MOCANU Andreea Gabriela1, NICOLAESCU Oana Elena1, BELU Ionela1
1 Pharmacy Department I, University of Medicine and Pharmacy, 2-4 Petru Rares Str., 200349 Craiova, (ROMANIA)
gabriela.mocanu@umfcv.ro, oana.nicolaescu@umfcv.ro, ionela.belu@umfcv.ro
Abstract
Poor quality sleep has become a major concern in recent years. A number of factors that include diet, lifestyle, and workload have been associated with this problem. Sleep quality may exert a certain effect in a number of health related issues including cardio-metabolic diseases and mental disorders.
Several strategies have been employed to improve sleep. They include reduction of external stimuli or relaxation strategies such as aromatherapy. Moreover, drug treatment is another highly used option. Studies suggest several dietary interventions that are a good alternative to these solutions. A diet low in various nutrients such as vitamins, minerals and dietary polyphenols is directly associated with poor sleep quality and sleep onset latency. Furthermore, a high consumption of confectionary and energy beverages has also been associated with poor sleep quality.
Keywords: poor sleep quality, sleep onset latency, insomnia, Mediterranean diet, energy intake, diet, vitamins, hydroxycinnamic acids
Introduction
Diet and its health impact has been a major focus. Recent studies show a bidirectional relationship between dietary factors and sleeping patterns, namely sleep quality and duration. Worldwide, poor sleep quality has been presented as an extensive public health issue. It has been reported that the average sleep duration has shortened by two hours in the last 40 years due to several factors such as lifestyle, workload and technology [1-3].
Sleep quality is assessed in most studies using the Pittsburgh Sleep Quality Index (PSQI) where each individual evaluates sleep duration, sleep efficiency, sleep quality, sleep onset latency, sleep disturbances, daytime dysfunction and use of sleep medication with a score which ranges from 0 to 3. A high PSQI total score expresses a low sleep quality. Furthermore, other objective measures of sleep such as amount of slow wave sleep or
duration of rapid eye movement (REM) sleep may also be used [4,5].
According to the National Sleep Foundation an optimal sleep duration is 7-9 hours for adults, aged 26-64 years and 7-8 hours for adults older than 65 years [6].
Sleeping habits are considered to exert a certain effect in a number of health related issues including both cardio-metabolic diseases such as diabetes or obesity and mental disorders. The mechanisms involved in this associations have not been entirely established. They include oxidative stress, inflammation, epigenetic modifications and gut microbiome. Furthermore, sleep deprivation may lead to increased C reactive protein and hypercortisolemia according to several experimental studies [3, 5, 7, 8].
Research studies show that unhealthy chronic sleeping patterns are linked to cognitive impairment. Moreover, results obtained in animal testing show that a long-term unhealthy sleeping behavior may determine both attenuation of synaptic efficiency and reduction of spine density [7].
Reduction of external stimuli or relaxation strategies such as aromatherapy are employed to improve sleep. Moreover, drug treatment is another highly used option. A number of studies suggest nutritional intervention as a good alternative to these solutions [3].
Dietary patterns and sleep quality
It has been reported that both short and long sleepers are more likely to have fewer main meals during the day and skip breakfast compared to subjects with a sleep duration of 7-8 hours [9].
Another study involving sleeping habits in Japanese female workers mentions worse sleep quality when irregular eating or skipping breakfast was involved [4].
High caloric intake may be associated with insomnia and poor sleep quality. Also, an increased intake of food per weight may promote longer sleep onset latency (Table 1). It has been suggested that increased ghrelin may play a role in this relationship [10]. Moreover, epidemiologic studies reported that a high total energy intake was consistent in short sleepers (5-6 hours) [6].
Philips et al showed that a diet high in carbohydrates and low in fat leads to reduced sleep onset latency and slow wave sleep. Furthermore, studies suggest that a diet high in fat lowers sleep efficiency and rapid eye movement sleep and increases slow wave sleep [11,12].
Previous studies have also reported that dietary proteins may affect sleep through tryptophan which is transformed into 5 – hydroxytryptophan and then to serotonin. Serotonin is further converted into melatonin which signals the onset of sleep and night time in the body. A study conducted among female Iranian students shows a link between a diet low in proteins, beans, fibers, fruits and short sleep duration [2,3,13].
Table I. Summary of clinical studies that assess the effects of dietary patterns on sleep quality
Study | Food | Subjects | Key observations |
Matsunaga et al. [5] | Various food groups, drinks and drugs | 124 male subjects, aged 19-29 years | Poor sleep quality was associated with higher intake of sugar sweetened beverages and lower intake of fat soluble vitamins and iron |
Katagiri et al. [4] | Various food groups and drinks | 3129 female subjects, aged 34 to 65 years | Poor sleep quality was related with a high frequency of energy drink consumption and higher intake of noodle |
Godos et al [8] | Dietary (poly)phenols | 2044 female and male subjects, aged above 18 years | Better sleep quality was linked to higher intake of some flavonoid subclasses, lignans and phenolic acids |
Jansen et al [14] | Dietary patterns | 4467 female subjects | Higher sleep quality was associated with a fruit and vegetable based dietary pattern in mid-life women |
Zuraikat et al [10] | Dietary patterns | 495 subjects, aged 20 to 76 years | Poorer sleep quality was associated with higher food weight and lower unsaturated fat intake |
Young et al [9] | Dietary behavior | 462 female subjects, aged 23 years | About 1.00 point higher PSQI scores were observed in subjects who reported drinking one or more high-calorie coffee drinks |
Matsuura et al [2] | Dietary pattern | 1997 subjects (940 men and 1057 women), aged 18-69 years | A total of 266 women and 205 men were reported as having moderate to severe insomnia symptoms. Moderate-severe symptoms were observed in men with inadequate intakes of vitamin C, total dietary fiber and zinc. |
Yajima et al [15] | Comparison between a high carbohydrate and a high fat diet | 10 healthy subjects | Reduced slow wave sleep was determined by a high carbohydrate diet as opposed to the high fat diet. |
Mediterranean diet
The Mediterranean diet represents the dietary pattern of most people in Southern Italy. This diet is characterized by a high consumption of vegetables, fruits and nuts. Moreover, it includes fish, whole grain cereals and dairy products as the main source of carbohydrates and proteins. The Mediterranean diet is also associated with a moderate intake of alcohol (red wine) and a daily consumption of olive oil [7].
The Mediterranean diet includes foods with a high content of flavonoid subclasses (apigenin), lignans and phenolic acids (hydroxycinnamic acids). These subclasses have been shown to lower oxidative stress, reduce systemic inflammation and express anti-neuroinflammatory properties. Furthermore, preclinical trials show that molecules such as apigenin are able to prolong sleep duration, decrease locomotor activity and potentiate sleep onset. Moreover, dietary polyphenols have been associated with improved resilience after sleep deprivation [7,8,16,17].
Several studies show that the Mediterranean diet may also benefit patients in the management of several conditions such as diabetes, depression, cardiovascular disorders, obesity and dementia. Epidemiological studies demonstrate that a high consumption of foods rich in hydroxycinnamic acids and flavanones lowers hypertension incidence. It has also been reported that a high adherence to the Mediterranean diet shows beneficial effects in increasing physical function and reducing pain in patients living with rheumatoid arthritis [7,8,18,19,20].
Sources that are high in apigenin include parsley, oregano, chamomile, celery and artichokes. Red wine is also a source that contains apigenin. The main sources for hydroxycinnamic acids are apple, pears, cherries, plums, kiwis, blueberries, artichokes, carrots, lettuce, eggplant and wheat [21].
Vitamins
Vitamins such as vitamin A, C, E and beta carotene have an antioxidant effect. Sleep regulation has been associated with oxidative stress, according to previous studies. Moreover, studies have reported an association between poor sleep and lower intakes of alpha tocopherol, beta carotene equivalents, retinol equivalents, vitamin K and vitamin B1. A preclinical trial reported that a vitamin A deficient diet determined lower deep sleep during non-REM sleep in mice. The best sources of alpha tocopherol are seeds, nuts and vegetable oil. In addition, carrots, apricots, sweet potatoes, cantaloupe are rich in beta carotene. Vitamin K sources include fermented soy beans and green leafy vegetables such as kale, spinach, turnip greens and lettuce [5,22].
Macrominerals
Calcium low intake has been linked with difficulty of falling asleep and sleep maintenance issues according to a US study [2].
Low levels of magnesium may determine moderate to severe insomnia symptoms. Magnesium helps in maintaining healthy levels of GABA, thus improving sleep quality. A study conducted on 46 elderly subjects showed that an intake of 500 mg for 8 weeks improved early morning awakening, sleep deficiency, sleep onset latency and sleep duration. Food sources high in magnesium are represented by nuts, seeds, seafood such as salmon and vegetables. Calcium rich foods include tofu, edamame, milk, cheese, yogurt and green leafy vegetables such as broccoli and cabbage [22,23].
Trace minerals
A lower intake of both iron and zinc has been related to poor sleep quality. A study conducted on Japanese subjects reported that participants with moderate to severe insomnia symptoms had a considerably lower intake of zinc and iron compared to those with no insomnia symptoms. Furthermore, sleep quality in patients with iron deficiency anemia is reportedly lower. This may be determined by the implication of iron in the dopamine system, which plays a role in sleep regulation. Seafood and vegetables, specifically spinach, sweet potatoes, kale, have a high content of iron. Meat and shellfish are excellent sources of zinc [2,5].
High caloric beverages and confectionary
High calorie coffee drinks consumption determined a longer sleep latency in a US study that included young adult women, aged 23. Another study conducted on Thai students showed that drinking one stimulant drink per week will increase the possibility of poor sleep quality by 50%. Furthermore, a high PSQI score was linked to the consumption of caffeinated beverages, alcohol and energy drinks [9]. Moreover, a high intake of soda and soft drinks may determine a shorter sleep duration, according to a Korean study [24]. Matsunaga et al determined that a higher intake of sugar-sweetened beverages leads to poor sleep quality [5]. This has all been confirmed by Katagiri et al who also mentions that high confectionary intake lowers sleep quality in Japanese women [4].
Conclusions
Diet is highly linked to sleep quality and sleep onset, with studies showing a bidirectional relationship between them. Moreover, sleep quality and duration may play a certain role in cardio-metabolic diseases and mental disorders. Dietary carbohydrates, proteins and fat all exert a certain effect in sleep quality and sleep onset latency.
A high adherence to the Mediterranean diet not only improves sleep quality by prolonging sleep duration and potentiating sleep onset, but it may also help in the management of several conditions such as cardiovascular disorders, diabetes, depression and metabolic disorders such as obesity.
Furthermore, the Mediterranean diet is high in polyphenols, which have been shown to lower oxidative stress, reduce systemic inflammation and express anti-neuroinflammatory properties.
A diet low in vitamins that include alpha tocopherol, beta carotene equivalents, retinol equivalents, vitamin K and minerals such as calcium, magnesium, zinc and iron has been associated with poor sleep in a number of studies. Furthermore consumption of caffeinated beverages, alcohol and energy drinks has been reported to determine poor sleep quality.
Thus, a balanced diet with a high intake of micronutrients and a low intake of both confectionary and energy beverages may promote better sleep quality.
Author Contributions: All authors have equally contributed to the work reported.
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