Fad diets come and go. So-called superfoods often garner flashy headlines. But dietitians say there are five functional, well-researched, nutrient-dense foods that should be on your weekly shopping list. According to the Food Network, these nutritious foods are powerhouses of vitamins, minerals and antioxidants.

• Spinach. Spinach is rich in vitamin C and is an excellent source of antioxidants that shield our immune system from environmental damage. “Plus, it has beta carotene, an essential component of proper immune function,” Dr. Seema Sarin, a holistic health practitioner, tells CNBC. This versatile leafy green also contains vitamins A and K and folate, along with minerals such as potassium, magnesium and iron.

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• Sweet potatoes. This popular and tasty vegetable is an excellent source of complex carbohydrates, dietary fiber and essential vitamins. Sweet potatoes contain vitamins C, A and several B vitamins along with potassium, manganese and antioxidants. The high beta-carotene content helps protect vision, skin health and boosts immune function.

• Honey. Honey is healthier than refined sugar because it has 35 naturally occurring vitamins, minerals, antioxidants and amino acids, says the Food Network. Raw honey, especially, benefits your heart and overall health. A University of Toronto study found that raw honey improves key measures of cardiometabolic health, including blood sugar and cholesterol levels. The researchers conducted a systematic review and meta-analysis of clinical trials on honey and found that it lowered fasting blood glucose, total and LDL “bad” cholesterol, triglycerides and a marker of fatty liver disease. It also increased HDL “good” cholesterol and some markers of inflammation.

• Tuna. Tuna, a great source of lean protein, is packed with omega-3 fatty acids. Omega-3s help reduce inflammation and lower triglyceride levels. Tuna also contains vitamin D, selenium and B vitamins to support energy production and immune function. Tuna is a very versatile fish that comes in canned, pouched and fresh varieties so it’s easy to use in cooking, and for lunches and healthy snacks.

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• Berries. Berries are bursting with antioxidants and it’s important to eat a variety — blueberries, strawberries, and blackberries ─ to get the rainbow of colors and nutrients. Berries are low in calories but high in fiber to support digestive health and weight maintenance. They contain antioxidants called anthocyanins that have anti-inflammatory effects that may reduce your risk of disease, says Healthline. Berries are also chock full of vitamin C.