Monday, October 3, 2016

Caffeine Consumption and Diabetes

Wendy Bricco-Meske, NMSU Dietetic Intern and Graduate Student

Caffeine, a chemical stimulant that occurs naturally in the leaves, seeds, and fruits of 63 species of plants, has
been a topic of discussion for many years when it comes to its effects on health. The most common sources of
caffeine include coffee, tea, chocolate, and cola. Coffee is one of the most popular beverages in the world
(International Agency for Research on Cancer [IARC], 2016), with 80% of U.S. adults reporting that they drink it,
60% of whom do so daily (Loftfield et al., 2015). While there is no nutritional need for caffeine, many individuals
use it for brain stimulation since it is easily absorbed into the body within 30 minutes. Due to the fact that coffee,
and therefore, caffeine, are consumed in such high amounts, numerous studies have been conducted to look at
the potential health risks and benefits associated with their consumption (Loftfield et al., 2015).
Over the course of many years, researchers have looked at specific diseases, as well as overall mortality, in
relation to coffee and caffeine consumption. One of the biggest health concerns related to coffee has been
cancer. Until recently, the International Agency for Research on Cancer (IARC) had not discussed coffee
carcinogenicity since 1991. Previously, coffee was classified as possibly carcinogenic to humans. When the IARC
Work Group met in May 2016, new research showed that there were either no associations or inverse
associations between coffee consumption and cancer. The new classification made by the IRAC is that coffee is
unclassifiable with its carcinogenicity towards humans. Instead, the Working Group classified drinking very hot
beverages (over 65 degrees Celsius or 149 degrees Fahrenheit) as probably carcinogenic to humans due to tumor
promoting activity (IARC, 2016). Caffeine actually contains antioxidants, which are linked to protecting against
certain diseases, including cancer, heart disease and Type 2 Diabetes Mellitus (T2DM) (Wolde, 2014).
Diabetes is the seventh leading cause of death in the United States. An inverse relationship was found between
coffee consumption and diabetes-related mortality (Loftfield et al., 2015). Wolde, 2014, found that a higher intake
of coffee is associated with a significantly lower risk of diabetes, while tea, which also contains caffeine, has no effect on diabetes risk. In fact, those who consumed
6 or more cups of coffee per day have a 35% lower risk of
diabetes than those who drink 2 cups or less per day
(Wolde, 2014). Using data from the Prostate, Lung,
Colorectal, and Ovarian (PLCO) Cancer Screening Trial,
the association between coffee consumption and
mortality was looked at, as were disease specific
associations. The study looked at the amount of coffee
consumed (no coffee, <1 cup per day, 1 cup per day, 2-
3 cups per day, 4-5 cups per day, ≥6 cups per day), as
well as type of coffee (caffeinated and decaffeinated).
The inverse association between overall mortality and
coffee consumption is thought to be due to the inverse
associations between coffee consumption and other
conditions including heart disease, chronic lower
respiratory disease, influenza/pneumonia, and
intentional self-harm (Loftfield et al., 2015). In 2013,
Jiang et al. conducted a meta-analysis of 31 prospective
studies to look at the associations between coffee/ caffeine intake and the risk of T2DM. In all 31 studies, the inverse relationship
of greater coffee consumption and lower diabetes risk was found, some with
greater significance than others.
Although the exact mechanisms as to why coffee aids in lowering the risk of
developing diabetes are not completely understood, multiple inferences have
been made (Loftfield et al., 2015). Caffeinated coffee was found to be positively
related to improved insulin sensitivity, while decaffeinated coffee has a positive
relation to beta-cell function (Jiang et al., 2013). Caffeine may also protect
against T2DM through an increase in metabolic rate and thermogenesis, which
stimulates fatty acid release and fatty acid oxidation, thus mobilizing glycogen
in the muscles (Jiang et al., 2013).
Other factors influence the extent to which caffeine consumption impacts the
risk of diabetes. Studies that included gender found that although both
genders had inverse relationships between coffee consumption and diabetes,
this association was higher in females. Body Mass Index (BMI) plays an
important role in determining how strong coffee’s effects are since higher
BMI’s can cancel out those benefits. Adverse outcomes from smoking may also
cancel out the positives of caffeine intake, as stronger associations were found
among non-smokers. Experiments have been conducted to show that smokers
eliminate caffeine from the body more quickly than non-smokers, thus limiting
the time they have to utilize the benefits of caffeine (Jiang et al., 2013).
There is currently no recommendation as to how much coffee is needed to
reap the protective behaviors against diabetes. However, research shows that
an intake of 4 cups of coffee per day or more has significantly greater benefits
than 2 cups per day when it comes to lowering the risk of diabetes (Wolde,

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