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Glycemic Index

What is glycemic index?

Glycemic index or GI is the measurement of the effect of carbohydrates on blood sugar levels in the body. Carbohydrates are either absorbed rapidly or slowly making the quality different depending on the food consumed. It is important for patients with diabetes to understand how the glycemic index affects blood sugar levels.

Certain carbohydrates are broken down quickly with digestion; releasing glucose into the blood stream rapidly. Foods with a low glycemic index are converted to sugar more slowly to provide needed energy for individuals with diabetes that is sustained. Food with a high glycemic index can be used if blood sugar levels fall too low but should be otherwise avoided in high quantities to prevent wide fluctuations in blood sugar levels that can complicate the management of diabetes.

The glycemic index uses a scale of 0 to 100. High GI foods cause the greatest elevations in blood sugar levels while low glycemic index foods provide blood sugar level stability. When blood sugar levels remain consistent the body performs optimally – information that is especially important for managing diabetes.

Significance and Importance of Glycemic Index

Including low GI foods in the diet helps control blood sugar and energy levels in the body and is a focus of diabetes and blood glucose management.

If blood sugar levels are very high, the pancreas produce more insulin. The glycemic index takes into account the quality of food as well as the quantity. For non diabetics quick energy might be needed after exercise, but for individuals with diabetes, rapid increases in blood sugar levels are undesirable unless low blood sugar symptoms of fatigue or lethargy are present or glucometer testing reveals hypoglycemia.

The prime objective of GI index is to regulate insulin related problems and minimize the consumption of foods that increase the sugar level in blood.

Low GI carbohydrate diet;

  • Helps in diabetes management
  • Reduces threat of heart disease
  • Enhances the body’s response to insulin
  • Helps in maintaining the body weight
  • Keeps the blood cholesterol level in check
  • Keeps you fuller in betwixt meals
  • Refills the carbohydrate supplies following any physical activity
  • Helps manage PCOS (polycystic ovarian syndrome) symptoms
  • Increases body’s endurance

Glycemic index of foods – The GI symbol

Almost all the foods can be classified as having low, medium and high glycemic index. The range exists as

Low GI Foods – having GI 55 or less

Medium GI Foods – having GI from 56-69

High GI Foods – having GI greater than 70


Low GI foods include primarily vegetables and fruits, with the exception of potatoes and watermelon. Legumes, bread (whole grain), dairy products like low fat milk and curd are particularly low in carbohydrates. Foods such as table sugar, sweet potato, basmati rice and wheat products bear medium GI. Mostly white rice, white bread, watermelon, corn flakes and straight glucose are rich in carbohydrates and are considered high GI foods.

Low Glycemic Index Foods – What food to eat?

Foods that are high in carbohydrate content might fall in low or intermediate GI scale. The following are foods with a low glycemic index:

  • Salads and vegetables like spinach, cabbage, broccoli, carrots, lettuce
  • Apples, grapefruit, citrus fruits like oranges except watermelon
  • Basmati or Doongara rice, lentils
  • Baked sweet potato
  • White capellini pasta, soba noodles & spaghetti
  • Wholegrain breads, sour dough
  • Cereals like barley, oats and bran ,legumes, natural muesli, porridge
  • Peanuts, bean sprouts
  • Low fat yogurt & milk
  • Salmon sushi

High Glycemic Index Foods – to be consumed occasionally in moderation

Certain high GI food can be taken in moderation to maintain a healthy blood sugar levels and include bananas, potato chips, honey, chocolate bars, watermelon, brown rice, ice cream, white rice, sugar, glucose, cheese, popcorn, and baked potato.

Two meals a day should include low glycemic index foods. The idea is that extremes should be avoided. Too much emphasis on low GI food for a diabetic can lead to Hypoglycemia, a condition of extremely low blood sugar.

For a non-diabetic, indulging in high GI foods after strenuous physical activity is recommended. After exercise the insulin tends to push the glucose into the muscles for repair of tissues. Thus the body has an increased requirement for carbohydrate rich food.

GI should not be the only criterion while selecting a particular food to consume. Emphasis should be on food that are rich in nutrients, proteins and have low levels of saturated fats.

Factors alternating Glycemic Index

Each person has different body chemistry and his or her response to the Glycemic Index may vary depending on insulin resistance and blood sugar levels. The GI is seen to be easily transformed by various other factors as well, like the type of food being consumed, its method of preparation, the storage medium, its readiness, the protein content and salts in the meals.

Certain key factors contributing to the alteration of Glycemic Index are;

Starch gelatinization: swollen or gelatinized starch is digested at a slower rate, in turn lowering the GI of the food containing it. Spaghetti and oatmeal contain such starch.

Amylose to Amylopectin ratio: amylose containing food tends to absorb less water thus gets digested slowly and has low GI. Legumes, lentils & basmati rice have high amylose content.

Fiber coating: beans and seeds generally have a fibrous covering around them; this restricts the penetration of digestive enzyme and slows the digestion of the starch within. Thus rendering a low GI to such foods

Acid content: citrus stuffs like lemon juice, vinegar, oranges have citric acid which tends to lower the rate of digestion. Foods like pickled vegetables, salads with lime juice are thus low GI foods.

Particle size: Larger sized food grains do not allow the enzymes to access them for digestion very rapidly making them low in GI.

Glycemic Load

The Amount and Type of carbs consumed alters the glycemic response of the body, this is called Glycemic Load. It is measured as

GL = GI/100 * NET CARBS

Net Carbs indicate the total carbohydrates consumed by you excluding any nutritive fiber. So by restricting your carbohydrate intake and indulging in low GI food one can easily keep a tab on their Glycemic Response.

Glycemic Index Food Chart

Every food item have a GI index as mentioned earlier which ranges from low, medium to high. It is necessary to know the GI of certain common food items consumed on a regular basis. This helps you to keep a check on the fact that what food should be consumed in what quantity on a daily basis to maintain healthy glucose level.

Glycemic Index food list

a) Glycemic index of foods in pdf format – uwex.edu , glycemic load index

b) Glycemic index database – glycemicindex.com

c) Glycemic index Calculator – shapefit.com

Using the glycemic index is just one tool to help with diabetes management. A disadvantage is that food impact on blood sugar levels varies greatly depending on time of day, blood sugar level, cooking time, ripeness of food, fat content and amount of fiber in the foods.

An example of when using the glycemic index would be useful is for diabetics who experience sudden elevations in blood sugar after eating breakfast – choosing a low glycemic index cereal would be beneficial. During exercise a higher glycemic food might be needed if blood sugar levels tend to drift downward.

It takes a combination of knowing your body, physician guidance, nutritional counseling from a professional, and consistency in daily activities that should include exercise to obtain the right combination of foods for managing diabetes and preventing emergencies and long term complications.

Resources:

The Glycemic Index

Mayo Clinic

GI Food List



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