The nightshade (or Solanaceae) family is made up of tomatoes, eggplant, potatoes, goji berries, tobacco and peppers. What do all of these fruits and vegetables have in common? They all contain alkaloids, a substance suspected to cause inflammation.

Alkaloids are a group of naturally occurring compounds that are rich in nitrogen. There are literally thousands of identified alkaloids. They are produced not only by plants, but also by fungi, bacteria and even animals. For example, did you know that Adrenaline, an important hormone produced by the body to help us deal with stressful stimuli, is also classified as an alkaloid?

In plants most of the known functions of alkaloids are related to protection, and it is for this reason that nightshade fruits and vegetables are suspected to cause inflammation. Specifically, it is the glycoalkaloids, a subclass of alkaloids that includes solanine and chaconine, which are thought to possess pro-inflammatory effects once ingested. This is because these glycoalkaloids act as natural pesticides and fungicides that defend the plant against animals, insects and fungi that may attack them.

But is there really any evidence to suggest that we should be excluding these fruits and vegetables from our diets? Not according to current research. To date, there is little proof to suggest that the small quantities of glycoalkaloids present in nightshades, can produce dangerous effects when consumed as a part of a balanced diet. This claim is backed by The Joint FAO/WHO Expert Committee on Food Additives, who have concluded that the levels of glycoalkaloids present in nightshade fruits and vegetables are not of a toxicological concern.

There is currently a limited number of studies available that explore the nutritional and inflammatory effects of glycoalkaloids. Further, to add to the confusion, the outcomes of these studies provide conflicting results. For example, a small number of mice studies have suggested that potato glycoalkaloids may adversely affect inflammatory bowel disease. However, by complete contrast, preliminary investigations using human cell studies, have demonstrated that these same glycoalkaloids may possess anti-inflammatory and anti-carcinogenic benefits.

So what’s the bottom line? If you suffer from an inflammatory condition, be assured that there is currently no conclusive evidence to suggest that you should exclude nightshade fruits and vegetables from your diet. Diets rich in fruits and vegetables including nightshades can help you to live a longer and a healthier life, providing your body with a diverse range of nutrients and phytochemicals that benefit your health.

Collectively tomatoes, red peppers and eggplants offer rich dietary sources of carotenoids (including β-carotene and lycopene), polyphenols, vitamin C, and fibre - just to name a few! All of these food components are thought to possess anti-inflammatory effects, either through their ability to scavenge and remove dangerous free radicals from the body, or via the promotion of good gut health.

These fruits and vegetables also form a large component of the Mediterranean diet; this is a diet characterised by high intakes of fresh fruits, vegetables, wholegrains, legumes, nuts/seeds and olive oil, and a moderate intake of fish and seafood. The Mediterranean diet is rich in antioxidants, heart healthy fats (including omega-3), and fibre. This explains why it has the potential to not only reduce elevated levels of inflammation in the body, but may also help to prevent the onset of many inflammatory conditions, including cardiovascular disease and diabetes.