Here are some foods which will help boost your immune system when you are feeling under the weather:
Yogurt/Kefir
Yogurt packs a healthy dose of good bacteria that can protect the body against harmful bacteria and infections. These good bacteria are called probiotics, and studies have shown eating yogurts rich in them can lead to an improved immune response by increasing the body's white blood cell count. Traditional kefir is similar to yogurt but cultured with special kefir grains, so it contains slightly different bacteria.
Turmeric
Turmeric is found in every yellow curry, and its golden color is the result of curcumin, a polyphenol with strong cold and flu-fighting properties. Curcumin prevents some immune cells from responding to stimulants and so has modulating and anti-inflammatory effects.
Garlic
Many of the immune-boosting properties of garlic come from its sulfur-containing compounds, particularly one called allicin. These compounds are effective against bacterial, viral, fungal and parasitic infections. They also enhance the immune system and have anti-tumor and antioxidant features.
Oregano
The antioxidant activity in oregano is due to its high content of phenolic acids and flavonoids, color compounds that are also anti-inflammatory. When eaten, oregano can protect against the common cold, influenza, fevers and indigestion.
Red Bell Peppers
Bell peppers are both low in calories and dense in nutrients. They are a good source of phytochemicals as well as beta carotenes and vitamin C. Gram for gram, red bell peppers have twice the vitamin C of most vitamin C-containing fruits and vegetables, including oranges.
Green Tea
Tea is the most widely consumed beverage in the world, after water. It is rich in polyphenols -- plant antioxidants -- as well as a number of other chemicals that can help protect the body against cold or flu.
Pumpkins
Pumpkins are packed with beta carotene, a nutrient that your body breaks down to make vitamin A. Vitamin A helps the proteins that regulate cell-to-cell communication, which is the foundation of the immune system. Vitamin A also aids in cancer prevention, because cell-to-cell communication breakdown is one of the primary causes of cancer.
Ginger
Ginger contains a compound called gingerol, a relative of capsaicin, the compound that gives chili peppers their zing and heat. When it is dried, ginger contains less gingerol and more shoagol, an anti-inflammatory agent. Ginger has been shown to reduce nausea and vomiting.
Oysters
Oysters are widely thought to be an aphrodisiac -- probably because of their high zinc content, which is necessary for testosterone production. Zinc is also very good at protecting the body against colds and flu. Zinc enhances the function of helper T cells, which are important in identifying foreign antigens and alerting other cells of the immune system to invaders. Even a mild zinc deficiency can have adverse effects on the immune system.
Broccoli
Broccoli is an excellent -- and cheap -- source of vitamins A, C and E. In addition, broccoli is high in glucosinolates, which stimulate the body's immune system. Broccoli is a doubly powerful food because of its high concentration of sulforaphanes, which are potent anti-cancer agents.