Cook the whole grain spaghetti according to package instructions until al dente. Drain and set aside, reserving a little pasta water.
While the pasta cooks, heat 2 tablespoons of olive oil in a large skillet over medium heat.
Add the garlic and red pepper flakes, sautéing until the garlic is golden and fragrant, about 1-2 minutes.
Increase the heat to medium-high and add the shrimp to the skillet. Cook until the shrimp are pink and cooked through, about 3-4 minutes.
Add the cooked spaghetti to the skillet with the remaining olive oil. Toss well to combine all the ingredients. If the pasta seems dry, add a little reserved pasta water to help coat the spaghetti with the sauce.
Remove from heat, and stir in the chopped parsley and lemon juice. Season with salt and pepper to taste.
Serve hot, garnished with grated Parmesan cheese if desired.