There are some complications with being vegetarian or vegan. It's widely encouraged that such a lifestyle is beneficial if you are migratory. Like Nomads of long ago and the birds, when the sun and growing season move south so did they.
Vitamin D is synthesized by our body through the absorbtion of sunlight.
Excess Vitamin D is stored in our fat cells. When winter and or stress hits and your body starts using this stored fat for energy the vitamin D is released. Vitamin D helps in the absorbtion of all the other vitamins. Guaranteed your body has amazing adaption abilities like in vegans where it requires much less Zinc but not here. Vitamin B-12 is another that's not found readily in the vegetable world.