Berries are the food group most cited on antioxidants. Part of that reputation is deserved and part of it is not.
What does antioxidant mean?
Free radicals form during metabolic processes in the body.
They are reactive molecules carrying an unpaired electron.
They can damage cell components.
Antioxidants neutralise those radicals by donating an electron.
The body produces its own antioxidant system too; superoxide dismutase and glutathione belong to it.
Antioxidants from food support that system.
Vitamin C, vitamin E and polyphenols are the principal dietary antioxidants.
Berries are rich in polyphenols, particularly anthocyanins.
That is the pigment group giving the fruits their red, purple and blue colours.
Up to that point the picture is uncontested.
Why were ORAC values withdrawn?
That is the turning point of the subject.
ORAC is a test measuring the antioxidant capacity of a food.
It was used for years to compare the antioxidant power of foods.
A high ORAC value was marketed as a healthy food.
But the limits of the test became clear.
ORAC is a measurement in a tube, looking at how far a food inhibits a particular chemical reaction.
That does not show its behaviour in the body.
There is no evidence that a food with a high ORAC value produces the same effect in a person.
The United States Department of Agriculture withdrew its ORAC database in 2012.
The reason was misleading use of the values in marketing and the lack of proven biological meaning.
Serious sources no longer use ORAC values.
| Concept | What it measures | Its limit |
|---|---|---|
| ORAC | Antioxidant capacity in a tube | Does not show effect in the body |
| Polyphenol content | Quantity of compounds | Absorption is a separate matter |
| Bioavailability | Amount reaching the blood | 1-2% for anthocyanins |
| Metabolite measurement | Compounds formed in the gut | New and developing |
| Clinical trials | Real health outcomes | Most reliable, least data |
Why is bioavailability a problem?
That is the real issue after ORAC.
For a compound to have an effect it must be digested, absorbed and reach the target tissue.
The bioavailability of anthocyanins is very low.
One to two percent of the intake reaches the blood.
The remaining 98 percent is not absorbed in the small intestine.
That was long interpreted as being wasted.
But the picture has changed in recent years.
Unabsorbed polyphenols reach the large intestine.
There they are metabolised by gut bacteria.
The small molecules that result — phenolic acids — are absorbed and reach the blood.
The effect is therefore not lost entirely; but it is not direct either, and it varies between people.
Two people with different gut flora produce different metabolites from the same fruit.
Where does the evidence stand?
There are three types of study with differing reliability.
The first is cell culture work, applying a compound to cells in a laboratory.
Those studies are valuable for understanding mechanisms but do not show the effect in people.
The concentrations used are generally far above what food could deliver.
The second is observational studies, comparing dietary habits and disease rates.
Those show association but do not establish causation.
People who eat a lot of fruit generally display other healthy behaviours too.
The third is intervention studies, giving a group fruit and measuring outcomes.
That type is the most reliable but the studies are few and short.
Those studies find modest improvements in blood pressure and some markers of vascular health.
But claims such as preventing cancer or delaying ageing are not supported by evidence at that level.
What is a reasonable expectation?
What is established is this: diets high in fruit and vegetables are associated with lower rates of heart disease and some cancers.
That association is strong and consistent.
But it arises from the overall diet rather than from one fruit.
Berries are a valuable part of that diet; but they are not decisive on their own.
Eating a handful of berries a day does not correct a poor diet.
Equally, not eating berries does not mean eating unhealthily.
The profile of compounds varies from one fruit to the next.
Variety is more effective than loading up on a single "superfood".
The term superfood is not a scientific category anyway; it is a marketing term.
How much survives in freeze-dried product?
Freeze-drying preserves polyphenols well.
The temperature is low and oxygen is removed.
Anthocyanin loss runs 5 to 15 percent.
In conventional hot-air drying that loss runs 40 to 70 percent.
Freeze-dried product therefore offers a compound profile close to fresh fruit.
Because the water is removed, the values concentrate per hundred grams.
But the portion shrinks too; the two offset one another.
The real advantage of freeze-dried product is accessibility; it is available out of season and keeps a long time.
That increases how often it gets eaten.
Regular consumption is more meaningful than a single large quantity.
What should be done in practice?
Four practical points can be listed.
The first is variety. Fruits of different colours carry different groups of compounds.
Four or five different fruits a week is a reasonable target.
The second is regularity. One portion a day is more effective than a large quantity once a month.
The third is preferring whole fruit. Juices and extracts lose the fibre and the matrix.
The compounds in whole fruit work together.
The fourth is realistic expectation. Eating fruit is part of a healthy diet; it is not a treatment or a means of protection on its own.
Taking it from food makes more sense than turning to supplements.
Supplements isolate a single compound and lose its interaction with everything else in the food.
Some studies find that high-dose antioxidant supplements fail to deliver the expected benefit and in some cases produce adverse results.
No such risk exists at the quantities obtained from food.
