Question 1) How do you reconcile a 100% plant-based diet with the fact that this will cause us to miss out on key nutrients, specifically vitamin B12 which you recommend supplementing multiple times throughout your book. It's not that I'm opposed to supplementation, but I'm having more of a philosophical debate on how healthy a 100% plant-based diet truly is if it would cause our bodies harm by missing key nutrients.
I guess I think of this from a few different angles.
Angle #1) All dietary patterns have pros and cons. Some dietary patterns are more nutritionally complete, some might fall short on a few nutrients. Some dietary patterns have a lighter environmental footprint, some are quite damaging to the planet. Some can be sourced mostly locally, some require more transport miles, The list goes on. So, while a 100% plant-based diet might require vitamin B12 supplementation (a con), it also has a lot of pros (light on the environment, nutritionally rich in other various micronutrients, promotes animal welfare, decreases chances of chronic disease, etc.).
Angle #2) I know that there is often a push in the nutrition world to get all nutrients from whole foods, without any type of modern intervention. And if someone cannot achieve adequate nutrient intake from whole foods alone, they are sometimes viewed as flawed or inferior. But I like to step back and consider all of the different areas where we rely on modern, man-made interventions to allow for a more seamless and healthy existence. We have cell phones, cars, medications, gyms with dumbbells, electricity, refrigerators, etc. These things aren't "from the earth" or "natural". But they can be very helpful in certain situations. So, I don't think using a man-made vitamin B12 supplement to round out a diet makes the diet flawed. There are plenty of omnivorous dietary patterns that lack certain nutrients and also require supplementation. No matter how someone eats, it's very difficult to meet all micronutrient needs with our soils becoming more depleted.
Angle #3) In parts of the world where people eat a highly plant based diet due to income limitations and not as much accessibility to meat, vitamin B12 deficiency still isn't very prevalent. This is because in these parts of the world they are still eating plants that have more bacteria on them (and vitamin B12 is a product of bacterial fermentation). In the US, we have such a sterilized food supply (which can be life saving in some cases, like ensuring that foods don't have harmful microorganisms) that we don't have access to the vitamin B12 on plant foods. So, it might be more of a food system issue rather than a dietary pattern issue.
Angle #4) Why does someone need to draw a line at 100% plant-based eating? In the past several years I’ve really transitioned away from encouraging people to adopt a vegan/vegetarian diet. Instead, I talk about the idea of ‘finding your minimal effective dose of animal products’. This is the amount that allows you to be happy, healthy, and sane while also minimizing environmental damage and harm to animals. Finding this minimal dose could allow someone to avoid supplementing other nutrients, if that makes them uncomfortable.