I was going to write a blog about the health benefits and nutritional composition of seaweed, but the tide turned and I see that BBC rocked up first: https://www.bbcgoodfood.com/howto/guide/health-benefits-seaweed. Sea la vie.
You can see that the calcium content in kelp is similar to spinach, also in kelp the folate and iron content beats that of land grown leafy veg. The land greens win in the quantity of fibre and vitamin K. Though, as dark, leafy veggies go, these sea and land veg seem broadly similar.
Seaweeds have unique bioactive compounds not present in terrestrial food sources, so are a novel source of compounds with potential to be exploited in human health applications.
So, if you are getting bored with spinach and broccoli, why not add some seaweed to your five-a-day routine?
All data exported from Nutritics with the sources of the original data as:
Seaweed and human health by Brown et al Nutrition Reviews Vol. 72(3):205–216