There is a theory of immunity in Ayurveda called the beej-bhumi theory, which means “seed and land.” In this theory the body is compared to being the land and infection or “bugs” are like seeds. When the body is filled with toxins (ama) and lacking in natural 
immunity (ojas), the infection will spread easily because the ground will be fertile, just as fertile land will sprout many seeds. If digestion is strong, and ojas rather than ama predominate in the body, then the bugs that can cause an infection will not be able to take hold.
Everyone is more susceptible to respiratory problems when the seasons are changing, especially in the autumn and early spring. This is because the body functions differently in each season. In the transition between the hot and cold seasons the agni (or digestive fire) can start to fluctuate dramatically which will create a fertile ground for diseases to sprout. For this reason it is important to adjust our diet and lifestyle according to the seasons.
Therefore, winter is a good season for building immunity as the digestion is stronger in cold weather. When digestion is strong and appetite is good, then immunity is strong. Whatever weakens digestion weakens immunity. (Please have a read of this blog on a Healthy Digestion if you would like to find out more)
Tips to Boost Natural Immunity
- Eat immunity boosting foods in winter – these include foods that are fresh, organic, easy to digest, pure and wholesome. It’s also important to eat light and warm food in winter.
- Get enough sleep – staying up late and working at night or sleeping during the day can affect the digestion and body rhythms and compromise immunity.
- Stay warm – getting cold gives the bugs a higher chance to survive and thrive in your body because when we feel cold our white blood cells and other parts of your intelligent natural immunity are not working at its best and are weakened.
- Stress less – stress is never beneficial for your immunity and decreases your natural immunity a lot. It is important to learn to manage stress. Please read more on Managing Stress here. And keep in mind; stress is only a thought!
- Exercise regularly – daily walks and yoga postures are good for balancing all the doshas and especially suit Vata types, while more vigorous daily exercise is required by Kapha types to stay healthy. Exercise is especially important during winter which is a Kapha season, because it helps to boost agni and your immunity when toxins are flooding the body.
- Avoid building ama (toxins) in your body – adjust your diet and routine and follow the Ayurvedic guidelines for the seasons. Cooking your food with immune-enhancing spices such as cumin, cinnamon, fennel, coriander, turmeric, ginger and black pepper is also an important way to enhance your digestive fire and reduce ama. It’s always important to avoid the factors that cause ama to accumulate, in any season. Stay away from leftovers, processed foods, ice-cold foods and drinks, and heavy foods such as fried foods.
- Follow a Vata pacifying diet in fall and early winter – eat all six tastes, but eat more of the sweet, sour, and salty tastes, as these enhance Vata (e.g. sweet as rice not sugar). Vata-pacifying foods include nourishing grains such as rice and couscous, sweet juicy fruits such as cooked apples or pears, squashes, zucchini, and asparagus, and light, easily digestible proteins such as panir (a freshly made cheese), lassi (a yogurt drink that aids digestion) and vegetable proteins such as mung dhal. Asparagus is especially good for enhancing the immune system.
These are some tips for boosting your immunity naturally through diet and lifestyle. Sometimes we do need to get some help from a qualified practitioner though who can give you some specific recommendation that works on you as an individual. A practitioner can also recommend a specific diet and lifestyle for you and supplements (like zinc) and herbs that might be beneficial for you.