According to the British Skin Foundation, around 2 in 100 people in the UK live with the skin condition psoriasis. It is not infectious, nor does it lead to cancer. But it may be highly distressing or uncomfortable. This has led people with the condition to try various remedies, including changes to diet or lifestyle. We look for evidence that eating or avoiding certain foods could help.
Psoriasis is an autoimmune condition where skin becomes inflamed and can break out into red, scaly patches which may become itchy. The elbows and knees are most commonly affected, but patches can appear all over the body - nails can also discolour and become pitted in around half of people with the condition. In addition, about 1 in 10 people with psoriasis develop debilitating arthritis linked to their condition.
It's a lifelong condition so expect flare-ups to happen from time to time. There is a strong genetic element meaning that your risk increases three to six times if one of your siblings has the condition. But can lifestyle changes help clear psoriasis up? We take a look at the evidence.
A large research study published in the Journal of the American Academy of Dermatology looked at three different areas of lifestyle change to see if these influenced symptoms of psoriasis. These were: weight control, gluten-free diets and certain supplements.
Weight loss was shown to be one of the most important ways of managing the condition. Studies show that, not only does excess weight increase the risk of developing psoriasis, but that losing weight can help as it calms chemicals in the body that promote inflammation.
"Obesity may provide the nudge that triggers psoriasis in people who are already predisposed to it," suggests lead researcher Dr Wilson Liao.
For some time now, scientists have noticed strong links between psoriasis and coeliac disease - an autoimmune condition which causes your body to react to gluten, which is a protein found in wheat and other grains. Studies show that following a gluten-free diet can reduce the severity of psoriasis symptoms, but only in those with coeliac disease.
Nevertheless, it is worth trying for a few months, as gluten-free options are more available than ever and there are few risks to cutting out gluten-containing foods in the short term. Ask your GP for a referral to the dietician if you're unsure where to start.
Nutritional supplements were also examined in the study. The most evidence was found for omega-3 fatty acids which are the anti-inflammatory fats found in oily fish (salmon, mackerel, herring, trout) and fish oil supplements. Vitamin D tablets were also found to be beneficial for managing psoriasis, but neither vitamin B12 nor selenium was shown to be helpful for the condition.
Other lifestyle changes
A study in the British Journal of Dermatology found that combining weight loss with regular exercise for five months reduced symptoms of psoriasis by 48%. Early work has also been done on low-carbohydrate diets but it's likely that any benefits from these are due to the resulting weight loss.
Do certain foods trigger flare ups?
Dr Anton Alexandroff of the British Association of Dermatologists says: "This includes healthy eating without over-eating, and including sufficient amounts fresh vegetables and fruits - basically similar to what we'd recommend for other patients with chronic conditions."
There is still debate about whether specific diets contribute to symptoms. Alexandroff says that, apart from high-calorie intakes (leading to obesity), there is no evidence that diet causes psoriasis to flare up, and patients don't need to avoid any particular foods.
However, chef and nutritional therapist, Christine Bailey, suggests that known inflammatory foods may have a negative effect. These include highly processed foods, ready meals, table sugar, sugary drinks, white bread and white rice. Whether or not evidence is found to back this up, it is well accepted that these foods are not the ideal option in a balanced diet and could be replaced by high-fibre whole grains, fruits, vegetables, dairy foods, and protein-rich poultry, fish and lean meat.
Long-term psoriasis sufferer, 45-year-old Steven Trotter, has been able to manage his symptoms with diet and weight loss.
He told us: "I'd had psoriasis for around six to seven years since I was diagnosed with type 2 diabetes. My toenails were completely white, opaque and crumbly while the back of my head near my ears had various small circular red plaques but no itchiness or pain. Firstly, I lost weight using portion control and a plant-based diet but there was no change to my psoriasis. Then I transitioned on to a 90% whole foods diet with just a little yoghurt and meat, which produced improvements. I also started daily jogging. Now my toenails are back to normal and the plaques on my head have regressed and look a lot less angry."
Foods to include?
Can adding rather than avoiding specific foods help with flare-ups? Again, specific studies are lacking but there is emerging evidence that a few foods could help.
Alexandroff says: "There is a small body of evidence that small amounts of raw (uncooked) cumin spice may calm flares of psoriasis; however, more evidence is needed here."
Bailey adds: "Supplements of vitamin D3 and omega-3 fatty acids are worth taking. Vitamin D regulates the normal growth and behaviour of skin cells, called keratinocytes, which calms psoriatic plaques."
Tips for diet and lifestyle
Try these tips to help manage your psoriasis but remember that what works for one person might not work for another. If psoriasis is getting you down or is particularly severe, talk with your GP or ask for a referral to a dermatologist.
Watch your weight
Check if you are overweight or obese. If so, aim for a healthy weight loss of 1-2 lbs (½ to 1 kg) a week by eating a balanced diet in small portions.
Sweat it out
Take regular exercise. 30-60 minutes of walking or another activity on most days of the week is a good start.
Eat oily fish once or twice a week or take a daily fish oil supplement.
Take a year-round supplement of vitamin D3. The UK recommendation is 10 micrograms daily but you can go up to 100 micrograms daily according to the European Food Safety Authority.
Try adding a tablespoon of cumin or turmeric to your meals, such as curry or stew, or make a warming turmeric latte.