Colds, Flu and Infection

See also:

Immune Support

Vitamin C

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.

Olive leaf

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.

Cat’s Claw

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 isopteropodhie 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)

Zinc (2)

Echinacea Extract(4% echinacosides) (3)

Elderberry Extract (30% polyphenols) (4)

Olive leaf extract (6% oleuropein) (4)

Cat’s Claw extract (15% polyphenols, 3%

alkaloids) (4,5)

500 – 1 OOOmg every 2-3 hours (during infection)

1 5 – 50mg per day (during infection)

300 – 500mg three times per day (during infection)

1 00 – 500mg three times per day (during infection)

200 – 500mg three times per day (during infection)

1 50 – 300mg three times per day (during infection)

Note: See immune support section for long term intake ranges

Reduce/avoid Increase

• Sugar

• Refined carbohydrates

• Dairy foods

• Alcohol

Complex carbohydrates


Fruit (especially berries)

Nuts and seeds

Whole grains

Lifestyle Factors

• 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 (>1 OOmg 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.