GI and GL are two tools among many that can help you compare and select foods for preventing and treating diabetes.
However, foods with a low GI or GL don’t automatically acquire a health halo.
While the GI and GL can help you choose foods that improve blood glucose control, these tools tell you nothing about the fiber, phytochemicals, antioxidants, pre- or probiotics, essential fatty acids, vitamins, and minerals provided.
Nor do they provide information about the harmful contaminants or the products of oxidation that may be present.
Foods that contain little, if any, carbohydrate, such as fried bacon, have a very low GI and a negligible GL. This doesn’t make it a healthy choice for people with diabetes. Although protein and fat have minimal impact on blood glucose levels in the short term, they have the potential to significantly increase insulin resistance and produce adverse effects on blood glucose control in the long term.
85 , 86
Likewise, the GI of potato chips is lower than baked potatoes, while candy bars, cupcakes, and ice cream also frequently fall within the low glycemic index range. In contrast, plenty of nutritious, higher carbohydrate whole foods, such as some fruits, starchy vegetables, and whole grains, have relatively high glycemic indexes (particularly watermelon) or glycemic loads (brown rice), but that does not make them off-limits.
Also, remember that the GI of sugar is determined by the amount of fructose in the mix. As the amount of fructose in a sugar source rises, its glycemic index falls. With most foods, a lower glycemic index is desirable, but when it comes to sugar, a lower GI (as we see with the listing of agave syrup in table 5.2 , page 79 ) means more fructose. So, with sugars, low GI is not a particularly favorable attribute.
While GI and GL have limitations, they are very useful when appropriately used. Among the best ways to use these tools is to compare similar foods or foods from the same category. Compare different intact grains, such as barley (GI = 28) and millet (GI = 71) or different types of nondairy milks, such soy milk (GI = 21) and rice milk (GI = 86).
Foods with a low GL have a relatively small impact on blood glucose, so these should be featured strongly in your diet. Fill your plate with legumes, nonstarchy vegetables, and fruits, along with smaller portions of nuts and seeds. Include moderate servings of high-carbohydrate foods, such as starchy vegetables and whole grains.
TABLE 5.7. GI and GL of Common Foods
KEY TO TABLE 5.7
Glycemic Index (GI)
Glycemic Load (GL)
Low (white) = 55 or less
Low (white) = 10 or less
Medium (light gray) = 56–69
Medium (light gray) = 11–19
High (dark gray) = 70 or more
High (dark gray) = 20 or more
Source
77 , 78
Kick Diabetes Essentials: The Diet and Lifestyle Guide
Chapter
Managing Protein and Fat
Like most people, Diane always thought that protein was the one macronutrient that could do no wrong.
She believed that protein from animal sources—meat, poultry, fish, and eggs—was best for people with diabetes because they were carbohydrate-free.
She had learned years ago that not only is the protein in plant foods minimal, but it’s also inferior.
So boiled eggs and yogurt became her breakfast staples, chicken and fish topped her salads, and beef and pork were the usual stars of the dinner show.
While she worried about eating too much fat when she was first diagnosed, her internet searches taught her that fat, even saturated fat, had been vindicated as a cause of heart disease, diabetes, and other chronic diseases.
The evidence was everywhere—on the covers of magazines, in newspapers, and on almost every website she visited.
It was a relief because fat made food taste better.
So when everything she thought she knew about protein and fat was turned on its head in her plant-based diabetes program, she was blown away.
She wondered how the media could have strayed so far from science.
THE POWER OF PROTEIN FROM PLANTS
M any popular diabetes diets are low in carbohydrates and high in meat.
Meat is emphasized because it is essentially carbohydrate-free.
But is being carbohydrate-free all it takes to make food diabetes-friendly?
The answer is an unequivocal no .
When you look at the evidence, meat doesn’t measure up to expectations.
Many studies have examined the link between meat intake and diabetes risk, and they consistently report higher rates of diabetes with higher meat intakes (see pages 53 – 54 ).
The strongest link is for processed meats and red meat.
Other studies have examined how different protein sources influence diabetes risk. Many of these studies have divided protein into animal versus plant protein. In 2016, a US study of over 200,000 participants reported that those eating the highest amounts of animal protein had a 13 percent increased risk of type 2 diabetes compared with those eating the least.
Those eating the most plant protein had a 9 percent risk reduction relative to those eating the least. Replacing just 5 percent of calories from animal protein with plant protein resulted in a 23 percent reduced risk of type 2 diabetes.
In the same year, an Australian study reported a 29 percent increased risk of type 2 diabetes with the highest versus lowest intakes of animal protein and a 40 percent risk reduction in women eating the most versus the least plant protein.
The researchers also reported on a meta-analysis of eleven studies with over 500,000 participants. Those consuming highest versus lowest intakes of meat had a 19 percent increased risk, while those eating the highest versus lowest intakes of plant protein had a 5 percent risk reduction.
A 2017 Finnish study examined the effect of protein sources in men who were followed for almost twenty years.
Replacing 1 percent of energy from animal protein with energy from plant protein was associated with an 18 percent decreased risk of type 2 diabetes. A 2014 Canadian study examined the risk associated with high-protein intakes. (Recall that keto weight-loss diets suggest 20 percent of calories from protein, and paleo diets suggest 30 percent of calories from protein—both relying mainly on animal protein.)
In participants ages fifty to sixty-five, those with intakes exceeding 20 percent had an increased risk of developing type 2 diabetes that was four times higher, while those over sixty-five had a risk that was ten times higher. However, in both cases the associated risk was eliminated or greatly reduced when the source of the protein was plants.
Why the discrepancy between animal and plant protein sources? Protein-rich plant foods are excellent sources of fiber, phytochemicals, antioxidants, and other protective compounds, whereas meats have little to none of these healthful components. In addition, animal protein sources, especially red and processed meats, are high in substances associated with inflammation and oxidative stress, such as saturated fat, heme iron, Neu5Gc, carnitine (which forms TMAO), and chemical contaminants (see table 6.1 , opposite page).
What this means in practical terms is that replacing even a small amount of meat with legumes will help to reduce diabetes risk, regardless of the fact that meat is carbohydrate-free and legumes are relatively rich in carbohydrates.
How is this best accomplished?
Instead of bacon and eggs for breakfast, try scrambled tofu or add some cooked or sprouted lentils to your breakfast bowl.
Rather than chicken noodle soup at lunch, opt for a split pea or bean soup.
At dinner, swap out meat for beans or tofu in family favorites, such as stews, chili, pasta dishes, or wraps.
Experiment with legume-, nut-, and seed-based veggie loaves and patties, or try some of the delicious ready-made options that are widely available in the marketplace.
Try more bean-based foods with multicultural flavors.
TABLE 6.1. Plant Protein versus Animal Protein
FOOD COMPONENT
PLANT PROTEIN SOURCES (LEGUMES, SEEDS, NUTS)
ANIMAL PROTEIN SOURCES (MEAT, PROCESSED MEATS)
PROTECTIVE
Fiber
high
none
Phytochemicals
high
none
Antioxidants
high
minimal
Plant sterols
high
none
Pre- or Probiotics
high
minimal
POTENTIALLY HARMFUL
Cholesterol
none
moderate
Solid fats (saturated fat)
low
high
Heme iron
none
high
Industrial pollutants
low
moderate/high
Neu5Gc
none
highest in red meat
Endotoxins
low
varies; highest in ground or processed products
Glycotoxins (advanced glycation end products)
low to moderate depending on cooking conditions
highest in processed meat; high in well-cooked meat
FAT FACTS AND FAIRY TALES
T he science is crystal clear: there is a broad spectrum of fat intake that can support and promote excellent health.
This is beautifully illustrated by the Blue Zones (see page 111 ), where the longest-living, healthiest populations reside.
In Okinawa, fat intake is only 6–11 percent of calories; in Ikaria, Greece, it is about 50 percent.
Intake in other Blue Zones range from 20–30 percent of calories from fat.
The most salient lesson these populations teach is that the sources of macronutrients (fat, carbohydrate, and protein) matter more than the relative percentages of those macronutrients.
There is good evidence supporting the use of very low-fat plant-based diets as a therapeutic treatment for diabetes. For example, in studies by the Physicians Committee for Responsible Medicine, good results were achieved using plant-based diets that provided only about 10 percent of calories from fat.
5 , 6
On the other hand, higher-fat plant-based diets have also been shown to be effective. For example, a Finnish study reported favorable findings using diets that provided approximately 25 percent of calories from fat.
An American study that did not specify percentages of calories from macronutrients achieved remarkable success using a plant-based diet that included moderate amounts of higher-fat plant foods, such as nuts, seeds, and avocados.
There may be advantages to including some higher-fat plant foods within the framework of a whole-foods diet. In establishing appropriate guidelines for people who are fighting cardiometabolic diseases, such as diabetes and heart disease, many factors need to be considered. Sufficient fat is necessary for the body to properly accomplish these functions:
■ provide structure and function for cell membranes and the brain
■ make hormones and bile acids
■ maximize absorption of critical fat-soluble nutrients and phytochemicals
■ maintain skin and hair
■ regulate gene expression
■ ensure a sufficient supply of essential fatty acids
There is a fine balance between keeping fats low enough to reduce lipotoxicity and exposure to potentially harmful fats while keeping them high enough to not compromise optimal body functioning.
One of the advantages of including some higher-fat plant foods, such as nuts, seeds, and avocados, is that these foods have a very low glycemic index, so they’ll help to lower the glycemic load of the total diet.
On the other hand, higher-fat foods are more calorically dense.
When you eat less fat, you can eat more food.
For example, you get 120 calories from 1 tablespoon (15 ml) of oil or 14 cups (3.5 L) of greens; you get 400 calories from ½ cup (125 ml) of nuts or four bananas.
Most major health and diabetes organizations suggest a range for recommended fat intake from a low of 15–20 percent of calories to a high of 30–35 percent of calories from fat.