We’re heading into peak ‘cold and flu’ season, so now is the perfect time to focus on our immune system. Getting enough sleep, minimizing stress, and maintaining good hygiene are paramount. So too, is proper nutrition. In fact, over 70% of your immune system is in your gut, and is directly influenced by your gut microbiome and your food choices. Furthermore, certain nutrients are known to have immune-boosting functions.
To help keep you fit and firing over winter, we’ve listed five key nutrients and food sources known to boost immunity.
Probiotics are live ‘good bacteria’ naturally occurring in fermented foods, and are known to support and strengthen your gut health. During food fermentation, natural sugars are converted into lactic acid, facilitating the growth of lactobacilli and other probiotics. People who have high levels of lactobacilli in their bowel usually have fewer Enterobacteriaceae – bacteria associated with inflammation and disease (1).Food sources: Kefir, yoghurt, sauerkraut, kimchi, miso, kombucha, probiotic supplement (i.e. Yakult).
- Vitamin C
Our bodies don’t make vitamin C, but we need it for immune function. The recommended daily intake is 75mg for women and 90mg for men. Whilst experts are undecided as to whether high doses of Vitamin C can prevent a ‘common cold’, long term intakes of 200mg per day (or more) may reduce the duration of cold symptoms. According to a review of 29 clinical trials written in 2013, higher levels of Vitamin C intake translated to about one less day of illness in both adults and children (2).We suggest you aim to meet Vitamin C targets with wholefoods, because you will benefit from other important nutrients. For example, blueberries are rich in Vitamin C and ‘pterostilbene’, a phytonutrient which may increase your number of infection-fighting T-cells, and CAMP – a protein that protects against bacterial infection (3).
Food Sources: Citrus fruits, berries, dark green leafy vegetables, sweet potato, legumes. Note – by consuming 5 servings of vegetables and 2 servings of fruit each day, you are likely to achieve the ‘cold-fighting’ Vitamin C goal of 200mg.
Zinc deficiency may compromise your immune health, which is concerning, as experts are predicting up to 65% of men and 85% of women in Australia are at risk of zinc deficiency. On the flip side, zinc supplementation has been shown to enhance T cell activation, and reduce both the severity and the duration of ‘common cold’ symptoms (4). You may wish to opt for an extra ‘boost’ with zinc supplements, if you feel a sniffle coming on – the recommended dose is 75mg/day (5).Food sources: Lean red meat, poultry, seafood, tofu, pumpkin seeds, cashews.
- Vitamin D
Vitamin D is known to play a protective role against viral and bacterial infections. Sun exposure is the best option for obtaining Vitamin D, however, this can be difficult in winter, when we need it most. Hence, why Vitamin D rich foods are so important.Food sources: Oily fish (i.e. salmon, sardines), egg yolks (particularly free range), mushrooms, fortified milk (i.e. Rev, Vitasoy Calci-plus), fortified cereals (i.e. Special K).
Phytonutrients are protective nutrients found in plants, outside the ‘vitamin’ and ‘mineral’ categories. Garlic contains Allicin – a phytonutrient that boosts the antibacterial and antiviral activities of white blood cells. Some studies have shown that garlic supplementation can prevent and/or reduce the duration of a common cold (6).Other phytonutrients linked with immunity and anti-inflammatory properties include gingerol (found in ginger) and curcumin (found in turmeric).