1 July 2008

Your Questions Answered

‘I’ve been attempting to use the glycemic index to help me consume the correct foods after intense workouts. But, I’m terribly confused as various articles on the subject sometime seems to contradict one another. Should I be having high or low GI carbs?’

[PIC]
Dr Emma Stevenson

GI News invited Dr Emma Stevenson from Northumbria University’s School of Psychology and Sports Sciences to answer this one: ‘The available literature is confusing and there are surprisingly few well controlled, scientific studies investigating the effects of high GI and low GI carbs on recovery from intense exercise. The early studies showed that consuming high GI carbs during recovery from exercise increased muscle glycogen resynthesis (over both a short recovery period of about 4 hours and over 22 hours) compared to consuming low GI carbs during recovery. This is not surprising as rapid muscle glycogen resynthesis requires a high insulin concentration and a high glucose concentration – both of which are observed following consumption of high GI carbs. More recently, my colleagues and I have shown in our studies that exercise capacity was improved in endurance athletes and following a low GI recovery diet over 24 hours as the low GI carbs allowed the athletes to burn more fat as a fuel and therefore possibly spare muscle glycogen. The same group also showed no differences in intermittent exercise performance in sports/games played when they consumed a high GI or low GI diet over 24 hours.

My advice based on our studies would be that if your recovery time between sessions is greater than a few hours then the most important thing is to consume sufficient carbohydrate and low GI carbs may provide the additional benefit of allowing your body to use fat as an energy source for a longer period after exercise. If your recovery time between sessions is short (i.e. less than 4 hours) then high GI carbs can provide a rapid source of glucose and result in a rapid insulin response that can speed the recovery of muscle glycogen. I would also recommend consuming a source of protein (milk, yogurt) during recovery to aid muscle recovery and reduce soreness.’

I am keen to bake my own low GI bread. I have found a recipe (it is one of Anthony Worral Thompson’s) that says: ‘This bread has an extremely low GI as the tough outer coating of the seeds makes them harder to break down.’ It has: ‘325 g strong wholegrain flour, 25 g wheatbran, 1 sachet fast action yeast (6 or 7g), 25 g sunflower seeds, 25 g sesame seeds, 25 g pumpkin seeds, 25g linseeds, 12.5 g muscovado sugar, half teaspoon salt, 1 tablespoon vegetable oil’. This is cooked at 200ºC for 40 minutes or so. How can I be sure it is low GI?

[PIC]

‘We are often asked about low GI bread recipes. Sadly, we don’t have one ourselves,’ says dietitian and co-author of The Low GI Diet, Kaye Foster-Powell. ‘In fact it’s impossible to predict the GI of a recipe for baked goods because of the way the starches can change with cooking and other ingredients in the recipe will exert an influence on it’s glycemic impact well. A recent study published in the European Journal of Clinical Nutrition showed that homemade breads that were proofed for shorter times had a lower final volume as well as a lower GI than those that were proofed for longer. Lower degrees of starch gelatinisation may explain this effect. Some early tests of the GI of specially manufactured breads suggested that at least half the “bulk” needed to be whole grains to effectively lower the GI. This would mean a recipe with for example, 250 g flour (wholemeal or white) plus 250 g whole cereal grains like rolled oats, rolled barley, kibbled wheat or seeds. These days, manufacturers use more novel ingredients like guar gum to lower the GI without using whole grains. With a staple, ‘everyday’ food like bread, testing is essential as it’s these foods (along with breakfast cereals) that can make a real difference to the overall GI of your diet.’

I only have a week to get into tip-top shape before a big, glamorous event. What can I do to reduce bloating and fluid retention and look and feel great?

[PIC]
Prof Jennie Brand-Miller

Here’s what Prof Jennie Brand-Miller suggests.
• Do two 30-minute walks every day for a week (a total of 60 minutes a day), including one first thing in the morning to set your body clock.
• Up your fruit and veggie (bar potatoes) intake. Eat nine serves of veggies and fruit everyday (at least six serves of veggies), and the more colourful the better.
• Eat for flavour, enjoyment and wellness, not weight loss.
• Cut back on salt and salty foods.
• Buy some magic underwear

14 comments:

Bart said...

I'm confused by the following paragraph from the July 2008 article on blood glucose levels and heart disease:

What’s the link between blood glucose and atherosclerosis? Inflammation. For some time now, heart disease researchers have suspected that the blockages in coronary arteries that can lead to a heart attack, aren’t just caused by the build up of cholesterol and other fats, but an inflammatory process in the arteries, similar to what happens when you get a bacterial infection, also plays a part. It’s thought that high blood glucose after meals contributes to chronic low inflammation by increasing oxidative stress (see below).

Should I worry about high or low inflammation?

GI Group said...

Most of us get concerned about high inflammation and act fast to do something. What we are saying here is that chronic (that's ongoing) low inflammation caused by high blood glucose levels after eating can be a troublemaker as well and a risk factor for cardiovascular disease. And you need to do something about it. Hope this clarifies things for you.

Julia said...

ROFLMAO!!! Magic underwear! What a funny!! Reminds us that in the midst of the disciplined life we lead, sometimes we just need to have a non-food/non-diabetes related treat!!! Onya Prof!!

hermin said...

i found 2 interesting questions from anonymous in the last month's "your questions answered" section, and thought it might be interesting to comment on.

this is their message:

Well it does seem the protein makes it a lower GI load as with the nuts and raisins.

Question #1

If I was to eat peanut butter that has little GI--it seems that if I ate alot of it at once like I've done sometimes out of the container as I do love peanut butter

Is it safe to eat alot of it glycemicly speaking--the GI doesn't go up if I have alot so then there's not much to worry about as far as a high glycemic load, right?

Question #2

Is would seem like anything with high fructose corn syrup in it would be higher glycemic-I had no fat yoplait yogurt over the weekend as it talks about again in the Shoppers Guide 2008-it is sweetened with Sucralose-Splenda and high fructose corn syrup--

It has 14 sugars like some candy out there and with high fructose corn syrup it seems like the glycemic index would be higher--

Is it because it is mainly dairy that makes it low glycemic?

Thank you ahead of time for your answers and yes I'm looking forward to the 2009 Shoppers Guide!

hermin said...

i think these are interesting "frequently asked questions" on GI

question 1 actually highlights how important it is NOT to see food from just its GI. although glycemically speaking it wouldn't raise the blood sugar, it doesn't mean we can eat it a lot. peanut butter has a lot of fat and if we overeat it, we can put on weight. unfortunately overweight and obesity are risk factors of heart disease, stroke and even diabetes.

as for question 2, indeed dairy makes it low GI. high fructose corn syrup contains some glucose too, which brings the GI up. but i think all types of yoghurt are a great snack/dessert choice as they are rich in nutrients, have lower GIs and less calories than most other desserts.

GI Group said...

First of all, thanks Hermin for bringing questions we missed to our attention. We'll post answers as soon as possible.

As for magic underwear Julia. We love the suggestion too and had a good giggle. Though we have to say we had a puzzled question about this from one of boys on the GI Team!

GI Group said...

Re the missing answers to questions in previous issues. Here's what our dietitians say:

Peanut butter has little carbohydrate content so a low GI and GL. It also contains mostly healthy mono-unsaturated fat so is fine in moderation. But it is high in fat and overeating it could lead to weight gain which can worsen blood glucose control. It therefore wouldn't be a good idea to eat it in large amounts on a regular basis (unless you were trying to gain weight!).

Yoghurt has a low GI largely due to the lactose content (the natural sugar in milk and milk products). Fructose actually has a low GI (much lower than other sugars like glucose and sucrose) so the combination of lactose and fructose in this yoghurt would give it a low GI. If it had a lot of added sugar from high fructose corn syrup this would increase the GL however. If it is sweeteneed with Splenda instead this would lower the GL.

Anonymous said...

I wanted to ask about the size amounts listed

For example in The New Glucose Rev 3rd edition p.296 1 cup of Instant oatmeal is a GI of 82
The Shoppers Guide 2008 p.110 it was changed to 3/4 cup

I would think that any amount of instant oatmeal 1/4 cup or 1.5 cups is still going to be a GI of 82 because of the substance

Question #1

Why do the sizes change when any amount could be a GI of 82?

Question #2

I've learned though that the glycemic index won't change when you double the serving size of oatmeal from 1 to 2 cups-but the glycemic load will double--In the 3rd edition it says the glycemic load of instant oatemeal is 17 so doubling the amount makes it a glycemic load of 34

This is correct right?

Question #3

Are there 3 levels that can be defined as what is low, med, and high for a glycemic load

1-7 is low
7-12 is med
13 and above is high

Is that a somewhat correct way to look at the levels of glycemic load?

Thanks so much

Anonymous said...

In 2006 I was diagnosed with polycystic ovarian syndome and have been trying to reduce my carb intake. However, I love white wine and consume approximately 4 glasses a day. Does wine increase blood sugar levels?

GI Group said...

We have done a few stories on alcohol in GI News. Use the Google search tool on the site to check them all. Meantime here's the main one.

"Generally, alcoholic beverages contain very little carbohydrate. Most wines and spirits contain virtually none; regular beer contains around 10 g carbohydrate per 12 fl oz can; stout around 14 g carbohydrate per 12 fl oz can while a light beer has from 3–7 grams of carbohydrate per serving (12 fl oz can). Compare this with 36 g carbohydrate in a can of regular (not diet) soft drink! So yes, a beer will raise your glucose levels but not excessively. And if you drink beer in large volumes (not a good idea really) then you could expect it to have a significant effect on blood glucose. Although we haven’t GI tested many brands of beer, there are some useful websites out there that will tell you how much carbohydrate there is in various brands. We use www.calorieking.com as a quick reference.

As for enjoying an occasional drink, researchers (Kaniz Fatima and Chris Middlemass) from the University of Sydney reported at the Nutrition Society of Australia (November 2005) that a pre-dinner drink tends to produce a ‘priming’ effect, flicking the switch from internal to external sources of fuel and keeping blood-sugar levels low. In one study, they gave healthy, young, lean people two standard glasses of beer, or wine, or gin and tonic or water to drink about an hour before eating a meal then they measured their blood glucose and insulin levels. They found that: ‘realistic amounts of beer, wine or gin reduce postprandial glycemia but not insulinemia’."

GI Group said...

Re amounts, our researchers have come back with the following to the 3 questions asked.

Question #1
Why do the sizes change when any amount could be a GI of 82?

The quantity of a food listed in grams refers to an average serving size, which has been determined by Dietitians based on the eating habits of most people. You are correct in saying that whatever the portion size listed, the GI will be the same, as the GI refers to the quality of the carbohydrate (i.e. How much a portion of that food containing 50g of available carbohydrate will increase your blood glucose), not the quantity (quantity is GL = GI x carbohydrate in grams/100).

Question #2
I've learned though that the glycemic index won't change when you double the serving size of oatmeal from 1 to 2 cups-but the glycemic load will double--In the 3rd edition it says the glycemic load of instant oatemeal is 17 so doubling the amount makes it a glycemic load of 34
This is correct right?

Yes, if you double the weight of available carbohydrate, you do double the GL, e.g. if you have two different portions of a food with a GI of 50 containing different amounts of available carbohydrate:
(GI 50 x carbs 20g)/100 = GL 10
(GI 50 x double carbs = 40g)/100 = double GL 20

If you double the weight of the food then you are still likely doubling the available carbohydrate content, e.g. If 1 apple contains 20g of available carbohydrate, then 2 apples will contain about 40g of available carbohydrate.

Optional extra: In reality, if you double the GL, you will see approximately a doubling of your blood glucose response (in healthy individuals), but only up to a point, because healthy bodies have a 'ceiling' concentration for blood glucose, i.e maximum concentration (even with high GI foods) = about 8-10 mmol/L. However, a healthy body will have to produce more insulin (=work harder) to drive the blood glucose out of the blood into cells, i.e. There is a higher work load on the body with higher GL. In addition, a higher blood glucose concentration due to higher GL (e.g. 9mmol/L) will have unwanted consequences compared to lower GL (e.g. 6mmol/L), such as increased damage to blood vessels, etc.

Question #3
Are there 3 levels that can be defined as what is low, med, and high for a glycemic load
1-7 is low
7-12 is med
13 and above is high
Is that a somewhat correct way to look at the levels of glycemic load?

A low GL food has been previously defined as ≤10, medium GL 11-19 and high GL ≥20, but there is less evidence of the reliability of these values compared to GI values in nutrition practice.

Eric said...

Thanks. The simple, clear breakdown with numbers helps folks like me.

Anonymous said...

What is magic underwear Prof Jennie

GI Group said...

Magic underwear is the slimming, shaping underwear made famous by TV style gurus Trinny and Susannah. The point is to make you look better in your clothes. Check it out at www.themagicknickershop.co.uk