Your immune system does more than fend off viruses and bacteria – it's involved in nearly every other bodily system too, from hormone regulation to nervous system function.
A weakened immune system is associated with increased susceptibility to viral and bacterial infections, frequent colds, hay fever and allergies, and has also been linked to autoimmune conditions and, in some cases, cancer risk.
Several factors can compromise immune function, including:
- Chronic stress
- Certain medications
- A sedentary lifestyle
- Over-exercising
- Smoking
- Insufficient sleep
- A poor diet
- Excessive alcohol consumption
- Grief and significant emotional stress
Key Nutrients for Immune Health
Vitamin D
Known as the "sunshine vitamin," vitamin D plays a key role in immune function, supporting the activity of T-cells and macrophages that help defend against pathogens. Some research suggests it may help reduce the risk of respiratory infections. Deficiency is common, particularly in colder climates with less year-round sun exposure.
Food sources include salmon, sardines, tuna, eggs, and fortified foods. During winter, supplementation is generally recommended by health bodies including the World Health Organisation – our guide to vitamin D testing can help confirm whether your levels need attention.
Fibre and Plant Foods
Fibre from plant foods – nuts, seeds, fruits, vegetables and legumes – feeds beneficial gut bacteria, and a healthy gut plays a genuine supporting role in immune function by helping prevent pathogens entering through the digestive tract. Good sources include fermented foods like tempeh and kimchi, along with bananas, leeks, onions, raspberries, black beans, asparagus and pears.
Vitamin C
Vitamin C supports immune function and has been associated with reduced severity and duration of respiratory infections. Since the body can't produce or store vitamin C, regular daily intake matters. Citrus fruits (grapefruit, lemon, orange) are well-known sources, alongside peppers, broccoli, pineapple, spinach and kiwi.
Healthy Fats
Healthy fats are associated with reduced inflammation, which supports overall immune response. While mild, short-term inflammation (such as from a minor injury) is normal and healthy, chronic inflammation can suppress immune function over time. Anti-inflammatory fat sources like olive oil, avocado, chia seeds, salmon, nuts and eggs are worth including regularly.
Zinc
Zinc deficiency is associated with reduced immune response, and some research suggests supplementation can help lower infection risk. Good dietary sources include lentils, chickpeas, beans, hemp and pumpkin seeds, almonds, pine nuts, cashews, eggs, brown rice, green beans and sweet potatoes. Our zinc supplement is worth considering if dietary intake alone isn't quite covering your needs.
Beyond Nutrition
An immune system that isn't functioning optimally doesn't just mean more frequent colds – it can also increase risk factors for more serious conditions over time, which makes prioritising these nutrients and habits a genuinely worthwhile investment in overall health.
