Cold and flu season is here. Do vitamins actually work?

Cold and flu season is upon us as well as the holiday travel season.

Patients driven to the ER who are battling a severe cold or the flu frequently ask me which vitamin supplements they can take to reduce the duration and severity of their illness.

The global cold and flu supplements market size was valued at $13.85 billion in 2019. But what does the science say? We know that vitamins haven’t proven effective against COVID-19 but what about for other illnesses? Are there studies that show a benefit either for protection from virus-causing colds or a reduction in days being sick?

Zinc, Vitamin C and Vitamin D are the most studied of the “immunity boosting” supplements.

Zinc is a required element for the development and function of multiple immune system cells including neutrophils, lymphocytes and antibodies. Easily obtained from diet, zinc is abundant in meat, eggs and oysters. Scientific studies consistently showed that taking zinc acetate lozenges reduces the duration of colds by 2-4 days if started within 24 hours of symptoms onset. The daily dose should not exceed 100mg and if you experience nausea and vomiting, stomach cramps or headaches, that means you’ve taken too much.

Vitamin C is certainly the most well-known and widely marketed immune supplement. Like Zinc, Vitamin C plays a key role in immune system function. But surprisingly, studies do not show a benefit to consuming large amounts of Vitamin C when you catch a cold. In fact, in a thorough analysis of 29 studies, Vitamin C was shown to reduce the duration and severity of symptoms only if you already took it daily as a preventative measure. But the good news is that the recommended daily intake for Vitamin C is easily obtained from diet, and it is abundant in sweet potatoes, red peppers, broccoli and citrus fruits.

Several studies demonstrated a moderate reduction in the rate of upper respiratory tract infections in those who supplement with Vitamin D. The majority of the Vitamin D we need is synthesized in the skin by UVB rays from the sun. But aside from people who live near the equator between the 37th parallels, most of us do not get sufficient natural sunlight exposure for an optimal level of Vitamin D. Although it can also be found in fish, eggs and fortified dairy products, most people would benefit from Vitamin D supplement of 1,000-2,000IU daily.

A lot of my patients swear by echinacea and elderberry supplements in reducing severity of colds, but these are understudied. As with all medical treatment, while there is an observed benefit, we must be careful to not confuse correlation with causation until there are definitive scientific studies.

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Unfortunately, none of the aforementioned supplements have demonstrated any effectiveness in either preventing or limiting the duration and severity of the covid-19 virus.

Bottom line: You can get most of your immune boosting vitamins from a diverse diet including fatty fish, meat, vegetables and fruit. Those who can’t get enough natural sunlight and are deficient in Vitamin D should consider supplementing in consult with their doctor. If you do get sick, sucking on zinc acetate lozenges could reduce the duration of illness. And remember, keeping up to date with vaccinations, staying hydrated, getting good sleep, practicing stress control and exercising daily should be the foundation of your immune system.