As primary eye care providers, we focus time and energy on how to treat the ocular complications associated with diabetes. However, we can do a lot within our scope of practice to prevent type 2 diabetes from ever developing. We need to concentrate on lifestyle modification, including proper dietary and exercise strategies. Here are some tips on how to address some of these with your patients.
The Glycemic Index
Glycemic Index (GI) describes how carbohydrate-containing food affects
blood glucose levels. When we eat carbohydrates, our body breaks them
down to produce glucose. For
glucose to move from the blood into the body’s cells, it needs insulin,
which, along with glucagon, plays a key role in determining whether the
body burns fat or carbohydrates for energy. The pancreas produces both
insulin and glucagon, which is stimulated through protein intake.
Whenever glucose is present in the blood, insulin is stimulated;
whenever protein is present, glucagon is stimulated. If the insulin is
insufficient, however, glucose levels rise. A high level of insulin
forces the body to burn carbohydrates rather than fat, which allows fat
to accumulate in the body. Therefore, if we control the rate of
glucose the body absorbs, we also control the amount of insulin
secreted. This is where the GI comes into play. The
GI ranks carbohydrates on a scale from 0 to 100 according to the
propensity for each to raise blood sugar levels after eating. (Go to
www.glycemicindex.com for the index and database.) Foods and drinks
with a high GI, such as fruit juices, sugary sweets, etc, are rapidly
digested and absorbed by the body. They result in an excess of insulin
in the blood stream. Controlling the glucose levels of these foods and
drinks allows for control over food-driven insulin stimulation and
reactive hypoglycemia. Low-GI
foods, by virtue of their slow digestion and absorption, produce a more
gradual rise in blood sugar and insulin levels, allowing the body to
utilize the glucose formed from the breakdown of complex carbohydrates
instead of storing it in a fat cell as glycogen. When excessive amounts
of fat are stored, they enlarge the fat cells in adipose tissue and
increase the risk of chronic disease, such as cancer or diabetes.17 As
a result, low-GI foods have proven benefits for health. While
the GI is an important concept, there is also the glycemic load (GL), a
scale for carbohydrate content in food portions based on their GI and
the portion size. The usefulness of GL is based on the idea that a
high-GI food consumed in small quantities would have the same effect on
blood sugar as larger quantities of a low-GI food on blood sugar. For
example, white rice is somewhat high-GI, so eating 50g of white rice at
one sitting would give a particular glucose curve in the blood, while
25g would give the same curve but half the height. Since the peak
height is probably the most important parameter, multiplying the amount
of carbohydrates in a food serving by the glycemic index gives an idea
of how much effect an actual portion of food has on blood sugar level.
The Diabetic Diet?
There are many concepts of the “proper” diet for any weight control issue, including diabetes prevention. Depending on the severity and length of time the condition has existed, various amounts of proteins, fats, fiber and carbohydrates are recommended.
The Glycemic Index
The Glycemic Index (GI) describes how carbohydrate-containing food affects blood glucose levels. When we eat carbohydrates, our body breaks them down to produce glucose.
For glucose to move from the blood into the body’s cells, it needs insulin, which, along with glucagon, plays a key role in determining whether the body burns fat or carbohydrates for energy. The pancreas produces both insulin and glucagon, which is stimulated through protein intake. Whenever glucose is present in the blood, insulin is stimulated; whenever protein is present, glucagon is stimulated. If the insulin is insufficient, however, glucose levels rise. A high level of insulin forces the body to burn carbohydrates rather than fat, which allows fat to accumulate in the body. Therefore, if we control the rate of glucose the body absorbs, we also control the amount of insulin secreted. This is where the GI comes into play.
The GI ranks carbohydrates on a scale from 0 to 100 according to the propensity for each to raise blood sugar levels after eating. (Go to www.glycemicindex.com for the index and database.) Foods and drinks with a high GI, such as fruit juices, sugary sweets, etc, are rapidly digested and absorbed by the body. They result in an excess of insulin in the blood stream. Controlling the glucose levels of these foods and drinks allows for control over food-driven insulin stimulation and reactive hypoglycemia.
Low-GI foods, by virtue of their slow digestion and absorption, produce a more gradual rise in blood sugar and insulin levels, allowing the body to utilize the glucose formed from the breakdown of complex carbohydrates instead of storing it in a fat cell as glycogen. When excessive amounts of fat are stored, they enlarge the fat cells in adipose tissue and increase the risk of chronic disease, such as cancer or diabetes.17 As a result, low-GI foods have proven benefits for health.
While the GI is an important concept, there is also the glycemic load (GL), a scale for carbohydrate content in food portions based on their GI and the portion size. The usefulness of GL is based on the idea that a high-GI food consumed in small quantities would have the same effect on blood sugar as larger quantities of a low-GI food on blood sugar. For example, white rice is somewhat high-GI, so eating 50g of white rice at one sitting would give a particular glucose curve in the blood, while 25g would give the same curve but half the height. Since the peak height is probably the most important parameter, multiplying the amount of carbohydrates in a food serving by the glycemic index gives an idea of how much effect an actual portion of food has on blood sugar level.
The American Diabetes Association recommends a diet consisting of:5
• Total fat intake that equals 25% to 35% of total calories.
• Saturated fat, less than 7% of total calories.
• Total cholesterol intake under 200mg/day (low-density lipoprotein < 100; high-density lipoprotein > 40).
• Carbohydrate intake equal to about 50% to 60% of total calories.
• Fiber between 20gm/day to 30gm/day.
But, many healthcare practitioners find this a poor diet due to the high carbohydrate allowance, since carbohydrate processing is one of the main concerns for a patient with diabetes. Glucose is the body’s primary energy source, fueling the activities of nearly every cell in the body. The availability and storage of blood glucose is tightly controlled by glucose homeostasis, which involves the hormone insulin. Insulin is produced by the beta cells of the pancreas in response to changes in blood sugar, and it works to maintain blood glucose levels within an optimal range—homeostasis. Overeating, physical inactivity and aging result in increased pro-inflammatory cytokine production.6 The over-production of pro-inflammatory cytokines may represent a triggering factor in the origin of heart, blood sugar and other metabolic concerns.7 Thus, reducing carbohydrates reduces the strain on the pancreas to produce more insulin.
Here are some of the other notable diets for patients who have diabetes. Each of these has different factors that may benefit patients with diabetes.
• “No Carb” Atkins diet. The “no carb” Atkins diet, which has been around since the 1960s, has gained worldwide attention as a way to eat a lot of food, not be hungry and still lose weight. The Atkins diet works on the theory that carbohydrates cause you to gain weight, and by eliminating or strictly limiting carbohydrates, it is possible to eat a lot of protein and fat while your weight decreases. When you do not consume carbohydrates, your body is forced to convert fat stores into carbohydrates, which is an inefficient process. So, your body uses its fat stores at a faster rate and you lose weight. This theory seems beneficial to dieters, especially for overweight diabetes patients who have trouble metabolizing carbohydrates due to insulin problems.
With the Atkins system, diabetes and pre-diabetes patients are encouraged to eat as few as 20g of carbohydrate a day for successful diabetes weight loss. There is no limitation on protein and fat (both saturated and unsaturated) consumption.
Using the “no carb” diet for diabetes has generated its share of criticism. First, this diet recommends eating greater amounts of animal protein and fat, and these foods cause people to lose a lot of water from their bodies. In turn, this puts extra strain on the kidneys, which are usually already weakened in people with diabetes.
Secondly, due to the heavy consumption of meat, the Atkins diet is thought to increase the chance for heart disease.
Finally, the Atkins diet can lead to dangerously low blood sugar levels (hypoglycemia). For a person with diabetes, extremely low blood sugar can lead to a coma. Most experts agree that using the Atkins diet for diabetes can be risky and should not be attempted without medical permission and supervision.8
• Vegetarian. While a traditional approach to diabetes focuses on limiting refined sugars and foods that release sugars, such a diet may contain an unhealthful amount of fat and protein. The vegetarian approach, on the other hand, focuses on limiting fat intake. The more fat there is in the diet, the harder it is for insulin to get glucose into the cells.
But, minimizing fat intake and reducing body fat help insulin to be more effective. Newer recommendations drastically reduce the suggested intake levels of meats, high-fat dairy products and oils. At the same time, they increase quantities of grains, legumes, fruits and vegetables. One study found that 21 of 23 patients on oral medications and 13 of 17 patients on insulin were able to get off of their medications after 26 days on a near-vegetarian diet and exercise program.9
According to the vegetarian model, eating soy foods can lower cholesterol, decrease blood glucose levels and improve glucose tolerance in people with diabetes.10 Researchers identified the molecular pathway that allows foods rich in soy bioactive compounds, isoflavones, to lower diabetes and heart disease risk.11 Researchers also found that the isoflavones daidzein and equol enhanced adipocyte differentiation, or the formation of fat cells, through activation of a key transcription regulator––the same receptor that mediates the insulin-sensitizing effects of anti-diabetes drugs. Thus, daidzein and equol seem to work in a similar manner as anti-diabetic drugs currently in the market. Soy isoflavones may exert anti-diabetic effects by targeting fat cell-specific factors and the downstream signaling molecules that are important for glucose uptake and thus insulin sensitivity.12
• The Paleo Diet. The Paleolithic, or Paleo, diet is based on evidence of what our species evolved to eat over millions of years. For almost all of our evolutionary history, humans and human ancestors survived on hunter-gatherer diets. This includes lean meats, seafood, vegetables, fruits and nuts, and it is lower in cereals and dairy products. It is also higher in unsaturated fatty acids, dietary cholesterol and several vitamins. It is lower in total energy, energy density, carbohydrate, dietary glycemic load (GL), glycemic index (GI), saturated fatty acids and calcium.
Studies have concluded that a Paleolithic diet improved glycemic control and several cardiovascular risk factors as compared to a diabetes diet. The Paleolithic diet produces lower A1c, triglycerides and diastolic blood pressure, as well as lower weight, body mass index (BMI), waist circumference and higher high-density lipoprotein (HDL) cholesterol.13
• Mediterranean Diet. Based on food patterns typical of Crete, much of the rest of Greece and southern Italy in the early 1960s, the Mediterranean diet, in addition to regular physical activity, emphasizes “abundant plant foods; fresh fruit as the typical daily dessert; olive oil as the principal source of fat; dairy products (principally cheese and yogurt); fish and poultry consumed in low to moderate amounts; zero to four eggs consumed weekly; red meat consumed in low amounts; and wine consumed in low to moderate amounts.”14 Total fat in this diet is 25% to 35% of calories, with saturated fat at 8% or less of calories.
The principal aspects of the Mediterranean diet include high rates of olive oil consumption, as well as that of legumes, unrefined cereals, fruits and vegetables, paired with moderate consumption of dairy products (mostly cheese and yogurt), moderate to high consumption of fish, low consumption of meat and meat products, and moderate wine consumption.
A new study from Italy shows that people with type 2 diabetes on a Mediterranean diet were better able to manage their disease without diabetes medications than those who ate a low-fat diet with no more than 30% of calories from fat (less than 10% coming from saturated fat choices). After four years, researchers found that 44% of people on the Mediterranean diet ended up requiring diabetes medications to control their blood sugars compared with 70% of those who followed the low-fat diet.15
• “Common Sense” Diet. Don’t forget, a simple, “common sense” diet can accomplish much for a diabetes patient. It focuses on both calorie counting and carb counting. The recommendation is to start out at 100g/day to 150g/day of carbohydrates. Reduce the carbohydrate intake by 10g/day for a week at a time. A target level of about 50g/day can allow the patient to adapt to the new levels sufficiently.
In addition, the type of carbohydrate is equally important. Complex carbohydrates that do not spike insulin levels and metabolize more slowly are preferred, as per the glycemic index concept.16
When considering nutrient supplements for diabetes, few recommendations are ever suggested because O.D.s are not comfortable doing so. Here are some nutrients that have proven beneficial for the diabetic patient.18-27
• Omega-3 essential fatty acids. Omega-3 fatty acid supplements have been shown to prevent cardiac arrhythmias and ameliorate clinical depression in type II diabetic patients. Several studies have demonstrated that docohexaenoic acid (DHA) and eicosapenaenoic acid (EPA) decrease amounts of plasma triglycerides, visceral fat (and concomitant production of inflammatory cytokines), free fatty acids, C-reactive protein, glucose and insulin, as well as reduce peripheral insulin resistance.18
• Xanthophyll carotenoids. Patients who demonstrate high levels of serum lutein/zeaxanthin and lycopene are 67% less likely to develop diabetic retinopathy than those with low levels.19
• Vitamin D. Vitamin D deficiency impairs insulin sensitivity and is associated with type I and II diabetes and metabolic syndrome, as well as increased risk of cancer.20
• Benfotiamine. Benfotiamine is a lipophilic analog of vitamin B1 that reduces activity in all four biochemical pathways implicated in microvascular diabetes complication.21
• Alpha-lipoic acid (ALA). ALA is a “super antioxidant” that preferentially distributes to mitochondria. It blocks glycosylation of protein, improves glucose transport into insulin dependent tissues and reduces both small and large blood vessel complications of diabetes in animal models.22
• Pycnogenol. This standardized extract of French maritime pine bark is composed of procyanidins and phenolic acids, which appear to have anti-inflammatory properties.23
• Taurine. This amino acid supports glial function within the retina. Higher doses may lower blood glucose in humans.24
• Chromium. Chromium potentiates the insulin receptors and consequently prevents insulin insensitivity.25
• Vanadium. This mineral has been proven effective in the enhancement of insulin receptor site function, in turn lowering the need for constant excessive insulin production. In the absence of excess insulin, the receptor sites work more efficiently. The end result is lowered blood sugar levels.26
• Herbal supplements. White mulberry is gaining popularity as a treatment for type 2 diabetes. This shrub has white or pinkish fruit, similar to that of a blackberry. But, it is the leaf of white mulberry that might be beneficial for diabetes. Its extract inhibits alpha-glucosidase enzymes in the gut, which prevents digestion of carbohydrates. This is similar to the mechanism of the prescription diabetes medications Precose (acarbose, Bayer Pharmaceuticals) and Glyset (miglitol, Pfizer). Evidence shows that taking 1g of white mulberry leaf powder t.i.d. for four weeks significantly reduces fasting blood glucose by about 27% in patients with type 2 diabetes. This is a promising holistic therapy, but more evidence is needed about long-term safety and effectiveness.27
Exercise plays an important role in diabetes management. Preventing diabetes is about lifestyle change; this includes smart dietary habits and regular physical activity. Too many individuals do not view diabetes as the serious disease that it is. On average, it shortens life by nearly 10 years and significantly reduces quality of life.28 Individuals with high-fat diets who consume far more calories per day than they need to avoid hunger and who don’t exercise at all do not seem to understand that their so-called “normal” lifestyle is slowly and literally killing them.
Muscular activity accounts for much of the body’s energy consumption. Muscles also store glucose in the form of glycogen, which can be rapidly converted to glucose when energy is required for sustained, powerful contractions. Muscle cells also contain globules of fat, which are used for energy during aerobic exercise. This is why it is important to continually use those muscles—to help burn off the accumulation of fat!
Here are some patient recommendations for lifestyle changes that result in more daily physical activity:
• Scheduling. Put aside a period of time every day to be used for walking and other forms of exercise. After meals, first thing in the morning, or during a mealtime (have a light lunch after your exercise session) are options; try to develop routines.
• Increasing daily activity as a lifestyle. Samples of increasing activity as part of one’s daily life include taking the stairs instead of an elevator or escalator, walking instead of driving whenever possible, parking further away from your destination—not to mention lifting weights, doing calisthenics (sit-ups, push-ups), or taking a walk as a break from remaining sedentary every few hours.
• Coaching. Exercising properly is a science. Visit a fitness facility and obtain professional fitness coaching. Get tested in various measures of fitness, learn how to lift weights properly, and receive an exercise “prescription.” We are motivated by numbers, so fitness tests give us the numbers for improving performance over time. Get a second test in six months to see if your fitness has improved.
• Live consistent to your values. Values are core beliefs about what you feel passionate about. What moves you? Remember what’s important in your life, and try to maintain a lifestyle consistent with your values. Health, family, faith, integrity and job performance are common values in our culture. Are you living a life consistent with your values? If not, the inconsistencies between your values and your unhealthy habits have pretty serious consequences. Do you find the disjunction between your values and bad habits acceptable? If not, make the effort to replace those unhealthy habits with positive, more desirable routines. There are people who love you and want to see you healthy and living a long, productive, and happy life.
Dr. Anshel is a 1975 graduate from the Illinois College of Optometry. He has lectured and written several books on eye health and computer vision and is president of the Optometric Nutrition Society.
Dr. Anshel thanks A. Paul Chous, O.D., Stephen Whiting, Ph.D., and Mark Anshel, Ph.D., for contributing to this article.
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