Many of us grew accustomed to drinking a cold glass of orange juice when we wake up in the morning. Most are fortified with calcium and vitamin D.
There exists different types of vitamin D: D1, D2, D3, D4 and D5. Most fortified food products, as well as most supplements sold over-the-counter, use the vitamin D3, whose origin is from animal sources. If you are following a vegetarian/vegan diet, you can substitute it with vitamin D2, whose origin is from plants. Vitamin D2 is not commonly sold at the grocery stores and pharmacies, but can easily be purchased on the internet.
Those following a plant-based diet can opt for some non-fortified, pure orange juice, and use vitamin D2 supplements (or get more sunshine exposure) if need be.
As a side note, consider that it’s also unclear whether we need that much vitamin D (minimum of 30 ng/mL – 75 nmol/L – in the US). There are studies that show that levels of 20 and higher are sufficient for our needs and some argue that it’s immensely profitable to the supplements industry to incite us to keep our level of vitamin D higher.