6 vitamins to boost immunity during winter

Season change increases the risk of common infections. To fight back, you need a strong immune system which is your body’s defense mechanism against bacteria, virus, and fungi. But there may be times, especially during monsoon and winter, that the disease-causing microorganisms manage to invade and make you ill. For your immune system to be strong, your cells, tissues, and organs need to work together to identify and destroy the foreign threats and keep you healthy. But if there is a vitamin deficiency, your immune system can take a hit. While all the nutrients are important, there are some key vitamins to boost immunity.

What are the vitamins to help boost immunity before winter?

Winter is almost here, so make sure your immune system is strong. Immunity in the nose can be affected in cold temperatures and make people more susceptible to viruses, as per a 2023 study published in The Journal Of Allergy And Clinical Immunology.

Here are some of the key vitamins that can help boost immunity:

1. Vitamin C

Make vitamin C your friend if you want to keep your immune system strong. Vitamin C is considered to be the most critical micronutrient for immune function, as per research published in the Cureus journal in 2023. It is an important antioxidant that supports the production and function of white blood cells, particularly phagocytes and lymphocytes, which help fight infections. It also strengthens skin barriers, which act as a defense against pathogens.

2. Vitamin D

Vitamin D plays a critical role in enhancing the pathogen-fighting abilities of monocytes and macrophages, which are two types of white blood cells. Vitamin D deficiency is associated with increased susceptibility to infection, according to research published in the Journal of Investigative Medicine in 2011.  “It also helps regulate the immune response, reducing the risk of infections like colds and flu, especially during winter when sunlight exposure decreases,” says nutritionist Pooja Kedia.

3. Vitamin E

A powerful antioxidant, vitamin E helps neutralize free radicals and protects immune cells from oxidative damage. Vitamin E is important for normal function of the immune cells, according to research published in the Vitamins & Hormones journal in 2011.  It supports the function of T-cells, which are essential for targeting and eliminating infected or abnormal cells.

4. Vitamin A

Vision is often associated with vitamin A. But vitamin A also plays a role in immune system regulation, as per research published in Nutrition Clinique et Métabolisme in 2022. Vitamin A helps maintain the integrity of the skin and mucous membranes in the respiratory and digestive tracts, which are the body’s first line of defense against infections. It also supports the production of white blood cells and plays a role in regulating the immune response.

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5. Vitamin B6

Vitamin B6 supplement may improve immune system of people who are critically ill. During a 2006 study published in the European Journal of Clinical Nutrition, it was found that taking vitamin B6 supplements (50 or 100 mg per day) could increase immune response of critically ill people. It is involved in the production of immune cells and antibodies. It supports biochemical reactions that help the body fight infections, and it plays a role in maintaining the health of the thymus, an organ that produces infection-fighting T-cells.

6. Vitamin B12

Vitamin B12 can be used to balance immune responses. It can help to fight viral infections, as per research published in Nutrition Reviews in 2021. Vitamin B12 helps support DNA synthesis, red blood cell production, and the health of the nervous system. “A healthy nervous system is linked to a well-functioning immune system, and vitamin B12 also contributes to the production of white blood cells,” says Kedia.

What are the sources of vitamins to boost immunity?

Here’s a look at the best food sources of the immunity-boosting vitamins:

1. Vitamin C

“Vitamin C, which must be consumed regularly through food since the body does not store it, is abundant in various fruits and vegetables,” says the expert –

• Citrus fruits like oranges, lemons, grapefruits, limes, and tangerines
• Berries such as strawberries, blueberries, raspberries, and blackberries.
• Bell peppers like red and yellow bell peppers.
• Broccoli, which is a cruciferous vegetable.

2. Vitamin D

Vitamin D is produced by the skin when you expose yourself to sunlight. But during winter, food sources of vitamin D become important, particularly the ones that are fortified.

• Fatty fish such as salmon, tuna, mackerel, and sardines.
• Fortified dairy products like milk, and yogurt.
• Fortified plant-based milks like almond milk, soy milk, and oat milk.
• Egg yolks
• Certain types of mushrooms, like maitake and shiitake.

3. Vitamin E

“Vitamin E is a fat-soluble vitamin mostly found in plant-based oils, nuts, and seeds,” says Kedia.

• Nuts like almonds, hazelnuts, and peanuts.
• Seeds such as sunflower seeds and pumpkin seeds.
• Vegetable oils such as sunflower oil, safflower oil, and olive oil.
• Green leafy vegetables such as spinach, Swiss chard, and collard greens.
• Avocados

4. Vitamin A

Vitamin A is available in two forms — preformed vitamin A (retinoids) found in animal products, and provitamin A (carotenoids) available in plant foods.

• Beef liver.
• Carrots
• Sweet potatoes
• Dark leafy greens such as spinach, kale, and collard greens.
• Dairy products like milk, butter, and cheese.
• Red and orange vegetables like butternut squash, red peppers, and pumpkin.

5. Vitamin B6

“Vitamin B6 is found in a variety of foods, making it easier to include in your diet,” says the expert.

• Chickpeas
• Poultry like chicken, and turkey
• Fish like tuna, and salmon
• Bananas
• Potatoes
• Fortified breakfast cereals

6. Vitamin B12

“Vitamin B12 is naturally found in animal products, making it harder for vegetarians and vegans to obtain adequate amounts unless they go for fortified foods or supplements,” says the expert.

• Fish like salmon, trout, and tuna.
• Meat like beef, chicken, and lamb.
• Dairy products like milk, cheese, and yogurt.
• Eggs
• Fortified plant-based products

Are there any side effects of taking vitamins?

“Vitamins are essential for good health, but taking them in excessive amounts, especially through supplements can lead to side effects,” says the expert. Here are some likely side effects of overconsumption:

• Since vitamin C is water-soluble, excess amounts are usually excreted through urine, making toxicity rare. However, very high doses (over 2,000 mg per day) can cause diarrhea, nausea and stomach cramps. “It is best to stick to the recommended daily intake (around 75 to 90 mg for adults) unless advised otherwise by a doctor,” says the expert.
• Vitamin D is fat-soluble, so it can build up in the body and cause toxicity if taken in excessive amounts (generally over 4,000 International Units daily for prolonged periods). Symptoms of vitamin D toxicity include nausea, vomiting, and fatigue. Have 400 to 800 International Unit daily to be on the safer side.
• High doses of vitamin E (over 1,000 mg daily) can interfere with blood clotting, increasing the risk of bleeding, particularly in people taking blood-thinning medications like warfarin. “Fifteen mg is fine for adults,” says Kedia.
• Vitamin A toxicity (hypervitaminosis A) can occur when large amounts of preformed vitamin A (retinoids, usually from supplements) are consumed over time. Symptoms include dizziness, vomiting, blurred vision, bone pain and liver damage. Do not exceed 10,000 IU daily of preformed vitamin A (retinol), and opt for food sources.
• Long-term use of high doses of vitamin B6 (above 100 mg per day) can lead to nerve damage, numbness in hands and feet, and difficulty walking. You can have 1.3 to 2 mg in a day.
• Rare side effects from injections of vitamin B12 may include allergic reactions like swelling, and rash. Don’t take more than 2.4 mcg of this vitamin in a day.

Vitamins like C and A may help to strengthen your immune system before winter. But you also need to focus on a balanced diet, staying physically active and sleeping well to reduce your chances of falling ill.