Easy (and just as healthy) swaps for when you can't find fresh foods in the supermarket

• Salmon fillets with caramelised onion and wilted greens

Whether you are struggling with the shopping at the moment due to a shortage of fresh food at your local outlets, or because you are at home isolating or dealing with COVID, not having access to healthy, fresh produce is both frustrating and concerning, especially when you are attempting to eat as well as possible to support immune function.

While fresh is generally best, there are some caveats to this, considering that many foods we have access are not always as "fresh" as we would like to think. Not being able to buy your usual fresh bread, fish and vegies does not need to be an issue. These smart swaps give you all the nutrients you would find in fresh produce, in other convenient options.

Green leafy vegies

If we rated foods for their nutritional value, you would be hard pressed to find foods that are as good for us nutritionally as leafy greens such as spinach, kale and rocket. Especially rich in key nutrients and with powerful anti-cancer properties, ideally we should consume at least one serve of leafy greens every day.

It's worth noting that the nutrients in leafy greens are not overly stable, meaning they lose some of their potency once they are harvested. This means that frozen varieties are a smart way to consume these foods, given they are snap-frozen at time of harvest and retain a higher proportion of nutrients.

So, heading to the supermarket freezer section to pick up your weekly kale and spinach is just as good, if not better, than waiting for the fresh bunches to return, and at reasonable prices.

Lean meat

Meat and chicken have been in especially high demand over the past couple of weeks with many a supermarket shelf bare come late afternoon. Lean meat and chicken are two of the richest natural sources of good quality protein in the diet, offering 20-30g per 100g serve compared to half as much in most plant-based protein serves.

A couple of eggs comes pretty close to adding 16-20g of high-quality protein, or if you opt for a vegetarian bean-based nachos or chilli con carne, and serve it with brown rice or corn, you will have a low calorie meal that still offers 10-15g of complete or balanced protein.

Shellfish

When we are staying close to home, fresh summer shellfish is not always easy to find or store, and can slip off the menu very quickly.

Shellfish, including oysters, mussels and prawns, is a rich source of a number of key nutrients including zinc, iron, Omega-3 fats and iodine, so don't be afraid to opt for tinned oysters and mussels for a protein- and nutrient-rich meal addition.

Frozen Aussie tiger prawns, available from most supermarkets, can easily be incorporated into evening meals while retaining all the nutrients of their fresh counterparts.

Fish fillets

Another fresh food that is proving pretty hard to find at supermarkets is fresh Aussie seafood, Atlantic salmon in particular.

Instead, you can opt for frozen fish fillets and be assured of a protein-rich meal but do not forget that tinned fish, such as tuna, salmon, herring and sardines, is a cost-effective way to get both your protein and Omega-3s when fresh fish is unavailable.

• Tinned fish dinners: 25 recipes that make the most of tinned tuna, anchovies and sardines
• Tuna and frozen pea spaghetti (pictured)

Summer fruit

'Tis the season of brightly coloured, vitamin-rich stone fruit yet accessibility and demand may mean that you are able to enjoy a lot less fresh fruit than usual.

While there are plenty of tinned options, many varieties contain added sugars via the concentrated juice they are packed with, and the fruit overall is a lot more kilojoule-dense when we buy only the flesh.

Dried fruit also lacks the bulk that whole fruit does, making it extremely easy to overeat (and it's exceptionally sweet).

For these reasons, if fruit is in short supply, your best option is to buy it frozen. Berries, mango, pineapple and even pomegranate and cherries can be found snap-frozen in as nutrient dense a form as their fresh counterparts.

Grainy bread

Supermarket bakery shelves might bestripped earlier in the day as more people prepare their lunches and breakfasts at home.

If you have the time and inclination, you can always bake your own loaf, but don't forget that there are plenty of crispbreads and crackers that are delicious teamed with your favourite toppings for a light lunch.

As a rule of thumb, the more grains the better. Brown rice and corn cakes are also great options topped with boiled eggs, tinned fish, baked beans or avocado.

• 32 bake-at-home bread and dough recipes

Susie Burrell is an accredited practising dietitian and nutritionist.