From what I can tell, nightshades aren’t so good for us – in mind, body or spirit. They are what I would call a “sattvic-inhibitor.” (see this post
Whether drug or food, one common denominator of all nightshades is that they contain alkaloids – a group of substances that has been scientifically proven to adversely impact both the digestive system and the nerve-muscle function of our bodies. I first heard of this “theory” from a yoga teacher. When I asked him why he doesn’t eat potatoes, he replied: “Because potatoes are hard to digest, and they make you stiff.” As it turns out, there is some science that backs this up.
The alkaloids in nightshades are naturally formed by the plants themselves, primarily to defend themselves from insects. There are several types of alkaloids found in nightshade plants. One basic type found in most nightshade foods – including potatoes and tomatoes – is known as the steroid alkaloids. These alkaloids (primarily solanine and chaonine) have been studied for their effects on the nervous system and joint health. The results are a bit eye-opening, even though not entirely conclusive.
First, these steroid alkaloids have the ability to cause cholinesterase inhibition – or to block activity of the cholintesterase enzyme in nerve cells. When cholintesterase is severely blocked, our nervous system and muscle movement becomes disrupted – causing muscle twitching, trembling and even restricted breathing. While the steroid alkaloid in potatoes has indisputably been shown to block cholinesterase activity, the blockage does not usually appear to be severe enough to produce noticeable nerve-muscle disruptions such as twitching or trembling. But what about the less severe disruptions? Perhaps this leads to some degree of aggravation or over-firing of muscle tissues, and hence to stiffness? Just a thought.
Second, these steroid alkaloids have been studied for their potential damage to the joints caused by inflammation and altered mineral status. The research is not conclusive, but some researchers speculate that these alkaloids contribute to excessive calcium loss from bone and excessive calcium deposit in soft tissue. Accordingly, many doctors encourage those suffering from joint conditions like osteoarthritis, rheumatoid arthritis and other joint problems to avoid all nightshades from their diets.
Also eye-opening, is the fact that both eggplants and tomatoes have been found to have the same type of alkaloids found in tobacco (monocyclic alkaloids) – otherwise known as nicotine. Though the amounts of nicotine in these foods is substantially less, their detectable presence begs the question of the subtle effects certain nightshade foods may have on our mental and energetic bodies.
From a mental/emotional perspective (i.e. food & the mind and spirit), nightshades are generally considered rajasic foods – in that they aggravate and agitate the inner-workings of the mind, which in turn affects the body. Depending upon how they are cooked, they could also be considered tamasic – indeed I vividly recall feeling quite heavy and lethargic when I used to eat generous helpings of creamy mashed potatoes or french fries. From a doshic or body/mind constitution perspective, nightshades are Pitta aggravating as they are heating and acidic. Potatoes can also be Kapha aggravating, as they are heavy, starchy and can be difficult to digest.
Cooking lowers alkaloid content of nightshades by only about 40-50%, and thus individuals that are particularly sensitive to these alkaloids should consider avoiding nightshades altogether. This includes individuals with joint problems, those concerned about muscle and joint stiffness – as well as those of us that are attentive to the potential subtle effects on the mind and spirit. Note that if you do choose to eat potatoes, be sure to take out the green spots or sprouting on potatoes as these usually correspond to an increased alkaloid content.
From a personal perspective, my husband and I have been limiting nightshades – to the best we can – for the past couple of years. I have since felt a difference in my body. It’s hard to say, as I can’t isolate this variable. But I feel more open in body – which follows mind and spirit. I do admit that eggplant used to be one of my all time favorite foods – from the Greek baba ganoush to the Indian (Punjabi) bhurtha to the Italian ratatouille. I often indulged in tomatoes both fresh and in sauces, sweet peppers roasted and just simply raw, as well as potatoes whether mashed, baked or as french fries, and I was infamous for adding tabasco sauce or other hot sauces into soups or other spicy creations. However, when I do eat these foods now, I’m particularly sensitive and notice certain effects – for example, eggplants tend to make me gassy, potatoes make me feel heavy and bloated, and I tend to get a bit of acid reflex when I eat tomatoes, sweet and red peppers, and Tabasco-like sauces. Simply put, I feel better without these foods, and find joy in creating dishes with suitable substitutes. This all seems supported by the above information from both science and Ayurveda. With that said, we continue to do our best to limit all nightshades.
Check out this post for our favorite nightshade substitutes.
For a fuller article on the health effects of nightshades, from which I relied for the above scientific information, see: What are nightshades and in which foods are they found?