Anthocyanins are the dark purplish-blue, red, and sometimes black color pigments that are the active ingredient of bilberries, blueberries, Maqui berries, and black currants. These berry extracts and powders are found in most every eye vitamin formulation for their powerful anti-oxidant effects.
These same substances can be found, in far lesser amounts, in other berries such as raspberries, strawberries, gooseberries, and cranberries. Anthocyanins can also be found in other fruits and vegetables such as sour cherries, plums, purple cabbage, grapes (& red wine), apples, red onions, and sweet potatoes.
The dark blue-purple -black anthocyanin pigment is prevalent, not only in the berry, but in the stems and leaves of the plant. The pigment absorbs the high-energy blue radiation of sunlight to protect the plant cells from photo-damage and decrease oxidative stress. By ingesting these anthocyanin rich berries we hope to protect our cells from damaging oxidative stress.
Anthocyanins are organic, water soluble members of the Flavonoid class of antioxidants. There are 100’s of anthocyanins, but there are 6 which are commonly found in foods: cyanidin, delphinidin, malvidin, peonidin, pelargonidin, and petunidin. (I mention these because you may see a specific anthocyanin listed in the ‘supplement facts.’)
The anthocyanins are rapidly absorbed by the digestive system, but are also rapidly excreted by the kidneys. After being ingested, it is absorbed within minutes and will clear the body within 4 hours. (Ref: Anthocyanins: structural characteristics…)
Anti-oxidants react with damaging free radicals in our bodies to prevent or reverse cell damage that can lead to disease.
Besides its anti-oxidant effect, there are other bioactive functions of anthocyanins:
- Anti-inflammatory,
- stabilizes DNA, anti-cancer,
- improve insulin secretion and sensitivity, and
- anti-bacterial.
How do anthocyanins affect the Eye?
They stimulate the regeneration of the light-sensing pigment of the photoreceptors of the eye (rhodopsin), important for dark adaptation.
Improves retinal blood circulation, important for low tension glaucoma and macular health.
Anti-inflammatory and anti-oxidant activity reduces damage due to inflammation and oxidative stress.
How Anthocyanins Affect Eye Health
Anthocyanins are beneficial to eye health for their protective effect on the collagen structure of blood vessels that support circulation to the eye. Studies have not shown that the anthocyanins are concentrated in the eye. (Ref; Distribution and excretion of bilberry anthocyanins )
There are not all that many studies linking the anthocyanins and vision health. Much focus has been on the effect of anthocyanin on cardiovascular health benefits and diabetes.
Macular degeneration
Its anti-oxidant function is beneficial for those with macular degeneration. Anthocyanins have been shown to protect DNA against oxidative stress induced by UV irradiation, which is a source of oxidative stress to the structures of the eye.
Glaucoma
Anthocyanins have been shown to increase vascular blood flow. This is significant for those with low tension glaucoma (Normal Tension Glaucoma, NTG). Studies have shown that increased blood flow in these NTG patients benefited with an improvement in visual field and visual acuity.
If you are interested in glaucoma herba treatments see article:
5 Novel Natural Dietary Supplements for Treatment and Control of Glaucoma
Diabetic Retinopathy
Studies of diabetic patients (and mice) given anthocyanins experienced a beneficial effect on lowing fasting plasma glucose levels and preventing insulin resistance.
Bilberry
Bilberry is notable for having the highest concentration of anthocyanins, meaning it has powerful anti-oxidant capability.
Bilberry is a small fruit berry found growing wild on scrubs in Europe. It is dark in color, purplish-blue and is similar to the blueberries found in the United States, but is actually more closely related to huckleberries. It is the dark purplish-blue color that is the anthocyanin active ingredient of bilberries.
The bilberry fruit has been used in herbal medicine to treat stomach problems, diarrhea, scurvy, infections, and kidney stones. The bilberry, when combined with other nutrients, such as vitamin C, E, and A, is thought to support blood vessel integrity by decreasing vascular permeability and capillary fragility.
Bilberry and the Eye
The story is that during World War 2, Royal Air Force pilots claimed greater night vision after consuming bilberry jam. This, it turns out, was a myth perpetrated by the RAF to explain away the sudden accuracy of bombing raids as a way to conceal the new technology of radar. The phenomenon of enhanced night vision and contrast sensitivity has not been proven by researchers to be an actual benefit of bilberry consumption.
The only study that I found that comes close to improving vision in healthy subjects was a 2005 study which concluded that given 100 mg/day purified extract of anthocyanin for 4 weeks, improved eyestrain and contrast sensitivity in nearsighted subjects. (Ref: Purified high-dose anthocyanoside oligomer …)
Bilberry and Myopia Control A German clinical trial using Difrarel®E (Bilberry extracts anthocyanosides and vitamin E) with 36 patients who had progressive myopia, were treated for 14½ months. Twenty nine patients saw a stabilization of any myopic changes and stable or improved visual acuity.
Bilberry and cataracts There is a study that linked bilberry extract with vitamin E (using Difrarel®E) as a way of halting the progression of cataracts.
Bilberry and Glaucoma Another study done on patients with normal tension glaucoma showed an improvement in visual function with a combination of Gingko biloba and bilberry extract. (Open angle glaucoma is the more common form of glaucoma.) At this time there is no herbal substitution recommendations for the treatment of glaucoma.
Bilberry and Diabetic Eye Disease Bilberry has also been recommended for diabetics as a way of glucose control and stabilizing blood vessels to prevent bleeding. This suggests that it may play a role in stabilizing the retinopathy associated with diabetic eye disease.
Bilberry Supplements and Dosages
Bilberry has the highest concentration of the active substance, anthocyanin. Bilberry supplement preparations are in the form of extracts, preservatives, powders, and liquids.
The manufacturer should indicate the percentage of anthocyanin. The percentage of anthocyanin should be a minimum of 25%. 37% would be a high percentage. The bilberry is listed in milligrams (mg) of 20 or 60 mg. Recommendations suggest 2 to 3 capsules per day for a useful dosage of 200 mg, total.
Safety and Side Effects of Bilberry Extract
Bilberry has been determined to be safe when consumed appropriately. It has no reported contraindications. Although relatively safe, it is recommended that high doses for extended periods of time could be toxic.
Blueberry
Blueberries, as a food product, have been called a ‘super food’ because of its anti-oxidant activity. 60% of its anti-oxidants are anthocyanins. Blueberries are recommended for cardiovascular disease, type 2 diabetes, neurodegenerative diseases, and vision.
Research has indicated blueberry active ingredients for:
- Anti-cancer,
- anti-diabetic, anti-obesity (significant for diabetic retinopathy),
- anti-neurodegenerative disease (AMD),
- anti-inflammatory (against light induced retinal injury).
Blueberries and Eye Health
The retina of the eye, because f its high metabolic rate and exposure to UV irradiation, is subjected to oxidative stress. Few studies showed an association between eating blueberries and a reduced risk of age-related macular degeneration.
Supplementing with Blueberries
Looking over the commercially available blueberry supplements, most indicate 400 to 500 mg blueberry extract. This is not an indication of the anthocyanin content or percentage, but does include the many other active compounds in blueberries.
Most labels indicate ‘wild’ blueberries as the source of the extract, the implication is that wild blueberries have more anti-oxidants, due to harsher growing conditions than cultivated berries.
What dose is clinically effective for the health benefits of blueberry extract is not clear. A moderate daily intake of whole blueberries is about 1/3 cup, which anticipates about 50 mg of anthocyanins.
Maqui Berries
Maqui berries are native to the southern tip of the South American countries of Chili and Argentina. It has the similar dark blue-purple appearance of the North American blueberry and European bilberry. It does have anthocyanins, with the same health benefits as indicated for other berries. What makes it different is its higher concentration of a specific anthocyanin, delphinidin- glucoside, which is higher than bilberry, blueberries, or black currants.
Maqui berry and Eye Health
There is not a lot of research data on Maqui berry for eye health and ocular disease. Maqui berries have been studied as a treatment for dry eye. The standardized extract of Maqui berry used for this purpose is MaquiBright®.
A 2014 study concluded that giving patients 60 mg of Maqui berry extract for 60 days increased tear fluid volume. It is thought to be its anti-inflammatory effect on the lachrymal glands of the eye which increased tear production. It is because of the higher percentage of the anthocyanin delphinidins which are concentrated in the lachrymal gland.
Ref study: MaquiBright™ standardized maqui berry extract … )
Ref: manufacturer website: MaquiBright
Supplementing with Maqui Berry
MaquiBright® is a standardized extract produced by a manufacturer and supplied to other manufacturers as a raw ingredient. It is standardized to 25%, which represents delphinidins(a specific type of anthocyanin) and 35% anthocyanins. MaquiBright® can be found in several commercially available vision supplements.
Black Currant
Black currants are small purplish-black berries commonly found in Asia, Europe, and New Zealand. They have been used in traditional Asia medicine for its anti-oxidant and anti-inflammatory effects. It is also thought to have anti-bacterial and anti-viral activity. Black currants ability to effect eye health parallels the other anthocyanin berries listed above.
The essential active ingredients are derived not only from the berries, but from the seeds, for a supplement listed as black currant seed oil. Additionally, black currant oil has other active ingredients beneficial to eye health: Vitamin C and gamma-linolenic acid (GLA is an omega-6 fatty acid). GLA is an anti-inflammatory, which is not formed in the body, but must be ingested. Vitamin C is an anti-oxidant. Both are important for the treatment of chronic inflammation and oxidative stress that results in eye disease.
Black Currants and Eye Health
Several research studies have implicated black currant oil as a supplement for the treatment of dry eye disease. The GLA reduces inflammation and the symptoms of dry eye. Sellers of black currant seed oil advertize it as a supplement for eye fatigue and discomfort. This claim is based on a study indicating less symptomatic eye fatigue experienced by users of technology, which were supplemented with black currant anthocyanin extracts. (Ref: Effects of black current anthocyanoside
Supplementing with Black Currants
Supplements come is several forms: juice, powders of the fruit, extracts of black currants, and black currant seed oil sofgels. There is no standardized black currant dosages. Clinical studies use extracts that are 50 mg of the active anthocyanin ingredients.
The black currant seed oil supplement s are produced as sofgels. The manufacturer will specify the amount of the active ingredient, GLA.
In the end…
Berries and their extracts have been used in traditional medicines for centuries. The anthocyanin class of organic substances have been studied and found to have powerful anti-oxidant properties. They have many other bioactive effects which have been shown to benefit human health.
While there are not a lot of definitive studies on anthocyanins and vision, there is enough evidence to link these bioactive substances to reducing the risk for eye disease.
These berry supplements have the effect of slowing blood clotting and have anti-platelet aggregation activity. This is significant for those on anti-coagulants or those who will be undergoing surgery. Consult with your physician before launching into a new supplement regiment.