Omega-3 deficiency symptoms can be subtle and non-specific, making them easy to overlook. Omega-3 fatty acids—particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—are vital for cardiovascular health, brain function, and inflammatory regulation. Whilst frank deficiency is uncommon in the UK, suboptimal intake affects many people, especially those who consume little oily fish. Recognising the signs of inadequate omega-3 levels, understanding who is at risk, and knowing how to address deficiency through diet are essential steps in maintaining overall health. This article explores the symptoms, risk factors, and evidence-based approaches to optimising omega-3 intake.

What Is Omega-3 Deficiency?

Omega-3 deficiency occurs when the body does not receive adequate amounts of omega-3 fatty acids through diet. Alpha-linolenic acid (ALA) is the only truly 'essential' omega-3 fatty acid, as the human body cannot synthesise it. The long-chain omega-3s—eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—can be synthesised from ALA in limited amounts, but dietary sources are typically needed to achieve optimal levels.

Omega-3 fatty acids play crucial roles in maintaining cellular membrane integrity, supporting cardiovascular health, modulating inflammatory responses, and contributing to neurological function. DHA is a major structural component of the brain and retina, whilst EPA is involved in the production of signalling molecules called eicosanoids that help regulate inflammation and immune function.

Whilst frank omega-3 deficiency is relatively uncommon in the UK, suboptimal intake is more prevalent, particularly among individuals who consume limited amounts of oily fish or plant-based omega-3 sources. The Scientific Advisory Committee on Nutrition (SACN) recommends a population average intake of 0.45g of EPA and DHA combined per day. This can be achieved by consuming at least two portions of fish per week, including one portion of oily fish (approximately 140g). For context, a 140g portion of salmon typically provides about 1.5-3g of EPA and DHA combined, depending on the species and preparation.

It is important to note that there is no universally agreed clinical definition of omega-3 deficiency, and routine testing of omega-3 levels is not standard practice in the NHS. Diagnosis is typically based on dietary assessment and clinical presentation rather than specific blood tests. The omega-3 index (the percentage of EPA and DHA in red blood cell membranes) is occasionally used in research or specialist settings but is not recommended for routine clinical assessment in primary care.

Common Symptoms of Omega-3 Deficiency

The symptoms associated with inadequate omega-3 intake can be varied and non-specific, often overlapping with other nutritional deficiencies or medical conditions. Recognising these signs requires careful clinical assessment, as there is no official link established between isolated symptoms and confirmed omega-3 deficiency in most cases, particularly for mild deficiency where evidence is limited.

Dermatological manifestations are among the more commonly reported signs. Individuals may experience:

• Dry, rough, or scaly skin

• Increased skin sensitivity or irritation

• Eczema-like rashes or dermatitis

• Poor wound healing

These skin changes may occur because omega-3 fatty acids help maintain the lipid barrier function of the epidermis and modulate inflammatory skin responses. However, if skin symptoms are severe, infected (weeping, crusting), or accompanied by fever, seek prompt medical advice.

Neurological and cognitive symptoms may include:

• Difficulty concentrating

• Memory problems

• Mood changes, including low mood or irritability

• Fatigue and reduced mental clarity

Given DHA's structural importance in neuronal membranes and its role in neurotransmitter function, inadequate intake may theoretically affect cognitive performance, though evidence linking mild deficiency to specific symptoms remains limited. Persistent low mood or thoughts of self-harm require urgent GP assessment.

Ocular symptoms can manifest as:

• Dry eyes or increased eye irritation

Importantly, sudden vision changes, eye pain, or significant visual disturbances require immediate medical attention and should not be attributed to omega-3 status without proper assessment.

Musculoskeletal complaints such as joint stiffness or discomfort may occur, potentially related to omega-3's anti-inflammatory properties. Some individuals also report brittle nails or hair changes, though these associations are less well-established.

It is crucial to emphasise that these symptoms are non-specific and can result from numerous other conditions. Anyone experiencing persistent or concerning symptoms should consult their GP for proper evaluation rather than self-diagnosing omega-3 deficiency. Unexplained weight loss, in particular, should always prompt medical assessment.

Who Is at Risk of Low Omega-3 Levels?

Several population groups face increased risk of suboptimal omega-3 intake due to dietary patterns, physiological factors, or medical conditions. Understanding these risk factors helps identify individuals who may benefit from dietary assessment and modification.

Dietary and lifestyle factors represent the most common risk category:

• Individuals who consume little or no oily fish (salmon, mackerel, sardines, herring)

• Those following strict vegan or vegetarian diets without adequate plant-based omega-3 sources

• People with limited dietary variety or restrictive eating patterns

• Individuals with food allergies or aversions to fish and seafood

Malabsorption conditions can impair omega-3 absorption even when dietary intake is adequate:

• Inflammatory bowel disease (Crohn's disease, ulcerative colitis)

• Coeliac disease

• Chronic pancreatitis or pancreatic insufficiency

• Cystic fibrosis

• Short bowel syndrome following intestinal resection

These conditions affect fat absorption generally, as omega-3 fatty acids require adequate bile acids and pancreatic lipase for proper digestion and absorption.

Pregnancy and lactation increase omega-3 needs, particularly for DHA, which is critical for foetal brain and eye development. The NHS recommends pregnant and breastfeeding women consume no more than two portions of oily fish weekly (avoiding high-mercury species like shark, swordfish and marlin), and should avoid fish liver oils due to their high vitamin A content. Women who don't eat fish may wish to discuss appropriate dietary strategies with their healthcare provider.

Older adults may have reduced omega-3 intake due to decreased appetite, dental problems affecting fish consumption, or limited access to fresh foods.

Individuals with certain chronic conditions, including cardiovascular disease, type 2 diabetes, or inflammatory conditions, may benefit from optimising their omega-3 intake through diet, though supplementation should be discussed with healthcare professionals. NICE does not currently recommend routine omega-3 supplementation for cardiovascular disease prevention.

Treatment and Dietary Sources of Omega-3

Addressing inadequate omega-3 intake primarily involves dietary modification, with supplementation reserved for specific circumstances. The approach should be tailored to individual dietary preferences, medical conditions, and nutritional requirements.

Dietary sources of omega-3 fall into two main categories:

Marine sources (providing EPA and DHA directly):

• Oily fish: Salmon, mackerel, sardines, herring, trout, fresh tuna (not tinned), and pilchards are excellent sources. A 140g portion of cooked salmon provides approximately 1.5-3g of omega-3 fatty acids.

• Shellfish: Mussels, oysters, and crab contain moderate amounts

Plant-based sources (providing ALA, which the body partially converts to EPA and DHA, though conversion rates are limited—typically less than 5-10% for EPA and often less than 1-5% for DHA):

• Seeds: Flaxseeds (linseeds), chia seeds, and hemp seeds

• Nuts: Walnuts are particularly rich in ALA

• Oils: Flaxseed oil, rapeseed oil, and walnut oil

• Green leafy vegetables: Spinach, kale, and Brussels sprouts contain smaller amounts

• Fortified foods: Some eggs, milk, yoghurts, and spreads are enriched with omega-3

• Algae-derived supplements: Provide direct sources of DHA for those avoiding fish products

Supplementation may be appropriate for:

• Individuals unable to meet requirements through diet alone

• Those with confirmed deficiency or malabsorption conditions

• Pregnant women with inadequate dietary intake (avoiding fish liver oils due to vitamin A content)

• People with specific medical conditions (as advised by their clinician)

Most omega-3 supplements are regulated as food supplements under food law, not by the MHRA. Only licensed omega-3 medicines (such as omega-3-acid ethyl esters for hypertriglyceridaemia) are regulated by the MHRA. Some international health organisations suggest 250mg of combined EPA and DHA daily for general health, though this is not a specific UK recommendation. The focus in the UK is on dietary sources rather than routine supplementation.

Patients taking anticoagulants, particularly warfarin, should consult their GP before starting omega-3 supplements. While clinically significant interactions at food supplement doses are uncommon, monitoring may be advised when starting or stopping higher-dose omega-3 products.

When to contact your GP:

• If you experience persistent symptoms suggestive of nutritional deficiency

• Before starting supplements, especially if you have existing medical conditions or take regular medications

• If you have a malabsorption condition requiring nutritional monitoring

• For dietary advice during pregnancy or when planning pregnancy

NICE guidance emphasises the importance of a balanced diet rich in oily fish for cardiovascular health, though routine omega-3 supplementation for primary prevention of cardiovascular disease is not currently recommended for the general population. Individual assessment by a healthcare professional ensures appropriate, evidence-based management tailored to personal circumstances.

Frequently Asked Questions