Vitamin C or Vitamin D – what’s best for immunity?

As we scramble to boost our immunity, most of us will follow the conventional A-B-C approach of dosing up on vitamins A, B (B6 specifically) and C.

The other compounds that are often promoted for their touted immune-boosting benefits include vitamin E, zinc, selenium, folic acid, copper, beta-carotene and coenzyme Q10, with various degrees of research and science backing their efficacy.

However, there is a glaring omission from most of our proactive strategies aimed at boosting our immune systems, and that is a lack of vitamin D. Yes, the so-called ‘sunshine vitamin’ is actually one of the more important substances in terms of immunity as it has the greatest link to immune function than all those already mentioned.

Unfortunately, there is often a lack of this vital vitamin at a time when we generally need it most due to the shorter days and weaker ultraviolet radiation from the sun during winter. We also wrap up warmly which reduces skin exposure to the sun’s rays.

Natural production

Thankfully the body is able to produce its own supply of this important vitamin via the action of sunlight on a form of vitamin D that is contained in the skin called cholecalciferol (also known as vitamin D3). However, if you choose to hibernate indoors during the colder months, diet-derived vitamin D is your next best option (but don’t miss an opportunity to expose your body to the sun’s rays whenever you can). The best dietary sources of vitamin D include egg yolks, beef liver, fatty fish such as tuna, herring, mackerel and salmon, and various fortified dairy and cereal products.

No bones about it

However, a growing body of evidence now suggests that the role of vitamin D in the body has far-reaching health benefits. These range from the prevention and treatment of common cancers, hypertension and cardiovascular disease, to optimal brain development and its role as an immunomodulator – a chemical agent that modifies the immune response or the functioning of the immune system.

We now know that vitamin D works in the immune system by reducing levels of inflammatory proteins. It also increases the amounts of antimicrobial proteins, which destroy invading germs and viruses, such as the B cells (also known as B lymphocytes) and killer T cells that constitute our adaptive immune system which builds immunity via immunological memory following exposure to specific antigens. These cells contain vitamin D receptors and are therefore capable of synthesising the active form of vitamin D, calcitriol. This means that vitamin D plays a vital role in modulating the adaptive immune system’s antimicrobial response to infections.

The real flu fighter

Vitamin D has been linked to a decrease in both a person’s susceptibility to and the duration of common infections, including the flu. This statement is backed by numerous studies which tend to show that people who have lower levels of vitamin D are more likely to get the flu and also tended to suffer from the infection for longer (nine days versus just two in those with higher vitamin D levels, according to one study).

Vitamin C – better as a cure than prevention

The reason why megadoses of vitamin C are often advised during the cold and flu season is that this antioxidant is highly concentrated in immune cells and is consumed quickly during an infection. However, the use of vitamin C as a preventative measure has been questioned recently, with a meta-analysis that examined 29 trials in a total of 11,306 participants revealing that supplementing with 200mg or more of vitamin C did not reduce the frequency of colds and infection. However, there was a tendency for vitamin C to reduce the severity and duration of colds. That means you’re better off saving your vitamin C supplement for when you get sick, rather than trying to boost your immunity with it.

Tips to boost vitamin D levels:

  • Expose as much of your skin as possible to the sun’s ultraviolet rays for a few minutes each day. Optimal durations vary depending on skin type.
  • Get this ultraviolet exposure as near to solar noon as possible – generally between 10h00 and 14h00.
  • If you use a sunscreen, opt for one that blocks only UVA.
  • Add more vitamin D-rich foods to your daily diet.
  • Supplement with vitamin D2 or D3, if additional support is required.

Author: Tanja Schmitz

Founder and Editor of Fitness Magazine. You’ll find her behind her computer or on her bike, dreaming up new ways to improve or create content for you.

Founder and Editor of Fitness Magazine. You'll find her behind her computer or on her bike, dreaming up new ways to improve or create content for you.

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