Nightshade foods

A Q&A with Elena Holmes Registered Nutritional Therapist

Many people suffer from inflammatory conditions – osteoarthritis, autoimmune diseases, or inflammatory bowel disease – to name just a few. No surprise that this makes one wonder if what we eat can affect this inflammation. And not surprisingly, this search for anti-inflammatory foods or diets results in hundreds of pieces of advice. We all know to be critical about what we find online, but even advice coming from qualified experts can appear confusing.

It is because, in some cases, the advice is far from ‘one-size-fits-all’. Enter the nightshades.

What are nightshades?

Nightshades are the plants from the Nightshade (Solanaceae) family that provide us with some prominent foods. The fruits from nightshades – tomatoes, bell peppers, aubergines (usually referred to as vegetables because, whilst botanically being fruits, from the nutritional and culinary point of view, they are more like vegetables), and physalis, spices, such as hot chillies and paprika – are among most common ingredients in many cuisines. White or purple-fleshed potatoes are also nightshades (it is important not to confuse them with sweet potatoes, which are not). The tobacco plant is also a nightshade.

Why are nightshade vegetables not suitable for everyone?

Some people who suffer from inflammatory diseases (arthritis, inflammatory bowel disease, etc.) notice that eating these vegetables worsens their inflammatory symptoms – joint pain, redness, swelling or causes nausea or indigestion. Some react to all nightshades, some – just to one or two types.

It happens because these people are sensitive to specific compounds, called alkaloids. Plants produce alkaloids to protect themselves from insects. The main alkaloid in the nightshades is solanine.

What health risks are associated with consuming nightshade vegetables?

It is important to point out that nightshades do not cause inflammation, they may just cause a flare-up where inflammation already exists. Therefore, nightshades ‘per se’ do not pose any health risks because the alkaloid content in them is usually negligible.

What people should avoid/cut down on these vegetables?

If a person notices a flare-up of their symptoms after having eaten a nightshade and, conversely, notices an improvement when they cut that food out, they should avoid eating these vegetables or considerably cut down their consumption.

Can the small alkaloid content in nightshades be harmful?

Most of the population does not have any issue with alkaloids in nightshades because the alkaloid content does not reach anywhere near the harmful levels.

It is important to note, though, the concentration of solanine may vary depending on the parts of the plant consumed and their ripeness.  For example, most of the solanine in tomatoes is in their stems and leaves, not the fruit. Plus, the riper the tomato fruit is, the less solanine it contains.

Conversely, potatoes that have turned green under their skin because they have been exposed to light develop a considerable amount of solanine.

Preparation methods that use heat – cooking, baking, steaming, etc. – further reduce the solanine content.

Because of this, even those sensitive to nightshades may discover they can eat without getting any symptoms a small quantity of solanine-containing food, such as a couple of tablespoons of well-cooked tomato sauce – but not a fresh tomato salad.

Are these vegetables safe for those without underlying health issues?

On the other hand, if a person is not experiencing any inflammatory or digestive issues after eating nightshades, they should enjoy these vegetables and spices and embrace the numerous health benefits they bring.

All nightshades are chock-full of vitamin C, gut-healthy dietary fibre, and innumerable antioxidant and anti-inflammatory phytonutrients.

Specifically, tomatoes are famous for their lycopene – an anti-inflammatory compound which also protects from cancer and heart disease.

Aubergines contain a different anti-inflammatory nutrient, anthocyanin. Bell peppers burst with yet another antioxidant, beta-carotene.

Potatoes are a superb source of heart-healthy mineral potassium and nervous system and metabolism-supporting vitamin B6.

All varieties of hot chillies and paprika are real concentrates of numerous carotenoids, such as carotene and lutein, and many other anti-inflammatory compounds.

What are the benefits of plant-based diets for people with inflammatory diseases?

In general, plant-based diets are outstandingly healthy for people with inflammatory conditions. The micronutrients and phytonutrients, in which these diets abound, are highly anti-inflammatory.

But this is far from all! A healthy, minimally processed foods plant-based diet, because of its antioxidants and a vast assortment of dietary fibre, enriches the diversity of beneficial microorganisms, called microbiome or microbiota, in our gut. The interaction between these microorganisms and our immunity is very close because 70-80% of immune cells reside in the gut. As a result, ‘healthy’, rich and diverse microbiota participates in managing inflammation.

Just think of the Mediterranean diet, which already has an impressive track record for its various health benefits, and the number of studies suggesting its anti-inflammatory properties keeps growing. Peppers, aubergines, hot chillies, but first and foremost tomatoes – are they not staple foods in all variations of the Mediterranean diet? Pasta al pomodoro, anyone?

What are the best plant-based foods for those who cannot eat nightshades?

As for replacing the nightshades for those who do get negative symptoms from these vegetables, the whole plant food world has so much to offer! Swap sweet potatoes, swedes, or parsnips for the ‘usual’ potatoes. For pasta sauce, enjoy courgettes, celery, carrots, broccoli, or butternut squash. Add leafy greens, fresh or steamed broccoli, sliced courgettes, fennel, cucumbers, onions, or even apples, pears, or stone fruit to salads to replace peppers and tomatoes, and use various cabbages, root vegetables, celery, carrots, pumpkin, squashes, courgettes, leeks, onions, okra, fennel, beets, and the whole plethora of other plants in stews, casseroles, curries, soups, or smoothies.