By Michaela Carrick, BSc Human Nutrition
Your immune system is a group of cells and proteins that protect your body against infections and getting sick. While it technically isn’t possible to ‘boost’ your immune system, a healthy diet can help keep it functioning properly. Some vitamins and minerals like vitamin C, vitamin D, and zinc can support your immune system as they are needed by immune cells to grow and work properly. If you don’t get enough of these essential nutrients, your immune system may weaken (1).
Luckily, you can often get enough of these nutrients from food without the need for supplements!
Vitamin C
You may have heard that vitamin C can treat a cold or flu. Unfortunately, there is no scientific evidence to support this claim. However, vitamin C plays an important role in supporting our natural immune system through its antioxidant effects (2).
The average adult needs 40 mg of vitamin C per day which can be easily reached through food alone. This means you do not need to take supplements to meet your vitamin C requirement.
Many fruits and vegetables are good sources of vitamin C, including:
- Citrus fruits like oranges, lemons, and grapefruits.
- Peppers of all colours but especially yellow
- Berries like strawberries and blackcurrants
- Leafy green vegetables like broccoli and brussels sprouts
- Potatoes, both regular white potatoes and sweet potatoes
If you would like to include more vitamin C in your diet, try these tips:
- Drink a glass of freshly squeezed orange juice with your breakfast. One average glass of orange juice contains about 50 mg of vitamin C. Eat an orange for a healthier choice with more fibre and less sugar.
- Add berries to porridge, yoghurt, or desserts. Half a cup of raw strawberries contains about 45 mg of vitamin C.
- Try stuffed peppers as an appetiser or side dish or add mixed bell peppers to stir-frys. Half a bell pepper contains about 100 mg of vitamin C, more than twice the amount your body needs!
Vitamin D
Vitamin D is famously known as the sunshine vitamin because your body can make vitamin D when your skin is exposed to light. Vitamin D can help regulate the immune system’s response to infection through its anti-inflammatory effects (3). Unfortunately, if you do not live in a country with year-round sunshine, your body may struggle to make enough vitamin D, especially in Winter. Vitamin D deficiency can cause you to be more susceptible to infection (4).
The average adult needs 10 ug of vitamin D per day which can be reached through foods naturally containing vitamin D, fortified foods, or supplements. In the UK, a daily supplement of 10ug (400IU) is recommended for all adults during Autumn and Winter.
Foods naturally containing vitamin D include:
- Oily fish like salmon, mackerel, and sardines
- Red meat, especially liver
- Egg yolks
If you would like to include more vitamin D in your diet, here are three tips:
- Aim to eat oily fish like salmon, sardines and mackerel at least once a week. One average salmon fillet (100g) baked contains 10 ug of vitamin D. Serve with new potatoes and mixed steamed vegetables or salad for a balanced meal.
- Avoid removing the egg yolk when cooking omelettes and other egg dishes. Each egg yolk contains about 2.3ug of vitamin D.
- Choose milk, spreads, and breakfast cereals fortified with vitamin D. These foods have added vitamin D and should have their vitamin D content listed on their nutrition label.
Zinc
Zinc is essential for the immune system as it has antioxidant effects and helps cells of the immune system to communicate with each other (5).
Daily, the average man needs 9.5mg of zinc while the average woman needs 7mg. These amounts can be reached through eating a variety of plant and animal foods.
Good food sources of zinc include:
- Meat
- Shellfish
- Milk and dairy products
- Beans
- Nuts and seeds
If you would like to be sure you are eating enough zinc, try out these tips:
- Choose porridge at breakfast. A medium portion of porridge made with milk contains about 1.8mg of zinc. Top with almonds, cashews, or pumpkin seeds for extra zinc!
- Add beans to curries, casseroles, and salad. A half a can of mixed beans or snack pot of baked beans contains 1.2mg of zinc.
- Choose wholegrain carbohydrates whenever possible. Wholegrain rice and bread can contain more than double the amount of zinc of white versions!
All nutrient content information was obtained using Nutritics nutritional analysis software.
References
Wu D, Lewis ED, Pae M, Meydani SN. Nutritional modulation of immune function: analysis of evidence, mechanisms, and clinical relevance. Frontiers in immunology. 2019 Jan 15;9:3160.
Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017 Nov;9(11):1211.
Di Rosa M, Malaguarnera M, Nicoletti F, Malaguarnera L. Vitamin D3: a helpful immuno‐modulator. Immunology. 2011 Oct;134(2):123-39.
Aranow C. Vitamin D and the immune system. Journal of investigative medicine. 2011 Aug 1;59(6):881-6.
Wessels I, Maywald M, Rink L. Zinc as a gatekeeper of immune function. Nutrients. 2017 Dec;9(12):1286.
