General, Immune | November 6, 2014 | Author: The Super Pharmacist
Many 'alternative medicine' or nutritional supplements are linked to considerable effects on the immune system or the resistance to infection in humans, and are thus sometimes termed 'immune stimulants'. The over-use of some conventional medications, most notably antibiotics, may lead to decreased susceptibility of bacteria or viruses that cause common illnesses such as upper respiratory tract infections. These include influenza viruses or rhinoviruses (which are associated with the common cold).
Winter is the season associated with the increased prevalence many infectious conditions and so investigating the evidence supporting some immune stimulants may be of use in choosing treatments and/or preventative measures against illness. Here we cover some popular immune stimulants.
Andrographis paniculata is a bitter herb known by various names, including kirayat, green chirayta, king of bitters and Indian echinacea. It has been used in traditional Indian medicine, and has been recently rediscovered by researchers for its apparent efficacy in uncomplicated upper respiratory tract infections.
A systematic review of seven double-blind controlled trials, including 896 particpants, concluded that A. paniculata was superior to placebo treatments in reducing the symptoms of acute respiratory tract infections, and may also have a prophylactic effect against them.
Another systematic review of three trials including 443 participants found that its extract (andrographolide and its derivatives), with or without added Siberian ginseng, significantly reduced the severity of these infections compared to placebo.
A. paniculata is often sold in combination with Siberian ginseng; this formulation is known as Kan Jang.
A pilot study on the effects of Kan Jang (88.8mg A. paniculata and 10mg Siberian ginseng) on the symptoms of influenza, administered this product 3 times daily to 71 patients and compared their responses to 469 other patients taking the conventional treatment amantidine. The symptoms of approximately 68% of the 'conventional treatment' group progressed compared to 30% of the Kan Jang group. Those in the Kan Jang group experienced a reduction in symptom duration compared to the 'amantidine' group. The next phase of this study randomised 66 patients to Kan Jang or conventional medication, and found that days of sick leave were significantly reduced for the first group compared to the second. It also found that the rate of complications resulting from influenza infection was 71%, compared to 31% for the Kan Jang group.
Also known as ascorbic acid, this molecule is associated with important roles in the health and integrity of many body tissues, immune system function and resistance to infection. Doses of 200mg or more a day may shorten the duration of a cold in up to 14% in children and 8% in adults.
A meta-analysis of 29 trials (over 11,000 participants) concluded that the vitamin appeared to reduce the duration and symptoms of the common cold, but not the incidence of the condition. Therefore, while Vitamin C may be a viable treatment for the symptoms associated with the common cold, it may not be effective as a prophylactic against infection. This meta-analysis found that vitamin C administered at the onset of colds did not significantly affect duration or severity, except in very high (8000mg) doses.
A drawback of many studies on the prophylaxis or treatment of infections with vitamin C is that they use relatively low doses (500mg or less), which may not be clinically effective due to the short half-life of activity in the body possessed by ascorbic acid. However, high-dose or chronic vitamin C intake is associated with an increased risk of gastrointestinal side effects.
Zinc is a mineral (or soft metal) also associated with optimal immune system function. It is associated with some efficacy in preventing childhood diarrhoea in developing countries, which is caused by bacteria such as Cholera difficle in most cases.
Zinc is also regarded as a preventative or treatment in some respiratory tract infections.
A controlled trial randomised 200 children to 15mg zinc or a placebo daily, doubling the concentrations of either at the onset of a cold, for 7 months. The incidence of colds was significantly fewer in the zinc group.
Another trial that randomised 65 adults and children with colds to 46mg, and then 23mg of zinc every two hours, or a placebo, found that the incidence of symptoms after 7 days was significantly lower in the zinc group compared to the placebo group. However, the results of other trials on zinc as an acute treatment for colds are often less positive. A triple-blind controlled trial randomised 301 preschool children to zinc amino acid chelate, zinc sulphate or placebo five days a week for 16 weeks. Respiratory tract infections were (slightly) significantly reduced by the amino acid chelate, but not by zinc sulphate, compared to placebo. In addition, diarrhoea in these groups was not significantly reduced by either zinc supplement.
Zinc taken in high doses may result in adverse effects, including:
Various sub-species of this plant (Echinacea spp.) have been used as a complementary treatment for some time, and also have a role in traditional herbal medicine. Echinacea species are linked to immune system support. However, conclusions based on the evidence confirming this are affected by the high variability of Echinacea species, extract types and doses (often difficult to determine or even standardise between individual administrations if unrefined herb or root products are used) incorporated into trials on their effect on infection or immune response.
A double-blind trial randomised 48 women to various combinations of Echinacea subtypes or placebo. Those on a combination of E. purpurea and E. augustifolia showed a significant (21%) increase in a biological marker of immune function.
A similar study randomised 282 adults to placebo or 10 dose-units of 28mg/ml mixed Echinacea extracts on the first day of the onset of a cold followed by 4 units a day for the next 7 days. Symptom severity was found to be reduced (albeit by a low value of significance) in the Echinacea group.
Another trial randomised 128 adults to a 100mg E. purpurea preparation or placebo 3 times daily until cold symptoms abated, and found no significant difference in this duration between the groups.
Preparations of unrefined E. purpurea leaf and root (50%) with E. augustifolia root (50%) in 1g doses or placebo were randomly administered to 148 students 6 times daily on the onset of a cold, then 3 times daily for each day afterward until symptoms had abated, or at a cut-off of 10 days. There was no difference between symptom duration or severity between these groups.
Extracts of the leaves of the Olea europaea tree have been used in traditional medicine for centuries. Cell culture and animal studies have shown that they are effective against some bacterial species, the coxsackie virus, influenza viruses and rotaviruses.
Some studies suggest it may reduce respiratory tract infections by inhibiting the infective potential and propagation of the viruses involved. Clinical trials on the effects of olive leaf extract on these infections in humans are unfortunately scarce (although there have been successful trials involving a range of other conditions and issues including hypertension and insulin resistance).
However, a double-blind trial randomised 25 head and neck cancer patients to a mouthwash containing either the extract or a placebo during chemotherapy found that olive leaf extract reduced two pro-inflammatory molecules involved in oral mucositis, an inflammation of tissues in the mouth associated with head or neck cancer treatment.
Therefore, olive leaf extract may have potential in reducing the inflammation associated with many bacterial and viral infections.
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