Low-Glycemic Foods: Healthful or Hyped?

Imagine a country with two major cities – Alpha and Omega. Alpha had small bouts of precipitation every day throughout the year, while Omega had all of its precipitation in the first two months!

Which of those two cities had more precipitation damage?  What does this have to do with diabetes and the Metabolic Syndrome? Let’s see.

If you were tempted to say Omega had more flooding, you would be almost right.  If both cities had poor drainage systems and other conditions were equal, then Omega would be the one.  But if Omega had an excellent drainage and runoff system with above-ground tanks and underground cisterns designed to collect rain water, there probably would likely be little or no flooding at all!  But who said that the precipitation was rain?  It could have been snow, ice, or even hail!  That would change things quite bit!  So, to know the effect, we need to know what the precipitation was, how much precipitation actually fell, and the condition of the place in question.

Not All Good Carbs are Created Equal

When we eat, it is like an episode of precipitation, but the effect that it will have on the person’s blood glucose (sugar in the blood) depends not only on the amount of sugar-raising constituents but also on the characteristics of the sugar-raising constituents and the physiologic condition of the individual eating! In the past, the dogma was: “Don’t eat simple sugars, eat complex carbohydrates.”This early approach may have served its purpose to bring attention to what in fact the individual is ingesting, but it was based on the simple chemistry of the carbohydrate in the food and not on the ultimate effect of the food on the metabolism.  It sounded good, but it was just not accurate.

Any food item can be indeed quite complex being made up of a specific combination of nutrients: carbohydrates, proteins, fats, vitamins, minerals, and water, along with a variety of types of phytochemicals and fiber. These constituents can be in different proportions (40% or 55% carbs), physical states (solid, pureed, or liquid; hot, cold, or reheated, etc.).  These items constitute the “chemistry” of the food, the answer to the question “what” is the food.  All of these constituents play a role on the eventual effect on the resultant blood glucose and metabolism after ingestion, but the carbohydrates are the principal immediate actors in this drama.

How Much … Counts too

But then there is the actual amount of the food that is consumed, and particularly of the constituents that have the greatest immediate effects on the blood sugar.  All things being otherwise equal, the more of a particular food you eat, the greater is its effect on raising your blood sugar. The amount of carbs, fats, and proteins (and not just the percentages of each) has an effect on the blood sugar after ingestion of a food.  This answers the question “how much” of the blood glucose-modulating food elements are being consumed.  Additionally, the amount of fiber, the type of fiber, and the physical form of the carbohydrate all affect the body’s response to a meal.

You Are Unique!

Furthermore, we are all similar but distinctly different, so that identical amounts of a particular food fed to 10 people can have 10 different “degrees” of effect.  “Who” is consuming the food is then also important.  To complicate matters, we all change depending on external and internal conditions, so our exact response will vary slightly over time.  This addresses the characteristics of the food consumer.  The analogy is this: the form of the precipitation (rain, snow, or ice) is the “what”; the amount of precipitation over time is the “how much,” and the characteristics of the city is the “who.”

What is the Glycemic Index?

The glycemic index (GI) estimates the degree to which each gram of available carbohydrate (total carbohydrate minus fiber) in a food raises a person’s blood glucose level following consumption of the food, relative to the consumption of pure glucose (used as a reference) whose GI is 100.  Since we usually do not eat just pure carbs, the measure is developed from the amount of the food that provides 50 grams of available carbohydrate.  The meal that you eat has proteins, fats, and carbohydrates; but the GI depends almost exclusively upon the carb content.  It should be obvious that those foods with a higher percentage of carb content will have higher GI, and that larger servings of the same food will have the same GI since the GI reflects the effect per 50 grams of carb.

That said, there must be a way to account for the “how much” part of the story, and that is where the glycemic load (GL) comes in.  The GL factors in the amount of carbohydrate actually consumed by multiplying the glycemic index of the food in question by the available carbohydrate content of the serving.  The higher the GL, the greater the effect on the blood sugar after ingesting the food.  Foods with GL greater than 15 are not to be considered optimal for people with diabesity, prediabetes, or diabetes.

Low GI Food Consumption Helps Obesity

Eating a diet of low glycemic (GI) foods or low glycemic carbs promotes rapid weight loss, decrease of fasting glucose and insulin levels, reduction of circulating triglyceride levels, and improvement of blood pressure.¹ Low-glycemic index carbohydrates and fiber consumption can delay hunger and decrease subsequent energy intake compared with high-glycemic index foods.² Meta-analyses of long-term studies has also indicated low GI or GL diets reduces body fat mass in obese patients.³

Low Glycemic Foods, Metabolic Syndrome, & Diabetes

Studies also suggest that consumption of predominately of low glycemic foods improves the ability of the body to burn fats and waistline circumference.⁴ Low GI diets stabilize the blood glucose curve in individuals with metabolic syndrome.⁵ Additionally, low glycemic diets help to protect the beta cells inside the pancreas, improve the ability of cells to respond to insulin, improve the ability of the blood vessels to dilate, and decrease the risk for undesirable clotting.⁶ All of these effects are important to people who have obesity, metabolic syndrome, diabetes, or prediabetes because these conditions increase inflammation, decrease the ability of the blood vessels to open up, and lower the threshold for abnormal clotting. Choosing fruits that have low GI scores instead of high GI ratings lead to a lower risk for diabetes.⁷ Lower GI and higher dietary or cereal fiber provide additive risk reduction for incident T2D.⁸

You Can React Differently to Foods

Up to this point, these concepts have been describing the characteristics and amounts of the constituents of the food, but the food has to be consumed by a person; so now we turn our attention to that.  The GI and GL are derived by evaluating the food itself.  But since each person is unique, how one person responds may be quite different from another, and how you respond in a month may also be different. This can be referred to what I call a person’s “Personal Postprandial Response”.  For example, many people may have a moderate blood glucose rise after eating oatmeal, but there are a few who have quite a significant spike in their blood sugars after an identical oatmeal breakfast.  Ultimately, each person has to evaluate his/her own response to certain meals but can use with great advantage the tables of GI and GL already developed using individuals who do not have diabetes.

Not All Low Glycemic Foods are Created Equal

Lastly, some situations exist in which a food has a low glycemic value but causes the body to secrete large amounts of insulin.  The Food Insulin Index (FII) helps disclose this particular characteristic of some foods.  The foods in this category include dairy foods and many energy-dense “goodies” or “indulgence foods.”  Meats, poultry, eggs, and fish contain no carbohydrate, just protein and fat, and essentially have a GI value of zero, yet they still stimulate significant rises in blood insulin, putting stress on the insulin-producing beta cells or requiring the use of more insulin in persons who inject insulin.  How this peculiar situation affects the metabolism over time is uncertain.  The increased demand for insulin may contribute to beta-cell “exhaustion” (or reprogramming) and the development of type 2 diabetes.  We know already that diets rich in vegetables and fruits decrease the incidence of type 2 diabetes, so that’s where I am headed.  How about you?

The choice you make is yours to live with.  But perhaps what was said in Genesis may eventually be accepted by all: vegetables, legumes, fruits, nuts, and seeds—of these ye may, within reason, freely eat!

Glycemic Index of Foods

A low-GI will release glucose more slowly and steadily, which leads to more suitable postprandial (after meal) blood glucose readings.  A high-GI food causes a more rapid rise in blood glucose levels and is suitable for energy recovery after exercise or for a person experiencing hypoglycemia.

Low GI – 55 or less

Most non-starchy vegetables, most whole intact grains: rye, barley, oats, spelt, kamut, wheat, millet, long grain or converted rice; beans, lentils, soy, almonds, peanuts, walnuts, chickpeas; small seeds: chia, flax, sunflower, pumpkin, poppy, sesame; most temperate fruits: apples, pears, plums, peaches, strawberries

Medium GI – 56-69

Not intact whole wheat or enriched wheat, pita bread, basmati rice, unpeeled boiled potato, grape juice, raisins, prunes, pumpernickel bread, cranberry juice, regular ice cream, sucrose, bananas

High GI – 70 and above

White bread and bagels, corn flakes and other extruded breakfast cereals, pretzels, most white rice, white potatoes, parsnips, carrots, maltodextrins, glucose, and high-fructose corn syrup

 

1. Radulian G. Metabolic effects of low glycaemic index diets. Nutr J. Jan. 29. 2009. www.ncbi.nlm.nih.gov/pmc/articles/PMC2654909/[↩]
2. Roberts SB. Glycaemic index and satiety. Nutrition in Clinical Care. 2003. 6:20–26. pubmed.ncbi.nlm.nih.gov/12841427/[↩]
3. Schwingshackl L., Hoffmann G. Long-term effects of low glycemic index/load vs. high glycemic index/load diets on parameters of obesity and obesity-associated risks: A systematic review and meta-analysis. Nutr. Metab. Cardiovasc. Dis. 2013; 23:699–706.[↩]
4. Pereira E. Effect of glycemic index on obesity control. Arch. Endocrinol. Metab. vol.59 no.3. June 2015. doi.org/10.1590/2359-3997000000045[↩]
5. Aston LM. Glycaemic index and metabolic disease risk. Proceedings of the Nutrition Society. 2006; 65:125–134[↩]
6. Radulian G. Metabolic effects of low glycaemic index diets. Nutr J. Jan. 29. 2009. www.ncbi.nlm.nih.gov/pmc/articles/PMC2654909/[↩]
7. Jenkins D.J. The relation of low glycaemic index fruit consumption to glycaemic control and risk factors for coronary heart disease in type 2 diabetes. Diabetologia. 2011; 54:271–279.[↩]
8. Livesay G. Dietary Glycemic Index and Load and the Risk of Type 2 Diabetes: Assessment of Causal Relations. Nutrients. 2019 Jun; 11(6): 1436. www.ncbi.nlm.nih.gov/pmc/articles/PMC6628270/[↩]