Make sure you eat "colourfully."
Green, yellow, orange, red or blue vegetables and fruits contain different plant substances, minerals and vitamins. The more varied our supply of these natural substances, the better for our immune functions.
Add variety to your diet
Your immune system loves diverse meals that include fresh vegetables, fruit, nuts and whole meal products. Our white blood cells also appreciate the nutrients contained in fish, meat, eggs, milk, dried fruit and even frozen vegetables. Highly processed products with minimal nutrients such as white bread, cheese, pasta, or lunch meat seldom have a place in a healthy diet to support immune health.
Add flavor and aroma
Herbs and spices have lots of value even in small quantities. Some examples include wild garlic, nettle, dandelion, turmeric, ginger, thyme, red coneflower or linden blossom. As an ingredient or extract, they have antibacterial and antiviral activity.
Cut back on processed foods
Your white blood cells will pass on foods that have gone through multiple processing steps and contain nutrient-poor ingredients and additives. These ultra-processed foods include soft drinks, ice cream, pastries, sweets, sausages and other meat products, dry soups and ready meals such as frozen pizza.
Vitamins and nutrients
Vitamins A, C and D as well as the B vitamins (B6, folic acid and B12), secondary plant compounds and the trace elements iron, copper, selenium and zinc contribute to the normal function of the immune system. Load your plate with different foods and you're more likely to ingest all of these nutrients.
- Numerous foods contain the mentioned trace elements. There is plenty of iron in meat, but also in beans, peas and lentils, which also provide a healthy amount of copper. You can get copper from seafood and nuts as well.
Apart from eggs, fish and meat, selenium can be found in cabbage, mushrooms, asparagus, nuts and onions.
Good sources of zinc include fish, seafood and meat, but also cheese, lentils and nuts.
- Vitamin A and C. A diet rich in vegetables will generally provide you with enough vitamin A and C, as well as the equally important dietary fibres. Vitamin C is a powerful antioxidant that can strengthen your body's natural defenses. Vitamin C deficiency, medically referred to as scurvy, practically no longer occurs in Canada. Incidentally, the body excretes large amounts of unused vitamin C.
- B vitamins are found in green vegetables (broccoli, spinach), in all legumes (beans, peas, chickpeas, lentils), in whole grain cereals and animal products (fish and meat). Vegans need to supplement with vitamin B12 to avoid deficiency symptoms including a feeling of pins and needles, muscle weakness, headaches, and impacts on mood and mental health.
- Vitamin D is a special case. Science understands that the "sun vitamin" strengthens the body's defences and in particular, activates the group of cells called macrophages. Though getting this vitamin from food alone is difficult, more so if you're vegan as larger amounts are only found in fatty fish such as salmon or mackerel. Some alternative sources include eggs and mushrooms, and smaller amounts through dairy products. Ultimately, dietary intake only accounts for about 10% of our daily needs. Therefore, it is critical that the body produce it via the skin and through exposure to UV radiation.
A minimum serum level of vitamin D - 75 nanomoles per litre (nmol/l) or 30 nanograms per millilitre (ng/ml) - is important for proper immune system function. It is essential that the value is determined by a primary care provider like your general practitioner or naturopathic doctor and a reputable laboratory. Have it measured first before you take vitamin D supplements to establish a baseline value.
A truly serious vitamin D deficiency is rare even in countries that aren't exactly considered sun-drenched. Adults who might be deficient are mainly seniors over 65, those who are bedridden, people with dark skin and those who do not leave the house at all or only for short periods. Other risk factors include cancer, smoking and obesity.
If you are concerned that your vitamin D level is too low, get it checked first, then seek advice from your doctor or pharmacist about supplementation. Since this is a fat-soluble vitamin, too much means it can build up in the system.