Colds, Flu and Infection
Vitamin C is often called the master immune nutrient, because of its essential role in
immune function. Many studies have shown vitamin C to reduce the duration and
severity of cold symptoms, and some research suggests it may reduce the risk of
catching a cold (although results of prevention studies have been mixed). Among other
relevant effects, vitamin C increases white blood cell function, interferon production
and antibody activity. Vitamin C requirements are higher during infection.
Zinc is another important immune nutrient, along with vitamin C. The lozenge form of
zinc has been shown to significantly reduce the duration and severity of common cold
symptoms. When the lozenges are dissolved in the mouth, the zinc appears to possess a
direct, local anti-viral activity. This benefit is in addition to the fact that zinc is a
primary nutrient in immune function, particularly due to its beneficial effects on
thymus gland function and white blood cell function.
Echinacea (echinacea augustifolia, echinacea purpurea)
Echinacea’s active compounds enhance immune function due to various mechanisms of
action such as; increasing the production of white blood cells (when they are low);
stimulating activation of white blood cells (such as macrophages, natural killer cells
and T-cells); boosting the production of various immune-potentiating compounds (e.g.
interferon); enhancing alternate complement pathway (which enhances the migration
of white blood cells to areas of infection); and reducing hyaluronidase (a compound
which allows infection to spread).
Please note: Although it appears that echinacea is most effective taken at the onset of
an infection, if the herb is to be used long-term many experts suggest that a 1-2 week
break be taken every 8 weeks or so.
Elderberry (sambucus nigra)
Studies show that oral administration of elderberry extract reduces the duration of
influenza symptoms from an average of 6 days down to 48 hours. Elderberry inhibits
viral DNA replication, and thus this herb may also be useful in non-flu viruses.
The active compound oleuropein has powerful anti-bacterial, anti-fungal and anti-viral
properties, the latter making it especially valuable in colds and influenza infection.
Extracts of olive leaf have been shown to inhibit a variety of organisms including
herpes virus, influenza A, Coxsackie, salmonella, staphylococcus, and E coli. Historical
use of the olive tree since the mid-19th century also suggests potential benefits in
lowering fevers, with studies suggesting that the key active in this regard is vauqueline.
Modern scientific studies have identified several active ingredients in cat's claw that
enhance the activity of the immune system and inhibit inflammation. Their presence
may help explain why this herb traditionally has been employed to fight infectious and
inflammatory conditions. The alkaloid isopteropodine is of particular interest and has
been found to increase phagocytosis (the ability of various white blood cells to attack
and engulf harmful bacteria, viruses, etc).
Colds, Flu and Infection Summary
Nutrient/Herb Typical intake range
Vitamin C (Ester-C or Calcium Ascorbate)1 500 – 1000mg every 2-3 hours (during infection)
Zinc2 15 – 50mg per day (during infection)
Echinacea Extract(4% echinacosides)3 300 – 500mg three times per day (during
Elderberry Extract (30% polyphenols)4 100 – 500mg three times per day (during
Olive leaf extract (6% oleuropein)4 200 – 500mg three times per day (during
Cat’s Claw extract (15% polyphenols, 3%
150 – 300mg three times per day (during
Fruit (especially berries)
Nuts and seeds
Wash hands to avoid hand-to-nose infection (most common route of infection)
Get adequate sleep and rest during infection.
1. High intake of ascorbic acid associated with loose stools. High doses may interfere with
Warfarin. High doses should be avoided by those with kidney disease, kidney stones or those
with sickle cell anaemia.
2. May cause nausea on an empty stomach. High doses (>100mg per day) may suppress the immune
system. Ensure sufficient copper and iron intake with zinc supplementation.
3. Do not use in pregnancy or lactation. Do not use in auto-immune conditions.
4. Do not use during pregnancy or lactation.
5. Avoid concurrent use with blood pressure medication, and insulin. May interact with hormone
medication made from animal products.