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The Effect of Coffee Consumption on Blood Glucose: A Review

OPEN ACCESS Pakistan Journal of Nutrition
ISSN 1680-5194
DOI: 10.3923/pjn.2020.420.429
Review Article
The Effect of Coffee Consumption on Blood Glucose: A Review
Amal Hassan Alshawi
Department of Nutrition and Food Science, Princess Nourah Bint Abdulrahman University, Riyadh, Kingdom of Saudi Arabia
This review describes the impact of drinking coffee on glycemic profile parameters (glycemic index [GI], glycemic load [GL], glucose
tolerance and insulin sensitivity) and diabetes mellitus. Coffee is very popular in Arab communities including Saudi Arabia. Clinical research
has revealed the negative effect of caffeine including a reduction in insulin sensitivity that impairs glucose tolerance. Epidemiological
studies also show that drinking coffee has positive effects on both glucose tolerance and sensitivity to insulin, which might assist in
reducing the risk of type 2 diabetes especially over long periods of consumption. More studies are thus needed to gain a deeper
understanding of how coffee drinking is linked to type 2 diabetes.
Key words: Caffeine, diabetes mellitus, insulin sensitivity, glucose tolerance, chlorogenic acid, coffee consumption
Citation: Amal Hassan Alshawi, 2020. The effect of coffee consumption on blood glucose: A review. Pak. J. Nutr., 19: 420-429.
Corresponding Author: Amal Hassan Alshawi, Department of Nutrition and Food Science, Princess Nourah Bint Abdulrahman University,
Riyadh, Kingdom of Saudi Arabia
Copyright: © 2020 Amal Hassan Alshawi. This is an open access article distributed under the terms of the creative commons attribution License, which
permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
Competing Interest: The author has declared that no competing interest exists.
Data Availability: All relevant data are within the paper and its supporting information files.
Pak. J. Nutr., 19 (9): 420-429, 2020
The word coffee derives from the Arabic word
, leading to the Latin botanical genus
. Of the
coffee which is actually drunk, 99% comes from just two of the
103 kinds of coffee that have been discovered:
Coffea arabica
(Arabica) and
Coffea canephora
(Robusta). Coffee growing
occurs in sixty tropical and subtropical nations. Around 60% of
the coffee produced globally is grown on the American
continent. Here, Arabica coffee with its low caffeine content
and bitterness predominates1. Golden coffee, which comprises
around 95% of all coffee exports, is produced through minimal
processing of the green coffee beans2. Coffee is very common
in many countries with the highest per capita consumption
being in Europe where the average consumption is between
2.4 and 12 kg per person per year3.
Coffee contains caffeine, which is a bioactive compound.
It stimulates the central nervous system and positively affects
long-term memory. Drinking coffee has historically been
associated with negative health effects, more recent studies
show that it may be beneficial1. Consuming approximately
#400 mg of caffeine daily (3-4 cups) of brewed coffee or
having five cups of tea or five caffeinated soft drinks regard as
moderate seems to affect health in a neutral to positive way.
Adolescents can safely consume 100-175 mg of caffeine per
day while the safe level for children aged 6-12 is 45-85 mg4. In
Saudi Arabia, the term Arabic coffee is usually applied to a
green coffee bean extract that is very popular. Spices such as
saffron and cardamom are added to the roasted green coffee
beans to enhance the color and taste of the resulting coffee
product. In Saudi Arabia, as in other Arab Gulf countries, coffee
is usually drunk with snacks especially soft dates.
The efficiency of consuming brewed coffee on human
health has been the focus of many studies5. This review aims
to evaluate how drinking coffee affects blood glucose and the
implications for insulin sensitivity and glucose tolerance as
well as its impact on diabetes.
Search strategy: Databases were searched for a randomized
controlled trial that examined the effects of coffee
consumption on blood glucose in healthy humans. The
following keywords in the title/abstract were used: caffeine,
diabetes mellitus, insulin sensitivity, glucose tolerance,
chlorogenic acid and coffee consumption. The reference lists
from selected reports were reviewed for further relevant
studies. Studies that investigated the effect of different coffee
drinks are included because coffee consumption occurs more
frequently than pure caffeine intake in daily life.
A review of the literature was conducted utilizing
databases such as PubMed, Google Scholar, LWW Health
Library and Science Direct. Furthermore, studies cited in the
selected articles were verified. Studies on association of
caffeine, coffee consumption and diabetes were included.
General properties of coffee: When coffee beans are ripe,
they can be processed by the wet method or by drying in the
sun for 3-9 days (the dry method). A temperature of 200EC is
required for the necessary transformation to take place during
roasting. When this occurs, the coffee beans become dry,
brittle and brown; they increase in size and develop their
characteristic aroma and flavor. Regardless of whether coffee
is prepared on an industrial scale or brewed at home, hydrous
extraction of the dissolved roast and ground coffee is
The coffee quality is determined by the chemical
composition of the roasted beans, which is also affected by
drying, storing, roasting and grinding after the harvest. The
coffee bean quality relies on color, shape and size of the bean,
the crop year, the processing methods, the roast potential and
the processing method as well as the flavour7. Roasting is vital
because the chemical compounds that are generated by the
changes that happen during the roasting process are what
gives coffee its characteristic flavour8.
Recent research has demonstrated that coffee and its
by-products are rich in antioxidants. They contain trigonelline
and chlorogenic acids as well as caffeine, which are all
bioactive compounds9. These compounds have a positive
effect on health and this means that coffee is potentially a
functional food product2.
The coffee plant has a secondary metabolite which is
caffeine, (1, 3, 7-trimethylxanthine)-a purine alkaloid. The
caffeine content in the green coffee beans varies. If calculated
by dry weight, it represents up to 2.3% of Robusta beans
and up to 1.3% of Arabica beans. Coffee beans also contain
fairly large amounts of chlorogenic acids, which are widely
distributed secondary metabolites in plants with 5-O-
caffeoylquinic acid being the most common6. After
investigating the effects of various methods of brewing on the
polyphenol, methylxanthine and antioxidant capacities of 13
different brews of coffee, Baeza
et al
.10 concluded that their
antioxidant capacities complied with the total phenol and
chlorogenic acid derivate contents. Wachamo
et al
suggested that the high phenolic content of green coffee
probably accounted for its association with the reduced threat
of diseases of oxidative etiology. The impact of drinking coffee
on various health consequences was reviewed by Bordenave
et al
.12 who concluded that it benefitted carbohydrate and
lipid metabolism as well as the cardiovascular system.
Pak. J. Nutr., 19 (9): 420-429, 2020
The blood glucose response to foods: Currently, the focus in
the glycemic response (GR) to foods is of considerable interest
because it is thought to have a relationship with chronic
diseases including obesity, diabetes and cardiovascular
disease13. GR to a food or meal for a person is specified by the
amount and quality of the carbohydrates14 and this can be
ascertained by the GI, GL, or glycemic impact15. The concept of
the GI was first coined in 1981 by Augustin
et al
.13 in their
research with patients who had type 2 diabetes mellitus. The
carbohydrate content of specific foods is evaluated by the GI
by measuring their glycemic effects after they have been
ingested16,17. The GI could be demonstrated as the incremental
area beneath the curve of the blood glucose response to a
50 g portion of available carbohydrate of a tested sample. It is
expressed as a percentage of the same person reaction after
eating an identical carbohydrate portion from standard food.
The variability and/or value of the GI results can be influenced
by a number of methodological factors; however, variation can
be minimized and reproducible findings obtained by careful
use of appropriate methods18.
The Food and Agriculture Organization of the United
Nations (FAO)/World Health Organization (WHO) outlines the
most appropriate method for calculating the GI19. The FAO, in
its consultation report on dietary carbohydrates in human
nutrition, suggests using GI values as well as other data on
food composition19. Low GI foods like legumes and low-fat
animal products are recommended as part of many
weight-loss diets20. All published data on the GI values of
600 particular foods was compiled and listed in a single table
by Fiona
et al
To assist in the creation of a local food exchange list for
diabetics, Al-Mssallem21 identified the GI value of popular
Saudi foods. Fohl, gareesh, korsan, kelija eneazaa and kelija
malkee are five common Saudi foods with high carbohydrate
content and were evaluated for their GI values (45, 89, 61, 58
and 51%, respectively). Alkaabi
et al
.22 assessed the GI values
of five popular types of dates in both diabetic and healthy
individuals. Their findings demonstrated a low GI value for all
five types of dates and the authors concluded that the dates
would not cause a significant rise in the concentration of
postprandial glucose if eaten by diabetics. Farhat
et al
investigated the GI values of Lebanese mixed meals and
desserts and found that they ranged from intermediate
(50-70%) to low (#50%). A study on the GI values of breakfast
cereals in the diet of United Kingdom (UK) citizens showed
that these ranged from high ($70%) to low (#55%); most had
a moderate GI of between 60 and 65%24.
To measure GL, the entire amount of ingested
carbohydrates (in grams) is multiplied by the GI value of each
food and then divided by 10025. Wh en t he e ffe ct of GI/ GL o n
appetite and GR were identified, there were no significant
differences in appetitive rating, plasma glucose, insulin
response, or food consumption26. The GR is modulated by
several aspects of the meal including the nutrient
composition, the duration, volume/weight, energy density,
rheology and palatability27,28.
The GR is a food's capacity to raise blood sugar29. The way
that food has been processed or cooked affects GR30. Because
dietary fats slow the absorption of glucose, they may delay the
blood glucose and insulin responses31,32. Bataineh investigated
the glycemic and insulinemic indices of some popular Arabic
sweets when ingested by healthy individuals and found that
substituting olive oil for ghee in maa'moul, ghuraybah and
hareesah lowered GRs without a significant effect on the
insulinemic responses33. The blood glucose response of foods
containing differing amounts of carbohydrates can be
compared directly with the glycemic glucose equivalent
(GGE); the glucose quantity in grams would result in a GR
equal to a particular weight of a food34,35. Observing the
glucose continuously might be used to record the GR with
levels of interstitial glucose reported every 5 to 10 minutes
continuously for 3-7 days for a comprehensive observation of
the GR of a single meal or food36.
Due to lack and/or resistance of insulin, type 2 diabetes
mellitus is linked with the target tissues impaired insulin
response. Although increased insulin secretion overcomes
insulin resistance at first, this compensation ultimately fails
and results in progressively raised blood glucose levels. Before
people develop type 2 diabetes, they go across a stage of
impaired glucose tolerance (IGT) and increased plasma
glucose levels during fasting; thus, this stage is an
intermediate dysglycemia state between diabetes and
normal glucose tolerance37. The American Diabetes
Association proposed a new diagnostic criterion in 199738
whereby diabetes screening was carried out by testing plasma
glucose levels during fasting39. The importance of measuring
insulin sensitivity is frequently highlighted due to its
important role in diabetes, cardiovascular and hypertension
disease40; tools to measure insulin sensitivity and resistance is
a key goal of many studies41-43. Song
et al
.44 studied the
relationship between insulin resistance and dietary behavior
among healthy people in Korea: They found that a pattern
based on beans and whole grains was linked with a lower
prevalence of insulin resistance.
The effect of coffee consumption on the glycemic profile: If
people are to make informed choices about drinking coffee
and public health initiatives are to be prioritized appropriately,
then it is important to know the benefits and adverse effects
Pak. J. Nutr., 19 (9): 420-429, 2020
on health45. The relationship between coffee components like
antioxidant phenolic compounds, c af fe i ne , m i cronutrients and
fiber suggests beneficial effects3. According to Van Dam
et al
coffee contains a number of substances that may impact
glucose metabolism.
The Hoorn45 study was a cross-sectional and prospective
study that was population-based and involved Dutch male
and female adults with a range of age 50-74 years. Initially, an
oral glucose tolerance test (OGTT) was conducted and a
follow-up was performed during an average period of six years
and four months. Some variables such as cigarette smoking,
alcohol intake, body mass index (BMI), physical activity and
dietary factors were adjusted. The results showed that habitual
coffee-drinking can lower the threat of IGT and impact post-
load rather than fasting glucose metabolism45. A link between
habitual coffee-drinking and the incidence of increased
plasma glucose levels during fasting, IGT and type 2 diabetes
was assessed.
Caffeine is one of the substances other than
macronutrients that can affect insulin sensitivity and blood
glucose concentrations in individuals with diabetes46. Despite
research carried out on short terms with people in good
health that continue to indicate that ingesting caffeine
cause acute transient insulin resistance and IGT47,48, these
conclusions appear to be contradicted by epidemiological
studies46. For an individual with existing diabetes, blood
glucose concentrations may be affected by caffeine in various
ways. Glucose transportation from blood to the muscles may
be hindered by caffeine as it acts as an adenosine receptor
antagonist to inhibit the uptake of glucose into muscle cells
even when insulin is present49. Moreover, elevated blood
glucose concentrations due to caffeine intake could be a
consequence of high epinephrine (adrenaline), which in turn
induces insulin resistance50,51. Other studies have also shown
how caffeine might impact glucose metabolism. Luiz
et al
found that caffeine intake led to a significant increase
in blood glucose concentrations. Robinson
et al
.53 and
et al
.54 c on fi r me d t h at i ng es t in g ca f fe i ne i nc r ea s ed g lu co s e
concentration and loaded when compared to a placebo. Both
studies noted that caffeine caused a reduction in the insulin
sensitivity index compared to placebo.
Several studies have addressed the short-term and
long-term effects of coffee or caffeine consumption on
glucose tolerance55; they concluded that coffee consumption
and/or caffeine impaired glucose tolerance in the short-
term56,57. IGT is a state of hyperglycemia where resistance to
insulin sensitivity happens in peripheral tissues as a response
to glucose58. Insulin resistance and glucose tolerance can be
impaired by short-term administration of coffee, which
blocks the impact of the adenosine AI receptor that regulates
the uptake of glucose in skeletal muscles59. However, the
findings from some epidemiological studies demonstrate
that long-term and habitual coffee drinking might support
standard glucose tolerance and enhance insulin sensitivity60-63.
Thus, coffee may suppress insulin sensitivity in the short-term
but drinking coffee regularly can stimulate glucose tolerance
and insulin sensitivity64-66. In other words, ingesting caffeine
habitually changes the negative impact of caffeine on glucose
tolerance and insulin sensitivity to a positive one55.
Consuming coffee and caffeine were linked to lower
serum levels of leptin and plasminogen activator
inhibitor-167. In elderly individuals, low coffee consumption
for short periods predicts impairment of normal glucose
tolerance68 while also lowering glucose tolerance in healthy
men69. However, other studies report different results:
et al
.70 demonstrated that subjects showed a marked
reduction in blood glucose concentration after drinking coffee
although insulin levels were not affected. Shengxi
et al
noted that just the intake of coffee polyphenols enhances
peripheral endothelial function after glucose loading among
adults in good health. Thom72 reported that instant coffee
enriched with chlorogenic acid lowered glucose absorption by
6.9% versus a control.
A lowered insulin sensitivity after short-term ingestion of
coffee72-74 may be due to the caffeine-induced antagonism
of adenosine receptors accompanied by a rise in levels of
epinephrine75. For individuals with type 2 diabetes mellitus,
the impact of drinking black espresso coffee does not seem to
be mediated by alterations in insulin sensitivity76. For the study
of insulin secretion and sensitivity, long-term trials on the
impact of caffeine and some components of coffee could be
more related. A cross-sectional study of 936 male senior
citizens without type 2 diabetes revealed that drinking coffee
was linked to higher insulin sensitivity but not a reduced
secretion of insulin61; however, a cross-sectional study of 2112
healthy women found a potential decrease of insulin secretion
as the result of consuming coffee. It is possible that this
decrease could be relevant to a constituent in coffee other
than caffeine62.
Recent research reported no alteration in postprandial
glycemic response to Lebanese mankoucheh when
accompanied by Turkish coffee77. Post-exercise insulin
concentrations and blood glucose were significantly changed
by caffeine and extract from green beans of coffee versus
Type 2 diabetes and consuming coffee: The global increase
in diabetes seems to be due to population ageing and
urbanization wi th ass oc iat ed alt er ati on s in ph ysi ca l a cti vi ty
Pak. J. Nutr., 19 (9): 420-429, 2020
and diet79. Specific criteria and diagnostic tests were used to
identify people who are pre-diabetic and thus at risk of
developing diabetes as well as those who have diabetes80.
Diabetes is classified into type 1, type 2, gestational and
secondary diabetes80. The vast majority of diabetics (90-95%)
have type 2, which used to be called non-insulin-dependent
or adult-onset diabetes81. Preventing type 2 diabetes is now a
significant public health issue. Type 2 diabetes can largely be
avoided by a healthy life style and a sound dietary pattern82.
Treatment of diabetes is focused on normalizing metabolism
with an emphasis on blood glucose and lipids especially
low-density lipoprotein (LDL), cholesterol and blood pressure
to prevent complications that are diabetes-related81.
Coffee contains a significant amount of caffeine and
chlorogenic acid and is a complex mix of chemicals. Over the
last few decades, studies have identified the benefit or
harm to health from drinking coffee83. Coffee may impact
postprandial hyperglycemic excursion, although there
have been conflicting results. Drinking coffee raises energy
expenditure and thermogenesis to induce insulin sensitivity84.
Coffee can produce an acute impairment of glucose tolerance
or insulin resistance in healthy, non-diabetic adults and has
been consistently demonstrated by a minimum of 17
short-term studies. We concluded that this effect contributes
to the progression of type 2 diabetes in susceptible people85.
Conversely, long-term coffee intake is possibly linked
with a lowered threat of type 2 diabetes86,87. Alkaabi
et al
suggested that eating dates with coffee was common among
Arabs and that this might affect hyperglycemic excursion after
meals. They studied the effect of coffee on the GI tract of type
2 diabetic and healthy subjects when eating a common variety
of dates. They found that coffee did not adversely impact
capillary glucose levels after the consumption of dates either
in diabetic or healthy subjects at least in the short-term
Information about the daily coffee consumption of a sample
of 1141 American Indian males and females with a range of
age 45-74 years was collected in a prospective cohort study.
The sample was within the normal average of glucose
tolerance at the baseline examination and was monitored with
a mean of 7.6 years. The findings indicated that subjects who
consumed more than 11 cups of coffee per day had a 67%
lower threat of developing diabetes through the follow-up
period compared to non-coffee consumers89. Another
prospective study followed 910 adults aged $50 years with a
mean of 8 years after their coffee consumption had been
assessed. These findings indicated that both former and
current coffee consumers had a reduced risk of diabetes
incident versus people who never ingest coffee. The subjects
with impaired baseline glucose who were former and current
coffee consumers also had a lower risk of diabetes. This
research strikingly demonstrates how caffeinated drinking
coffee can protect against the incidence of diabetes63.
Furthermore, according to Hamer
et al
.90, more than
fourteen cohort studies have revealed a reverse association
between drinking coffee beverages and the threat of
type 2 diabetes. Hamer
et al
.90 investigated the prospective
association between consuming coffee and tea beverages
and the threat of type 2 diabetes mellitus. The study was
conducted for 11.7 years of follow-up with a sample of
4055 males and 1768 females from the Whitehall cohort in the
UK; they concluded that drinking a moderate amount of
coffee and tea (more than 3 cups a day) was not prospectively
linked with the incidence of type 2 diabetes90. A cross-
sectional study of 954 non-diabetic adults who drink
caffeinated coffee on a regular basis based on a food
frequency questionnaire found a positive link to insulin
sensitivity that was inversely related to 2 h post-load glucose
levels91. Dutch male and female adults were followed for
a mean duration of 6.4 years in another prospective
cross-sectional study. They found that drinking coffee favored
post-load rather than fasting glucose45. Research conducted
with 2434 Finnish men and women reported that drinking
coffee had a significant and inverse link with both fasting
glucose and insulin and also with the response to a 2 h
glucose tolerance test55,92.
A review of these epidemiologic studies showed that
drinking coffee can significantly decrease the threat of type 2
diabetes93-96. Akash
et al
.55 found a number of mechanisms
that might be involved. Ryanodine receptors are activated by
caffeine and this improves the insulin secretion of $-cells of
the pancreatic islets. Glucose metabolism and homeostasis are
regulated by chlorogenic acid and magnesium55. Chu
et al
reported numerous compounds in coffee that may produce a
matrix effect by working together and providing bioactivities
that lower the threat of evolving type 2 diabetes. Finally,
coffee consumption is linked with the threat of diabetes
mellitus, the occurrence of stroke, heart failure and some
cancers in an inverse dose-dependent fashion; however, there
may be harmful effects related to high anxiety, insomnia and
acute myocardial infarction97,98. However, until the association
between the threat of type 2 diabetes and long-term coffee
consumption is more thoroughly understood, it would be
premature to suggest coffee intake consumption as a way of
preventing type 2 diabetes mellitus55,99,100.
Pak. J. Nutr., 19 (9): 420-429, 2020
Generally, the literature on short-term clinical trials that
addressed the link between consuming coffee and type 2
diabetes mellitus shows that caffeine decreases insulin
sensitivity and negatively affects glucose tolerance.
Nevertheless, several prospective cohort studies in various
countries have demonstrated that drinking coffee is linked
with a significant decrease in the threat of developing type 2
diabetes mellitus. More studies are required to clearly
understand how the main components of coffee affect
glucose metabolism. Moreover, epidemiologic research needs
to be carried out in Arab populations and specifically in the
Saudi community to accurately identify how drinking coffee
affects blood glucose and other aspects of health. Effective
strategies in clinical research and related epidemiological
studies are needed to clarify the effect of coffee consumption
for people with type-diabetes especially in the local contest.
The use of coffee drinks could be a practical, effective and
environmentally friendly method to enhance insulin
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... Information regarding the spread of coffee and caffeinated products consumed by the Saudi population, particularly individuals with type II diabetes, remains unclear [28,29]. An exploration of the effect of habitual caffeine intake among adults with diabetes in the Saudi context is needed [30]. The prevalence of type II diabetes is high among the Saudi adults and considered a major public health problem. ...
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Information regarding the spread and effect of coffee and caffeine intake by individuals with type II diabetes remains unclear. This study aims to identify the amount and sources of habitual caffeine intake by individuals with type II diabetes and to investigate its association with other health outcomes, especially HbA1c. This is a cross-sectional survey involving 100 people medically defined as having type II diabetes comprising both genders, recruited from a care centre. All participants completed a caffeine semi-quantitative food frequency questionnaire (C-FFQ) to estimate their caffeine consumption, a two day 24-h recall, and a detailed questionnaire. The average caffeine intake was calculated from all sources and the differences in mean by gender were tested using a regression model (adjusted to important confounders). Regression models were used to verify the association between average caffeine intake on HbA1c and other health outcomes with adjustment for important confounders. A p value < 0.05 represented statistical significance. Arabic coffee (gahwa) and tea were the most common sources of caffeine among Saudi adults living with diabetes. Average caffeine intake for the whole sample was 194 ± 165 mg/day, which is 2.3 ± 2 mg/kg. There was an inverse association between caffeine intake and age: difference in mean −3.26 mg/year (95%CI: −5.34, −1.18; p = 0.003). Males had significantly higher consumption of caffeine compared to females: difference in mean 90.7 mg/day (95%CI: 13.8, 167.6; p = 0.021). No association was found between average caffeine intake and HbA1C or any other cardiovascular risk factors. This information can help public health practitioners and policy makers when assessing the risk of caffeine consumption among this vulnerable group.
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Background and aims: Despite the proven evidence of high glycemic index (GI) and glycemic load (GL) diets to increase cardiometabolic risks, knowledge about the meta-evidence for carbohydrate quality within world geographic regions is limited. We conducted a meta-analysis to synthesize the evidence of GI/GL studies and carbohydrate quality, gathering additional exposures for carbohydrate, high glycemic carbohydrate, total dietary fiber, and cereal fiber and risks for type 2 diabetes (T2DM), coronary heart disease (CHD), stroke, and mortality, grouped into the US, Europe, and Asia. Secondary aims examined cardiometabolic risks in overweight/obese individuals, by sex, and dose-response dietary variable trends. Methods and results: 40-prospective observational studies from 4-Medline bibliographical databases (Ovid, PubMed, EBSCOhost, CINAHL) were search up to November 2019. Random-effects hazard ratios (HR) and 95% confidence intervals (CI) for highest vs. lowest categories and continuous form combined were reported. Heterogeneity (I2>50%) was frequent in US GI/GL studies due to differing study characteristics. Increased risks ((HRGI,T2DM,US=1.14;CI:1.06,1.21), HRGL,T2DM,US=1.02 (1.01, 1.03)), HRGI,T2DM,Asia=1.25;1.02,1.53), and HRGL,T2DM,Asia=1.37 (1.17, 1.60)) were associated with cardiometabolic diseases. GI/GL in overweight/obese females had the strongest magnitude of risks in US-and Asian studies. Total dietary fiber (HRT2DM,US = 0.92;0.88,0.96) and cereal fiber (HRT2DM,US = 0.83;0.77,0.90) decreased risk of developing T2DM. Among females, we found protective dose-response risks for total dietary fiber (HR5g-total-dietary-fiber,T2DM,US = 0.94;0.92,0.97), but cereal fiber showed better ability to lower T2DM risk (HR5g-cereal-fiber,T2DM,US = 0.67;0.60,0.74). Total dietary-and cereal fibers' dose-response effects were nullified by GL, but not so for cereal fiber with GI. Conclusions: Overweight/obese females could shift their carbohydrate intake for higher cereal fiber to decrease T2DM risk, but higher GL may cancel-out this effect.
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Sugar types, sugar amounts, phenolic contents constituents were determined in fresh fruits of 17 Saudi date cultivars and the obtained values were correlated with the corresponding vales of glycemic index. Glucose and fructose were presented in all tested cultivars in the range 104–395 g kg⁻¹ and 82–361 g kg⁻¹, respectively. Glucose/fructose ratio constituted between 1.03–1.27. Sucrose was considered the main sugar in four date cultivars. Total phenolics presented in the range 2.15–3.86 g kg⁻¹. Antioxidant activities varied between tested cultivars and ranged from 2.46 to 9.80 µmol Trolox g⁻¹ as assayed by DPPH method and from 5.90 to 17.78 µmol Trolox g⁻¹ as assayed by FRAP method. No significant correlation was found between the levels of glucose, fructose, sucrose, total phenolics and antioxidant activity with the corresponding glycemic index values.
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Background: Reports from previous studies on the effects of adenosine and caffeine on blood glucose are controversial and inconclusive. The present study sought to investigate the effect of acute adenosine infusion and caffeine injection on blood glucose level in rats. Materials and Methods: Thirty-four male albino rats (300-400 g) were randomly divided in a blinded-fashion into six groups, namely, Group I (n = 6) received normal saline (0.1-0.2 ml), Group II (n = 6) received adenosine (347.8 µg/kg/min), Group III (n = 5) received caffeine (6 mg/kg), followed by adenosine (347.8 µg/kg/min), Group IV (n = 5) were diabetic rats that received adenosine (347.8 µg/kg/min), Group V (n = 6) received caffeine (6 mg/kg), and Group VI (n = 6) received nifedipine (300µg/kg), followed by caffeine (6 mg/kg). Administrations were done through the femoral vein, while blood samples were taken from the carotid artery for glucose measurement. Results: Adenosine caused a reduction in blood glucose level in normal and diabetic rats, though the reduction was more noticeable in diabetic rats. Pretreatment of rats with caffeine completely abolished the adenosine-induced reduction in blood glucose and produced an exaggerated increase in blood glucose comparable to the level seen in rats that received caffeine alone. Pretreatment of rats with nifedipine reduced the caffeine-induced hyperglycemia by two-third. Conclusion: This study suggests that adenosine receptors could be of therapeutic target in the treatment of Type 1 diabetes due to its blood glucose-lowering potential in both diabetic and normal rats. It also suggests that intracellular calcium mobilization is more implicated in caffeine-induced hyperglycemia than adenosine receptor antagonism, even though other unidentified mechanism(s) remain to be explored.
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Epidemiological studies indicate an inverse association of coffee consumption with risk of type 2 diabetes mellitus. However, studies to determine the clinical effects of coffee consumption on the glucose metabolism biomarkers remain uncertain. The aim of this systematic review was to evaluate the effects of coffee consumption on glucose metabolism. A search of electronic databases (PubMed and Web of Science) was performed identifying studies published until September 2017. Eight clinical trials (n = 247 subjects) were identified for analyses. Participants and studies characteristics, main findings, and study quality (Jadad Score) were reported. Short-term (1–3 h) and long-term (2–16 weeks) studies were summarized separately. Short-term studies showed that consumption of caffeinated coffee may increase the area under the curve for glucose response, while for long-term studies, caffeinated coffee may improve the glycaemic metabolism by reducing the glucose curve and increasing the insulin response. The findings suggest that consumption of caffeinated coffee may lead to unfavourable acute effects; however, an improvement on glucose metabolism was found on long-term follow-up. © 2018 Center for Food and Biomolecules, National Taiwan University
Epidemiological studies show a convincing long-term and dose-dependent protection of coffee and decaffeinated coffee against developing type 2 diabetes. The mechanisms of this effect are still not understood even though several have been proposed, including a potential effect on blood glucose by chlorogenic acids. However, there is minimal effect of decaffeinated coffee on postprandial blood glucose and insulin when consumed with carbohydrates, although there may be effects on incretin hormones, but these have been measured in only a few studies. Although chlorogenic acids do not affect carbohydrate digestion directly, they may affect glucose absorption and subsequent utilisation, the latter through metabolites derived from endogenous pathways or action of the gut microbiota. To advance understanding of the protective effect of coffee chlorogenic acids, more chronic intervention studies are needed on decaffeinated coffee, coupled with mechanistic studies in vitro using more realistic concentrations of the relevant chlorogenic acid metabolites.
Background: In observational studies, coffee consumption has been consistently associated with a lower risk of type 2 diabetes mellitus. Trials examining the effect of coffee consumption on glucose metabolism have been limited by the use of surrogate insulin sensitivity indices, small sample sizes, lack of blinding, and short follow-up duration. Objectives: We aimed to overcome limitations of previously conducted coffee trials in a randomized placebo-controlled trial of the effect of coffee consumption on insulin sensitivity. Methods: We conducted a 24-wk randomized placebo-controlled trial in 126 overweight, non-insulin sensitive (HOMA-IR ≥1.30), Chinese, Malay, and Asian-Indian males and females aged 35-69 y. Participants were randomly assigned to receive 4 cups of instant regular coffee (n = 62) or 4 cups of a coffee-like placebo beverage (n = 64) per day. The primary outcome was the amount of glucose metabolized per kilogram of body weight per minute (Mbw) assessed during steady-state conditions with a hyperinsulinemic euglycemic clamp. Secondary outcomes included other clamp-based insulin sensitivity measures, biological mediators of insulin sensitivity, and measures of fasting glucose metabolism. Results: Coffee consumption did not significantly change insulin sensitivity compared with placebo (percentage mean difference in Mbw = 4.0%; 95% CI: -8.3, 18.0%; P = 0.53). Furthermore, no significant differences in fasting plasma glucose (2.9%; 95% CI: -0.4, 6.3%; P = 0.09) or biological mediators of insulin resistance, such as plasma adiponectin (2.3%; 95% CI: -1.4, 6.2%; P = 0.22), were observed between coffee and placebo groups over 24 wk of intervention. Participants in the coffee arm experienced a loss of fat mass (FM) (-3.7%; 95% CI: -6.3, -1.1%; P = 0.006) and reduction in urinary creatinine concentrations (-21.2%; 95% CI: -31.4, -9.5%; P = 0.001) compared with participants in the placebo arm over 24 wk of intervention. Conclusions: Consuming 4 cups/d of caffeinated coffee for 24 wk had no significant effect on insulin sensitivity or biological mediators of insulin resistance but was associated with a modest loss of FM and reduction in urinary creatinine concentrations.This trial was registered at as NCT01738399. Registered on November 28, 2012. Trial sponsor: Nestlé Research, Lausanne, Switzerland. Trial site: National University of Singapore.
Background: Previous studies have examined dairy products with various fat contents in relation to type 2 diabetes (T2D) risk, although data regarding dairy fat intake per se are sparse. Objectives: We aimed to evaluate the association between dairy fat intake and risk of T2D in 3 prospective cohorts. We also examined associations for isocalorically replacing dairy fat with other macronutrients. Methods: We prospectively followed 41,808 men in the Health Professionals Follow-Up Study (HPFS; 1986-2012), 65,929 women in the Nurses' Health Study (NHS; 1984-2012), and 89,565 women in the NHS II (1991-2013). Diet was assessed quadrennially using validated FFQs. Fat intake from dairy products and other relevant sources was expressed as percentage of total energy. Self-reported incident T2D cases were confirmed using validated supplementary questionnaires. Time-dependent Cox proportional hazards regression was used to estimate the HR for dairy fat intake and T2D risk. Results: During 4,219,457 person-years of follow-up, we documented 16,511 incident T2D cases. Dairy fat was not associated with risk of T2D when compared with calories from carbohydrates (HR for extreme quintiles: 0.98; 95% CI: 0.95, 1.02). Replacing 5% of calories from dairy fat with other sources of animal fat or carbohydrate from refined grains was associated with a 17% (HR: 1.17; 95% CI: 1.13, 1.21) and a 4% (HR: 1.04; 95% CI: 1.00, 1.08) higher risk of T2D, respectively. Conversely, a 5% calorie replacement with carbohydrate from whole grains was associated with a 7% lower risk of T2D (HR: 0.93; 95% CI: 0.88, 0.98). Conclusions: Dairy fat intake was not associated with T2D risk in these cohort studies of US men and women when compared with calories from carbohydrate. Replacing dairy fat with carbohydrates from whole grains was associated with lower risk of T2D. Replacement with other animal fats or refined carbohydrates was associated with higher risk.
Background & aims: Although the association between dietary Glycemic Index (GI), Glycemic Load (GL) and general/abdominal obesity has extensively been examined, limited data are available in this regard in developing countries. The aim of this study was to examine the association between dietary GI and GL with general and abdominal obesity. Methods: This cross-sectional study was conducted among adults in Isfahan, Iran. Dietary GI and GL were assessed using a validated dish-based 106-item semi-quantitative food frequency questionnaire (DS-FFQ). Data regarding height, weight and waist circumference were collected using a self-reported questionnaire. Overweight or obesity was defined as body mass index ≥25 kg/m2, and abdominal obesity was defined as waist circumference ≥80 cm for women and ≥94 cm for men. Results: There was no significant association between dietary GI and GL and general obesity. After adjustment for potential confounders, participants in the highest quintile of dietary GI had a higher chance for abdominal obesity (OR: 1.29; 95% CI: 1.01-1.64), compared with those in the lowest quintile. No significant association was observed between dietary GL and abdominal obesity. After adjustment for potential confounders, women in the top quintile of dietary GI had higher chance for abdominal obesity compared with those in the bottom quintile (OR: 1.48, 95% CI: 1.02-2.15). No significant association was found between dietary GI and abdominal obesity among men. We failed to find any significant association between dietary GI and general obesity in either gender [Comparing top vs. bottom quintiles, for men: OR: 0.97; 95% CI: 0.74-1.29 and for women: OR: 1.01; 95% CI: 0.75-1.40]. No significant association was found between dietary GL and general [for men: OR: 1.13; 95% CI: 0.85-1.49 and for women: OR: 1.01; 95% CI: 0.76-1.35], as well as abdominal obesity [for men: OR: 1.21; 95% CI: 0.88-1.67 and for women: OR: 1.25; 95% CI: 0.88-1.77]. Conclusions: We found a significant positive association between dietary GI and abdominal obesity. When we conducted analyses stratified by gender, we also observed such association in women, but not in men. No other significant associations were observed between dietary GI and GL with general or abdominal obesity.
Aging and diabetes mellitus are 2 well-known risk factors for cardiovascular disease (CVD). During the past 50 years, there has been an dramatic increase in life expectancy with a simultaneous increase in the prevalence of diabetes mellitus in the older population. This large number of older individuals with diabetes mellitus is problematic given that CVD risk associated with aging and diabetes mellitus. In this review, we summarize epidemiological data relating to diabetes mellitus and CVD, with an emphasis on the aging population. We then present data on hyperglycemia as a risk factor for CVD and review the current knowledge of age-related changes in glucose metabolism. Next, we review the role of obesity in the pathogenesis of age-related glucose dysregulation, followed by a summary of the results from major randomized controlled trials that focus on cardiovascular risk reduction through glycemic control, with a special emphasis on older adults. We then conclude with our proposed model of aging that body composition changes and insulin resistance link possible dysregulation of physiological pathways leading to obesity and diabetes mellitus-both forms of accelerated aging-and risks for CVD.