Introduction
Dietary intakes affect the physiology of the body and different foods have various effects on the organ functions. Dietary intakes and patterns are important determinants for maintaining health and disease prevention [1, 2]. Previous studies have reported that an appropriate healthy diet can prevent, control, and treat some chronic non-communicable diseases such as diabetes, hypertension, dyslipidemia, cardiovascular diseases, and cancer. Additionally, it can improve the immune system, reducing the risk of viral, bacterial, and fungal diseases [1, 2].
In modern medicine, nutrients and bioactive components of the food item determine the nutritional value of foods and their effects on the human body. Major parameters including moisture content, ash, energy, macronutrients (carbohydrates, proteins, and fats), and micronutrients (water-soluble vitamins, fat-soluble vitamins, and minerals) are considered in routine diet planning [3–5]. In recent decades, modern nutrition has been shifted towards a personalized diet planning approach to have the best positive health benefits from dietary intakes in healthy individuals as well as patients [2].
In philosophers’ opinion, maintaining health and disease treatment with appropriate foods and drinks is essential. Food is the primary substance of metabolism producing four humors (blood, yellow bile, phlegm, and black bile) [6–8]. The quality and quantity of consumed food has a direct effect on the produced humor and most diseases are caused by lack of attention to healthy diet and lifestyle by people [3–5, 7, 8]. Mohammad Zakaria Razi said: “whenever you can use food for treatment, do not use drugs” [7]. The mentioned narration is considered as a major determinant point of view in the medical management of healthy subjects as well as patients in the traditional philosophic approach [7].
From the philosophers’ point of view, an individualized nutrition program is recommended for each person according to his/her characteristics such as age, season, gender, weather, occupation, climate, and gastrointestinal tract function and considering food properties including temperament [9, 10]. Four major temperaments of food items include warm, cold, wet, and dry. Identification of the food temperament is based on comparative (comparison with other foods in terms of color, taste, smell, etc.) and experimental (observation effects of food consumption by animals or humans under certain conditions or accidentally) models. Moreover, foods are divided into three degrees in each of the four temperaments based on the severity of their induced effect on the organ functions as well as the whole body physiology [9–14].
A comprehensive and integrated approach to individualized diet planning may lead to greater beneficial effects of dietary intake. Therefore, we investigated the probable relationships between temperament and nutritional facts of Iranians’ frequent foods in the present study.
Material and methods
This study was carried out in three phases using the summative content analysis method during September-November 2019.
Extraction of the Iranians’ frequent food items
First, in order to extract the Iranians’ frequent food items, an academic discussion panel consisting of seven physicians specializing in nutrition and Iranian medicine was held and a list of frequent foods was prepared.
Secondly, the list was compared with the Iranian Food Composition Table (published by the National Nutrition and Food Technology Research Institute, 2018) and some available food frequency questionnaires (FFQ) [11–15] and a list of 152 food items was obtained.
Then, to reach a reviewable list for the integrative studies of nutrition and traditional medicine concepts, foods with the following characteristics were excluded:
Compound foods: due to lack of traditional medicine information and sometimes accurate nutrition information in compound foods.
In this study, in order to reduce the study error, the following substances were excluded from the study: pickles, sausages, pasta, cream, and some dairy products such as cream cheese, pizza, cheese, and jams.
Missing names in traditional medicine texts or not being found by the researcher: due to the impossibility of collecting traditional medicine information.
In this study, in order to reduce the study error, the following substances were excluded from the study: tomatoes and paste, soybeans, green beans, peas, onions, persimmons, peanuts, cocoa, potatoes, maize and maize oil, tangerines, and carrots.
Lack of required nutritional information or not being found by the researcher: the impossibility of collecting nutritional information.
In this study, in order to reduce the study error, the following substances were excluded from the study: Damask rose, rosewater, okra, shallot, fumitory, coriander, jujube.
By excluding the above, the list of 110 frequent foods finally became the focus of this study.
Determination of the extracted food items’ temperament and nutritional facts
Through a comparative study with Iranian medicine, textbooks including Al-Qanun, Al-Jame Le-Mofaradat Al-Adviah, va Al-Aqziah, Makhzan Al-Adviah, Al-Shamel, Tohfa Al-Momenin, Al-Ma, Farhang Nafisi, Farhang Taj Al-Arus and Farhang Arabic, the traditional names of these substances were extracted [10, 16–22].
Temperament of food has been determined from two valid books, Al-Qanun Fi Al-Tib (written by Sheikh Al-Ra’is Hakim Bu’Ali Sina) and Makhzan Al-Adviah (written by Hakim Mohammad Hussein Aghili Khorasani) [16, 21]. In case of differences between the two texts, due to the late use of Hakim Aghili, it was based on the opinion of Makhzan Al-Adviah.
Nutritional facts were also extracted from two references, the Iranian Food Composition Table and the USDA International Database (official website of the United States Department of Agriculture) [12, 19].
The food list table was completed by including food names (custom names, frequent/common English names, names in traditional medicine texts, and scientific names), temperaments, and nutritional facts.
Statistical analysis of the extracted data via SPSS software
Finally, using SPSS software and Jonckheere-Terpstra test, the probable association between temperament and nutritional facts was investigated. The statistical test determined whether due to changing different temperaments of food items (cold-moderate-hot and wet-moderate-dry), their nutritional facts change or do not change.
The study method process is summarized in Figure 1.
Results
Food temperaments
In this section, the temperaments of the analyzed foods are classified based on warm and cold temperaments (Table I) and wet and dry temperaments (Table II).
Table I
Food assortment based on warm and cold temperaments
Table II
Food assortment based on wet and dry temperaments
Water, ash and macronutrients
Ash, moisture and macronutrients including protein, total carbohydrates, fiber, total sugar, total saturated fatty acids, total monounsaturated fatty acids, total polyunsaturated fatty acids, and total trans fatty acids.
Table III shows the food assortment based on water, ash, and macronutrients.
Table III
Food assortment based on water, ash and macronutrients
Vitamins
Vitamins are organic molecules that are needed and their supply is completely dependent on food intake (except for vitamin D).
Vitamin content of different food items is determined using High-Performance Liquid Chromatography (HPLC) method [12, 23].
Table IV shows the extracted food assortment based on the highest content of vitamins.
Table IV
Food assortment based on vitamins
Minerals
Minerals are inorganic molecules which are divided into macro- and microminerals. Macrominerals include calcium, phosphorus, magnesium, potassium, sodium, chlorine, and sulfur and some highlighted microminerals are iron, zinc, copper, iodine, fluorine, and selenium.
In food items, after determining the content of ash (g per 100 g of food), the content of minerals is determined using the Atomic Absorption method.
Table V shows the food assortment based on the highest content of minerals.
Table V
Food assortment based on minerals
Food temperaments and their nutritional facts
Table VI shows the probable associations between warm and cold temperaments and nutritional facts. Nutritional facts with a higher mean of numbers in foods with warm temperament include energy, iron, and manganese, and cold temperament foods had higher amounts of moisture.
Table VI
Relationship between warm/cold temperament and nutritional facts
The association between wet and dry temperaments and nutritional facts was also investigated. The results are summarized in Table VII.
Table VII
Relationship between wet and dry temperament and nutritional facts
As it is demonstrated in Table VII, nutritional facts with a higher mean of numbers in foods with wet temperament include moisture, total trans fatty acids, cholesterol, vitamin B12, vitamin A, and retinol. On the other hand, dry foods had higher content of ash, total carbohydrates, fiber, vitamin B6, calcium, iron, magnesium, potassium, and manganese.
Discussion
According to our search, few studies have been conducted on the relationship between modern scientific findings and traditional temperament of foods or drugs. To the best of our knowledge, this study was the first research investigating the probable association between nutritional facts and food temperaments.
Studies of Ardekani et al. on temperaments and chemical compounds of medicinal plants indicated that plants containing phenol compounds mostly have warm and dry temperaments; those containing tannins frequently have cold and dry temperaments and those containing volatile oils often have warm and dry temperaments. Moreover, plants with volatile oils with an alcoholic structure have cold and dry temperaments and those containing alkaloids based have cold or warm and dry temperaments. So, this study showed that plants have a special temperament based on their active ingredients and the effect of each plant based on the active ingredient is somehow related to the temperament [24].
In another study conducted on rats, Parvinroo et al. investigated different parameters by giving hot spices including fennel, apricots, and anise seeds, and cold foods including watermelon, cucumbers and squash seeds. This study showed a significant increase in thyroid hormones using hot spices (FT4 in fennel and T3 in fennel, anise, and aloe) and a significant increase in corticosteroids in cold foods [25]. According to the changes in the body’s hormones by food, it can be said that an increase in thyroid hormones increases the body’s metabolism and indicates the warm temperament of food consumed and an increase in corticosteroids as an anti-inflammatory marker indicates the cold temperament of food consumed. The results of another study conducted by Jafari Nejad Bajestani et al. on feeding rats with foods having different temperaments showed that feeding with watermelon juice reduced nerve conduction velocity and memory in rats, and feeding with carrot seed extract was effective on increasing thyroid hormones. This study also showed the effect of different temperaments of foods on physiology of the body [26, 27].
The classification of foods into cold-warm and dry-wet temperaments has caused different reactions in different people according to their temperament, from fluids (blood, lymph, interstitial fluid, and plasma) to organs (including the gastrointestinal tract, liver, heart, as well as the arterial and venous walls) and these effects can be acute, sub-acute or chronic.
Moreover, in our study, according to the obtained results, an association was found between nutritional facts and four temperaments. Energy, iron, and manganese were observed more frequently in foods with the warm temperament and were statistically significant. According to Iranian medicine, foods with the warm temperament have the ability to perform more metabolism and energy in the body due to the production of warm humors. Therefore, the component of energy is directly related to the discussion of foods with the warm temperament. To the best of our knowledge, the warm temperament itself increases molecular activity and energy production, and in this study, the association between energy and foods with warm temperament was significant [10, 23].
The results of the present study demonstrated that a higher amount of iron was found in warm temperament foods than cold temperament ones. From the philosophers’ point of view, iron has a warm temperament leading to blood production as one of the four main humors having warm and wet temperament. Similarly, iron is considered as an essential agent for hematopoiesis in modern medicine [10, 23].
Manganese is a mineral playing a role in regulating blood pressure and heart rate, as well as energy extraction from foods. Regarding the aforementioned association between energy and the warm temperament, it may be claimed that this mineral would have a warm temperament. Moreover, the heart as a dynamic organ that is constantly contracting, has a warm and dry temperament from the philosophers’ perspective; and it is the warm temperament that causes this muscle contraction. Therefore, manganese seems to have a warm temperament due to its heart desire and its function in regulating blood pressure and heart rhythm. This mineral was found to be at higher levels in foods with a warm temperament.
The statistical analysis of the extracted data of the present study showed that zinc was also found to be at higher amounts in warm foods. Zinc is a micronutrient involved in protein synthesis, cell growth and proliferation related pathways. From the perspective of traditional medicine, the phenomenon of growth requires a warm temperament because it causes expansion and volume increase. In this regard, we can refer a warm temperament to individuals having larger physique and limbs.
There was a positive association between coldness of foods and the content of moisture in the present study.
Additionally, vitamin A was reported to be more in foods with cold and wet temperaments. Vitamin A is a fat-soluble vitamin that plays a role in the vision and preservation of the body’s mucous membranes. Vitamin A deficiency causes the cornea to become dry and thick, which is called exophthalmia. It can be said that this vitamin has cold and wet temperaments and with these temperaments, it keeps the necessary moisture for the eyes from drying out [23]. The cold and wet temperament may also be effective in creating anti-inflammatory properties for the healing of skin wounds and mucous membranes. Furthermore, the total trans fatty acids (TFAs) and cholesterol levels were higher in foods with high moisture, which similarly may be due to the wet temperament of fats in Iranian medicine [18, 20, 22].
On the other hand, the average amounts of minerals including calcium, iron, magnesium, potassium, and manganese in foods with dry temperament were higher than the mineral content of cold foods. Ash was also observed at higher levels in foods with a dry temperament. By definition, ash is the residual of minerals of foods after the extraction of organic matter; so ash could have a dry temperament due to its mineral and soil components.
The obtained data from the present study showed that dry foods have higher amounts of fiber in comparison to wet foods as well. Consistently, dryness is a factor leading to food indigestion and malabsorption from the philosophers’ point of view [28]. Further studies, especially food analytical studies, are required to investigate the accuracy of aforementioned findings.
Notably, the effect of each food item on the whole body function and organ physiology are not only affected by its temperament from the traditional medicine approach. In this medical approach, the complex of foods’ matter, forms and accident may determine the net effect of that dietary intake on the body [18, 21, 22]. Therefore, we cannot exclusively address all findings of the present study to the temperament concept. Moreover, philosophers have a holistic approach to all phenomena including body and foods: as each food may have a unique effect on each consumer body and each food may be effective in the prevention and treatment of diseases without separating its constituent elements. Therefore, further studies are required to investigate the exact relationships between nutritional facts, foods’ matters, forms, and accidents.
In conclusion, the summative qualitative content analysis of the obtained data in the present study demonstrated positive associations between warmness of the food temperament and their energy, iron, and manganese content. On the other hand, cold foods had higher amounts of moisture, fat, and fat-soluble vitamins. Additionally, ash and mineral content of dry foods were at higher amounts in comparison to foods with a wet temperament. These findings indicate probable relationships between the traditional philosopher’s opinions and their medical approach and modern nutrition. However, further food analytical, experimental, and clinical studies are required to investigate the exact relationships between modern nutritional scientific facts and traditional foods’ characteristics.
