A dietitian has revealed what happens when you give up important food groups including seafood and red meat to follow a trendy 'elimination diet' like Paleo or gluten-free.

Dietitian Susie Burrell, from Sydney, said if you give up dairy, red meat, seafood or poultry, you can expect there to be serious health effects for your body - and these vary from acne to brittle bones and weakened immunity.

'If you cut something from your diet, you need to replace the banned food with something else to ensure you're not missing out on something the body really needs to keep it healthy long term,' Susie wrote on her blog.

Sydney-based dietitian Susie Burrell (pictured) said if you give up dairy, red meat, seafood or poultry, you can expect there to be repercussions for your body

Susie warned that giving up milk and other dairy foods (stock image) can lead to brittle bones and osteoporosis

DAIRY

More people than ever have ditched traditional cow's milk and dairy in favour of soy, oat, almond and other alternative varieties.

But Susie warned that giving up milk and other dairy foods doesn't only mean you're denying your body vital calcium content, but other important nutrients such as magnesium, vitamin B12, phosphorous, protein, vitamin D and vitamin A too.

Vitamin B12 deficiency can lead to liver and kidney failure and heart disease, while a lack of magnesium can lead to osteoporosis.

'As dairy is such a rich natural source of calcium, it is very difficult for adults to get the 800-1000mg of calcium they need each day for healthy bones without any dairy in the diet,' Susie said.

Nut milks and soy products can be fortified with calcium, but it's rarely enough for the required daily amount.

A lack of calcium can mean you get brittle bones in later years, by which time Susie said there is little you can do about it.

If you do want to ditch dairy altogether, the dietitian explained you must make sure you are choosing 'nut or grain-based milks that are fortified with calcium'.

Alternatively, take a calcium supplement to make sure you get the 800-1000mg of calcium you need each day.

Ditching dairy can lead to: Brittle bones and osteoporosis.

Alternative sources: Nut or grain-based milks that are fortified with calcium or a calcium supplement.

There could be any number of reasons why you choose to not include red meat (pictured) in your diet, but doing so means you are eliminating one of the 'richest natural sources of iron'

RED MEAT

There could be any number of reasons why you choose not to include red meat in your diet, but doing so means you are eliminating one of the 'richest natural sources of iron'.

'While white meat, eggs, wholegrains and leafy greens do contain some iron, the reality is that this iron is relatively poorly absorbed compared to that found in red meat,' Susie said.

Low iron levels are relatively common for women, Susie said, with up to 25 per cent of us battling it.

She said low iron can lead to feelings of fatigue, breathlessness and low immunity.

'While vegetarians adapt over time and become more efficient at absorbing their iron from plant foods, it tends to be those who consume red meat occasionally who are at higher risk of developing iron deficiency, as their body is used to absorbing iron from animal sources,' Susie said.

If you do ditch red meat, the dietitian said you need to look for iron-rich foods in every meal and snack, so you get the required daily amount of 18mg each day.

Good examples of iron-rich foods that aren't meat include tofu, tempeh, lentils, Brazil nuts, cashews, spinach, potatoes and mushrooms.

Ditching red meat can lead to: Fatigue, breathlessness and low immunity.

Alternative sources: Tofu, tempeh, lentils, Brazil nuts, cashews, spinach, potatoes and mushrooms.

If you are lacking in zinc, which can be found in shellfish including mussels (pictured) and oysters, you might get acne or a weakened immune system.

FISH AND SEAFOOD

Susie said seafood, including all fish and shellfish, is 'extremely good' for us.

High in protein, nutrient-rich and relatively low in calories, she said the two key nutrients you stand to miss out on if you ditch fish are omega 3 fats and zinc.

Oily fish including salmon, sardines and fresh tuna are one of the very few natural foods where you can find omega 3, while oysters, mussels and shellfish are packed full of zinc.

'Zinc is crucial for hormone production, immune function and good skin,' Susie said.

If you are lacking in zinc, you might get acne or a weakened immune system.

'The other less frequently mentioned nutrient we get from our seafood is iodine,' Susie said.

'This is notoriously low in Australian soil, and low iodine is linked to impaired thyroid functioning long term.'

If fish or shellfish aren't your thing, a zinc or omega 3 supplement may be needed.

Ditching fish and seafood can lead to: Bad skin, poor hormone production and weakened immune function.

Alternative sources: Zinc and omega 3 supplements.

WHITE MEAT AND POULTRY

White meat including chicken and turkey is not as nutrient-dense as red meat, but it does contain vital sources of protein, vitamin B6, selenium and vitamin B12 which we all need to function.

Selenium is an important mineral and depleted levels can lead to infertility, muscle weakness, hair loss and mental fog.

If your body is very low on vitamin B6, you can get anaemia, which is too few red blood cells - meaning you're tired and weak.

'If you are still including eggs and/or dairy you will be getting enough of these vitamins and minerals,' Susie said.

But it's worth keeping in mind that lean chicken and turkey meat are rich in protein, which if depleted can mean weight loss, muscle weakness, and lethargy.

Ditching poultry can lead to: Weight loss, muscle weakness, and lethargy.

Alternative sources: Eggs and/or dairy.

'Eggs are a nutritious food containing more than 20 essential vitamins and minerals including good quality protein, good fats and vitamins A and E,' Susie said (stock image)

EGGS

While eggs fall under the dairy category, Susie revealed that eliminating them from your diet has such an effect that they are worthy of their own section.

'Eggs are an extremely nutritious food containing more than 20 essential vitamins and minerals including good quality protein, good fats and vitamins A and E,' she said.

You can get many of these vitamins and minerals from other foods, but the one exception is selenium, a 'powerful antioxidant that plays a key role in cell health and is found in very few foods including eggs and Brazil nuts'.

A single egg, for example, provides a quarter of your daily selenium requirement.

As well as infertility, muscle weakness, hair loss and mental fog, depleted selenium can lead to a weakened immune system.

If you are cutting eggs, Susie recommends you still eat poultry and plenty of good fats.

Cutting eggs can lead to: A weakened immune system.

Alternative sources: Poultry and/or vitamin D supplements.