Essential vitamins for the winter season by Julie Zeithuber

Boosting our immune system with nutritional remedies can aid our body’s power to fight against cold and flu. Adequate healthy food deliver tons of vitamins which each participate in thousands of activities throughout our body.

You will hear a lot about anti-oxidants in the lines below. Everyone talks about anti-oxidants. Your pharmacist, nutritionist, TV commercials, health blogs, supplement companies…We all know it benefits our health. But how? Metabolic processes in our body or external environmental factors such as smoking produce free radicals. Those free radicals are very reactive and can cause massive damage in our bodies. Free radicals can cause cell membrane damage and consequently DNA, RNA and protein damages, which result in impaired cell function and inflammation. Consequences are cell damage, disease progression and, also aging.

The good news is, our body has its own defence mechanism, that consists of enzymes whose activity depends on minerals (selenium, copper, manganese and zinc) as well antioxidant vitamins (Vitamin C, Vitamin E, beta carotene) If our diet lacks in those nutrients, your defence mechanism weakens. A balanced diet rich in vegetables and fruit, whole grains and healthy fats provide all these nutrients in sufficient amounts.

To name a couple, Julie listed the main players:

Omega 3 fatty acids are an integral component to our wellbeing and health. Cell membranes in our body are made up from such omega 3 fatty acids. Building this layer for our cells results in a sort of fluid and flexible “wall” as protection for toxins and viruses. Further, it enhances the immune function and promotes immune cell development. It also acts as an anti-inflammatory and modulator for allergic reactions. It improves your mood and mental focus. Make sure your diet includes fish, nuts, hemp, chia, flax, pumpkin seeds, avocado and green leafy vegetables.

Vitamin C

Vitamin C is probably first vitamin that comes to our mind when we think of cold prevention. However, research shows that it might only cause a slight reduction in symptoms and duration. It might be useful for preventing/treating conditions like colds, influenza, urinary tract infection, muscle cramps, depressions, soreness and aging processes. More importantly, it’s main role is to be an anti-oxidant and to defend against free radicals that damage our cells. It plays an important role as a co-factor in the formation process of collagen. Further, Vitamin C is involved in the making of hormones. Most importantly, it strengthens our immune system.

The Recommended Daily Allowances (RDA) according to the Institute of Medicine is are 75mg for women and 90mg for men. These numbers can be more than easily achieved on a balanced diet.

Foods high in vitamin C are citrus fruit, Brussel sprouts, bell peppers, broccoli, strawberries, cauliflower, potatoes, parsley

If you consume 1 cup of orange juice, 1 salad, 1 cup of steamed broccoli and potatoes on one day you already have a vitamin C intake of 300mg…so more than enough. 

Vitamin D

If you are lucky and get some sun in the winter, get out there and soak in the sunshine aka refill your Vitamin D storages!

Vitamin D plays a major role in the modulation of immune functions and thus may help in prevention of infectious diseases. It might be useful in prevention or treatment of colds, fatigue, influenza and osteoporosis. Research underlines that low vitamin D concentrations are associated with depression, however, prevention and treatment of depression with vitamin D supplementation needs more evidence.

It enhances the intestinal absorption of calcium and phosphorus and is therefore crucial for our bone health.

Our body can synthesize Vitamin D with the help of sunlight. In grey winter month, our body own vitamin D production might not be sufficient to provide adequate levels. Thus, dietary Vitamin D intake is important. Good food sources for Vitamin D are fortified milk, cod liver oil, certain mushrooms, egg yolks and oily fish such as salmon, sardines or mackerel. Vitamin D supplementation is recommended when exposure to sunlight is very little and dietary needs are not met. 

Vitamin A

Vitamin A and its various forms is crucial for eye and skin health. It plays an important role in immune function, reproduction and growth. Vitamin A occurs in animal food. However, plants provide Pro-Vitamin A called carotenoids with a high anti-oxidant potential, some of which can be converted to vitamin A.

Excellent sources for Vitamin A are liver and fish liver oils. Other great sources include dairy products, butter, eggs, fortified foods. Carotenoids are found in carrots, spinach, kale, sweet potatoes (dark green leaves and deep yellow/orange/red vegetables and fruits).

Since Vitamin A is a fat-soluble vitamin (needs fat to be absorbed) make sure you consume a source of fat when you eat vitamin A rich food, e.g. drizzle a little bit of olive oil into your carrot juice, dip carrots in hummus or other dips, salad + dressing etc. Don’t be too religious about it though, you can eat a carrot without nibbling on nuts at the same time. Animal based vitamin A sources are usually also combined with fat (milk, liver, eggs) so you don’t have to worry about fat intake, and plant based foods which provide carotenoids are high in fiber, need longer to digest, thus the possibility that you consume fat within 2-3h before or after you ate your carrot is very likely.

Vitamin E

Its main function is that of anti-oxidant. It stabilizes cell membranes and has great anti-inflammatory powers. Further, it enhances immune function when intake is moderate. However, high doses can inhibit immune functions.

Nuts and seeds, unprocessed vegetables oils, whole grains, egg yolks and leafy greens are good sources for vitamin E. Since it is destroyed in with heat, fresh and unprocessed foods are recommended. Supplementations are usually not necessary. 


Include a whole list of water soluble vitamins (B1,2,3,5,6,7,12 and folic acid.) All of them play crucial roles in our energy metabolism, neurovascular and neuromuscular systems as well as blood cell formation.

A well-balanced diet rich in vegetables, fruit, lean meat, healthy fats, whole grains and milk products provide all B vitamins needed. Vitamin B12 is only present in animal based food, however, thanks to Vitamin B12 enriched products (Plant milks, tofu, cereals) vegans are also on the safe side.


Iron is vital for our metabolic machinery and many cell activities. To prevent fatigue, make sure you eat enough iron containing food. Excellent sources are meat, fish and poultry. Good sources are legumes and eggs, iron fortified foods, whole grains, dark greens and dried fruit.


I cannot say it often enough. If you consume a well-balanced diet, meaning a diet high in fruits, vegetables, nuts, healthy fats, lean meats and low fat milk products and if you spend time in the sun you will be all covered in terms of nutrients. Consume a wide variety of whole foods and do not isolate single foods. In certain life circumstances, such as pregnancy, growth or due to diseases, supplementation of some vitamins is recommended.

To prevent vitamin deficiencies, most commonly supplemented are Vitamin D and Vitamin B12 as well as fish oil (omega 3 fatty acid), magnesium for those who are physically very active to aid muscle recovery. However, I would consult a GP and check blood levels before taking any supplements. High doses can result in adverse effects and increase mortality (e.g. excessive beta carotene consumption increases the risk of lung cancer in smokers)

For nutritious recipes packed with vitamins and immune boosters visit Julie’s website and get inspired. Julie is a scientist and food lover who graduated with a Master in Nutritional Science from the University of Vienna, Lived and worked in Melbourne, worked at the WHO in Geneva and currently lives in Vancouver.

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