Diet and insomnia

Consumption of higher amounts of dietary starch, refined grains and added sugars have been shown to:

• increase the risk of insomnia (Gangwisch et al., 2020)
• reduce quality of sleep (Alahmary et al., 2019)
• decrease total sleep time in children (Al-Disi et al., 2010, Firouzi et al., 2014)

Higher intakes of added sugar are known to decrease (Firouzi et al., 2018):

• sleep quality
• sleep duration

Elevated intake of sugar-sweetened beverages is known to result in:

• poor sleep quality (Boozari et al., 2021)
• decreased sleep duration (Anjum et al., 2018)

Increased consumption of dietary fibre, whole grains, vegetables and fruit are associated with decreased likelihood of insomnia (Gangwisch et al., 2020).

Insomnia, blood sugar, and cravings

Insufficient sleep can promote carbohydrate and sugar consumption. Lack of sleep can result in:

• impaired glucose metabolism and elevated blood sugar level (Alahmary et al., 2019)
• decreased amounts of the hormone leptin and increased amounts the hormone ghrelin – which can result in an increased appetite for unhealthy foods – especially those that are starchy, sweet, and salty (Boozari et al., 2021)

Commorbidities and insomnia

Health conditions commonly seen with obesity and diabetes that can contribute to insomnia include (Alahmary et al., 2019):

• sleep apnea
• restless leg syndrome
• nocturia (nighttime urination)
• drop in nighttime bloodsugar levels

Caffeine is a natural molecule found in coffee, tea, chocolate and other sources, that has stimulant properties.

Negative effects of caffeine consumption on sleep

Caffeine consumption can increase (Chaudhary et al., 2016):

• difficulty falling asleep
• time to fall asleep
• awakenings
• daytime sleepiness
• nighttime worrying
• perceived sleep quality (Clark & Landolt, 2017)

Caffeine consumption can decrease:

• total sleep duration (Bonnet, n.d.) (Chaudhary et al., 2016)
• sleep efficiency – the amount of time asleep compared to time in bed (Clark & Landolt, 2017)
• stage 2 and stage 4 sleep (REM sleep) (Bonnet, n.d.)

Caffeine and insomnia

• Caffeine is known to disrupt sleep in a dose-related manner – the more caffeine consumed, the greater the effect (Bonnet, n.d.).
• Caffeine consumption is often encountered as a cause of insomnia in patients in sleep disorder clinics (Walsh et al., 1986).
• Many studies in sleep laboratories using EEG or actimetry (measuring limb movements) during sleep implicate caffeine in reduced sleep quality (Clark & Landolt, 2017).
• Consuming caffeine multiple times during the day, or later in the day increases its effects on sleep (Drake et al., n.d.).
• Caffeine consumption within 3 hours of sleep is known to consistently lower total sleep time (Sher & Fashner, 2019).
• Consumption of caffeine within six hours of going to bed is known to interfere with normal sleep (Drake et al., n.d.).
• Low to moderate caffeine consumption in the morning is not likely to cause sleep issues (Youngberg et al., 2011).
• People with anxiety may be more susceptible to insomnia due to caffeine consumption (Boulenger & Udhe, 1982).

Amounts of caffeine typically found in drinks and food (Harvard T.H. Chan School of Public Health, 2020):

• Coffee (1 cup) – 95 mg
• Coffee, instant (1 cup) – 60 mg
• Coffee, espresso (1 shot) – 65 mg
• Tea, black (1 cup) – 47 mg
• Tea, decaffeinated (1 cup) – 2 mg
• Tea, green (1 cup) – 28 mg
• Soda, cola (12 ounces) – 40 mg
• Soda, Mountain Dew (12 ounces) – 55 mg
• Chocolate, dark – (1 ounce) – 24 mg
• Guarana-based drinks – up to 125 mg per serving
• Energy drinks – 85–170 mg per serving
• Energy drink shots – 200 mg per serving

Commercially available 16-ounce servings of coffee can contain up to 500 mg of caffeine (Drake et al., n.d.)

Caffeine intake and insomnia

Studies of caffeine and sleep have shown:

• the average daily caffeine consumption is between 130 and 500 mg (Drake et al., n.d.)
• higher amounts of caffeine result in more sleep interruption than lower amounts of caffeine (Clark & Landolt, 2017)
• 300 mg of caffeine given to late middle-aged adults before bed, increased the time required to fall asleep by an average of 66 minutes, and decreased total sleep time by an averange of two hours (Březinová, 1974)
• 300-400 mg of caffeine near or at sleep time decreased total sleep time by 30–80 minutes (Bonnet, n.d.)
• adolescents who consumed more than one caffeinated drink a day were 1.9 times more likely to have trouble sleeping when compared with those who drank less than 1 cup a day (Clark & Landolt, 2017)
• college students with who consumed 3–5 cups of coffee a day regularly got six or less hours of sleep per night (Chaudhary et al., 2016)

Caffeine and hyperarousal

Metabolic hyperarousal decreases sleep pressure, which in turn, increases risk of sleep issues.

Administration of caffeine in studies has been shown to raise indicators of increased metabolism including:

• oxygen consumption during sleep (Bonnet, n.d.)
• plasma free-fatty-acid levels and fat burning (oxidation) (Acheson et al., 1980)
• carbohydrate burning (oxidation) (Bracco et al., 1995)
• With chronic consumption of caffeine the perceived stimulation and energy,  shifts to an “uncomfortable inability to rest or relax” (Bonnet, n.d.).

Caffeine and the circadian rhythm

Caffeine is known to affect key molecules involved in regulation of the circadian rhythm – adenosine and melatonin.

• Caffeine reduces night-time melatonin levels (Wright et al., 1997).
• Caffeine reduces the normal evening temperature drop (Wright et al., 1997). A drop in body temperature is key aspect of sleep initiation.

Caffeine and adenosine receptors

• Adenosine receptors perform a central role in inducing sleep (Huang et al., 2014; Frozi et al., 2018)
• Molecules that interfere with adenosine receptors promote wakefulness.
• The sleep-inhibiting effects of caffeine are primarily caused by blocking adenosine receptors (Fredholm et al., 1999). (Frozi et al., 2018).

Degree of caffeine effects

The amount of effects from caffeine are influenced by:

• adaptation to caffeine
• rate of caffeine metabolism
• age
• estrogen
• genetics

Adaptation to caffeine

• Adaptation by the body to chronic caffeine consumption can reduce its insomnia-promoting effects (Bonnet, n.d.).
• Caffeine-associated sleep problems have been shown to decrease with chronic caffeine consumption (Chaudhary et al., 2016).

Rate of caffeine metabolism

• People who have insomnia due to caffeine consumption have been shown to detoxify caffeine less effectively compared to those not negatively affected by caffeine (Levy & Zylber-Katz, 1983).

Age and caffeine metabolism

• Older adults can be more sensitive to the effects of caffeine than younger adults (Clark & Landolt, 2017).
• Caffeine-induced insomnia has been shown to increase with age (Frozi et al., 2018).

Estrogen and caffeine

• Estrogen is known to negatively affect sleep (Eichling & Sahni, 2005)>
• Estrogen is known to decrease the number of adenosine receptors, and decrease release of adenosine (Dorsey et al., 2021)>

Genetics and caffeine

• Genetics affect susceptibility to insomnia by influencing caffeine intake and body response to caffeine (Yang et al., 2010).
• Genetic polymorphisms related to caffeine are associated with decreased capacity to detoxify caffeine (due to polymorphisms of the CYP1A2 gene) (Clark & Landolt, 2017)

Genes implicated in increased sensitivity to caffeine as well as caffeine-induced insomnia include Clark & Landolt, 2017):

• ADORA2A (adenosine A2a receptor)
• ADA  (adenosine deaminase)
• DARPP-32 (dopamine- and cAMP-regulated neuronal phosphoprotein)
• PRIMA1 (Proline Rich Membrane Anchor 1)

Medications that are known to increase risk of insomnia include:

• anticonvulsants (Pagel & Parnes, 2001)
• bronchodilators (Pagel & Parnes, 2001)
• diuretics (Pagel & Parnes, 2001)
• opioids and analgesics (Garcia & Salloum, 2015)
• Parkinson’s disease medications (Pagel & Parnes, 2001)
• SSRIs (selective serotonin reuptake inhibitors) (Welsch et al., 2018)
• statins (Tuccori et al., 2008)
• steroids (Pagel & Parnes, 2001)