Natural Frontier has all of the organic/healthy groceries you might want: green and protein powders, sweets, frozen meals, produce, bulk bins, etc. Juice and smoothie bar is more expensive than elsewhere in LIC, but apparently everything is organic-- I opt for the bigger size for $1 more to get a decent sized drink. They have a decent organic, fair-trade coffee bean section too.
Prices are definitely lower here than at Food Cellar on Center Boulevard, but since it's mostly organic/"specialty" items here, it tends a bit toward the moderate-expensive side. I come here often though because I think the quality is worth it.