Final answer:
The best way to prevent colds is by regularly washing your hands, which removes pathogens that could potentially cause infection. Nutritional supplements like vitamin C may aid in reducing cold severity, but are not as effective in prevention as hand hygiene.
Step-by-step explanation:
To prevent colds, it is highly recommended to maintain good hygiene practices, particularly regular hand washing. Studies have confirmed that hand washing is one of the most effective ways to prevent the spread of infections, including the common cold. While nutritional supplements like vitamin C may have a modest effect on reducing the duration and severity of cold symptoms in some cases, consistent hand washing has a more direct impact on preventing illness.
Regarding the options provided in the question, taking echinacea supplements has insufficient evidence to recommend it for the prevention of colds. Similarly, there's no strong evidence that cobalamin (vitamin B12) supplements are effective at preventing colds. Vitamin C supplements may be somewhat beneficial but they are not as effective as hand hygiene in the prevention of colds.
A healthy lifestyle, including avoiding smoking, getting enough exercise, and frequent hand washing, can help reduce the risk of infectious diseases. While a probiotic pill may improve the immune system's function, regular hand washing is an immediate action that can prevent the transmission of pathogens that can lead to colds.