<http://schema.org/alternativeHeadline>
"Vegetables high enough in nutrients like calcium, fiber, iron, potassium, protein and zinc could be considered 'powerhouses' as well, like chard or spinach."^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.mnn.com/food/healthy-eating/stories/watercress-named-top-powerhouse-veggie>