One of our Listeners Kyle is an MD who works in the arctic on remote Inuit communities, emailed us a some more info on supplements;
First of all, a correction: I believe that the Vitamin B family has been referred to a couple of times as fat soluble. B Vitamins are considered water soluble and there are a whole bunch of them in the family.
Below is a horribly truncated rundown of some keto-friendly vitamin sources. Many vitamins are needed in much less quantity since they are only needed for metabolism of carbohydrates, others are manufactures by our gut flora regardless of dietary sources:
Niacin is available in many foods and for keto'ers is found in liver, poultry, and fish in quantity.
Riboflavin (B2), is found in yogurt, cheeses, and liver.
Thiamin (B1) is a co-enzyme essential for carbohydrate metabolism. When carbohydrate levels are high, thiamin levels need to be high. With keto, thiamin requirements are negligible. The best source of natural thiamin that is keto-friendly: pork. Yum.
Pyridoxine is a coenzyme required for metabolism of amino acids and is available in meat, fish, and poultry. No lack of that on a keto diet.
Cyanocobalamin (B12) and folic acid are available in animal sources as well. If you're eating meat, deficiency is extremely unlikely.
Pantothenic Acid: needed to produce enzymes needed in multiple hormone and metabolic pathways, it is present in virtually all foods. There are no known deficiency of this one - so no worries on keto.
Biotin: Essential for reactions involving carb and fat metabolism. It is available in foods, but also produced by normal gut flora. No need to worry here either.
Vitamin A (retinol) requirements can be met by eating preformed retinol or by eating foods containing preformed Vit A (ex of one is beta-carotene). You don't need to eat your carrots for vitamin A. In fact, its bioactive form is only found in animal sources.
Vitamin K occurs in 2 forms naturally: Vitamin K1 and Vitamin K2. Vitamin K1 is available in many foods and Vitamin K2 is synthesized by bacteria in the gut so VitK deficiency is very rare.
Vitamin D: Occurs as VD2 (ergocalciferol) and VD3 (cholecalciferol). Both forms produce near identical effects. D3 is the type produced naturally by humans when skin is exposed to sunlight. Dietary sources include shiitake mushrooms and oily fishes such as salmon. Or just spend a short time outdoors with some skin exposure. It's free.
I usually recommend to my patients to supplement every once in a while with a multi vitamin. If they take one or two a week, that often covers any deficiencies, although true deficiency in today's diet are quite rare. Here in the Arctic, I usually recommend a VitD3 supplement because of the long dark winters and the very low UV levels in the summer due to solar angle. But even that is usually unnecessary due to the high amount of salmon and other oily fish consumed in the diet here. Anyway, just my take.
We often think of our bodies as these isolated closed systems operating independently of other organisms. We as humans appreciate that autonomy. But we often forget about the helpful travelers living in our gut. They synthesize many of the vitamins and other bioactive chemicals that permit us to continue to KETO ON without deficiencies. Some of them are only needed in quantity to process carbohydrates - so, low carbs, low requirements.