carbohydrates are digested and broken down into
glucose. Glucose is the body's favorite substrate (starting material) for
making energy; in the form of glycogen. However, if glucose molecules are
not quickly used for energy or the body's glycogen stores are full, then
the molecules are quickly converted then stored as fat and cholesterol by
an enzyme called “ATP-citrate lyase”.
The body has another glucose manufacturing pathway, called gluconeogenesis,
that involves the hepatic (liver) conversion of certain “glycogenic” amino
acids into glucose. Due to hepatic regulatory factors, the amount of glucose
produced through gluconeogenesis closely matches the body's needs! This is
an amazing process and justify's the statement above that it is possible
to live without eating carbohydrate. This may alarm you at this stage but
note, this introductory paragraph is just stating scientific fact.
If a sufficient amount of protein is ingested to constantly fuel both gluconeogenesis
and protein synthesis, the body naturally fails to synthesize adipose (fat)
tissue; due to enzymic down regulation of ATP-citrate lyase. So how much
of an ascending individuals daily calories need to come from carbohydrates?
None actually! However, 20% of total daily calories can come from carbohydrates,
if they are ingested within the first 90-180 minutes post-training only.
For the hard-gainers among you, therein lies the key to “bulking-up” leanly.
During periods of high anaerobic or aerobic exertion the body begins to up-regulate
the release of catecholamines (adrenalin and noradrenalin). One of the primary
functions they have is to increase the amount of fatty acids being released
from adipose sites and burned for energy by metabolically active cells, like
muscle tissue. They have a protein sparing (anti-catabolic) effect on muscule
and a wasting (catabolic) effect on fat. When a “give up the stores” signal
is transmitted to a fat cell, it can no longer feed on the macronutrients
(even glucose) available to other cells from the vascular system.
The catecholamines that are secreted during hard training remain elevated
for up to 3 hours post-workout. As a result, an athlete has little reason
to fear increased adipose tissue synthesis as hepatic (liver) glycogen stores
become the top of the feeding hierarchy. The take away message is “Starve
the fat and feed the muscles”.
Glycemic Index (GI)
Definition: The GI of a food, is a number given to that
food which reflects its potential to raise blood sugar level. Glucose
is given an arbitrary value of 100 and other carbs are given a number
relative to glucose.
The GI can be useful for managing blood sugar level; the greater the number, the greater the potential to increase blood glucose level. For example, if your blood sugar is low and continuing to drop during exercise, you would prefer to eat a carb that will raise your blood sugar quickly e.g glucose. On the other hand, if you would like to keep your blood sugar from dropping during a few hours of mild activity, you may prefer to eat a carb that has a lower glycemic index and longer action time e.g. starch. If your blood sugar tends to spike after breakfast, you may want to select a cereal that has a lower glycemic index.
The numbers below give that food's glycemic index relative glucose. Faster carbs (higher numbers) are great for raising low blood sugars and for covering brief periods of intense exercise. Slower carbs (lower numbers) are helpful for preventing overnight drops in the blood sugar and for long periods of exercise.
Note that these numbers are compiled from a wide range of research labs, and often from more than one study. These numbers will be close but may not be identical to other glycemic index lists. The impact a food will have on the blood sugar depends on many other factors such as ripeness, cooking time, fibre and fat content, time of day, blood insulin levels, and recent activity.
Below is a list of the GI of some common foods. This list uses glucose as the standard and has a rating of 100.
Breads
White bread 96, Waffle 76, Donut 76, Whole
wheat bread 75
Bread stuffing 74, Kaiser rolls 73, Bagel, white
72, Melba toast 70
Tortilla, corn 70, Rye bread 65, Whole wheat pita
58
Cereals
Puffed Rice 90, Corn Flakes 84, Rice Krispies
82, Cocopops 77
Cheerios 74, Shredded Wheat 69, Puffed Wheat 67, Oatmeal
55
Special K 54, All Bran 42, Crackers/Cookies, Vanilla
Wafers 77
Rice Cakes 77, Water Crackers 72, Golden Grahams
71, Shortbread 64
Dairy
Ice Cream 61, Pizza/cheese 60, Ice Cream/low fat
50, Milk/skim 32
Yoghourt/with sugar 33, Yoghourt/no sugar 14
Fruits
Watermelon 72, Dried fruit 70 ,Pineapple 66 , Cantaloupe
65,
Blueberry 59, Orange juice 57, Mango 55, Fruit
cocktail 55, Banana 53, Kiwi 52, Orange 43, Grapes
43, Pear 35, Apple 35, Strawberry 32, Grapefruit
25, Plum 25, Cherries 23
Grains
Rice/instant 88, Millet 71, Rice/white/not instant 70, Cornmeal 68,
Rye flour 65, Couscous 65, Bran 60, Barley, pearled 25
Legumes
Fava beans 80, Baked beans/canned 68, Romano beans
46
Black eyed peas 42, Chick peas 33, Split peas
32,Lima beans/frozen 32,
Butter beans 31, Black beans 30, Lentils 29, Beans/dried
29, Kidney beans 27, Soybeans 18
Pasta
Brown rice pasta 92, Refined pasta 65, Whole grain/thick
45, Whole grain spaghetti 37
Vegetables
Parsnips 97, Potato/baked 85, Potato/instant 83, Pumpkin
75,
French fries 75, Potato/fresh/mashed 73, Rutabaga
72, Carrot 71
Beets 64, New Potato 62, Sweet corn 55, Sweet
potato 54, Yam 51
Tomato 38, Green vegetables low, Bean sprouts
low, Cauliflower low
Eggplant low, Peppers low, Squash low, Onions
low, Water chestnuts low
Miscellaneous
Tofu frozen dessert 115, Maltose 105, Glucose
100, Rice cake 82, Jelly beans 80, Pretzels 80, Honey
73, Corn chips 73, Soft drink 70,
Sucrose 65, Hamburger bun 61, Sponge cake 54, Chocolate
49
Instant noodles 47, Fructose 23
How to use the GI to Increase Your Energy and Lose Weight
Diets that decrease and in some cases eliminate carbohydrates
have become extremely popular in the past couple of years e.g. Atkins Diet.
Just look in the diet section of your local bookstore. It is filled with
dozens of books telling you that carbohydrates is the greatest nutrition
evil of our time.
Carbohydrates are not evil, its a question of type and quantity. They are
useful source of energy. Carbohydrates supply the needed energy to keep your
heart, brain and vital organs operating. However, these types of diets do
have a basis in fact. Some carbohydrates cause you to store fat.
The reason some carbohydrates make you fat is because when they hit your
bloodstream they cause insulin to be dumped into your bloodstream. Insulin
is a hormone that has one primary job. That job is to regulate your blood
sugar. Too much sugar in your blood can lead to vision loss, kidney disease
and heart disease. So don't listen to anyone that says insulin is a bad thing.
Without insulin, we would be in a lot of trouble.
High insulin levels do cause an increase in body fat stores (see insulin
section). When you eat a food that is high on the GI, your blood sugar increases
rapidly. This results in large amounts of insulin being dumped into your
blood stream. The easiest thing for insulin to do with it is to store it
in your body as fat. In fact, insulin is 30 times more efficient at storing
the excess glucose as fat than sending it to the muscles where it would be
burned for energy. You can't and don't want to stop this insulin response
to stop. However, you need to decrease the need for large insulin dumps;
so avoid the foods that cause the large increases in insulin. That is where
the GI is useful. There are a two different indexes available; one uses white
bread as a standard, with the white bread rated as 100. And the other scale,
as used above, uses glucose at the standard, with glucose rated as 100.
The GI was developed in the early 1980's to assist diabetics. Eating foods
that are low on the GI would help them avoid dangerous increases in blood
sugar. This will also help non-diabetics with body fat reduction. Staying
away from the foods high on the index will decrease the amount of insulin
and as a result will decrease the amount of stored fat: Low GI, Low Body
Fat !
Eating foods low on the glycemic index will also help increase your energy
levels during the day. When you eat a high GI food, you get an immediate
rush of energy because of the high blood sugar levels. The resulting insulin
response removes the sugar from your blood, so you now begin to feel fatigued.
Eating foods low on the GI will keep you from going through this roller coaster
of high and low blood sugar. Your blood sugar levels will remain more level
throughout the day, which will give you a feeling of high energy all day
long.
The GI of a specific food can vary. Cooking, especially overcooking foods
will increase their GI. The GI of bananas will increase as they ripen. The
GI of pasta can vary by protein content, size and even shape. Each individual
will also have a slightly different insulin response to each food.
Fat Kids Can Become Fat Adults
An interesting study from the Journal Of Paediatrics looked
at how the GI affected eating behaviour in obese teenage boys. First the
subjects consumed a high, medium or low GI meal at breakfast and lunch. The
researchers then measured how much they ate for a 5hr period after lunch.
Researchers found that voluntary food intake was 53% greater after the medium
GI meal and a whopping 81% greater after the high GI meal, when compared
to the low GI meal. Also, insulin levels were dramatically higher after the
high GI meal. So even though each meal had the same number of calories, it's
clear that the impact on how you eat later is dramatically different!
Please note, you do not have an unlimited metabolism with a license to eat
endlessly on low GI foods. Eating too much of anything may make you increase
body fat level. But if given a choice, choose the low GI foods. In the long
run, you will probably end up eating just a little less afterwards.
Eat Low Glycemic For A Healthy Heart
Though having a healthy heart and being disease-free is not
a primary concern for most people, fact remains we're all getting older and
our hearts are not getting any cleaner. Eating high glycemic foods can by
itself increase your risk of coronary heart disease. In fact, carbohydrates
classified by their GI rather than as either simple or complex, were shown
to be a better predictor of coronary heart disease. Though this study examined
women only, it is a good possibility that similar results would be found
in men.
GI Summary:
Eating low GI foods 30-60 minutes before exercise minimises the
hypoglycemia that might occur at the start of exercise.
Eating low GI foods prior to exercise may increase the amount of free fatty
acids in the blood therefore increasing fat oxidation.
Eating low GI foods will result in less eating later, greater appetite suppression,
and perhaps fewer cravings for “junk” foods.
Eating low GI foods is healthier for you metabolically (insulin levels are
stable) and for your cardiovascular system (decreased risk of heart disease).
Eating low GI foods may promote lower body fat levels and leaner, muscular
physique.
Satiety Index (SI)
Definition: The satiety Index of a food, is a number ascribed
to that food which is a reflection of its ability to suppress appetite.
What we eat and how much we eat have an influence on our health
and well being. But what kinds of foods make us feel ‘full' and why do
so many of us tend to over-eat?
The main role of food is to satisfy hunger and to provide essential energy,
nutrients and other substances for growth and the maintenance of health.
Much of what we choose to eat is influenced by the palatability of foods;
i.e. taste, smell and texture, as well as the social setting. Our appetite
reflects a conscious sensation of hunger, a learned or habitual pattern of
eating at times throughout the day, our preferences for different kinds of
foods and the sheer pleasure of eating or indulging in particular foods we
like.
During a meal, the stomach expands, and internal nerve receptors sense the
volume of food and the pressure on the stomach wall. These receptors send
hormonal signals (see gut hormones and appetite section) to the brain (via
the vagus nerve), causing the sensation of fullness. When the stomach contracts
and empties, the desire to eat is felt again. Larger meals fill the stomach
for longer periods of time and are more satisfying than smaller meals. The
actual components of the meal and the temperature of the food can also influence
how quickly the stomach empties and, therefore, feelings of fullness.
"Satiating power"
Some foods can more easily contribute to the feeling of fullness
(satiety) than others, and this is referred to as their "satiating
power". The calorie-counting tables, used widely by slimmers and the
weight conscious, do not necessarily reflect this satiating power and studies
examining the effects of foods on "feelings of fullness" can
be helpful. In one study of 38 common foods, both men and women subjects
consumed foods with equal calorie contents and their feelings of fullness
were recorded every 15 minutes for 2 hours. Highest satiating power was
found with high levels of protein, dietary fibre and water and low satiating
power was related to higher fat foods. Fruit and vegetables (especially
boiled potatoes) proved to have high satiating values, whereas bakery products
like cakes, croissants and biscuits were the least satiating foods. Protein-rich
foods (fish, meat, baked beans, lentils and eggs) and carbohydrate-rich
foods (pasta, rice, wholegrain breads and cereals) were among the most
satiating foods.
While protein seems to stave off hunger for longer than carbohydrate, fat
exerts the weakest effects on both satiation and satiety. This probably accounts
for the capacity of a high fat diet to lead to passive over-eating, often
resulting in weight gain.
So is a breakfast of wholegrain bread and lean ham a good choice to stave
off hunger pangs until lunch? It would appear so, however, scientists still
know little about the satiating power of complete meals that combine various
nutrients.
Other influences
The large number of different factors that affect appetite
and food intake complicates studies in the area of hunger and satiety.
In addition to food types, satiety ratings and palatability, social settings,
customs, education levels, financial income, serving sizes and even mood
are just some of the factors that can affect food intake and body weight.
Scientists are still working on unravelling all of the factors influencing
what we eat and why.
Satiety Index of Common Foods
All the foods below are compared to white bread, ranked as "100"
Each food is rated by how well it satisfied their hunger; If you want to lose weight, avoid the lower numbers!
Bakery Products
Croissant 47% , White bread 100%, Cake 65%, French fries 116%
Doughnuts 68%, White pasta 119%, Cookies 120%, Brown Rice 132%,
Crackers 127%, White rice 138%, Snacks and Confectionery,
Grain bread 154%, Mars candy bar 70%, Wholemeal bread 157%,
Peanuts 84%, Brown pasta 188%, Yoghourt 88%, Potatoes 323%,
Crisps 91%
Protein Rich Foods
Ice cream 96%, Lentils 133%, Jellybeans 118%, Cheese
146%,
Popcorn 154%, Eggs 150%
Breakfast Cereals
Baked beans 168%, Muesli 100%, Beef 176%,Sustain
112%,Fish 225%,
Special K 116%
Fruits
Cornflakes 118%, Bananas 118%, Honeysmacks 132%, Grapes
162%,
All Bran 151%, Apples 97%, Porridge/Oatmeal 209%, Oranges
202%
Using this study, the May 1996 issue of the "University of California-Berkeley Wellness Letter," gave suggestions for weight-watchers trying to get the most satisfaction from the fewest calories:
Potatoes gave the highest satisfaction, seven times higher than the
least-filling croissants.
Whole grain breads are 50% more filling than white breads.
Cakes, donuts, and cookies are among the least filling.
For fruits, oranges and apples outscore bananas.
Fish is more satisfying, per calorie, than lean beef or chicken.
Popcorn is twice as filling as a candy bar or peanuts.
Holt's Food Satiety Index is the first of its kind demonstrating that
foods with a high-fat content create almost instant cravings for more of
the same. Croissants, for instance, had the lowest score of all the foods
tested, even though most people think of them as filling. Chips gave almost
twice as much satisfaction as doughnuts, and popcorn scored higher than All-Bran.
The very best thing to eat is potatoes, which gave much more satisfaction
as the same number of calories in the form of white bread.
"Fatty foods are not satisfying, even though people expected them to be",
says Dr Holt. 'We think the reason is that fat is seen by the body as a fuel
which should be used only in emergencies - it stores it in the cells instead
of breaking it down for immediate use. Because it doesn't recognise the fat as
energy for immediate use, the body does not tell the brain to cut hunger signals,
so we go on wanting more. Carbohydrates are the opposite - they raise blood glucose
so the body knows it has got enough fuel to be going on with.'
Overall, the carbohydrates deter nibbling best, while protein-rich foods
such as cheese, eggs, baked beans, meat and fish come second, and fruit third.
But there are big differences between the satisfaction value of foods within
the same group.
"You can't just say that vegetables are satisfying or that bakery products
aren't, because there can be a two-fold difference between two similar foods," says
Dr Holt.
"We found that bananas are much less satisfying than oranges or apples,
and that wholemeal bread is half as satisfying again as white bread. And a diet
which simply recommends cereal for breakfast overlooks the fact that muesli is
only half as satisfying as porridge."
"One thing that I am concerned about, is that many people do not know how
to interpret these findings properly. The SI scores reflect the total amount
of fullness produced by the set 1000 kJ portions of the test foods over 2 hours;
i.e. short-term satiety. Although most foods with high SI scores kept fullness
relatively high for the whole 2 hours, there were a few exceptions. The fruits
were served in very large portions, but fullness dropped off quickly towards
the end of the 2nd hour, reflecting the rapid rate of gastric emptying (oranges
and apples and grapes are mainly sugar and water)."
"Many "health-conscious" dieters will eat a meal based on several
pieces of fruit and some rice cakes (in Australia anyway) and then wonder why
they feel ravenous a few hours later. These kind of extremely low-fat, high-carb
meals do not keep hunger at bay because they are not based on slowly-digested
carbs and probably don't contain enough protein. A dieter would be better off
eating a wholesome salad sandwich on wholegrain bread with some lean protein
like tuna, or beef and an apple. This kind of meal can keep hunger at bay for
a very long time."
One thing that makes a food satisfying is its sheer bulk. 'You can eat an
awful lot of popcorn without taking in a lot of calories,' says Dr Holt.
'It may not weigh much, but it makes your stomach feel full just because
it takes up so much space. Oranges come out very high on the index for the
same reason - but orange juice probably wouldn't, even though it has the
same number of calories.'
Chemical constituents of foods also make a difference. 'Beans and lentils,
for example, contain anti-nutrients which delay their absorption so they
make you feel full for longer,' says Dr Holt. 'Roughly speaking, the more
fibre, protein and water a food contains, the longer it will satisfy. but
you have to look at each foodstuff individually and that is why we think
our index will be so useful.'
Carbs and the FDA
The Food Label terms for carbohydrates defined by the FDA are
as follows:
Total carbohydrate: calculated by subtraction of the
sum of the crude protein, total fat, moisture, and ash from the total weight
of the food.
Sugars: the sum of all free mono (glucose, fructose) and
disaccharides (lactose, sucrose).
Sugar alcohol: the sum of saccharide derivatives in which
a hydroxyl group replaces a ketone or aldehyde group whose use in the food
is listed by FDA (mannitol, xylitol) or is general recognised as safe (sorbitol).
Other carbohydrates: the difference between total
carbohydrate and the sum of dietary fibre, sugars, and sugar alcohols if
present.
Glycerol and glycerin refer to the same substance. FDA nutrition labelling
regulations require that when glycerin is used as a food ingredient, it
must be included in the grams of total carbohydrate per serving declaration.
Also, when the label of a food containing glycerin has a statement regarding
sugars, the glycerin content per serving must also be declared as sugar
alcohol.
The relatively new phrases "net carb," "low carb," and "impact
carb" are not defined by the FDA; they were created by companies to
give their products more shelf appeal, as consumers are not likely to have
the time or interest in the calculations of crude protein, total fat, moisture,
and ash.
Consumers should not be fooled by promises on wrappers. One needs to remember
that calories count. Special low-carb food products are not calorie-free.
Non-Impact Carbs:
Non-Impact carbs are carbs that have very little effect on blood
sugar levels when they are eaten. They include fibre, sorbitol, maltitol,
and glycerol.
Fibre is completely indigestible by the body and passes through unused. Sorbitol,
maltitol and glycerol are what are known as "sugar alcohols." They
are digested by the body but have little to no effect on blood sugar levels.
Impact (Effective) Carbs
Impact (or effective) carbs are the opposite of the Non-Impact
Carbs. They will have an effect on blood sugar levels i.e. increase blood
sugar level. In most low-carb diets, the idea is to place a limit on Impact/Effective
Carbs to keep blood sugar and, therefore, insulin levels under control.
Impact carbs can be divided into two basic groups: simple and complex carbs.
Simple carbs are rapidly converted into glucose by the body while complex
carbs generally take longer to convert (break-down) to glucose.
Net Carbs
Net carb count is the total number of carbs in the food minus the
non-impact carbs; effectively the same as total impact carbs, e.g. a food
that contains 35 grams of carbs and 7 of those carbs are fibre, the food
contains 28 grams of net carbs.
The term "Net Carb" was coined by supplement makers after glycerol
(the non-impact sugar alcohol discussed above) was reclassified by the FDA
as a carbohydrate. Previously, it had not been classified as either a carb
or a fat and supplement makers were able to use it as a sweetener without
adding to the carbohydrate count.
Good Carb Sources
Here are a few sources that will fuel your body with the carbohydrates
that it needs.
Pasta
Rigatoni, ziti, spaghetti, angel hair, it doesn't really matter. Pasta
in all forms is a great source for energy. Many power lifters or marathoners
load up on pasta before a big event. While pasta is low in fat, some forms
(lasagna, manicotti) are packed with fattening cheeses. Try to avoid applying
butter to your pasta dishes while using lighter, healthier tomato sauces.
Also, keep pasta consumption in moderation; try to substitute it regularly
with other carbohydrate soucres.
Baked Potates
The average-sized potato contains about 50 grams of carbohydrate,
and are fat free. The key to adding potatoes to your diet is to consume
them without any added spreads like sour cream or butter.
Rice
Rice is another excellent source of carbohydrate, also free
of fat. Brown rice has more protein compaired to white rice and is often
the choice for athletes.
Others
Beans are packed with carbohydrates and will provide your diet with
the healthy energy kick it needs. Black beans, pinto beans, and kidney
beans are all proof of this; generally consisting of 40 grams of carbohydrate
per cup. Bananas pack around 27 grams of carbohydrates for an average sized
banana. Medium sized apples pack 21 grams of carbs.
Bread is deliberately not listed as a good quality source for carbohydrate.
Please include as many vegetables (especially green veggies) as possible
in your diet as they provide countless health benefits. They can be neglected
when controlling carbohydrate intake.