So often I have patients who are asking me about what supplements they should be taking, they bring a plastic bag filled with little bottles and line them up in front of me. As a dietitian, I’m usually encouraging my client to harness their nutrients by eating a healthy diet and suggest supplements to complement an inadequate diet due to sensitivities/intolerance or dislikes. Admittedly I too like to take some calcium, vitamin D & zinc, or multivitamins, in the winter with the lack of sunshine, being restricted indoors, or exposed to rampant flu,; vitamins can give you that extra edge to keep you healthy..
Watching David Jocker’s Keto diet summits, I realize that it is almost impossible to follow this diet without taking nutritional supplements, be they electrolyte powders, 
MCT, exogenous ketones, and if you have poor digestion and elimination, herbal adaptogens, stomach acids, digestive enzymes, probiotics, betaine HCL bile salts or oz bile. Poor thyroid function can be a limitation for adapting to a keto diet and you may need extra iodine, selenium, iron, B12, Zinc, Vit D, amino acids and magnesium. Actually I’m curious to try the Thyroid Strong- containing bovine glandular thyroid hormones, iodine, selenium and zinc. Or perhaps super glutathione which acts as an antioxidant reducing inflammation. Then you may find you need mitochondrial support with CoQ10, Acetyl-L Carnitine and B Vitamins which will definitely be deficient in this diet.
You suspect that I’m not a promoter of the ketogenic diet. In the long term, the literature has shown time after time that a high fibre diet or plant based diet improves longevity whereas the high fat diet cause inflammation and can shorten lifespan. However there may be merits to cycling carbohydrate and changing eating patterns.
One supplement which is not often discussed and is controversial is cannabis CBD, the form that doesn’t get you high. I liked the post that Desiree NIelsen wrote about this subject and checked out the website she recommended at icaria.co. I’ve seen CBD work wonders for some clients with multiple GI problems, pain control, reducing anxiety, improving appetite and movement. Thinking about it, there are cannabinoids in many plants ,ie., clove, black pepper, echinacea, broccoli, ginseng, carrots, sunflowers, cacao and ;hemp. This could lead to a conversation about how many of our medicines are plant-based.
When we are treating chronic diseases, many of these supplements are a poor replacement for eating a well balanced plant-based diet, which would give you more energy, maintain healthy bowel and GI function, cost less and enhance one’s appreciation of our planet.