Garlic

Although we generally use garlic to flavour food, it has traditionally been used to treat infection, with medicinal use dating back to ancient Egypt1.

Scientific studies now show that garlic has powerful antibacterial and antiviral actions2,3, thanks to the naturally occurring sulphur containing compounds in the herb. It can also have positive effects on the immune system.

As a treatment garlic can be consumed orally, applied topically or taken as a powder or extract (known as aged garlic extract, or AGE) where garlic cloves are soaked in an alcohol solution to extract the helpful compounds.

What do we know about garlic and psoriasis?

Studies show people with psoriasis have higher than normal levels of free radicals (unstable molecules which damage cells) in their skin, together with low levels of antioxidants4, cell protecting compounds which are needed to ‘mop up’ or neutralise free radical damage.

Because one of the active compounds in garlic (called allicin) has potent anti-oxidant activity5,6, it may help to protect against free radical damage in psoriasis. In animal and in vitro studies (outside of the body) allicin has been shown to protect against free radical damage.

Compounds in garlic have also been shown to block the activation of kappa B,7 a protein complex which controls a number of pro-inflammatory genes8. Studies show the activation of kappa B is likely to trigger inflammation in psoriasis9.

Animal studies also show garlic can alter the action of Th1 cells; special immune cells that release inflammatory proteins into the skin in psoriasis10,11 contributing to inflammation and irritation.

These findings suggest that garlic may benefit psoriasis by;

  • Increasing antioxidant defences
  • Modulating immune function
  • Inhibiting kappa B, an inflammatory protein which is raised in psoriasis  
  • Modulating the action of Th1 cells  

What does the science say?

Although studies have demonstrated the antioxidant and anti-inflammatory benefits of garlic12,13, there are no clinical studies that have looked specifically at the effects in psoriasis.   

In one laboratory study, researchers found that garlic extract was effective in inhibiting the inflammatory response in the blood of people with inflammatory bowel disease14, an autoimmune condition which shares some similarities with psoriasis15.

Other studies have found garlic extract can reduce airway inflammation and inhibit histamine release13; others have shown it can actually stimulate hypersensitivity reactions in people with dermatitis, possibly due to allergy16.

In a 2011 review of all the research evaluating the effects of garlic in dermatology researchers identified 23 studies17. Overall, they found evidence that garlic could positively affect the immune function and offer protection against ultraviolet rays (the type of sunlight which causes redness and burning), but more research is needed to confirm the benefits.

Some people have reported an improvement in their psoriasis after consuming raw garlic based on their personal experience. Other people have found no benefit.

Side effects

Garlic is considered safe with minor complaints limited to garlic breath and body odour. A number of case reports have found that garlic may cause allergic reactions when applied topically to the skin18.  

Because it can prevent blood clotting, garlic may interfere or enhance the effect of blood thinning medications like warfarin. However, consuming garlic through diet is not thought to be a problem19.

How much do I need to take?

Because there are no studies, it’s difficult to say how much may be effective. Doses of 600-1200 milligrams of garlic extract have been shown to have a positive effect in cholesterol lowering studies.

Learning points

  • Garlic has powerful anti-oxidant and anti-bacterial properties. It can also influence the body’s inflammatory response.  
  • Garlic might benefit psoriasis by helping to control inflammation, but there are no clinical studies to confirm the effects  
  • Garlic may have a positive effect on cholesterol levels, which are often raised in psoriasis  

 

Sources

  1. Rivlin, R. S. Historical perspective on the use of garlic. J. Nutr. 131, 951S–954 (2001).
  2. Hughes, B. G. & Lawson, L. D. Antimicrobial effects of Allium sativum L. (garlic), Allium ampeloprasum L. (elephant garlic), and Allium cepa L. (onion), garlic compounds and commercial garlic supplement products. Phyther. Res. 5, 154–158 (1991).
  3. Ankri, S. & Mirelman, D. Antimicrobial properties of allicin from garlic. Microbes Infect. 1, 125–129 (1999).
  4. Kadam, D. P., Suryakar, A. N., Ankush, R. D., Kadam, C. Y. & Deshpande, K. H. Role of oxidative stress in various stages of psoriasis. Indian J. Clin. Biochem. 25, 388–92 (2010).
  5. Das, I. & Saha, T. Effect of garlic on lipid peroxidation and antioxidation enzymes in DMBA-induced skin carcinoma. Nutrition 25, 459–71 (2009).
  6. Prasad, K., Laxdal, V. a., Yu, M. & Raney, B. L. Antioxidant activity of allicin, an active principle in garlic. Mol. Cell. Biochem. 148, 183–189 (1995).
  7. Aggarwal, B. B. & Shishodia, S. Suppression of the nuclear factor-κB activation pathway by spice-derived phytochemicals: Reasoning for seasoning. Ann. N. Y. Acad. Sci. 1030, 434–441 (2004).
  8. Tak, P. P., Firestein, G. S., Tak, P. P. & Firestein, G. S. NF-kappaB: a key role in inflammatory diseases. J. Clin. Invest. 107, 7–11 (2001).
  9. Moorchung, N. et al. Role of NF-κB in the pathogenesis of psoriasis elucidated by its staining in skin biopsy specimens. Int. J. Dermatol. 53, 570–574 (2014).
  10. Kagami, S., Rizzo, H. L., Lee, J. J., Koguchi, Y. & Blauvelt, A. Circulating Th17, Th22, and Th1 cells are increased in psoriasis. J. Invest. Dermatol. 130, 1373–1383 (2010).
  11. Lowes, M. a et al. Psoriasis vulgaris lesions contain discrete populations of Th1 and Th17 T cells. J. Invest. Dermatol. 128, 1207–1211 (2008).
  12. Zare, A. et al. Purified aged garlic extract modulates allergic airway inflammation in BALB/c mice. Iran. J. Allergy. Asthma. Immunol. 7, 133–141 (2008).
  13. Arreola, R. et al. Immunomodulation and Anti-Inflammatory Effects of Garlic Compounds. J. Immunol. Res. 2015, 1–13 (2015).
  14. Hodge, G., Hodge, S. & Han, P. Allium sativum (garlic) suppresses leukocyte inflammatory cytokine production in vitro: Potential therapeutic use in the treatment of inflammatory bowel disease. Cytometry 48, 209–215 (2002).
  15. Yates, V. M., Watkinson, G. & Kelman,  a. Further evidence for an association between psoriasis, Crohn’s disease and ulcerative colitis. Br. J. Dermatol. 106, 323–330 (1982).
  16. Cronin, E. Dermatitis of the hands in caterers. Contact Dermatitis 17, 265–29. (1987).
  17. Pazyar, N. & Feily, A. Garlic in dermatology. Dermatology Reports 3, 5–7 (2011).
  18. Hallel-Halevy, D. Multifaceted dermatitis artefacta caused by garlic. J. Eur. Acad. Dermatology Venereol. 9, 185–187 (1997).
  19. Heck, A, Dewitt, B and Lukes, A. Potential Interactions Between Alternative Therapies and Warfarin. Medscape (2000). at <http://www.medscape.com/viewarticle/406896_2>
  20. Salihbegovic, E. M. et al. Psoriasis and high blood pressure. Med. Arch. (Sarajevo, Bosnia Herzegovina) 69, 13–5 (2015).
  21. Dreiher, J., Weitzman, D., Davidovici, B., Shapiro, J. & Cohen, A. D. Psoriasis and dyslipidaemia: a population-based study. Acta Derm. Venereol. 88, 561–5 (2008).
  22. Sobenin, I. a, Andrianova, I. V, Demidova, O. N., Gorchakova, T. & Orekhov, A. N. Lipid-lowering effects of time-released garlic powder tablets in double-blinded placebo-controlled randomized study. J. Atheroscler. Thromb. 15, 334–338 (2008).
  23. Cavagnaro, P. F., Camargo, A., Galmarini, C. R. & Simon, P. W. Effect of cooking on garlic (Allium sativum L.) antiplatelet activity and thiosulfinates content. J. Agric. Food Chem. 55, 1280–8 (2007).

 

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