Diet is a complex combination of foods from various groups and nutrients, and some nutrients are highly correlated. It is challenging to separate the effect of a single nutrient or food group from that of others in free-living populations.
Many studies have evaluated the role of individual nutrients on the development of psoriasis. Some of them are really fruitful during management of psoriasis. After searching more than 300 articles from PubMed with key word diet and psoriasis, here I am discussing about the diet and nutrients which can affect the chronic course of psoriasis.
Mediterranean diet
The Mediterranean diet is a healthy eating pattern, associated with reduced risk for metabolic, cardiovascular, and neoplastic diseases,that has consistently been shown to provide a degree of protection against chronic degenerative diseases. One of the most accredited hypothesis of this association is that the high content of different beneficial compounds, such as antioxidants and polyphenols, largely present in Mediterranean foods, such as plant foods, fruits and red wine, have anti-inflammatory properties. In particular, the monounsaturated fatty acids intake, whose major source is represented by extra virgin olive oil (EVOO), was found to be associated with a reduced prevalence of risk factors for major chronic inflammatory diseases. The Mediterranean diet it is characterized by a high intake of fruit and vegetables, legumes, grains and cereals, fish and seafood and nuts; a low intake of dairy products, meat and meat products; and a moderate ethanol intake mainly in the form of wine and during meals.
Fish Oil
Oils of cold water fish rich in omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) have been considered for use in psoriasis treatment. Several uncontrolled, open studies have also shown that supplementation of fish oil, ranging from 0.54 to 13.5 grams EPA and 0 to 9.0 grams DHA daily for 6 weeks to 6 months, resulted in clinical improvement, measured by erythema, induration, and scaling. These studies have also demonstrated clinical improvement associated with inhibition of leukotriene B4 production in peripheral leukocytes in vitro, decreases in platelet malondialdehyde production, changes in abnormalities of erythrocyte lipid membrane pattern, and increase in leukotriene B5 to leukotriene B4 ratio in peripheral blood neutrophils. Consumption of omega-3 fatty acids from fish oil forms leukotrienes and prostaglandins that are of odd-number, such as prostaglandin E3 and leukotriene B5, which oppose the even-numbered inflammatory mediators, decreasing overall inflammation. A high consumption of omega-3 fatty acids is found in the populations of the West African countries, and this dietary intake of omega-3 has been linked to a low incidence of psoriasis in this region. The most common side effects of fish oil include nausea, which may be dose dependent, indigestion, diarrhea, and fishy taste in the mouth.
Vitamin D
Vitamin D deficiency associated with psoriasis has been reported. Vitamin D derivatives have been widely used as a treatment for psoriasis in topical form. Vitamin D has been found to be immune regulators that may benefit inflammatory diseases like psoriasis through its effects on T-lymphocytes type 1 (Th1) cells. Vitamin D3 acts through the vitamin D receptor, which activates transcription of genes that affect keratinocyte proliferation and differentiation. Genetic polymorphisms in the vitamin D receptor and vitamin D metabolic pathway may impact levels of circulating vitamin D3. Vitamin D has also been found to impair the capacity of human plasmacytoid dendritic cells to induce T-cell proliferation and secretion of the T helper 1 cytokine interferon-gamma. A brief exposure of sunlight to bare body is sufficient for the formation of endogenous vitamin D formation. The flesh of fatty fish (salmon, tuna and mackerel) and fish liver oils are among the best sources of dietary vitamin D supplementation. Mashrooms, cheese and egg yolks are also contain vitamin D. Possible side effects of oral vitamin D supplementation include hypercalcemia, hypercalciuria, and kidney stones. Long-term vitamin D overdose can also lead to bone demineralization.
Vitamin B12
Vitamin B12 deficiency associated with psoriasis has been reported. As this vitamin is animal derived so late onset psoriasis in vegetarian diet people are quite severe. Shellfish, organ meat (liver), crab, fortified soy products and cereals, swiss cheese and eggs contain higher amount of vitamin B12. Vitamin B12 has no common side effects reported. Rare side effects include hypersensitivity reaction, nausea, vomiting, myalgia and swelling.
Selenium
Selenium is an essential element with anti-proliferative and immunoregulatory properties. Selenium has been hypothesized to regulate immune processes in psoriasis by increasing the number of CD4+ T cells in the reticular dermis of plaques Several trials have assessed the role of selenium supplementation in psoriasis. Seafoods and organ meats are richest food sources of selenium. Pork, turkey, chicken, fish, shellfish and eggs contain high amounts of selenium. Some beans and nuts especially Brazil nuts, contain selenium. Side effects with selenium are quite uncommon and are observed at doses above 400 mcg/ day. They include nausea, vomiting, nail changes, loss of energy, and irritability. Long-term selenium toxicity can mimic arsenic poisoning and can include nail changes, nausea, vomiting, garlic breath, metallic taste, and hair loss.
Gluten-free Diet
It is well established that psoriasis patients are more likely to have concurrent autoimmune diseases, particularly those affecting the gastrointestinal tract such as Crohn’s disease and ulcerative colitis. Recent large study showing that psoriasis patients have 2.2 fold risk of being diagnosed with celiac disease compared to matched controls. Epidemiological and clinical studies suggest there is an association between psoriasis, celiac disease, and celiac disease markers. So switching to a gluten free diet may improve the psoriasis. Gluten free diets are beans, seeds, nuts, fresh eggs, meats and fish, fruits and vegetables and dairy products. Suspected psoriasis patient with celiac disease must avoid barley, rye, triticale and wheat.
Pepper
An experimental study showed that consumption of red pepper produced exfoliation and nitrosation of the intestinal epithelium of rats because it has nitrophenols, resulting in chronic inflammatory bowel disease with neutrophil infiltrate and transepithelial neutrophil migration as markers. Evidence shows that induction of IL8 in the intestinal epithelium acts as a trigger factor for neutrophil recruitment in several types of inflammation, including colitis and psoriasis. Studies of the colonic mucosa in rats showed that, under the action of capsaicin, there was increased expression of transforming growth factor (TGF). The transforming growth factor TGF-alpha is a polypeptide produced by keratinocytes whereas the epidermal growth factor is produced anywhere in the body. Both bind to the same active receptor tyrosine kinase in the basal and immediately suprabasal epidermis to stimulate cell proliferation. In psoriasis, the keratinocyte intensely participates in the multicellular and multimolecular activation of the network coordinated by cytokines.
Caffeine (1,2,7 trimethylxanthine)
Caffeine is quickly and completely absorbed in the digestive tract, being distributed to all body tissues. It has a half-life of 2.5 to 10 hours. Plasma concentrations are reached within one hour. Metabolism occurs mainly in the liver; 95% of its transformation occurs in cytochrome P 450, originating more than 25 metabolites, while the remaining 5% are excreted in urine. The main mechanism of action of caffeine is due to its structural similarity with the adenosine molecule, being able to bind to its receptors (A1, A2A), blocking them and, therefore, having a stimulating action. Caffeine has pro-inflammatory effects when administered in the presence of an acute inflammatory process in rats, increasing tissue damage evidenced by increased mRNA levels of TNF-alpha, TNF-beta, lymphotoxin-beta, IL-6 and IFN-gamma in the spleen and increased IFN-gamma in peripheral blood. Cytokines such as IFN-gamma act as mitogens for keratinocytes in psoriasis.
The caffeine and chlorogenic acid present in coffee contribute to increased homocysteine, which is a risk factor for cardiovascular disease. Homocysteine requires folic acid, vitamin B12 and vitamin B6, which act as cofactors for its metabolism. In psoriasis, plasma homocysteine is increased and correlates directly with the PASI score and inversely with folic acid levels; there is probably an increase in consumption or a decrease in absorption.
At least half of the world population consumes tea. Prepared from the leaves of Thea sinensis, tea contains caffeine, theobromine and theophylline. 13 Theophylline has the ability to enhance epidermal keratinization, possibly by restricting the activity of the gene associated with proliferation, and to strengthen activities related to the maturation and cell differentiation of normal or psoriatic epidermis.
Smoked food and barbecue
These foods lead to functional and morphological alterations in polymorphonuclear leukocytes and it can also cause a higher release of chemotactic factors, with an increase of interleukin 1 B, TNF-alpha and transforming growth factor-beta, which have been associated with the severity of psoriasis.
Cooking methods that use high temperatures and low humidity (frying, roasting, grilling), especially food high in lipids, contribute to the high dietary content of AGEs-Advanced glycated-End Products, which damage cells and bind to specific receptors, causing the production of inflammatory cytokines and growth factors.
Miscellaneous
High fiber diets may reduce circulating endotoxins. Elevated endotoxins are positively associated with psoriasis.
Fruits and vegetables (especially carrots) may alleviate psoriasis.
One clinical observation is that psoriasis patients given a rice diet showed a dramatic reduction in or disappearance of their skin lesions.
The skin lesions in four cases of long- standing psoriasis cleared strikingly when the patients were placed on a low-tryptophan diet. In three of the four patients the lesions cleared completely.
The last but not the least one is that concomitant use of curcumin with methotrexate decreases the hematological side effects of methotrexate during treatment of psoriasis.
ACKNOWLEDGEMENT
I pay my sincere thanks to Dr. Rashmi Gupta consultant “Pearl-The Skin & Cosmetic Clinic” for her efforts in preparing the article.
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