Oats: Background. Actions

Common Name

Oats

Other Names

Groats, green oats, green tops, haver, oat herb, oatmeal

Botanical Name / Family

Avena sativa (family Poaceae (Graminaceae))

Plant Parts Used

The whole flowering plant, including the oat straw and the seed (also used for porridge). Oat bran is also used in some clinical trials.

Chemical Components

Beta-glucan (soluble fibre), triterpenoid saponins (including avenacosides A and B), phenolic compounds (avenanthramides A, B, C), alkaloids (including indole alkaloid, gramine, trigonelline, avenine), sterol (avenasterol), flavonoids, starch, phytates, protein (including gluten) and coumarins.

Nutrients such as silicic acid, calcium, potassium, phosphorus, iron (39 mg/kg), manganese (8.5 mg/kg), zinc (19.2 mg/kg), vitamins A, B-complex, C, E and K, and amino acids.

Historical Note

Culpeper (1652) recommended that ‘a poultice made of meal of oats and some oil of bay helpeth the itch and the leprosy‘. By the end of the 18th century oats was the main grain used by all levels of the population in Scotland. Students would arrive at university after the summer with a bag of oatmeal to live on during the term. The older Scottish universities still call the autumn mid-term break ‘Meal Monday’ because traditionally at that time the students would return home to replenish their supplies.

Oats: Main Actions

LIPID LOWERING

Beta-glucans increase bile acid synthesis and thus decrease serum cholesterol. The fibre binds to cholesterol, preventing initial absorption and enterohepatic recirculation of cholesterol, and the two are excreted together.

Clinical trials have shown that oat bran contains soluble fibres, such as beta-glucan (e.g. 75 g extruded oat bran, equivalent to 11 g beta-glucan), which nearly double the serum alpha-HC concentration within 8 hours, indicating increased bile acid synthesis and thus decreased serum cholesterol.

ANTIATHEROGENIC EFFECTS

In vitro studies suggest that the phenolic anti-oxidants known as avenanthramides, present in oats, may exert anti-inflammatory and anti-atherogenic effects by inhibiting smooth muscle cell proliferation and increasing nitric oxide production.

ANTIHYPERTENSIVE EFFECTS

A reduction in blood pressure has been observed in clinical trials; however, the mechanism of action has not been fully elucidated.

HYPOGLYCAEMIC (BLOOD SUGAR CONTROL)

Oats have been shown in clinical trials to reduce the postprandial glycaemic response. Whilst the mechanism of action is unclear, the ability of beta-glucans to slow stomach emptying and increase the viscosity of food in the small intestine, resulting in delayed glucose absorption, is most likely a factor.

ANTIPRURITIC EFFECTS

External application of oat preparations has been shown to relieve itch.

Oats: Other Actions

Due to its vitamin, mineral and amino acid content, oats are a nutritious food. Internally, oats also act as a bulk-forming laxative.