Chicken Soup and Vitamin C: The Science Behind Folk Remedies

Does grandma’s chicken soup really help relieve cold symptoms? Was Linus Pauling on to something with his proposal that mega doses of vitamin C could prevent colds and reduce symptoms? A look at the medical literature may offer some interesting findings.

Chicken soup and hot water vapors

The most notable study examining the effects of chicken soup on cold symptom severity was conducted in 1978.1 Nasal mucus velocity and nasal airflow resistance were measured in 15 healthy subjects before and at five and 30 minutes after drinking hot water by sip or straw, hot chicken soup by sip or straw, and cold water by sip. A sham drinking procedure with straw was also employed.

Hot water by sip increased nasal mucus velocity from 6.2 to 8.4 mm/min, hot chicken soup by sip from 6.9 to 9.2 mm/min, and chicken soup by straw from 6.4 to 7.8 mm/min five minutes after administration. These increases were statistically significant compared to cold water, hot water by straw and sham. All values returned to their baseline at 30 minutes except cold water which significantly decreased the nasal mucus velocity from 7.3 to 4.5 mm/min. There were no significant changes from baseline in nasal airflow resistance five and 30 minutes following the above treatments.

The authors concluded that drinking hot fluids transiently increases nasal mucus velocity in part or totally through the nasal inhalation of water vapor. Hot chicken soup, either through the aroma sensed at the posterior nares or through a mechanism related to taste, appears to possess an additional substance for increasing nasal mucus velocity. Finally, hot liquid might be superior to cold liquids in the management of fluids in upper respiratory tract infections.

Heated, humidified air is used by common cold sufferers since the invention of the steam kettle. There is scientific literature available investigating this mode of therapy using a rhinotherm. The present reviews addresses to the use of hot, humid air in common cold.

A more recent review assessed the effects of inhaling heated water vapor with the help of a rhinotherm (an equipment designed to deliver heated water vapor to a person’s nasal cavity), in the treatment of the common cold by comparing symptoms, viral shedding, and nasal resistance after a natural or experimentally induced common cold.2

Randomized trials using heated water vapor in a standardized way in patients with the common cold or volunteers with experimental induction of rhinovirus infection were included in the review.

All the articles retrieved were initially subjected to a review for inclusion/exclusion criteria. Review articles, editorials, and abstracts with inadequate outcome description were excluded. Studies selected for inclusion were subjected to a methodological assessment.

The results of a systematic review of six trials with 319 participants support the use of warm vapor inhalations in the common cold in terms of relief of symptoms (odds ratio with 95% confidence interval 0.31, 0.16-0.60, relative risk 0.56, 0.4-0.79). Results on symptom score indices were equivocal. None of the studies demonstrated a worsening of clinical symptom scores. One study demonstrated increased nasal resistance one week after steam inhalation in contrast to an earlier study that showed improvement in the nasal resistance. There was no evidence of decreased viral shedding measured by virus isolation in the nasal secretions or measurement of viral titers in nasal washings among treatment group. The rhinovirus titers in the nasal washings from the treatment group were the same as those of the placebo group on day one prior to the treatment and on all four days after the treatment. The area under curve also was similar in the placebo and treatment groups for titers of virus in the nasal washings as were the average viral titers across five days of follow up, the maximum values after treatment, and viral shedding velocity, i.e. amount of virus shed per day. Minor side effects due to thermal stress were reported in all the studies.

Three trials demonstrated beneficial effects on the symptoms of the common cold. One study from Israel showed a decrease in nasal resistance measured by peak nasal expiratory and inspiratory flow rate. Studies done in North America failed to show any objective improvement in outcome measures with the study intervention.

Vitamin C

Controversy over the benefit of vitamin C in the prevention and treatment of the common cold has been a constant since Linus Pauling first proposed it in 1970. Investigators increasingly have moved away from Pauling’s mega doses and have produced interesting, if not conflicting, results. Two recent studies have added support to vitamin C proponents.

A prospective, randomized, double-blind, multicenter, four-arm, controlled trial was carried out in 1,167 patients with common cold treated with one of the following medications: Grippostad-C, a combination of acetaminophen, caffeine, chlorpheniramine, and ascorbic acid (verum); ascorbic acid (control); chlorpheniramine and ascorbic acid (reference 1); and acetaminophen, caffeine, and ascorbic acid (reference 2).3 A score of common cold symptoms (headache, throat pain, extremities and joint pain, cough, blocked nose, and disturbances of sleep quality) was the primary outcome. The test drug was first compared with the control using a hierarchic test strategy, then with reference 1, followed by reference 2 with the aim of proving superiority.

A clinically relevant and statistically significant difference was demonstrated at each level of the hierarchy. Grippostad-C was significantly superior to all other treatment groups, the combination of acetaminophen, caffeine, and ascorbic acid was significantly superior to the control, and the combination of chlorpheniramine and ascorbic acid was not statistically different from the control.

The findings demonstrate that the combination is superior to each of its separate components and each of the components has its own distinctive contribution to the efficacy of the combination product.

In another study, 168 volunteers were randomized to receive a placebo or a vitamin C supplement, two tablets daily, over a 60-day period between November and February.4 They used a five-point scale to assess their health and recorded any common cold infections and symptoms in a daily diary.

Compared with the placebo group, the active-treatment group had significantly fewer colds (37 vs. 50, P < 0.05), fewer days challenged virally (85 vs. 178), and a significantly shorter duration of severe symptoms (1.8 vs. 3.1 days, P < 0.03). Consequently, volunteers in the active group were less likely to get a cold and recovered faster if infected. Few side effects occurred with the active treatment, and volunteers reported greatly increased satisfaction with the study supplement compared with any previous form of vitamin C.

The authors concluded that the well-tolerated vitamin C supplement used in this study may prevent the common cold and shorten the duration of symptoms. They noted that volunteers were generally impressed by the protection afforded them during the winter months and the general acceptability of the study medication.

References

1. Saketkhoo K, et al. Effects of drinking hot water, cold water, and chicken soup on nasal mucus velocity and nasal airflow resistance. Chest 1978;74:408-410.

2. Singh M. Heated, humidified air for the common cold. Cochrane Database Syst Rev 2001;(4):CD001728.

3. Koytchev R, et al. Evaluation of the efficacy of a combined formulation (Grippostad-C) in the therapy of symptoms of common cold: a randomized, double-blind, multicenter trial. Int J Clin Pharmacol Ther 2003;41:114-125.

4. Van Straten M, Josling P.Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled survey. Adv Ther 2002;19:151-159.