Nutritional deficiencies or excesses, such as Vitamin B12 deficiency in non-meat eaters or mercury excess in high-seafood consumers, can be measured in blood, urine, or hair.

“obviously we can measure uh certain deficiencies Andor excesses uh in in the blood most commonly but also in the urine or even in the hair so in other words you could you could give you an example right you could see a person who is you know B12 deficient that's a very common finding in people who don't eat meat uh and similarly you can see an excess of mercury which would be considered quite toxic if it gets to a high enough level for someone who for example is eating a lot of seafood and especially Seafood that is uh coming from really large fish who are high enough on the food chain that they're eating a lot of other fish and accumulating Mercury themselves”