The present study is the first to analyze dietary patterns among MS patients and controls based on the traditional concept of food nature. As reported above, four major dietary patterns were recognized, explaining 57.8% of the total variance. This study showed that cold-natured foods, high-fat diets, additives, and acidic seasonings might elevate the risk of MS, whereas hot and balanced foods, fruits, starches, and nuts might offer protection against the disease. The dairy and legumes food pattern showed no significant association with MS.
Recently, contradictory findings have emerged about the impact of food patterns and diet quality on MS. A systematic review on the influence of diet on MS indicated that deficiencies in micronutrients (vitamin D and vitamin B12) can influence the progression of MS . Mitochondrial dysfunction, epigenetic modification, gut microbiota, and neuroinflammation are major pathways that are accountable for food action on brain health [28, 29]. A previous study indicated that dietary antioxidants and abnormalities in lipid and glucose metabolism may influence the progression of neurodegenerative diseases [30, 31]. Healthy eating patterns, such as a low-fat or Mediterranean diet, may reduce systemic inflammation and MS attacks, thereby improving the quality of life . However, another previous study showed that there is no evidence of a correlation between diet quality and the risk of developing MS among women . Nonetheless, maintaining a healthy diet (high in poultry, fish, eggs, vegetables, and legumes) instead of a Western diet (high in meat, full-fat dairy; low in whole grains, nuts, fresh fruit, and low-fat dairy) may be beneficial for those at high risk of MS . Hence, further research into the relationships between dietary patterns and MS seems warranted.
The theory of “hot and cold natures” is based on the beliefs of Hippocrates (Greek physician, 460—375 BC) and Galen (199—129 BC) [24, 34]. A recent study found that cold- or hot-natured foods did not affect the brain health or behavior of students . A study by Chunhong Liu et al. evaluated 284 foods according to their cold or hot nature, suggesting that the nutrients of foods could be one of the distinguishing factors for categorizing their cold or hot essence . Another multivariate analysis found that 18 food components had major effects on the cold or hot properties of foods .
In this study, cold-natured foods included cold-natured meats (cow and veal meat, hen and chicken, fish/seafood, canned tuna, hamburgers, sausages, bologna, and pizza), cold-natured fruits (watermelon, apricot, cherries, peach, nectarine, greengage, grapefruit, orange, tangerine, pomegranate, plum, and strawberry), and additives (chips, cheese balls, sugar, salt, etc.). The analyses in the current study showed that food patterns that include foods with a cold-nature, a high-fat diet, additives, and acidic seasoning may increase the risk of MS. The results of this study indicated that a high-fat diet (butter, olive oil, animal fat, margarine, hydrogenated vegetable oil) could increase the risk of MS. In line with this finding, a previous study showed that animal fat can affect the progression of MS through the mechanism of low-grade systemic inflammation . The current results are also in accord with the authors’ earlier observations, which showed that animal fat may increase the risk of MS . However, this data must be interpreted with caution, because saturated fatty acids, monounsaturated fatty acids, and multi-unsaturated fatty acids were not distinguished in our analysis. The current study showed that some cold-natured foods can increase the risk of MS. The exploration of potential mechanisms is difficult, but recent Chinese studies have shown that low levels of antioxidants or vitamins (B6; folate) may contribute to the cold essence of certain foods [23, 37]. This finding is in agreement with recent studies indicating that deficiencies in folate, vitamin B12, and other vitamins might contribute to the progression of MS.
The current study showed that food patterns that include hot-natured meats or fruits, starches, and nuts with a hot and balanced nature might be protective against the development of MS. Here, hot-natured foods included sheep meat, eggs, and organ meats (tongue, rumen, face meat, foot, heart, and liver), while hot and balanced fruits consisted of pears, apples, fresh berries, cantaloupe, melon, fig, grapes, kiwifruit, persimmon, banana, fruit juices, and compote. Consistent with this study, in a double-blind randomized trial, a hot-natured diet had beneficial effects on improvement in the clinical scores and immunological indicators (IL-4, IFN- and IL-17) of 100 MS patients . Another possible explanation for this is that the total antioxidant capacity of the hot-natured diet is higher relative to the cold-natured diet . This finding is in part contradictory to previous studies that suggested a high intake of unprocessed red meat may decrease the risk of MS, though no distinction was made between sheep meat and cow meat in these studies [20, 39]. Additionally, research has shown that the restriction of dietary red meat has no major effect on the severity of the disease [40, 41].
In the current study, based on theories of traditional medicine, fruits were categorized according to their cold or hot nature, and the results showed that hot-natured fruits had a protective role, whereas cold-natured fruits increased the risk of MS. However, the findings of the current study do not completely support the previously established literature. Abdollahpour et al. indicated that fruit and vegetable intake might serve as a protective factor against MS . Furthermore, in other studies, high fruit and vegetable intake was linked with a reduced risk of MS [8, 42]; a possible explanation for this may be that fruits and vegetables are rich in vitamins B and C [43, 44]. As mentioned, cold-natured fruits increase the risk of MS. This partial inconsistency may be due to the fact that hot- and cold-natured fruits were not separated in the previous studies. Generally, nuts have a hot nature according to TPM and fulfill a protective role against MS. Based on previous studies, nuts are rich in minerals and omega-3; therefore, they could have an anti-inflammatory effect on pathways of inflammation and MS [8, 45].
The strong point of the analysis in the current study is the use of the FFQ. Due to the limitation in the number of cases, however, a case-control design with three-times more controls was utilized to improve the validation of analyses. In addition, based on the design of study, these studies cannot prove causality, but they can provide strong evidence and strength association. To develop a full picture of dietary patterns based on the traditional concept of food nature, powerful research methods, such as clinical trial studies, will be needed.