A note on phytonutrients and stuff in plants:
Phytonutrients are just nutrients within plants (that’s what “phyto” means, “plant.”) They are a tiny subset of the bigger category, phytochemicals. Depending on your source and how they define things, we’re told there are anywhere from a few thousand phytochemicals to 25,000 phytochemicals already identified.
One group of them are the carotenoids, which we’ve found to be good for us, so we call them phytonutrients. Beta-carotene is a carotenoid, it makes carrots orange and it’s a primary source of Vitamin A. Lycopene is another carotenoid; it makes tomatoes red, and has also been found to be good for us - it’s not essential, so you can be fine without it, and it’s not a vitamin, but it’s still a nutrient.
However, there are also other groups in the phytochemicals which are toxins. Unprocessed cassava - a major food crop - is toxic. Cherries, peaches, apples, all have toxic leaves and seeds. Kidney beans need to be processed to be edible; if you eat them raw, the toxins can make you very ill (there have been outbreaks of poisoning from slow cooker recipes, because the low heat doesn’t break down the toxins.)
Tomato plants - and the rest of the nightshade family - have toxic leaves. Potatoes are in the same family; the root tubers of potato plants are safe to eat, but the greens are toxic. If a potato tuber grows partially above ground and exposed to the light, it will be green instead of brown. Don’t eat a potato with green on it! It will make you sick, because although the green comes from chlorophyll, it will also contain some potent toxins.
Nightshades are a family of poisonous plants - ever heard of “deadly nightshade?” Other plants well-known to be toxic: wolf’sbane, belladonna, yew, strychnine (yes, it comes from the nuts of the strychnine tree), snakeroot (cows eat the greens, we drink their milk and die.)
Of course, most of highly toxic plants are not sold as food for people… but some are. We just know how to process them to make them safe. Castor seeds - the source of castor oil - also contain ricin, the deadly neurotoxin used in the Japanese subway attacks. Clearly, castor oil does not.
So, what about all the random phytochemicals in a particular food? Are they nutrients? Toxins? Neither? The only thing we can be sure about from the fact that a plant is a “traditional” foodstuff is that it doesn’t rapidly kill people - and that’s only if you know the right way to prepare it.
The truth is that plants don’t “want” to be healthy for us to eat. By and large, being eaten is not beneficial for plants (or animals.) It’s important to remember that nature is not out there trying to make food healthy for us! Rather, it’s our nature that we’ve evolved to tolerate and thrive such a wide variety of natural food substances despite the fact that they’re trying to stop us. Also, we tend to cultivate those plant species with weaker defenses against us.
So. coming back to Soylent… they are not currently adding things like greens and fruits and extracts to the formula. This means we’re not getting any of the known phytonutrients, which ought to be beneficial. It also means we’re not getting any of the toxins, which are bad for us. We’re not getting the substances which appear to be cancer-protective, but we’re also not getting others which are carcinogenic. Yes, there are plenty of cancer-promoting phytochemicals.
When you add a plantstuff to a meal, you’re adding a wide variety of phytochemicals, not just nutrients - many are inert, but some are nutrients, some are toxins, some (aflatoxins, alkenylbenzenes, etc.), are known to be carcinogenic!
You may not need as many cancer-protective substances if you’re not consuming as many cancer-causing substances.
We need to remember that when a plant is not added to Soylent, we may miss the good, but we also miss the bad. Remember, they’re trying to make “everything you need and nothing you don’t,” not a super-food chock full of everything that may be good for you. The super health-promoting variant may be on the future road map, along with the keto version, and the low-fat version, and the low-protein version for people with kidney problems… but that’s not what this version of Soylent is supposed to be.
You can always add things to your Soylent diet. Eat some greens. Have some berries. I’m a fan. (But not to much spinach, especially if you have kidney problems, because of the oxalates.) With my DIY, I use a vitamin supplement with a variety of phytonutrients intentionally added; if you want, you can probably find a supplement that focuses on the phytonutrients without the vitamins - but at least you can choose what you’re adding.