# RKS: GI CONUNDRUM - GI - The New Jargon In Carbs

   

# RKS: GI CONUNDRUM

“GI - THE NEW JARGON IN CARBS”

RKS / 2026-2027 / Ser 9 / Blog 3

1st June 2026

THE GI IMPLICATIONS LAID THREADBARE

GI ASCERTAINING & UNDERSTANDING

Dear Reader,

Diabetes is a disease under the radar for the healthcare providers, dieticians and common man alike. So much has been the spread of its awareness, including the complications and so much has been professed about diabetes by self-created and projected experts that the unwitting lay population fall prey to even information viralled by unqualified Dieticians or even housewives! The latest craze is discussions on the Glycemic Index of various carbs contained in food items and the scare about the same has even put to shame the roar of lions and tigers. Healthy, non-diabetics and with no even any risk factor have become unnecessarily worrisome regarding the GI of the foods they consume! This is a longish mathematically-intense blog to fathom how GI of carbs should not concern the non-diabetics or those sans any risk factors of the disease. It could be challenging to fathom the calculated calculations but for those serious about their healthy living, food focusing, desirous to enjoy culinary pleasures it would make a difference to one’s lifestyle after having imbibed the medical facts and not myths regarding GI of carbs and their consumption preferences.

CARBS

ABSORPTION OF CARBS

Carbohydrates (carbs) account for approximately 60-70% of total caloric intake, driven by high consumption of rice, rotis, and other cereals in India. The National Institute of Nutrition (NIN) and Indian Council of Medical Research (ICMR) data indicate that the average Indian diet contains about 289 to 368 gms of carbs per day with roughly 95-150 gms being consumed per meal. 

90% of the 95,000-1,50,000 mg of carbs consumed during each meal is absorbed, i.e., 85,500-1,35,000 mg is absorbed; the balance 10% is the indigestible fiber component.

ABSORPTION BASICS

The gastrointestinal (GI) tract, as it is medically referred, comprises the stomach and intestine (both small and large). The small intestine has 3 parts:

1. Duodenum
2. Jejunum
3. Ileum

For absorption of glucose it needs to be digested by enzymes which for carbs are generically referred to as amylases. These enzymes are typically present in the salivary, pancreatic and, to a certain extent, intestinal juices.

1. Salivary juice: 40-50% of total proteins in saliva are amylases enzymes. These typically breakdown complex starches into disaccharides like maltose, sucrose and lactose.
2. Pancreatic juice: Amylases constitute 50-60% of total protein content of pancreatic juice. These convert complex carbs as well as breaks down disaccharides into ready-for-absorption monosaccharides like glucose, galactose and fructose.
3. Intestinal juice: The intestinal juice is primarily secreted in duodenum, with lesser in quantity in jejunum and very little in ileum; it does not contain true amylases. Intestinal juice only creates ready-to-absorb carbs. The maltase, sucrase and lactase enzymes (of intestinal juice) remain in the wall of the small intestine such that when maltose, sucrose and lactose (respectively) attempts to enter the mucosa (lining of small intestine), these are converted promptly to glucose which is then absorbed. 

The saliva and pancreatic juice amylases commence breakdown of carbs which is complete by the time the chyme (digested food mixed with juices) reaches the jejunum. Zero carbs are absorbed from stomach and large intestine.

The absorbed carbs are 70-85% glucose, whilst fructose and galactose make up the remaining 15-30%. The absorption of glucose is 90-95% from the duodenum and jejunum whilst only 5-10% enters the blood via the ileum. 40-45% of fructose and ~10% of galactose is converted within the intestinal wall into glucose before these gain access into blood. Hence, glucose is the primary monosaccharide present in the blood and thus dictates the plasma sugar levels.

THE CARBS CALCULATION

• Glucose per se constitutes 70-85% of carbs consumed.
• 40-45% of fructose absorbed is converted to glucose before it enters the blood stream.
• Even ~10% of fructose that has entered the intestinal mucosa is also converted to glucose before its gains access to blood.
• Hence, 76-99% of carbs are absorbed in the form of glucose.
• Per meal consumption of carbs in 95-150 gms. 
• Thus the glucose quantity that enters the blood per meal is 72-149 gms (i.e. 72,000-1,49,000 mg).

GLYCEMIC INDEX

The GI is a rating system that measures how quickly carbs-containing foods raise blood sugar levels compared to pure glucose. 

GI GRADES

Foods are ranked on a scale of 0 to 100 with respect to their GI.

• Low GI: 55 or less (preferred)
• Medium GI: 56-69
• High GI: 70 or more (to be shunned)

The rate at which pancreas release insulin in blood post-meal is directly determined by the GI of food. Hence, it is indeed enlightening to note that in a normal individual, devoid of insulin resistance, the ability of pancreatic insulin to maintain normoglycemia is indeed intact and irrespective of the GI of carbs consumed!

ABSORPTION DYNAMICS

More than 80-90% of absorbed glucose is from jejunum (duodenum contributing mere 5-15%) since it’s mucosa has maximum capacity for carbs uptake.

• 0.5 gm glucose per min. per 30 cms of jejunum length is maximal absorbable.
• Jejunum length is 200 to 250 cms (6-8 feet) long.
• Per minute absorption of glucose from whole length of jejunum is 3.3 to 4.2 gms. 
• The transit time in jejunum is 3-6 hours i.e. 180-360 mins.
• Glucose absorption is completed within 1-4 hours which is well within the period during which chyme persists in the jejunum.
• The maximum glucose that can absorbed per meal is 600-1,500 gms from jejunum.
• As per NIN / ICMR only 95-150 gms are consumed per meal. 
• Hence, irrespective of glycemic index (GI), even carbs with least GI will fully and completely enter the blood within <4 hours!

INSULIN

BASICS

Insulin is a hormone secreted by pancreas in response to entry of glucose in blood. Blood fructose is a weak stimulator of pancreatic insulin secretion compared to glucose. Galactose does not influence the "glucose-stimulated insulin secretion" (GSIS).  

Insulin secretion from pancreas over a 24-hour period operates in a distinct pattern designed to maintain blood glucose homeostasis, characterized by a continuous low-level basal release and high-amplitude bolus spikes following meals. This 24-hour cycle is highly pulsatile, with roughly 10-15 distinct pulses occurring throughout the day.

Pulsatile release of insulin is not exclusively related to consumption of carbs. The ongoing in-between meals release of insulin is important to stimulate the insulin receptors after they have rested during the “off” (meals) periods thus ensuring they remain active.

OVERNIGHT / IN-BETWEEN MEALS INSULIN

The pancreas releases a low, steady baseline level of insulin [roughly 0.25-1.5 units (IU) per hour] during the fasting spells (in-between meals period). This accounts for approximately 50% of the total daily insulin output. The insulin released during fasting spells is for regulating blood glucose concentrations that is maintained via either the breakdown of stored glycogen (glycogenolysis) or conversion of triglycerides / amino acids into glucose (gluconeogenesis) by liver for the post-meal periods.

The fasting insulin blood levels are 3-15 mIU/L; the levels typically stay below 25 mIU/L in-between meals. These low levels act mainly to limit liver glucose output rather than stimulate high peripheral transport of the blood glucose into tissues. Basal insulin secretion ensures that glucose production by liver does not raise the blood glucose excessively (hyperglycemia) during the fasting phases.

POST-MEALS INSULIN

The intent is to ensure all the meal-derived glucose in blood is into cells and tissues. There are 2 types of tissues:

• Insulin-Dependent Tissues: Muscles (70-80% of glucose) and fat cells (0-10% of glucose) require insulin for glucose to enter.
• Insulin-Independent Tissues: 20-30% of blood glucose enters organs like the brain, nerves and liver but do not require insulin for its uptake.

When the plasma glucose exceeds 140-180 mg/dL as following a meal, an insulin spike occurs so as to reverse these concentrations and restore blood sugar levels to fasting values within 2 hours. It is normal to have one insulin spike per meal.

A GI of 30 causes a single, gradual, and low-amplitude insulin rise resulting in pancreatic liberation of 0.3 IU/min. of insulin. Conversely, a GI of 70 causes a sharp, high-amplitude insulin spike with insulin secretion of 0.6 IU/min. While both scenarios typically produce only 1 main insulin peak per meal, they result in very different physiological profile. Not only is the amount of insulin produced is more with food having high GI carbs, even the total insulin load is greater in comparison to when carbs consumed have low GI.

Post-meal, the insulin peaks in 45-60 mins. following the initial entry of glucose in blood.

• Fasting: <25 mIU/L
• 30 mins post-meal: 30-230 mIU/L
• 1 hour post-meal: 18-276 mIU/L
• 2 hours post-meal: 16-166 mIU/L

The food-derived glucose which has entered the blood will be thus efficiently disposed of by means of adequate insulin production by pancreas within 2-3 hours. The clearance of glucose from blood is smooth and steady being independent of its concentration in plasma provided the levels are <199 mg/dL and circulating insulin is >25 mIU/mL.

INSULIN RESISTANCE

Insulin resistance is typically graded using the HOMA-IR (Homeostatic Model Assessment for Insulin Resistance) score, calculated from fasting blood glucose and fasting insulin levels.

1. Fasting Glucose: Optimal levels are typically <100 mg/dL.
2. Fasting Insulin: 

• Optimal levels are usually <8.5 mIU/mL, with metabolic experts often aiming for <5 IU/mL.
• Borderline / Early resistance: 8.5-10 mIU/mL
• Moderate / Significant resistance: >10-25 mIU/mL

HOM-IR score vs insulin sensitivity / resistance:

• Grade 0 - Optimal sensitivity: HOM-IR <1.0
• Grade 1 - Normal sensitivity: HOMR-IR 1.0-1.9
• Grade 2 – Early / Mild resistance: HOM-IR 2.0-2.9
• Grade 3 – Significant / Moderate resistance: HOM-IR 3.0-4.9
• Grade 4 – Substantial / Severe resistance: HOM-IR >5.0

Hence, in a normal individual (nondiabetic / non-prediabetic), the plasma insulin concentrations fasting always are below 8.5 mIU/mL. 1-2 hours post-meals the amount of insulin in blood can measure between 18-276 mIU/mL in a normal non-pre-/diabetic individual.

FATE OF DIETARY GLUCOSE vs GI VALUES OF CARBS 

It takes 10-15 mins. for the absorbed glucose from jejunum to enter into the blood. However, the minute glucose gains entry in blood, the pancreas releases proportionately extra insulin to handle the carbs load.

• The minute the pancreas detects the rise in blood glucose insulin secretion is enhanced.

• From the fasting insulin concentrations of <8.5 mIU/mL, the levels in a normal individual rise to 18-276 mIU/mL depending upon the quantum of glucose entering the blood after a meal consumption.

• GI 30: Glucose rate of entry in blood is 180-325 mg/min.* 

• Corresponding* plasma glucose rise: 3.6-6.5 mg/dL/min.

• Peaking of blood glucose: 60-120 mins.

• GI 70: Glucose rate of entry in blood is - 450-630 mg/min.**

• Corresponding** plasma glucose rise: 9.0-12.6 mg/dL/min.

• Peaking of blood glucose: 30-60 mins.

• The amount of insulin naturally secreted is directly proportional to the amount of glucose in blood. 

• GI 30 - Peak insulin response: 60-90 mins.; insulin produced by pancreas: 0.3 IU/min.

• GI 70 - Peak insulin response: 30-60 mins.; insulin produced by pancreas: 0.6 IU/min.

• Peaking of insulin response by pancreas parallels the peaking time of blood glucose rise. Also the quantum of insulin secreted rises parallel to the rise in GI of consumed carbs.

Irrespective of GI of the consumed carbs, the body can effectively maintain normoglycemia albeit in an healthy individual.

INSULIN & CARBS DISPOSAL

THE INSULIN EQUATION

• Over a 3-hour period post meal 12 IU (10-15 IU) of insulin is secreted. 
• Total insulin secreted from pancreas in 24 hours from the pancreas is 40-50 IU including the surges during the 3 meals.
• 50% insulin i.e. 20-25 IU is secreted during the 3 post-meal periods spanning over 3 hours each.
• 50% of remaining insulin is secreted during the in-between meals spells which can be ~15 hours in a day.

• Insulin secretion is at a steady rate of 0.5-1.0 IU/hour in healthy humans in basal state. This rate surges to 0.3-0.6 IU/min. post-meal to process carbs.

• Depending upon the GI, the pattern of insulin secretion by pancreas differs: 

• GI of carbs 30: Peaking of blood glucose: 60-90 min.; Peak insulin response: 60-90 mins.
• GI of carbs 70: Peaking of blood glucose: 30-60 min.; Peak insulin response: 30-60 mins.

• Rate of glucose entry:

• GI 30 of carbs: Rise in plasma glucose: 3.6-6.5 mg/dL/min; Entry of blood glucose in blood: 180-325 mg/min.
• GI 70 of carbs: Rise in plasma glucose: 9.0-12.6 mg/dL/min; Entry of blood glucose in blood: 450-630 mg/min. 

• Insulin secretion vs carbs intake: (factoring 1 IU of insulin can dispose of 10 gms of carbs)

• Entry of glucose in blood per meal: 72-149 gms
• Insulin needed: 7.2-14.9 IU
• Insulin secreted by pancreas during each meal: 10-15 IU

• Insulin secretion vs meal-consumed carbs’ GI: (insulin spike occurs when plasma glucose exceeds 140 mg/dL)

• GI 30 of carbs 
• Rate of entry of glucose in blood per meal: 180-325 mg/min.
• Plasma glucose rise: 3.6-6.5 mg/dL/min.
• Plasma glucose rises to >140 mg/dL (normal blood glucose is considered as <100 mg/dL): 6-11 mins.
• Insulin concentrations needed per minute for GI 30 carbs consumed: 0.018-0.033 IU
• Extra insulin surge for GI 30 carbs: 0.3 IU/min. and occurs within 6-11 mins. which is sufficient to tackle the normal intake per meal quantity of carbs having a GI of 30.
• GI 70 of carbs: 
• Rate of entry of glucose in blood per meal: 450-630 mg/min. 
• Plasma glucose rise: 9.0-12.6 mg/dL/min.
• Plasma glucose rises to >140 mg/dL (normal blood glucose is considered as <100 mg/dL): 3.0-4.5 mins.
• Insulin concentrations needed per minute: 0.045-0.063 IU 
• Extra insulin surge for GI 70 carbs: 0.6 IU/min attained in 3-4.5 mins. which is sufficient to tackle the normal intake per meal quantity of carbs having a GI of 70.

Post-meal, irrespective of the GI of carbs consumed, the pancreas very capably dispose off the slow or quick rise of blood glucose very efficiently by enhancing accordingly the surge in insulin liberation.

TOTAL INSULIN LOAD

Ordinarily the carbs with high GI can be detrimental not because of a high GI but because it depends on how much of these specific high GI carbs are consumed [determined as glycemic load (GL)]. 

GL = GI x carbs

    100   

50-70% action of insulin is facilitating glucose transport into tissues for its use as energy utilization. For this it is not the high GI values that determine glucose disposal but it is the GL. Even if carbs with higher GI indexes are consumed, it does not matter since even up to GI 90 carbs are definitely not going to increase blood glucose beyond 140 mg/dL since at this juncture there occurs a proportionate parallel insulin spike to ensure normoglycemia within 2-3 hours.

CONCLUSION 

One lives only by breathing air and eating besides merry-making. Food thus constitutes an important aspect of our being and one does toil and labor basically for ‘रोटी, कपड़ा और मकान’. The clothes and dwelling are dispensable but not the ‘रोटी’. For Indians, 60-75% of calories consumed are contributed by carbs! It is interesting to note which food items are assigned what GI values.

If one is normal and healthy and devoid of risk factors trust the pancreas to cope up efficiently and effectively with the carbs irrespective of its GI. Even for GI 90 carbs the insulin of an otherwise healthy individual knows how quick, how long and how well to tackle so the normoglycemia status is never disrupted

DR R K SANGHAVI

Prophesied Enabler

Experience & Expertise: Clinician & Healthcare Industry Adviser

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