# RKS: GI vs GL FACE-OFF

GI - THE FAD, BUT GL - A DICTATING HEALTH REALITY

RKS / 2026-2027 / Ser 9 / Blog 4

1st July 2026

THE GI & GL COMBAT

EDUCATING CONSUMER ON IMPORTANCE OF GL

Dear Reader,
Diabetes is a disease under the radar for the healthcare providers, Dieticians and common man alike. So much has been the spread about its awareness, including the complications and so much has been professed about diabetes by self-created and projected experts that the unwitting lay population has fallen easy prey to even information viralled by unqualified Nutritionists or even housewives! The latest craze is discussions on the Glycemic Index (GI) of various carbohydrates (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 zero risk factor have become unnecessarily worrisome regarding the GI of the foods they consume! It is not essential to dwell on what we eat and get alarmed at graphs depicted by the CGM (Continuous Glucose Monitoring) patches immediately after a particular carb-containing food item is consumed. The quantity of carbs intake is a bigger determinant of the pancreatic response and is expressed as Glycemic Load (GL). The consumer should accordingly be aware not beware of his / her carb-containing food items preferences.

CARBS

Carbs account for approximately 60-70% of total calorific 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.

ABSORPTION BASICS

The gastrointestinal tract, as it is medically referred to, comprises the stomach and intestines (both small and large).

The small intestine has 3 parts:

Duodenum
Jejunum
Ileum

For absorption of glucose it needs to be digested by enzymes which, for carbs, are generically referred to as amylases. These enzymes, which are actually proteins in nature, are typically present in secretions from the salivary and pancreatic glands, and as well as to a very limited extent in the intestinal juice.

Salivary Juice: 40-50% of total proteins in saliva are amylases enzymes. These typically breakdown complex starches of carbs into more simple form - disaccharides like maltose, sucrose and lactose.
Pancreatic Juice: Amylases constitute 50-60% of total protein content of pancreatic juice. These not only convert complex carbs but also breakdown of disaccharides into ready-for-absorption monosaccharides like glucose, galactose and fructose.
Intestinal Juice: The intestinal juice is primarily secreted in duodenum, with lesser amount in jejunum and very little quantity in ileum; it does not contain true amylases. Intestinal juice only create 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) attempt to enter the inner lining (mucus membrane or mucosa) of small intestine, these are all converted promptly to glucose which is then absorbed.

Summarising, complex carbs (starches) are broken down to simpler disaccharides and further to single absorbable molecules of glucose, fructose and galactose (all the 3 latter clubbed as monosaccharides).

GLUCOSE ABSORPTION CALCULATIONS

The breakdown of carbs is complete before the chyme (digested food material admixed with juices) exit the jejunum.

95,000-1,50,000 mg carbs consumed.
10% is fiber which is non-digestible and cannot enter blood.
90% of 85,500-1,35,000 mg carbs consumed is absorbed i.e. 76,950-1,21,500 mg.
70-85% of absorbed carbs is glucose. Thus sugar entering blood as glucose is 53,865-1,03,275 mg.
Carbs other than glucose absorbed are as or derived from fructose and galactose. The ratio of these in foods is <10:1.
15-30% of carbs absorbed are as fructose or galactose is 8,550-13,500 mg.
Since the presence of fructose and galactose is in ratio of <10:1:

Fructose absorbed is 7,773-12,273 mg.
Galactose absorbed is 777-1,227 mg.

Conversion of fructose to glucose is 40-45% whilst it is ~10% for galactose:

Glucose absorbed as available from fructose is 3,304-5,216 mg.
Glucose absorbed as available from galactose is 78-123 mg.

Thus, the total carbs that enters blood as glucose totals up to:

Minimum glucose entering blood per meal: 53,865 (from food) + 3,304 (from fructose) + 78 (from galactose) = 57,247 mg

Maximum glucose entering blood per meal: 1,03,275 (from food) + 5,216 (from fructose) + 123 (from galactose) = 1,08,514 mg

On an average, 57,250-1,10,000 mg glucose enters from the carbs consumed in food blood per meal.

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)

A food with a GI of 55 means its carbs causes roughly a 55% as large a blood sugar rise compared to consuming the exact same amount of pure glucose.

The rate at which pancreas release insulin in blood post-meal is directly determined by the GI of food. However, there is no fixed or standardized mathematical metric for the entry of glucose into the blood per minute (min.) per every 10-unit difference in GI. This is because the GI does not measure the speed or rate of glucose entering the plasma per min. but, instead, it measures the total cumulative exposure of blood to carbs over a full 120-minute window compared to a reference food.

INSULIN

INSULIN BASICS

Insulin is a hormone released by pancreas in response to entry of glucose in blood. Blood fructose is a weak stimulator of pancreatic insulin secretion whilst galactose does not influence the "glucose-stimulated insulin secretion" (GSIS). 1 unit / international unit (U or IU) of insulin secreted from the pancreas equals 1,000 mIU/L (milli-units per litre) corresponding concentration in blood.

Continual insulin manufacturing is because of a 24-hour working pancreatic factory. Specialized cells in pancreas called beta-cells produce insulin but only 1-2% of their stored insulin is released. Total insulin secreted in a day is approximately 40-50 IU and comprises of: [J Clin Invest 1988; 81(2): 442-448.]

~10.5 IU insulin release with breakfast.
~11.2 IU insulin release with lunch.
~10.8 IU insulin release with dinner.
6-12 IU insulin release during the 12 hours night-time and in-between meals period at a rate of 0.9 IU (0.5-1 IU)/hour.

It is pertinent to note that same or similar amounts of insulin is released whether it is breakfast, lunch or dinner. The release pattern of insulin can be segregated as:

Basal ongoing in-between meals release of insulin.
Pulsatile release every 3-6 mins. throughout 24 hours with special spiking associated with meals in response to entry of glucose.

2 spikes occur after breakfast.
3 spikes of insulin recorded after lunch as well as dinner.

Significant pulsatile release or a true spike of insulin release occurs only when plasma glucose rises by at least >30 mg/dL over and above the baseline concentrations.

OVERNIGHT / IN-BETWEEN MEALS INSULIN

30-50% of total day’s insulin is released at the rate of 0.25-1.5 IU/hour (0.004-0.025 IU/min.) from pancreas during the night and in-between meals period. The corresponding plasma levels for fasting insulin measure 3-15 mIU/L (micro-units/L) (and never rise beyond 25 mIU/L).

When there is no food consumed, normal blood sugar levels (normoglycemia) are maintained by either breakdown of stored glycogen (glycogenolysis), or conversion of triglycerides / amino acids into glucose (gluconeogenesis) by liver. Basal insulin secretion ensures that glucose production by muscles or liver does not raise the blood glucose excessively (hyperglycemia) during the fasting phases. Moreover, it is important to stimulate the insulin receptors during the “off” (meals) periods to ensure they remain active.

POST-MEALS INSULIN

Post-meal there is rapid “first phase” of insulin release within 1 min., peaking at 3-5 mins., and lasting about 10 mins.; the slower onset “second phase” of insulin secretion begins shortly thereafter but this lasts for the whole duration till normoglycemia is restored.

Irrespective of the quantum of released insulin, its concentrations return to basal levels of <10 mIU/mL within 2-3 hours after the meals. This parallels the exact time taken for the raised blood glucose levels, on account of the carbs consumption, to revert back to normal fasting range.

GI & POST-MEALS CARBS ABSORPTION

Irrespective of GI of the consumed carbs, the body can effectively maintain normoglycemia albeit in an healthy individual. Rate of entry of glucose in blood per meal:

GI <55 carbs: 180-325 mg/min.

GI 56-69 carbs: 450-630 mg/min.

GI >70 carbs: ~833 mg/min.

Hence, if carbs with GI <55 are consumed, it will take 175-600 mins. (~3-10 hours) for 57,250-1,10,000 mg glucose to completely enter the blood. For those consuming carbs with GI 56-69, the time span for glucose to gain entry in blood will be within 90-245 (~1.5-4) hours. In the case of GI >70 carbs intake, these will all be absorbed in 70-130 mins. (~1-2 hours).

The food takes 6-8 hours to pass from stomach and via the duodenum, jejunum and ileum. Also, the chyme (digested food mixed with juices) persists for 4 hours in the jejunum wherein maximal absorption of carbs is occurs. All the medium and high GI carbs will reach the blood stream within their transit time during their passage across the jejunum. Although mathematically the low GI carbs take longer (up to even 10 hours) than intestinal transit time to be fully absorbed it yet does not escape entering fully into blood.

ABSORPTION OF LOW GI CARBS

Whenever lower GI carbs are consumed the stomach slows down their passage into the duodenum. Thus, the entry of low GI carbs is more gradual in the jejunum to facilitate their absorption fully during the span of time the chyme transits through this part of small intestine. It is further essential to dissect absorption of carbs in detail to understand how the wonderful gastrointestinal tract deals with the same in a normal individual.

Carbs leave the stomach in 1-2 hours.

Zero carb is absorbed from stomach.

Food exits duodenum in 0.5-1 hour.

10-20% of carbs absorbed from duodenum.

Food exits jejunum in 4 hours.

80-90% of carbs absorbed from jejunum.

When 57,250-1,10,000 mg consumed glucose per meal is considered to be of low GI all 100% of the same will not be having GI <55. In such cases, only maximum of 70% of any low GI carb-containing meal will be truly be having GI values of GI <55 (low GI) and balance 30% consumed will be of medium GI (56-69).

17,250-33,000 mg apparently ‘low’ GI carbs consumed actually have a median GI.

Absorption in duodenum @ 10-20% = 1,725-3,300 mg
Rate of absorption: 450-630 mg/min.
Absorption time for all carbs (17,250-33,000 mg) entering duodenum (@ 450-630 mg/min.): 2.5-7.5 mins.
Time available for absorption in duodenum: 30-60 mins.
ALL THE 17,250-33,000 MG CARBS OF MEDIAN GI ABSORBED FULLY IN DUODENUM itself.

40,000-77,000 mg low GI carbs consumed actually have a GI of <55.

Absorption in duodenum @ 10-20% = 4,000-15,400 mg
Rate of absorption: 180-325 mg/min.
Absorption possible in duodenum (@ 180-325 mg/min.) in 1 hour: 19,500 mg
Balance glucose entry in jejunum: 36,000-61,600 mg
Time taken for absorption: 110-340 mins. (2-5.5 hours)

In spite of various mechanisms of the body to tackle the carbs of varying GI, including slowing down stomach emptying time, low GI (<55) carbs consumption exceeding 40,000 mg cannot be fully assured to be absorbed. Thus, what is important is not the GI of carbs but how much is the glucose load in the meal.

GLYCEMIC LOAD

Ordinarily the carbs on the mere basis of its higher GI values have been castigated to be detrimental. However, it is not the high GI that matters but how much carbs are consumed irrespective of their GI. This is expressed 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. The pancreas are geared to release proportionate spike release of insulin parallel to speed of glucose entry in blood (as determined by the GI value of carbs) and normoglycemia is thereby ensured within the usual 2-3 hours post-meal period.

GL is classified as:

Low GL Foods (<10): Cause minimal fluctuations in blood sugar and are ideal for steady energy and diabetes management.

High GL Foods (11-19): Offer a steady release of energy without causing rapid blood sugar spikes.

High GL Foods (>20): Lead to sharp blood sugar spikes; these should be consumed in smaller portions or be paired with fiber, protein, or healthy fats to slow down digestion if GL is high.

A healthy total daily GL is generally recommended to be <100. For a complete GI & GL chart visit: https://glycemic-index.net/glycemic-index-chart/.

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.

GI doesn't indicate how high the blood sugar could go when one actually eats the food. It is the GL which gives a more accurate picture of a food's real-life impact on the blood sugar. Watermelon, for example, has a high GI (80) but a serving of watermelon has so little carb that its GL is only 5.

If one is normal and healthy and devoid of risk factors trust the pancreas to cope up efficiently and effectively with the carbs consumed 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.

The upcoming next blog dwells on how the insulin manufacturing and release is fine-tuned by pancreas in response to carbs with differing GI values. Only a deep-dive indeed into the mathematics provided can be assuring to enjoy food or else one will continue to lead lifestyle and be bound by compulsions in choosing carbs-containing based on one’s perception and lesser knowledgeable influencers.

DR R K SANGHAVI

Prophesied Enabler
Experience & Expertise: Clinician & Healthcare Industry Adviser

-------------------------------------------------------------------------------------

POWERED BY -

# fuzionnutra.com

Search This Blog

Dr R K Sanghavi