Heart-Healthy Shrimp Salad with Grapefruit and Avocado

Ingredients

• 3 pink grapefruits
• 2 Tbsp wine vinegar
• 2 tsp Dijon mustard
• 1/8 tsp salt plus 1/2 tsp salt
• 1/4 tsp black pepper
• 4 Tbsp olive oil
• 1 1/2 lbs shrimp, peeled and deveined
• 1 1/2 lbs baby spinach (about 3 1/2 qts)
• 1 Tbsp chopped fresh mint
• 1/2 red onion, thinly sliced
• 1 avocado, pitted, peeled and sliced