Science on Sunday: Glycemic Index

One of the problems with science is how it is reported in magazines and newspapers.  Also how it is reported on the web can be a problem.  This problem came to light for me when I was reading the free magazine “Better Nutrition”.  In the February issue there was a short article on “The best weight management diet” which talked about a New England Journal of Medicine article which showed that high protein-low glycemic index diets were better for maintaining weight loss.  This sound realistic and was confirmed by reading the article, but what peeked my interest was the table of glycemic index values in the Better Nutrition article because apparently sourdough bread has a lower GI (54) than white bread (100).

This did not seem possible as sourdough bread is essentially made from the same ingredients as white bread with a different starter is added instead of yeast for proofing.  There is nothing in the process of making sourdough bread that should change the carbohydrates, which are from wheat flour.

So I looked up how glycemic index was measured.  What I found was that glycemic index (GI) ranks foods by how quickly they increase blood sugar (glucose) levels.  Foods that increase blood sugar rapidly after being consumed have a high GI.  For example, honey has a GI of 85 and sucrose, table sugar, has a GI of 70. Conversely foods which are slowly digested and absorbed have a low GI.    Examples of these foods are green vegetables (GI = 15) and dark chocolate with greater than 70 % cocoa solids (GI = 22).

GI is measured by feeding measured portions of the test food containing 10 – 50 grams of carbohydrate to 10 healthy people after an overnight fast.  Blood samples are taken at 15-30 minute intervals over the next two hours and used to construct a blood sugar response curve. The area under the curve (AUC) is calculated to reflect the total rise in blood glucose levels after eating the test food.  The results for a test food is divided by the results of the standard containing the same amount of carbohydrate, either glucose or white bread are used as standards, and multiplied by 100.  The result gives a relative ranking for each tested food.  There is some concern, firstly that the standards used are different and secondly two hours after a meal is too short.  Food is known to stay in the stomach for over 4 hours, so longer term blood glucose monitoring might be better.

The glycemic index was developed at the University of Sydney (Australia) originally to aid people with diabetes control their blood sugar levels.  Low GI diets are useful for people with diabetes as it allows them to regulate their blood sugar levels and this in turn helps with insulin levels and may reduce insulin resistance for people with Type II diabetes.

So the more I read, the less likely it seemed that sourdough bread could have a lower glycemic index than white bread, which by the way, in some measurements of GI is set as the reference with a GI of 100 and in others, where glucose is the reference, white bread has a GI of 70.  Yes, not even the measurements of GI are standardized.

Interestingly it seems that the reason the high protein/low glycemic index diets work is that protein fills you up and after eating a meal that is high in protein you are more satisfied.


Thomas Meinert Larsen, et al, Diets with High or Low Protein Content and Glycemic Index for Weight-Loss Maintenance N Engl J Med 2010; 363:2102-2113 doi:10.1056/NEJMoa1007137


Health Care Reform ’09

Last Friday, I went to hear Dr Howard Dean talk about health care reform.  This is a good article about the meeting.   Since that meeting President Obama gave this speech and Dr Dean announced publication of his book on health care reform.  Coming from the UK, where there is universal health care, improving coverage in America is very important to me.

As some one who grew up with what has been variously (by Americans) called single-payer health care or socialized medicine, I do have a hard time understanding why there is not universal coverage in America. Continue reading


Last year sometime, Molecule of a Day posted on Limonene, which I was interested to read because it is an important flavoring in citrus and considered to be an off-flavor product in the storage of ascorbic acid (vitamin C).

The last paragraph asks:

Green or not, limonene isn’t totally safe. You can actually get sensitized to it – essentially developing an allergy – and then you’re in the unpleasant position of being allergic to citrus peels. Careful lab technique and a certain amount of luck have allowed me to avoid sensitization to any lab chemicals. And that’s a great thing – everyone I’ve talked to who was appreciably sensitized to a chemical said it seemed to turn up EVERYWHERE after that.

Now, I have been tested for allergies and have no response.  Those skin prick tests – Nada, rien, zilch, nothing.  But I still sneeze when peeling oranges or when using Citrasolv for cleaning. I have other sensitivities too – hyacinths were the first I noticed. The hyacinth  story goes:

Back when I was a teenager, Mum gave me a hyacinth for my room.  I got a bad cold.  Hyacinth died.  I got better.  I was sad because I had missed the hyacinth.  So Mum gave me another;  cold came back.  I can now smell hyacinths ~100 m away.

Feathers in pillows murder sleep.  How can a hotel run out of hypoallergenic pillows?

Honeysuckle flowers take away the enjoyment of being in the garden and they grow like weeds in my garden.

Tea Tree Oil:  Shampoo is a nightmare – it all seems to contain sodium lauryl sulfate which makes my head itch, and tea tree oil and/or citrus oils.  It took me a couple of months to realize that one of the reasons I was waking up in the night snuffly was because my shampoo had tree oil in it and this was getting on the pillows and from there up my nose.  In fact, I would rather have citrus shampoo than tea tree oil.  But why cannot shampoo makers produce a scent-free sodium lauryl sulfate -free shampoo.  Even kids’ shampoos are too highly scented for me.

Some of my sensitivities may have developed because my PhD research was with sulphites;  well known allergy and asthma triggers.  My advisor used to joke that when I drank wine, and sneezed, we could determine the sulphite concentration by the number of sneezes. Also, if I spilt any sulphite powder, I had to go outside and get a lungful of fresh air before being able to clear up the mess.

PS To all airline passengers sitting near to me,

I do not have a cold.  If you were not wearing so much scent I would be fine.  There is no need to complain, within my hearing, that you have caught some dreaded disease and people with colds should not be allowed to travel.  I was fine until I sat NEXT TO YOU 🙂

Luv LabCat

Self Diagnosing Food Allergies

Continuing discussion on food allergies, there is concern amongst dietitians in Australia that people are self-diagnosing themselves as having food allergies and intolerances. While avoiding a food items is not the issues, there is a problem:

The number of adults being diagnosed with food allergies has remained constant, but the number of people incorrectly self-diagnosing food allergies and intolerances has skyrocketed,’ Ms Graham said.

She said a problem with self-diagnosis was the risk of missing an underlying health problem.


Not mentioned in the article is that fact that if wheat or dairy are being excluded from the diet, the diet could missing essential nutrients and sufficient energy, especially for children.

The bottom line, as always, is if you think you may have an allergy visit your doctor and get tested.

Another Cold

Bleuh! 😥

I have another cold and I’m all achy. It was three weeks since my last one – I have had a lot of colds this winter and I thought I was going to get away with it. Until I had little sleep on Saturday night and the weather went cold on us.

Sniffle, snuffle.

Some good ideas for posts lined up. I just have to get my head unblocked and be able to think.

I am eating lots of soup and planning nice warm stews to eat for the next few days 🙂

Food Allergies

Professor Richard E. Goodman, from Nebraska-Lincoln visited the local Institute of Food Technologists’ (IFT) section and gave a very interesting talk about food allergies. He is an active member of FARRP (Food Allergy Resource and Research Group), which is a resource for the food industry to test for and research known and potential allergens.

In this post, I tried to summarize the bits I remember but as I did not take notes, I found this information on the web. Thus, if anything is wrong, it is my fault, not Dr Goodman’s.

Food allergy is an adverse clinical reaction to food due to any type of abnormal immune response to food protein.

There are two mechanisms by which a food allergy can trigger the immune system. The first is IgE-mediated:


IgE-mediated food allergies are mostly immediate reactions, occurring within in minutes to hours of ingestions. The IgE response is the cause of anaphylactic shock, which is the cause of death after eating peanuts and bee stings. In this case, the allergic response is so extreme that it causes the air passages to swell; blood pressure drops leading to the inability to breathe and eventually, if not treated, it is fatal.

The second mechanism, which is mentioned by Dr Goodman and on the Act Against Allergy website, is Non-IgE mediated and involves the interaction of T-cells with the allergen and the part of the body where it is located.

Non-IgE mediated food allergies are usually delayed, taking 24 -48 h for a reaction.

Key symptoms of food allergies include hives, hoarse voice and asthma. In a severe reaction, there may be low blood pressure and blocked airways. Other symptoms that may occur include abdominal pain, angioedema (swelling, especially of the eyelids, face, lips, and tongue), diarrhea, difficulty swallowing, light-headedness or fainting, nasal congestion, nausea, and oral allergy syndrome (OAS). Symptoms of OAS are:

  • Itchy lips, tongue, and throat
  • Swollen lips (sometimes)

This last interested me. I have already discussed the problems I have when drink alcoholic beverages, especially beer, but I also have OAS in response to fennel and ginger*.

Common food allergens seem to vary depending on where you live. In the US, since January 2006

…the Food and Drug Administration (FDA) is requiring food labels to clearly state if food products contain any ingredients that contain protein derived from the eight major allergenic foods. As a result of the Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA), manufacturers are required to identify in plain English the presence of ingredients that contain protein derived from milk**, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, or soybeans in the list of ingredients or to say “contains” followed by name of the source of the food allergen after or adjacent to the list of ingredients.


[highlights mine]

Peanuts, treenuts and shellfish are the most common foods to trigger anaphylactic shock.
In Europe, the EU directive since November 2005 states that:

The 13 main food allergens must be listed: gluten-containing cereals, shellfish, fish, egg, peanut, soy, milk, tree nuts, celery, mustard, sesame seed, lupine and mollusks. Products derived from these allergens must be named without exception if used as an ingredient. In addition, sulfite must be listed if more than 10mg/kg is used.


Currently, the only way to prevent an allergic response to a food item is avoidance. Ephedrine can be used, via an EpiPen to stop an anaphylaxis response, but will not prevent the reaction occurring again.

More food allergy links:


FamilyDoc: Just the Facts



There is also a consumer advocacy and support group: The Food Allergy and Anaphylaxis Network (FAAN).


*I have another response to ginger in that it irritates my urethra (the passage from the bladder out) and so when I eat or drink anything gingery (ginger beer anyone), I have to remember to drink lots of water to reduce this irritation. I used to get, I thought, a lot of cystitis or infections in my urethra. Finally, I noticed that “infections” were linked to the day after when I went out for a curry, which was fairly frequent as a graduate student. Sigh. I probably should be grateful that curryhouses are not so common here in the US.

**Fortunately all the websites I found differentiate between food intolerance and food allergy. A food intolerance is when you cannot digest something properly, such as lactose. This means that the ingredient remains intact until the colonic microflora get hold of it. Then the gut bugs have a party. Seriously. A serious party.

Eating Broccoli Protects Your Heart

A recent study published online by the Journal of Agriculture and Food Chemistry reports on the role of broccoli as a cardioprotector. Broccoli contains high concentrations of selenium (65 nanograms/g broccoli) and glucosinolates, especially isothicyanate sulforaphane (23.6 micrograms/g broccoli). Both selenium and sulforaphane are shown to protect the heart and the cardiovascular system. Sulforaphane induces the redox regulator protein, thioredoxin, which has a cardioprotective role by reducing oxidative stress.

A clinical study reported that eating fresh broccoli sprouts for a week lowered serum low density lipoprotein levels (LDL is the so-called “bad” cholesterol) and a prospective study in Iowa showed a strong association between broccoli consumption and a lowering of the risk of coronary heart disease.

In the study reported in JAFC, rats were either feed, on top of regular rat chow, a broccoli slurry or water for a month before slaughter. At which time the hearts were isolated, stabilized and then subjected to 30 minutes of total ischemia followed by reperfusion*. Heart function was assessed 10, 30, 60, 90 and 120 mins after ischemia finished.

Hearts from rats fed on broccoli slurry showed faster recovery in left ventricular function and aortic flow. Heart rate was not affected by treatment. In addition, hearts from broccoli-fed rats had a smaller myocardial infarct size and the number of cardiomyocytes which under went cell death (apotosis) was reduced.

Hearts from broccoli-fed rats showed a similar response to ischemia as hearts in which thioredoxin had been upregulated. Broccoli possibly limits heart damage by inducing the production of thioredoxin and related proteins. These proteins play important roles in maintaining the inner cell redox potential. Selenium is required as part of the enzymes glutathione peroxidase and thioredoxin reductase, and sulforaphane up-regulates thioredoxin reductase stimulating thioredoxin production and reducing oxidative damage in the cell.


Mukherjee, S.; Gangopadhyay, H.; Das, D. K. Broccoli: A Unique Vegetable That Protects Mammalian Hearts through the Redox Cycling of the Thioredoxin Superfamily. J. Agric. Food Chem. 2007. (online)


From what I scan-read in Wikipedia, ischemia occurs by preventing blood flow to the heart and reperfusion is when blood is allowed back. Reperfusion can cause injury because the sudden influx of oxygen and blood can cause oxidative damage and inflammation.