Are tomatoes and potatoes flaring your psoriasis?
Nightshades Vegetables and Skin
The potential problems associated with fruits and vegetables of the nightshade family can be a little difficult to understand, after all we were brought up to believe that fruit and veg were good for us, right? There’s a little bit of science involved when it comes to explaining the potential problems nightshades can cause, but I’ll try and keep it simple.
Edible plants that come under the ‘nightshade’ banner are not advisable for those of us struggling with autoimmune skin conditions such as psoriasis. They’re also worth temporarily eliminating if you suffer from rheumatoid arthritis, to establish whether or not they’re exacerbating your condition. Now, before you rush to the fridge and bin all your tomatoes, it’s important to emphasise these are not a problem for everyone, nor relevant to every skin complaint. When it comes to problems with nightshades, I’m referring specifically to autoimmune related skin conditions such as psoriasis.
You’ve probably heard of the most poisonous of the nightshade family, the flower known as ‘Belladonna’ or ‘Deadly Nightshade’. There are actually over two thousand species which fall into the nightshade category, a few of which are classed as edible.
The most common, edible nightshades are: tomatoes, white potatoes, aubergine (egg plant) and peppers. These plants harbour chemicals called alkaloids which they use to shield themselves from harm, essentially they act as natural pesticides - think of them as a sort of self contained fly spray. Whilst the plant is alive and growing, these chemical compounds are designed to protect it from insects; in other words they are meant to be toxic.
Healthy guts can cope just fine with alkaloids, but those of us with autoimmune skin issues or compromised digestive systems can be a little more sensitive to them. Alkaloids, after all, can prove incredibly powerful. The glycoalkaloid α-tomatine in tomatoes for example, is so potent that it’s used in vaccines to ensure that the recipient develops immunity against the virus they are being inoculated against. Certain alkaloids can rev up our immune response, and that’s the last thing we want when dealing with over active immune condition.
Furthermore, recent scientific studies are supporting the theory that autoimmune problems are intrinsically linked to intestinal permeability - more commonly referred to as ‘leaky gut’. Proponents of "leaky gut syndrome" claim that certain skin conditions, such as psoriasis, are triggered by the immune system reacting to germs, toxins or other substances that have been absorbed into the bloodstream via a porous "leaky" bowel.
The alkaloids in nightshade vegetables are believed to provoke gut irritation. It’s thought they can attack the healthy cells that line the intestinal tract, making it more permeable. As a result, proteins which should stay inside the digestive tract, instead make their way out into the bloodstream, this in turn sets off an autoimmune response. It’s the bodies immune system sensing danger and sending out a little army to protect itself.
If you look online, there aren't a great deal of peer-reviewed studies to support the nightshade-inflammation connection, largely because there’s no profit to be made in that area of research and therefore no funding. There is however, a great deal of anecdotal evidence and blog posts from people who have found that nightshades aggravate their autoimmune illness.
Everyone is different, so as always, it’s important to establish whether these foods are posing a real problem for you. We’ve all become quite overly reliant on seeking the answers outsides of ourselves, trawling the internet looking for evidence. I can give you all this information and point you to studies and articles about nightshades and their effects, but at the end of the day, your body and it’s reactions are the best barometer.
As with any food sensitivity, the only way to truly find out is to remove nightshades from your diet to see if you feel better. If you suffer from psoriasis, rheumatoid arthritis or any other autoimmune condition, I would suggest it’s definitely worth avoiding all nightshades for a month or two. (Remember to read ingredients carefully to ensure they’re not present in any of the pre-packaged foods you eat). Then, reintroduce them into your diet as a test. Eat them at least 4 times over a 2-day period, then stop again, and monitor your symptoms for 72 hours.
If you don’t feel you can cut nightshades out entirely, peeling potatoes will help as the alkaloids are mostly found in the skin. Avoid green tomatoes as unripe nightshades are higher in alkaloids and cook nightshade vegetables whenever you eat them as this will reduce alkaloid content even further.
Speaking from personal experience and from talking to others, nightshades, especially tomatoes and chilli peppers, can be a difficult food group to reintroduce. If you do find you’re sensitive to nightshades, it’s worth considering permanently eliminating them. The vitamins and nutrients in these plants can be sourced elsewhere so they’re non-essential to our diet and there are some great alternatives such as sweet potatoes instead of regular white potatoes and my recipe for tomato-less sauce (page **).
It’s important to remember that the problems posed by nightshades are not relevant to everyone and every skin problem. They’re only relevant to people who are nightshade-sensitive. If you are not sensitive to them, there’s absolutely no reason to eliminate this group of foods from your diet as a precaution.
Common Nightshades
- Tomato
- Aubergine / Eggplant
- Potato (excluding sweet potato)
- Peppers - includes hot and sweet varieties as well as spices like paprika, chilli powder, cayenne, and Tabasco, jalapeños, habaneros, chilli-based spices (excluding black pepper)
- Pimento
- Paprika
- Goji berry (wolfberry)
- Cape gooseberry / ground cherry —not to be confused with regular cherries
- Garden huckleberry (not to be confused with regular huckleberries)
- Tobacco
Studies
https://www.ncbi.nlm.nih.gov/pubmed/20198430
http://www.ncbi.nlm.nih.gov/pubmed/22109896
http://www.ncbi.nlm.nih.gov/pubmed/12479649
http://www.ncbi.nlm.nih.gov/pubmed/20650190
