Once again, I have recently talked to two friends who are modifying their diets in similar but poorly informed ways. They are both male, “overweight” (or maybe “obese”), and recently diagnosed with diabetes. They are quite proud of themselves for having lost a significant amount of weight, as they were instructed to do so by their physicians.
I asked them what they were told to do with their diets. Both answered that they were told to stop eating white foods (as in white bread, white pasta, etc.). It made me think - table sugar is white, but is brown sugar any better? (No!)
One of my friends mentioned that he has started steaming vegetables. He told me something I didn’t know – that you can buy plastic bags made for steaming vegetables in the microwave! I happen to know that this particular person is a big fan of Waffle House, so that might give you a little bit of a clue as to what his diet was like before he got the diabetes diagnosis. He also mentioned that he is a big fan of Hamburger Helper. He told me that after he got the instruction to stop eating white foods, he gathered up all the Hamburger Helper that went against the white food rule, and gave it away to a friend in need. Now, it is commendable to help a friend in need, for sure, but was it really necessary for him to get rid of those foods? In my professional opinion, it was not necessary at all.
So, why all the fuss about white bread, white pasta, white potatoes, etc.? Supposedly, it’s because they make your blood sugar go up more than their counterparts (whole wheat bread and pasta, and sweet potatoes, perhaps).
But how true is that? Actually, it’s more conventional wisdom than science, especially regarding wheat and rice.
The Facts About Glycemic Index
Glycemic Index is a measure of how much and how fast blood sugar rises in response to the carbohydrate in a food, compared to effect of carbohydrate from pure glucose on blood sugar.
There is an excellent scientific website about the glycemic index that has a comprehensive list of foods that have been tested to determine their glycemic index (www.glycemicindex.com). Pretty much everything you need to know about glycemic index is on that site, with a lot of useful info in the FAQ section. I want to share a few of the important points. (The site is run by Australian researchers, so the terminology and spelling used is a bit different from that used in the United States.)
From the website FAQ (the italics are mine, for relevance to my topic here):
Why do many high-fibre foods still have a high GI value?
Dietary fibre is not one chemical constituent like fat and protein. It is composed of many different sorts of molecules and can be divided into soluble and insoluble types. Soluble fibre is often viscous (thick and jelly-like) in solution and remains viscous even in the small intestine. For this reason it makes it harder for enzymes to move around and digest the food. Foods with more soluble fibre, like apples, oats, and legumes, therefore have low GI values.
Insoluble fibre, on the other hand, is not viscous and doesn’t slow digestion unless it’s acting like a fence to inhibit access by enzymes (eg. the bran around intact kernels). When insoluble fibre is finely milled, the enzymes have free reign, allowing rapid digestion. Wholemeal bread and white bread have similar GI values. Brown pasta and brown rice have similar values to their white counterparts.
Some vegetables like pumpkin and parsnips appear to have a high GI. Does this mean a person with diabetes should avoid eating them?
Definitely not, because, unlike potatoes and cereal products, these vegetables do not contain a lot of carbohydrate. So, despite their high GI, their glycemic load (GI x carb per serve divided by 100) is medium. These vegetables contain loads of micronutrients and can be consumed as part of a healthy balanced meal.
Why does pasta have a low GI?
Pasta has a low GI because of the physical entrapment of ungelatinised starch granules in a sponge-like network of protein (gluten) molecules in the pasta dough. Pasta is unique in this regard. As a result, pastas of any shape and size have a fairly low GI (30 to 60). Asian noodles such as hokkein, udon and rice vermicelli also have low to intermediate GI values.
Pasta should be cooked al dente (‘firm to the bite’). And this is the best way to eat pasta - it’s not meant to be soft. It should be slightly firm and offer some resistance when you are chewing it. Overcooking boosts the GI. Although most manufacturers specify a cooking time on the packet, don’t take their word for it. Start testing about 2-3 minutes before the indicated cooking time is up. But watch that glucose load. While al dente pasta is a low GI choice, eating too much will have a marked effect on your blood glucose. A cup of al dente pasta combined with plenty of mixed vegetables and herbs can turn into three cups of a pasta-based meal and fits easily into any adult’s daily diet.
Most breads and potatoes have a high GI. Does this mean I should never eat them?
Potatoes and bread, despite their high GI, can play a major role in a high carb/low fat diet, even if your goal is to reduce the overall GI. Only about half the carbohydrate needs to be exchanged from high to low GI to derive health benefits. Of course, some types of bread and potatoes have a lower GI and these should be preferred in order to lower the GI as much as possible.
The good news for potato lovers is that a potato salad made the day before, tossed with a vinaigrette dressing and kept in the fridge will have a much lower GI than potatoes served steaming hot from the pot. There are a couple of simple reasons for this. The cold storage increases the potatoes’ resistant starch content by more than a third and the acid in the vinaigrette whether you make it with lemon juice, lime juice or vinegar will slow stomach emptying.
What is the difference between glycemic index (GI) and glycemic load (GL)?
Your blood glucose rises and falls when you eat a meal containing carbs. How high it rises and how long it remains high depends on the quality of the carbs (the GI) and the quantity. Glycemic load or GL combines both the quality and quantity of carbohydrate in one ‘number’. It’s the best way to predict blood glucose values of different types and amounts of food. The formula is:
GL = (GI x the amount of carbohydrate) divided by 100.
Do I need to eat only low GI foods at every meal to see a benefit?
No you don’t, because the effect of a low GI food carries over to the next meal, reducing its glycemic impact. This applies to breakfast eaten after a low GI dinner the previous evening or to a lunch eaten after a low GI breakfast. This unexpected beneficial effect is called the “second meal effect”. But don’t take this too far, however. We recommend that you aim for at least one low GI food per meal.
While you will benefit from eating low GI carbs at each meal, this doesn’t have to be at the exclusion of all others. So enjoy baking your own bread or occasional treats. And if you combine high GI bakery products with protein foods and low GI carbs such as fruit or legumes, the overall GI value will be medium.
What about flour? If I make my own bread (or dumplings, pancakes, muffins etc) which flours, if any, are low GI? What about sprouted grain breads?
To date there are no GI ratings for refined flour whether it’s made from wheat, soy or other grains. This is because The GI rating of a food must be tested physiologically that is in real people. So far we haven’t had volunteers willing to tuck into 50 gram portions of flour on three occasions! What we do know, however, is that bakery products such as scones, cakes, biscuits, donuts and pastries made from highly refined flour whether it’s white or wholemeal are quickly digested and absorbed.
What should you do with your own baking? Try to increase the soluble fibre content by partially substituting flour with oat bran, rice bran or rolled oats and increase the bulkiness of the product with dried fruit, nuts, muesli, All-Bran or unprocessed bran. Don’t think of it as a challenge. It’s an opportunity for some creative cooking.
Low GI and Beyond
The same scientists who run the website have also written some books, one of which is entitled The Low GI Diet Revolution. This particular book is about how to lose weight using low GI foods, and I don’t necessarily advocate that as a goal, but the book does contain some important background information that is relevant to diabetes.
The following excerpts from the book help to explain why sugar is really not the villain it was once thought to be. Do keep in mind, thought, that sugar does add calories without adding nutrients, and fructose, which is a part of white sugar as well as high fructose corn syrup, does seem to have a tendency to be converted to fat rather than to glucose.
“Traditionally, the nature of carbohydrates was described by their chemical structure: simple or complex. Sugars were simple and starches were complex.”
Starches are actually made of a bunch of glucose molecules linked together in long chains, while sugars consist of either one or two sugar molecules. What makes one starch type differ from another is the nature of the chains of glucose molecules (specifically the branching of the chains).
“By virtue of their size, complex carbohydrates were assumed to be slowly digested and absorbed, causing only a small and gradual rise in blood glucose levels. Simple sugars, on the other hand, were assumed to be the villains—-digested and absorbed quickly, and producing a rapid rise in blood glucose. We now know that the whole chemical concept of ‘simple’ versus ‘complex’ carbohydrates tells us nothing about how they really behave in our bodies. “
“It may seem surprising today, but scientists did not study the actual blood glucose responses to common foods until the early 1980s. Since 1981, hundreds and hundreds of different foods have been tested as single foods and in mixed meals on both healthy people and those with diabetes.”
“This research has turned some widely held beliefs upside down. The first surprise was that the starch in such foods as white bread, potatoes, and many types of rice is digested and absorbed very quickly—- not slowly, as had always been assumed.
Second, scientists found that sugar in foods (such as fruit, chocolate, and ice cream) did not produce more rapid or prolonged rises in blood glucose, as had always been thought. The truth was that most of the sugars in foods, regardless of the source, actually produced quite moderate blood glucose responses—- lower than most starches.
So we can discard the old distinctions that were made between starchy foods and sugary foods, or simple versus complex carbohydrates. They have no relevance at all when it comes to blood glucose levels. Even an experienced scientist with a detailed knowledge of a food’s preparation and chemical composition finds it difficult to predict its GI value.”
(I included the quotes here because I wanted to be sure you read the information. I could not have worded it better than the original authors, so I quoted rather than trying to paraphrase.)
I hope this will give you some insight into how our bodies handle carbohydrates. I am not a big fan of oversimplifying nutrition. Maybe telling a person to stop eating white foods results in them making a lot of changes in their diet that are beneficial, but in reality, the white foods are not toxic, as some would have us believe.
Enriched refined grains do not have exactly the same nutrient profile as the whole version of the same grain, but they do have many nutrients added back to compensate for what gets depleted in the refining process. Trace minerals, however, are not added back. Some vitamins and minerals are actually absorbed better from refined grains than from whole grains. The first known zinc deficiencies actually occurred in a culture that used whole grains exclusively, didn’t leaven their bread, and didn’t have many animal foods in their diets.
Remember, nutrition is complex. It is true that many of us now eat a lot of foods that have been processed, but processing is not ALWAYS a negative thing. Originally, foods were processed in order to preserve them. Modern food processors do have many other motives than preservation, and modern consumers need to be savvy enough to decipher which aspects of processing are truly problematic, rather than assuming that all processed foods and all white foods are bad.
If you have any additional questions about Glycemic Index, be sure to check out the website I mentioned above or leave a comment below!
My interest in nutrition developed from the weight issues I had in my youth. My sister and I always tended to be heavier than other kids, and we were teased about it, so naturally I wanted to "fix" myself by dieting. That worked pretty well in my teenage years, but adulthood was much more challenging. I started out as a dietitian who advocated dieting, but due to my own experience with my weight and dieting, as well as my extensive study of the subject of weight management, I have become an advocate of Health at Every Size. The first fellow professional who influenced my "conversion" was Ellyn Satter, who is also a dietitian. I got my Bachelor's Degree in Dietetics in 1975, (LSU) followed by a Master's in 1981(Univ of TN), and a PhD in 1997 (Univ of TN). I have worked in longterm care, public health, and one hospital. For the last 8 years, I have been teaching at the college level. I am the proud mother of a 24 year old son, and have been single since my divorce in 1993. That is when I moved to Atlanta from Cookeville, Tennessee. I moved around a lot in my childhood due to my father's job, but my parents grew up in Texas, and that is where my roots are. I lived in Brazil for 3 years as a teenager, and one of my sisters still lives there.