• Sharply bordered reddened rash or plaques covered with overlapping silvery scales
• Characteristic locations: scalp; back of the wrists, elbows, knees, buttocks, and ankles; and sites of repeated trauma
• Family history in 50% of cases
• Nail involvement results in characteristic “oil drop” stippling (thimble-like appearance)
• Possible arthritis
Psoriasis is an extremely common skin disorder. In the United States, it occurs in 2 to 4% of the population. Psoriasis affects mainly Caucasians. It affects few blacks in tropical zones but is more common among blacks in temperate zones. It appears commonly among Japanese but is rare in American Indians and is entirely absent in natives of the Andean region of South America. Psoriasis affects men and women equally, and the mean onset is 27.8 years of age, although 2% show onset by two years of age.1
In addition to affecting the skin, psoriasis can cause an inflammatory form of arthritis and affect the nails. The nails take on a characteristic thimble-like appearance referred to as “oil drop” stippling.
Causes
Psoriasis is caused by a pileup of skin cells that have replicated too rapidly. The rate at which skin cells divide in psoriasis is roughly one thousand times greater than in normal skin. This high rate of replication is simply too fast for the cells to be shed, so they accumulate, resulting in the characteristic silvery scale of psoriasis.
Psoriasis is the result of a basic defect that lies within the skin cells. The frequency of psoriasis is increased in people with certain genetic markers, reflecting a possible genetic error in the control over how skin cells divide. The genetic link is also confirmed by the observation that 36% of psoriasis patients have one or more family members with psoriasis. There are also multiple defects noted in the skin and immune cells of psoriatic patients, indicating a complex interplay of genetic factors.2–4 The primary defect in psoriasis appears to be an increase in cell signaling through compounds known as chemokines and cytokines, secreted by white blood cells, which cause skin cells to replicate excessively. It appears that rather than being a disorder of the skin cells, psoriasis is primarily a condition that affects the immune system.5–7
Perhaps the strongest evidence of a link to the immune system is that psoriasis has been shown to develop in those who have received bone marrow transplants from donors with psoriasis and to clear up in bone marrow recipients with psoriasis when they receive a transplant from donors without psoriasis. Drugs that suppress the immune system are effective in reducing psoriasis.8,9
While psoriasis has a very strong genetic component, how those genes are expressed can be modified. There is a clear relationship between psoriasis and conditions associated with altered gastrointestinal permeability, such as celiac disease10 and Crohn’s disease,11 and in conditions associated with impaired liver function.12 Furthermore, the gastrointestinal lining of psoriatic patients has shown microscopic lesions and greater intestinal permeability.13Factors leading to poor intestinal function and increased gut permeability ultimately allow food and microbial antigens and endotoxins to be absorbed from the gastrointestinal tract, travel through the bloodstream, and initiate activated immune activity that ultimately leads to skin cell replication. These data provide a clear focus of therapy.
Therapeutic Considerations
Although psoriasis has a significant genetic component, addressing the factors that can activate the immune system or skin cells can result in significant clinical improvement.
Incomplete Protein Digestion
Incomplete protein digestion or poor intestinal absorption of protein breakdown products can result in elevations of amino acids and polypeptides in the bowel. These are metabolized by bowel bacteria into several toxic compounds. In particular, toxic metabolites of the amino acids arginine and ornithine, known as polyamines (e.g., putrescine, spermidine, and cadaverine), have been shown to be higher in the blood in individuals with psoriasis. These polyamines have been shown to contribute to the excessive rate of cell proliferation in psoriasis.14–16 Lowered skin and urinary levels of polyamines are associated with clinical improvement in psoriasis.14
A number of natural compounds can inhibit the formation of polyamines and may be of benefit in the treatment of psoriasis. For example, vitamin A and the alkaloids of goldenseal (Hydrastis canadensis)such as berberine inhibit bacterial decarboxylase, the enzyme that converts amino acids into polyamines.17,18 However, the best way to prevent the excessive formation of polyamines is to ensure adequate hydrochloric acid and pancreatic enzyme secretion in the gastrointestinal system. See the chapter “Digestion and Elimination” for more information, as ensuring proper digestion is a key step in dealing with psoriasis.
Bowel Toxemia
A number of gut-derived toxins are also implicated in the development of psoriasis, including endotoxins (cell-wall components of gram-negative bacteria), Candida albicans, and yeast compounds.19–21Endotoxins have been found in high levels in the blood of psoriatic patients,22 and these compounds lead to dramatic increases in the rate of skin cell proliferation. Overgrowth of C. albicans in the intestines (chronic candidiasis) may play a role in some patients with psoriasis.
A diet low in dietary fiber is associated with increased levels of gut-derived toxins.19 Dietary fiber is critical to maintaining a healthy colon. Many fiber components bind bowel toxins and promote their excretion in the feces. It is therefore essential that the diet of an individual with psoriasis be rich in beans, fruits, and vegetables. Natural compounds that bind endotoxins and promote their excretion may also be used. For example, an aqueous extract of the herb sarsaparilla (Smilax sarsaparilla) was found in a 1942 study to be effective in psoriasis, particularly the more chronic, large-plaque-forming variety.23 In this controlled study of 92 patients, sarsaparilla greatly improved psoriasis in 62% of the patients and resulted in complete clearance in another 18% (i.e., 80% of the subjects experienced significant benefits). This benefit is apparently due to the components of sarsaparilla binding to bacterial endotoxins and promoting their excretion.
Because the severity of psoriasis as well as therapeutic response have been shown to correlate well with the level of circulating endotoxins, control of gut-derived toxins is important in the treatment of psoriasis.
Liver Function
The correction of abnormal liver function may be of benefit in the treatment of psoriasis.12,24 The connection between the liver and psoriasis relates to one of the liver’s basic tasks—filtering and detoxifying the blood returning through the portal circulation from the bowels. Altered liver function is common in psoriatic patients.25 As mentioned previously, psoriasis has been linked to the presence of several microbial by-products in the blood. If hepatic function is compromised by excessive levels of these toxins from the bowel or if there is a decrease in the liver’s detoxification ability, the systemic toxin level rises and the psoriasis worsens.
Alcohol consumption is known to significantly worsen psoriasis.26 Alcohol has this effect because it both increases the absorption of toxins from the gut (by damaging the gut mucosa) and impairs liver function. Alcohol intake must be restricted in individuals with psoriasis.
Silymarin, the flavonoid component of milk thistle (Silybum marianum), has been reported to be of value in the treatment of psoriasis.27 Presumably this is a result of its ability to improve liver function, inhibit inflammation, and reduce excessive cellular pro-liferation.27,28
Bile Acid Deficiency
In the psoriatic patient, endotoxins are absorbed from the intestine into the bloodstream.22 Bile acids normally present in the intestines act to detoxify bacterial endotoxins. In the absence of sufficient amounts of bile acids, endotoxins can move into the bloodstream and produce a variety of problems, including the release of inflammatory cytokines known to play a role in psoriasis.
A study of 800 psoriatic patients was conducted in which 551 were treated with oral bile acid (dehydrocholic acid) supplementation for one to six weeks for acute cases and three to eight weeks for chronic cases. Conventional therapies were administered to 249 patients as a comparison group. Both groups were encouraged to eat a diet high in vegetables and fruits and were instructed to avoid hot spices, alcohol, raw onion, garlic, and carbonated soft drinks. Of the 551 patients receiving the bile acid, 434 (78.8%) experienced complete resolution of their psoriasis, whereas only 62 (24.9%) of the 249 patients receiving conventional therapies demonstrated clinical recovery during this treatment period. Additionally, the curative effect of bile acid supplementation was more pronounced in the acute form of psoriasis: 95.1% of the patients in this group became asymptomatic. In follow-up assessments two years later, 319 of the 551 patients with acute and chronic psoriasis who had been treated with bile acid (57.9%) were asymptomatic, compared with only 15 of the 249 patients (6%) who had received the conventional treatment.22 The dosage of dehydrocholic acid used in the studies was 250 mg per day given in two to three doses. Dehydrocholic acid is available by prescription, but mixtures of bile acids from ox bile are available in health food stores and may prove to be suitable alternatives.
Diet and Nutrition
Omega-3 Fatty Acids
Just as in other inflammatory conditions (e.g., rheumatoid arthritis), it is important to reduce the consumption of meat and dairy products to reduce the intake of arachidonic acid—a fatty acid that is known to increase the inflammatory response and is found in high levels in psoriatic skin—while increasing the intake of the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Several double-blind clinical studies have demonstrated that supplementing the diet with 3,000 mg EPA and DHA results in significant improvement in psoriasis.29–32 Detailed studies support a number of beneficial effects of EPA and DHA in psoriasis, including a reduction in the production of inflammatory compounds that stimulate skin cell proliferation. In addition, EPA and DHA tamp down some of the immune mechanisms that also trigger skin cell replication. While increasing the intake of EPA and DHA is important in improving psoriasis, it is imperative to reduce the intake of arachidonic acid as well.
Fasting, Vegetarian Diet, and Food Allergy Control
Dietary treatment of psoriasis is very similar to that for rheumatoid arthritis (see that chapter). Research studying the effects of fasting and vegetarian regimens on chronic inflammatory disease found that a therapeutic fast followed by a vegetarian diet with careful attention to any food allergy is very therapeutic in both conditions. The fast consisted of herbal teas, garlic, vegetable broth, a decoction of potatoes and parsley, and the juice of carrots, beets, and celery. The fast was followed by a systematic reintroduction of a single food item every two days with elimination of foods that aggravated symptoms.33 The improvement was probably due to decreased intestinal permeability, leading to reduced levels of gut-derived toxins and polyamines entering the bloodstream. Other studies have also shown considerable benefits from elimination diets as well as gluten-free diets (see the chapter “Celiac Disease”).34,35
A vegetarian diet often includes the herbs and spices turmeric, red pepper, cloves, ginger, cumin, anise, fennel, basil, rosemary, garlic, and pomegranate, all of which can block the activation of the inflammatory cytokines linked to psoriasis, providing another possible route of benefit with such a diet.36 Liberal use of these herbs and spices is recommended.
Individual Nutrients
Decreased levels of vitamin A and zinc are common in patients with psoriasis.37–39 Given the critical roles of these nutrients in the health of the skin, supplementation might be warranted even without this association.
Chromium supplementation may be indicated to increase the sensitivity of insulin receptors, since psoriatic patients typically have evidence of insulin resistance (increased serum levels of both insulin and glucose) and carry an increased risk for type 2 diabetes and metabolic syndrome.40
Substantial evidence indicates that psoriasis is an independent risk factor for cardiovascular disease.41 Inflammatory factors such as C-reactive protein (CRP) and other risk factors for atherosclerosis are found significantly more often in psoriasis patients.42 This association alone stresses the importance of omega-3 fatty acids, folic acid, vitamin B6, and vitamin B12.43 High homocysteine (a metabolite of the amino acid methionine that is linked to atherosclerosis; levels will be elevated if a person is low in folic acid, vitamin B6, and vitamin B12) and decreased folic acid levels are linked to an increase in the severity of psoriasis. The rapid skin cell turnover rate in psoriasis may result in increased folic acid utilization and subsequent deficiency.44 The authors of one study concluded that “dietary supplementation of folic acid, B6, and B12 appears reasonable in psoriasis patients, particularly those with elevated homocysteine, low folate and additional cardiovascular risk factors.”45
Levels of the selenium-containing antioxidant enzyme glutathione peroxidase are low in psoriatic patients, possibly because of such factors as alcohol abuse, malnutrition, and the excessive replication and loss of skin cells. Depressed levels of glutathione peroxidase normalize with oral selenium and vitamin E therapy.46 Several investigations have found that patients with longer-term psoriasis (three years or more) demonstrated low plasma selenium status.47,48
Vitamin D status is low in patients with psoriasis and appears to be a contributing factor.49 Skin cells convert naturally produced 7-dehydrocholesterol to vitamin D3 in the presence of ultraviolet B light. Not surprisingly, sunlight, UVB phototherapy, oral vitamin D analogues, and topical vitamin D3 all improve psoriasis, validating vitamin D’s ability to control the excessive skin cell replication seen in psoriasis.50Vitamin D also favorably affects the immune system and the expression of genes by skin cells in a way that could also explain the improvements seen in psoriasis.51–54
Given the importance of vitamin D in psoriasis as well for general health, supplementation seems critical. And while sunlight can be helpful in psoriasis, it may not help increase vitamin D levels. Studies conducted in Honolulu, Miami, and southern Arizona showed that abundant sun exposure did not necessary ensure vitamin D adequacy; this finding points to the need for vitamin D supplementation to achieve optimal blood levels.55 In psoriasis, we recommend the upper limit of vitamin D: doses of up to 5,000 IU per day.56
Fumaric Acid
Over the past three decades, fumaric acid therapy has become increasingly popular in western Europe for psoriasis. Therapy consists of the oral intake of dimethylfumaric acid (240 mg per day) or monoethylfumaric acid (720 mg per day) and the topical application of 1% to 3% monoethylfumaric acid. Clinical studies have shown that it is useful in many patients with psoriasis,57 but side effects such as flushing of the skin, nausea, diarrhea, general malaise, gastric pain, and mild liver and kidney disturbances can occur.58 We recommend using fumaric acid therapy only after other natural therapies have proved ineffective.
Psychological Aspects
Stress is often a precipitating factor in psoriasis flare-ups. Hence stress management, psychotherapy, and biofeedback training can be of benefit.59 For more information, see the chapter “Stress Management.”
Sunlight and Ultraviolet Light
Exposure to sunlight is extremely beneficial for individuals with psoriasis.60,61 In one study, an outdoor four-week sunbathing therapy was shown to promote significant clearance of psoriatic symptoms in 84% of 373 subjects.62Studies employing commercial tanning beds have shown that a majority of patients find them helpful;63 they also facilitate improvements in quality of life.64
Sunlight and ultraviolet light exposure may also be of benefit owing to its induction of vitamin D synthesis in the skin. The standard ultraviolet medical treatment of psoriasis typically involves the use of the drug psoralen and ultraviolet A (PUVA therapy). Ultraviolet B (UVB) exposure alone also leads to inhibition of cell proliferation; in certain studies, it has been shown to be as effective as PUVA therapy, with fewer side effects.65,66 At the Dead Sea, where 80% to 85% of psoriatic conditions clear in four weeks, UVB wavelengths are known to be dominant.67,68 All together, what these studies indicate is that the drug psoralen may not be necessary and the key factor may be sunlight or UVB exposure; both need to be used carefully, especially by those at risk for skin cancer.
Topical Treatments
A number of natural proprietary formulas as well as over-the-counter preparations can be used to provide symptomatic relief in mild to moderate psoriasis.
Topical Vitamin D
Topical corticosteroids are the most common treatment for psoriasis; however, their long-term use is associated with a potential risk for side effects. Topical vitamin D modulators have been developed as an option for use in place of or in addition to topical corticosteroids. Topically, vitamin D inhibits skin cell proliferation and modulates immune cell activity in a positive manner in psoriasis.69 Calcipotriene (Dovonex), an analogue of vitamin D, is the most widely used topical vitamin D. Although evidence suggests that in the long term it is approximately as effective as low- to medium-potency corticosteroids (response is not obtained as quickly as with corticosteroids), it is associated with skin irritation, especially when used on sensitive skin. Calcitriol ointment was recently approved; it contains the naturally occurring active form of vitamin D3 and is associated with a low rate of cutaneous and systemic adverse effects.
Aloe Vera
One double-blind study found that topical application of an aloe extract in a cream was highly effective in psoriasis vulgaris.70 Sixty patients with slight to moderate chronic plaque-type psoriasis applied either the aloe or a placebo cream three times a day. By the end of the study (4 to 12 months of treatment), the aloe extract cream had improved the psoriasis in 25 of 30 patients (83.3%) compared with the placebo improvement rate of only 2 of 30 (6.6%), resulting in significant clearing of psoriatic plaques (82.8% with the aloe vs. 7.7 % with the placebo). In another double-blind study, 80 patients with psoriasis applied either aloe vera or a popular prescription corticosteroid cream (0.1% triamcinolone acetonide).71 After eight weeks of treatment, the mean psoriasis clinical score decreased from 11.6 to 3.9 in the aloe group and from 10.9 to 4.3 in the corticosteroid group. These results indicate aloe’s effects may be on a par with conventional corticosteroid cream, but without the side effects.
Capsaicin
Capsaicin, from cayenne pepper (Capsicum frutescens), is known to stimulate and then block small-diameter pain fibers by depleting them of the neurotransmitter substance P, which is thought to be the principal chemical mediator of pain impulses. In addition, substance P has been shown to activate inflammatory mediators in psoriasis. Several clinical studies have found that the topical application of 0.025 or 0.075% capsaicin is effective in relieving psoriasis.72,73
For example, in one study 98 patients applied 0.025% capsaicin cream four times per day for six weeks, while 99 patients applied a placebo cream.72 Efficacy was evaluated based on a physician’s global evaluation and a combined psoriasis severity score including scaling, thickness, redness, and itching. Capsaicin-treated patients demonstrated significantly greater improvement in global evaluation and in relief of itching, as well as a significantly greater reduction in combined psoriasis severity scores.
Curcumin
Curcumin, from turmeric (Curcuma longa), is a well-known anti-inflammatory agent. In one study, topical application of curcumin in a gel yielded 90% resolution of plaques in 50% of patients within two to six weeks; the remainder of the study subjects showed 50% to 85% improvement.74 Curcumin was found to be twice as effective as calcipotriene cream, which generally takes three months to exert its full effect.
Emollients
The scaliness and hardness of psoriasis skin benefits from the use of emollients (skin softening agents) such as ceramides. These compounds can help improve the skin’s water-holding capacity, and it has been shown that ceramides are decreased in psoriatic skin. Newer ceramide-containing emollients (e.g., CeraVe, MimyX, Aveeno Eczema Therapy, etc.) have shown benefit in psoriasis and may improve skin barrier function and decrease water loss.75
QUICK REVIEW
• Psoriasis is caused by a pileup of skin cells that have replicated too rapidly.
• There are multiple abnormalities noted in the skin and immune cells of psoriatic patients, indicating a complex interplay of genetic factors.
• Although psoriasis has a significant genetic component, addressing the factors that can activate the immune system or skin cells can result in significant clinical improvement
• Incomplete protein digestion, bowel toxemia, impaired liver function, and bile acid deficiency are linked to psoriasis.
• Reducing the intake of arachidonic acid, a fat found exclusively in animal foods, while increasing the intake of omega-3 fatty acids is a primary nutritional recommendation.
• A therapeutic fast followed by a vegetarian diet with careful attention to any food allergy is very therapeutic in psoriasis.
• Sunlight, UVB phototherapy, oral vitamin D analogues, and topical vitamin D3 all improve psoriasis, validating vitamin D’s effect on controlling the excessive skin cell replication seen in psoriasis.
• Outdoor sunbathing therapy was shown to promote significant clearance of psoriatic symptoms.
• Topical treatments with preparations containing vitamin D, aloe vera, curcumin, or capsaicin can be helpful.
TREATMENT SUMMARY
Despite the complexity of this disease, the therapeutic approach is fairly straightforward: decrease bowel toxemia, rebalance fatty acid levels and inflammatory processes systemically and in the skin, reduce the abnormal proliferation of skin cells, and apply topical agents to provide quicker symptom relief and aid the healing process. The protocol given below accomplishes all of these goals. In the case of psoriatic arthritis, we recommend following the treatment summary for rheumatoid arthritis (see that chapter).
Diet
The first step is a therapeutic fast or elimination diet, followed by careful reintroduction of individual foods to detect those that trigger symptoms. Although any food can cause a reaction, the most common are wheat, corn, dairy products, beef, foods in the nightshade family (tomatoes, potatoes, eggplant, peppers), pork, citrus, oats, rye, egg, coffee, peanuts, cane sugar, lamb, and soy.
After all allergens have been isolated and eliminated, a vegetarian or Mediterranean-style diet rich in organic whole foods, vegetables, cold-water fish (anchovies, mackerel, herring, sardines, and salmon), olive oil, and berries and low in sugar, meat, refined carbohydrates, and animal fats is indicated. The recommendations in the chapter “A Health-Promoting Diet” are appropriate for long-term support.
Nutritional Supplements
• A high-potency multiple vitamin and mineral formula as described in the chapter “Supplementary Measures”
• Key individual nutrients:
Vitamin C: 500 to 1,000 mg per day
Vitamin E (mixed tocopherols): 200 to 400 IU per day
Vitamin D3: 5,000 IU per day (ideally, measure blood levels and adjust dosage accordingly)
Vitamin B6: 25 to 50 mg per day
Folic acid: 800 mcg per day
Vitamin B12: 800 mcg per day
Selenium: 100 to 200 mcg per day
Chromium: 200 to 400 mcg per day
• Fish oils: 3,000 mg EPA + DHA per day
• One of the following:
Grape seed extract (>95% procyanidolic oligomers): 100 to 300 mg per day
Pine bark extract (>95% procyanidolic oligomers): 100 to 300 mg per day
Some other flavonoid-rich extract with a similar flavonoid content, super greens formula, or another plant-based antioxidant that can provide an oxygen radical absorption capacity (ORAC) of 3,000 to 6,000 units or higher per day
• Specialty supplements:
Soluble fiber (psyllium, pectin, guar gum, etc.): 5 g at bedtime
Bile acids (mixed, from ox bile): 500 mg with meals
Pancreatin (10X USP): 350 to 750 mg with meals three times per day; or equivalent multiple enzyme formula with meals
Probiotic (Lactobacillus species and Bifidobacterium species): a minimum of 5 billion to 10 billion colony-forming units
Fumaric acid: dimethylfumaric acid (240 mg per day) or monoethylfumaric acid (720 mg per day) and topical application of 1% to 3% of monoethylfumaric acid (to be used only when other approaches fail)
Botanical Medicines
• Milk thistle (Silybum marianum): Dosage is based on silymarin content (standardized extracts are preferred) and the best results are achieved at higher dosages, i.e., 140 mg to 210 mg silymarin three times per day; dosage for silymarin phytosome is 120 mg two to three times per day between meals.
Consider the following if suffering from impaired digestion:
• Goldenseal (standardized extracts preferred):
Dried root or as tea: 2 to 4 g three times per day
Fluid extract (1:1): 2 to 4 ml (0.5 to 1 tsp) three times per day
Solid (powdered dry) extract (4:1 or 8 to 12% alkaloid content): 250 to 500 mg three times per day
• Sarsaparilla:
Dried root or as decoction: 1 to 4 g three times per day
Liquid extract (1: 1): 4 to 8 ml (1 to 2 tsp) three times per day
Solid extract (4: 1): 250 to 500 mg three times per day
Psychological Measures
Utilize stress management strategies.
Physical Medicines
• Sunbathing (taking precautions not to become sunburned): as much as possible.
• UVB: 295 to 305 nm, 2 mW/cm2, three minutes three times weekly
Topical Treatments
• Vitamin D, aloe vera, capsaicin, or curcumin creams: apply to affected areas of the skin two to three times per day (try different ones to see which works best)
• Ceramide-containing emollient: apply to affected areas of the skin two to three times per day