What we do know is several nutrients are required to support the immune system which include vitamins A, C, D E and minerals such as selenium and zinc, said Rob Hobson, registered nutritionist at Healthspan. He added: “The BMJ Research suggests that ensuring a good intake of these nutrients may help to prevent respiratory infections and lessen the time taken to recover.”
So how much of these nutrients do we need?
Findings from the UK National Diet and Nutrition Survey (NDNS) have shown that gaps do exist in the diet for some of the key nutrients required to support immunity.
Understanding the importance of these nutrients and where to find them in the diet can help to ensure a good intake.
Vitamin A
UK recommended daily allowance (RDA) = 700mg a day for men and 600mg a day for women
Immunity: Maintains integrity of mucosal cells in the GI tract, eyes, nose and lungs acting as the first line of defence. Also involved in the production of antibodies which fight infection.
Deficiency risk: According to the National Diet and Nutrition Survey (NDNS) 16 percent of men and 10 percent of women aged 19 to 64 have low intakes.
Top foods:
- 80g carrots = 1,569mcg
- 150g sweet potato =982mcg
- 150g butternut squash = 850mcg
- 80g kale = 420 mcg
- 100g calf’s liver = 18800mcg
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Vitamin C
UK RDA = 40mg a day for men and women
Immunity: May help to reduce the risk of catching a cold and length of infection. Also required by immune cells to perform their tasks.
Deficiency risk: Most people manage to achieve adequate intakes of vitamin C.
Top foods:
- 80g red pepper = 101mg
- 80g lemon = 46mg
- 80g broccoli = 63mg
- 80g kiwi fruit = 47mg
- 180g potatoes = 30mg
Vitamin D
UK RDA = 10mcg a day for men and women
Immunity: Has numerous effects on cells of the immune system – thought to enhance the function of T cells and macrophages. Low levels have been associated with increased risk of upper respiratory tract infections.
Deficiency risk: Everyone during the winter months due to a lack of sunlight. Elderly and housebound may be at risk all year round. Supplements recommended during the winter as you can’t get everything you need from food alone.
Top foods:
- 120g salmon fillet = 5.6mcg
- 2 eggs = 3.5mcg
- 80g mushrooms (grown under UV light) = 5mcg
- 250ml fortified plant milk (e.g. soya) = 1.9mcg
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Vitamin E
UK RDA = 4mg a day for men and 3mg a day for women
Immunity: Helps with the regulation and function of immune cells such as T cells, B cells and macrophages.
Deficiency risk: No data available for UK intakes but anyone with a diet that lacks wholefoods is at risk of not enough vitamin E.
Top foods:
- 30g sunflower seeds = 7.4mg
- 30g almonds = 7.3mg
- 1 tbsp olive oil = 1.9mg
- 80g spinach = 1.5mg
- 80g avocado = 1.1mg
Zinc
UK RDA = 9.5mg a day for men and 7mg a day for women
Immunity: May help to protect against viral infections such as the common cold. Also shown to have antibacterial effects in the body.
Deficiency risk: According to the National Diet and Nutrition Survey (NDNS) 7 percent of men and 8 percent of women aged 19-64 have low intakes.
Top foods:
- 100g lean red meat = 4mg
- 100g turkey (dark meat) = 3.1mg
- 50g quinoa (dry) = 1.7mg
- 30g nuts = 1mg
- 2 eggs = 1.4mg
Selenium
UK RDA = 75mcg for men and 60mcg for women
Immunity: required for the synthesis of antibodies and also stimulates the production and activity of T lymphocytes and natural killer cells which help to fight viral and bacterial infections.
Deficiency risk: According to the NDNS 25 percent of men and 47 percent of women aged 19-64 have low intakes.
Top foods:
- 30g Brazil nuts = 76mcg
- 50g cooked crab meat = 77mcg
- ½ can tuna = 44mcg
- 100g tofu = 17.4mcg
- 75g wholewheat pasta (dry) = 11.2mcg
So can supplements play a role?
While food should always come first, we do know that vitamin D is hard to get from diet alone, a recent study found vitamin D intake from supplements may be associated with fewer respiratory complaints.
Dr Sarah Brewer, Medical Director of Healthspan, added: “While diet should always come first, this study found that only vitamin D from supplements rather than food provided protection against respiratory complaints. This is most likely because it is difficult to obtain significant amounts of vitamin D from diet alone, unless you eat a lot of oily fish.
“The authors of the study noted an estimated one in five of the UK population have low vitamin D levels, and that almost one in three older adults aged 65 years and over do not achieve recommended vitamin D intakes.”
Should we be complementing our diet with supplements?
The potential role of supplements alongside diet to support immunity was also highlighted in a recent white paper written in cooperation with the Swiss Society of Nutrition.
The recommendations outlined in this paper include both diet and supplementation to support immunity amongst the population (especially those over 65) during the current COVID-19 pandemic.
The panel of experts involved in the paper recognised the nutrient gaps that exist within the population and stated, “to change nutritional habits on a population level is difficult and a long-lasting endeavour and does not correspond to the urgency of the pandemic. Furthermore, an optimal nutritional status is often not achieved without a compliment (supplement)”
Rob Hobson, Registered Nutritionist at Healthspan, concluded: “In conclusion this study and many others show that it is not always possible to eat a balanced diet and gaps do exist.
“Investing in a multivitamin and mineral supplement (try Healthspan MultiVitality Gold – £10.95 for 180 tablets) is a simple and cost-effective way to bridge these gaps which may be especially relevant during the winter months when we are more exposed to infection.”