As the winter weather continues to keep people close together indoors, viruses causing influenza and the common cold are able to more easily multiply. However, there are ways to prevent these unwanted germs from invading your body. Here is a list of the top ten dietary supplements that help the immune system fight and repel cold and flu bugs.

AHCC (active hexose correlated compound) is made from mushrooms. This supplement was first developed in Japan in the late 1980s and has been used and studied for its effect on the immune system. Last year's research showed that AHCC can boost the activity of natural killer cells, which destroy the cells that have become infected with a virus.

Andrographis has long been used in Ayurvedic and Traditional Chinese Medicine to boost the immune system. Actually, andrographis was first used during the Indian flu epidemic of 1919, where it was credited with stalling the spread of the disease. According to research, andrographis works better than a placebo for reducing the symptoms of respiratory infections and it may even prevent the infection in the first place. These studies used a proprietary andrographis product which combines the herb with a Siberian ginseng.

Beta glucan is a fiber-like complex sugar that can be found in oats, barley, and the cell walls of mushrooms. It provides a boost to the immune system which enhancing resistance to viruses and bacteria. In fact, beta glucan has been shown to boost the activity of phagocytes, special immune system cells which engulf and destroy germs.

Echinacea has a long history of traditional use; with it actually being one of the most widely used herbs in Native American medicine. Instead of having a direct germ-killing effect, Echinacea stimulates the body's own immune defenses. Many studies go back as far as 1970 have shown that Echinacea boosts the immune system so that it can protect against infections invaders. A new study has found that Echinacea can reduce the odds of developing a cold by 58 percent and shortens the length of a cold to 1.4 days.

Elderberry was considered in Roman times to be a flu remedy. Recently, elderberry extract has been researched for its role in treating influenza infections, especially when it is taken with in the first 24 hours of developing symptoms. One recent study proved that individuals who were taking elderberry recovered four days sooner from influenza than those taking a placebo. Additionally, the use of other medications was less for those who used elderberry.

Garlic improves resistance to disease by boosting immune function. Many studies have found that garlic stimulates immunity because it increases the number of white blood cells and other immune system team members. A recent study proved that a group of individuals taking garlic caught significantly fewer colds and recovered more quickly from the colds they did come down with than the other group which was taking a placebo.

Ginseng boosts immune function in all of its forms. A study of adults who were taking American ginseng daily during the winter months found that those people, compared to those taking a placebo, caught fewer colds and needed less sick days. Additionally, Siberian ginseng and Asian ginseng can also build defenses against winter germs.

Propolis is created by bees when resins from plants are mixed with wax. This propolis coats the inside of the beehive with an antiseptic layer and it can have similar benefits when taken by humans. Propolis stimulates the body's immune system. It has been proven in studies that taking propolis extract can protect against colds and other upper respiratory infections. Children who take propolis daily for three winter months have been proven to catch fewer colds than those kids who are taking a placebo.

Many research reviews have found that Vitamin C does reduce the length of a cold episode and weaken the severity of an infection for the general population. For those individuals who are engaged in extreme exercise, vitamin C can also help prevent a cold.

Zinc lozenges, when they are taken within 24 hours of the first cold symptom, can keep cold viruses from taking ground in the respiratory tract. The use of a zinc lozenge every couple of hours also causes colds to resolve more quickly and symptoms to be less severe.

Our immune system is our first line of defense against the cold and flu, as well as the diseases we may come down with. Keeping our immune system in tip top shape is key to a happier and healthier life. The above herbs can help boost the immune system along with a dietary change and exercise plan one can reduce the length of or prevent sickness over a life time.