The science of eye health ingredients

nutraingredients-usa.com • 07/14/10

The science of eye health ingredients

By Stephen Daniells, 13-Jul-2010

Related topics: Research, Antioxidants, carotenoids, Minerals, Nutritional lipids and oils, Vitamins & premixes, Eye health

In the second part of our special series on eye health, NutraIngredients takes a closer look at the science behind lutein, omega-3 and the other ingredients eyeing a place on the podium for eye health.

The health condition garnering most of the attention in the eye health segment is age-related macular degeneration, or AMD. As the name suggests, this is a degenerative retinal disease that causes central vision loss and leaves only peripheral vision.

Despite the fact that approximately 25 to 30 million people worldwide are affected by AMD, awareness of the condition is low, says AMD Alliance International. And as the generation of Baby Boomers gets older, the Alliance expects incidence to be on the rise and triple by 2025.

The macula is a yellow spot of about five millimeters diameter on the retina. As we age, levels of the pigments in the macula decrease naturally, thereby increasing the risk of AMD. The yellow color is due to the content of the carotenoids lutein and zeaxanthin, which we derive from the diet.

These compounds are the only carotenoids capable of filtering the harmful blue light than can damage cells in the eye, the rods and the cones, explains Holger Becker, PhD, Xangold Global Product Manager at Cognis.

A thin macular pigment can allow the blue light through and destroy the cells. Maintaining high levels of both carotenoids, and therefore the macular pigment, is a valid approach to maintaining eye health and reducing the risk of AMD, adds Becker.

Scientific advances

In 1994, Dr Johanna Seddon and her co-workers at Harvard University reported a link between the intake of carotenoid-rich food, particularly dark green leafy vegetables like spinach, and a significant reduction in AMD.

“Although these observational nutritional data do not establish causality, it seems prudent to concur with the recommendation of increasing the consumption of vegetables in the diet and, in particular, to include dark green, leafy vegetables that are rich in lutein and zeaxanthin,” concluded the researchers in the Journal of the American Medical Association (Vol. 272, pp. 1413-1420).

Since then scores of studies have come out supporting the benefits, and elucidating the mechanisms involved. Commenting on the strength of the lutein-AMD science, Dr Diane Alexander, technical service manager, R&D for Kemin Health said: "I think the science is conclusive. There is a lot of epidemiological evidence, as well as many supplementation studies, which show that increased serum levels of lutein and zeaxanthin are associated with increased macular pigmentation."

Dr Alexander pointed to a recent review by five experts that concluded that macular pigment optical density (MPOD) - an indicator of xanthophyll levels in the eye - may also "potentially serve as a biomarker not only for predicting the risk for eye disease but also for visual function" (Vision Research, 2010, Vol. 50, pp 716–728).

Ratios of lutein to zeaxanthin are important, said Abhijit Bhattacharya from OmniActive Health Technologies. “When you look at data of levels in healthy diets – based on serum concentrations we typically need 5:1 lutein to zeaxanthin,” he said. “So we probably need to be supplementing at this 5:1 ratio.”

Final support for the link may be a few years away if the high profile AREDS2 (Age-Related Eye Disease Study) reports positive results. The intervention, expected to end in 2013, is using a formulation which includes lutein and zeaxanthin, and the omega-3 fatty acids DHA and EPA. The nutrients for the new study are supplied by DSM Nutritional Products using Kemin’s FloraGlo lutein ingredient.

Another carotenoid, astaxanthin, has also been linked to eye health. A patent by the University of Illinois’ Mark Tso in 1996 reports a method “to prevent, retard or treat eye and central nervous system diseases or injuries, such as age-related macular degeneration” using astaxanthin (US Patent #5527533).

Health claims

While the science appears substantial, the European Food Safety Authority’s (EFSA) Panel on Dietetic Products, Nutrition and Allergies (NDA) is not yet convinced. The NDA’s lutein opinion found that while the carotenoid had the ability to raise macular pigment density, this effect did not necessarily benefit, “maintenance of normal vision”. A similar response was issued for meso-zeaxanthin.

Lutein producers are not accepting the decision lightly and there is some collaboration to ensure future health claims success. NutraIngredients will cover the regulatory aspects of eye health in the fourth parts of its series.

Looking to fish oil

Beyond lutein and zeaxanthin, a growing body of science supports potential benefits for omega-3 fatty acids in AMD. The mechanism behind omega-3's putative effect was proposed by researchers from the University of Sydney to be down to insufficient fatty acid intake causing abnormal metabolism in the retina, which affects cell renewal (Archives of Opthamology, Vol. 124, pp 981-986).

 

Furthermore, a meta-analysis by Australian scientists reported that a high intake of omega-3 fatty acids and fish may reduce the risk of AMD by up to 38 per cent (Archives of Ophthalmology, 2008, Vol. 126, pp. 826-833).

This was followed by a study published in the American Journal of Clinical Nutrition (2009, Vol. 90, pp. 1601-1607), which found that increased intakes of omega-3 fatty acids may reduce the risk of developing age-related blindness by 30 percent. The results were derived from a sub-section of 1,837 people participating in AREDS. All the participants were considered to be at a moderate-to-high risk of advanced AMD.

Vision loss beyond AMD

Eye health is not all about AMD, however. The benefits of lutein may also extend to rentinitis pigmentosa – a group of inherited eye diseases that affect the retina. It causes the degeneration of photoreceptor cells in the retina, bringing progressive vision loss to about one in 4,000 people worldwide.

A study published in the Archives of Ophthalmology, found that a combined supplement of lutein and vitamin A may slow vision loss associated with these diseases. A daily supplement containing 12 milligrams of lutein in combination with 15,000 International Units of vitamin A (retinyl palmitate) was associated with a preservation of mid-peripheral vision.

There is also significant evidence for the benefits of lutein and zeaxanthin for cataracts and cataract-related conditions, said OmniActive’s Bhattacharya.

This makes sense, said Kemin’s Alexander since lutein is present in the lens of the eye, and cataracts are caused in part by oxidation of the lens.

Healthy eyes in healthy people

Beyond AMD, there is also data that lutein may also protect against the detrimental effects of long-term computer display light exposure, according to a Chinese study published in the British Journal of Nutrition (2009, Vol. 10, pp 186-190).

“Visual function in healthy subjects who received the lutein supplement improved, especially in contrast sensitivity, suggesting that a higher intake of lutein may have beneficial effects on the visual performance,” wrote the researchers from Peking University.

Another study with subjects aged between 22 and 45 found that a combination of lutein, zeaxanthin and blackcurrant extract may reverse signs of visual fatigue. Researchers from Japan and Singapore reported that visual fatigue, caused by many factors, not least staring at computer monitors for long hours, may be eased a daily supplement containing blackcurrant fruit extract (200 mg), lutein (5 mg), and zeaxanthin (1 mg) (Applied Ergonomics, 2009, Vol. 40, pp. 1047-1054).

Furthermore, a study published in the journal Optometry and Vision Science (2008, Vol. 85, pp. 82-88) reported that lutein and zeaxanthin may reduce the deleterious effects of glare on a test group of people with normal eyesight.

Researchers from the University of Georgia, Athens recruited 40 healthy subjects with an average age of 23.9 and assigned them to receive daily supplements of lutein (10 mg, FloraGlo, Kemin) and zeaxanthin (2 mg, OptiSharp, Kemin) for six months.

"The positioning of lutein is changing," said Kemin’s Dr Alexander. "[These new studies show] it is an essential nutrient that everyone needs everyday to protect their vision."

Dry eyes

Another area not to be over-looked in eye health is dry eyes. Keratoconjunctivitis sicca, or dry eye syndrome, is a condition where the eyes do not make enough tears, or the tears evaporate too quickly. This produces dry eyes and increases the risk of inflammation. According to a recent study by Finnish researchers, the prevalence of dry eye can be up to 30 per cent in people aged 50 y and older.

Fatty acids are again linked to a potential benefit, and the omega-3 and omega-6 content of sea buckthorn was recently touted as the main bioactives behind sea buckthorn’s ability to potentially reduce symptoms of dry eye syndrome.

Scientists from the University of Turku reported in the Journal of Nutrition (doi: 10.3945/jn.109.118901) that the linolenic acid contained in the oil is a basis for anti-inflammatory compounds, which could reduce inflammation. The researchers also note that sea buckthorn oil is a rich source of vitamin E and that antioxidants “may protect the eye from oxidative damage leading to activation of inflammatory cascades”.

NutraIngredients’ series will continue with the next section looking at the supply of eye health ingredients.

 

Sea buckthorn oil may ease dry eye symptoms

nutraingredients-usa.com • 06/30/10

Sea buckthorn oil may ease dry eye symptoms

By Stephen Daniells, 28-Jun-2010

Related topics: Research, Antioxidants, carotenoids, Nutritional lipids and oils, Phytochemicals, plant extracts, Eye health

An oil rich in omega-3 and omega-6 fatty acids from sea buckthorn may reduce symptoms of dry eye syndrome, says a new study from the University of Turku.

Daily supplements of the oil for three months also produced improvements in symptoms for contact lens wearers, according to findings published in the Journal of Nutrition.

Keratoconjunctivitis sicca, or dry eye syndrome, is a condition where the eyes do not make enough tears, or the tears evaporate too quickly. This produces dry eyes and increases the risk of inflammation. According to the Finnish researchers behind the new study, the prevalence of dry eye can be up to 30 per cent in people aged 50 y and older.

“The results of this study suggest that sea buckthorn oil consumption can attenuate the increase in tear film osmolarity occurring during the cold season,” wrote the researchers, led by Riikka Jarvinen. “It may also influence the maximum intensity of redness and burning symptoms in participants with dry eye.

“Further studies should investigate the effects of sea buckthorn oil on more defined populations and aim to determine the mechanisms of a positive sea buckthorn oil effect,” they added.

Sea buckthorn oil has been reported to have a number of other health applications, including atopic eczema, other skin problems related to deficient regeneration, UV radiation stressed skin, mouth dryness, mouth ulcers, gastric ulcers, urinary tract inflammations, cervicitis, genital ulcers, sinus inflammation and eye dryness.

Study details

Dr Jarvinen and her co-workers recruited 86 people aged between 20 and 70 to participate in their double-blind, randomized, parallel trial. The participants were randomly assigned to receive either two grams of sea buckthorn oil (Aromtech, Finland) or placebo oil ever day for 3 months from fall to winter. People with both types of dry eye syndrome were included – people who can’t make enough tears, and people whose tears evaporate too quickly.

 
Results showed that all the people in the study experienced an increase in the concentration of water evaporation from the eye, but people receiving the sea buckthorn supplement experience a significantly smaller increase in this measure. Furthermore, people who complied well with the regime and took at least 80 per cent of their supplements experienced greater reductions in this increase.

“The maximum intensities of redness and burning tended to be lower in the sea buckthorn group,” added the researchers.

Commenting on the potential mechanism and the bioactives involved, the researchers note that the linolenic acid contained in the oil is a basis for anti-inflammatory compounds, which could reduce inflammation. The researchers also note that sea buckthorn oil is a rich source of vitamin E and that antioxidants “may protect the eye from oxidative damage leading to activation of inflammatory cascades”.

Source: Journal of Nutrition
Published online ahead of print, doi: 10.3945/jn.109.118901
“Oral Sea Buckthorn Oil Attenuates Tear Film Osmolarity and Symptoms in Individuals with Dry Eye”
Authors: P.S. Larmo, R.L. Jarvinen, N.L. Setala, B. Yang, M.H. Viitanen, J.R. K. Engblom, R.L. Tahvonen, H.P. Kallio

 

Managing Dry Eye

Optometric Management • 12/18/09

A HEALTHY DIET: THE PROVEN ENHANCEMENT FOR DRY EYE TREATMENT

In the prevention and treatment of dry eye syndrome (DES), is a prudent healthy diet more effective than oral supplements that contain Omega-3 and Omega-6 fatty acids? To answer this question, we’ll explore:

  1. Which vitamins are essential for both the eyes and the tear film?
  2. Does Vitamin B6 (Pyridoxine) help treat DES and protect the tear film?
  3. Are Omega-3 and/or Omega-6 fatty acids beneficial in treating DES?
  4. Should protein supplements be used in treating the tear film?
  5. Is inflammation healthy or unhealthy?

Which vitamins are essential for both the eyes and the tear film?
All vitamins are equally essential for the eyes, vision and tear film. Why is it, then, that some vitamins appear to be more important than the others? For the most part, there is a scarcity of four major vitamins in the diet and hence in the body due to food processing: Vitamin B6 (Pyridoxine), Vitamin B9 (Folic Acid), Vitamin C (Ascorbic Acid), and Vitamin B12 (Cobalamin).

Vitamin B6 and Folic Acid are intimately connected to the remodeling and repairing of tissue. Potassium and other minerals are also required for a normal tear film. Additionally, the mucous membranes of the eye have a high requirement for folic acid. Research published by Lane, Hart and Josephson reported the depression of tear-film break-up time (TBUT) to be less than 10 seconds when the ratio of sucrose intake/food-folic-acid intake > 6x10-2 teaspoons/microgram. Simplified, this means that ingesting six teaspoons of table sugar per day requires 1,000 micrograms of folic acid to prevent the TBUT from dropping below ten seconds. For comparative purposes, a can of Pepsi delivers 9 teaspoons of sugar.

The team of Lane and Hart also reported that depressed intake of food-potassium (as from fruits and vegetables) of less than 2,500 mg per day was likely associated with reduced TBUT. Other minerals measured in tears and considered essential for maintenance of corneal epithelium integrity are calcium, magnesium, and sodium (Graeme Wilson et al, 1983).

Does Vitamin B6 (Pyridoxine) help treat DES and protect the tear film?
Most of our patients need supplemental pyridoxine. First, check whether the patient has been taking mega-doses of “Vitamin B6” or has DES due to other factors. As little as 3 mg can be useful if taken at the time of ingesting denatured protein. However, at least 50 mg is recommended and has been shown to be effective if taken within 12 hours before ingestion of major cooked protein (Lane, JACN, 2005; Lane ARVO, 2006; Emily Chew, 2009). Daily dosing in excess of 200 mg per day is not recommended and may produce undesirable neurological effects.

Are Omega-3 and/or Omega-6 fatty acids beneficial in treating DES?
The answer for most of our DES patients is yes. Though if the patient has already been taking Omega-3 supplements for many months with adequate (400 mg or more) docosahexaenoic fatty acid (DHA) and (400 mg or more per day) eicosapentaenoic fatty acid (EPA) or has been consuming small fish at least once per week, then it is possible that the DES may not be due to Omega-3 deficiency. We recommend measuring the fasting blood concentrations of Omega-3, Omega-6, saturated and trans-fatty acids. Then look at the ratio of blood plasma concentrations of (DHA + EPA) / Arachidonic Acid. Too high a concentration of DHA + EPA promotes hemorrhaging. Additionally, too high a concentration of Arachidonic acid as an end-product of Omega-6 metabolism promotes blood clotting. Proper balance is the key.

Should protein supplements be used in treating tear film?
My research at Columbia evidenced that intake of too much denatured protein (>300% RDA for protein) had an adverse effect on the tear film, disturbing it beyond excessive alcohol intake. This was, more often than not, the same case with excessive intake of saturated fat and cholesterol—two other significant factors regarding tear film. Powdered protein supplements, taken for "body building" but without replacement vitamin B6, were a special problem in young people.

Is inflammation healthy or unhealthy?
There is no question as to the involvement of inflammatory processes in DES. Entire books have been published listing nutrients which help to quiet inflammation; however, such suppression is not always healthy. Inflammation is an important aid in the repair of tissues and systems. It helps to provide the scaffolding and fluid that assists in the repair and remodeling within the body. Under normal conditions, healing will take longer when normal inflammation is thwarted. Almost all non-toxic fish, colorful vegetables, and ripe fruits that we can consume are relatively anti-inflammatory in their effect. Anti-oxidant vitamins and certain minerals, including selenium and chromium, are considered to be relatively anti-inflammatory and they do deliver essential nutrients to the tissues. Good nutrition is a key component in the successful reduction of inflammation.

Dietary Intervention Can Help
An alternative measure for recovery and prevention of DES is a well balanced diet. Here are some key points to help in planning patient diets.

  1. If potassium intake < 4000 mg daily, encourage the non-diabetic patient to consume additional fresh fruit such as bananas, oranges, cantaloupe, or tomatoes.
  2. If food folate < 500 µg (mcg) daily, suggest ingesting additional raw, fresh fruits and vegetables, especially green, leafy ones like kale and spinach. Raw vegetables include Brussels sprouts, red cabbage, asparagus spears, string-beans, broccoli, chick peas (soaked 24 hours in refrigerator), spinach, yams, or hazelnuts. Fruits include avocado, cantaloupe and oranges.
  3. Avoid added sugar which depletes potassium. Sucrose intake greater than 11 teaspoons significantly increases the risk for contact-lens intolerance and dry eyes.
  4. If food-ascorbic acid ≤ 400 mg, the solution is an even greater intake of raw, fresh fruits and vegetables.
  5. If food pyridoxine (B6) ≤ 4 mg, encourage switching to high-in-protein foods that may be eaten safely either raw or rare-cooked. For example, raw walnuts, hazelnuts or spinach, or a rare fillet of salmon (cooking fish or meat well-done depletes most of the available pyridoxine).
  6. Conventionally prescribed diuretic drugs deplete potassium and, along with aspirin, contribute to DES and contact-lens intolerance. Take note: conservative supplementation with B6 and C can create diuresis while ameliorating dry-eye syndrome.
  7. Especially in cases with arthritis, add chondroitin and glucosamine sulfate to the diet (100-500 mg QD).

The single most effective therapeutic measure is increasing the intake of fresh, ripe, raw fruits of all kinds and vegetable salads, while decreasing intake of refined or highly processed foods that are poor and unbalanced in vitamins and minerals. Fresh fruits are excellent balanced sources of potassium, calcium, magnesium, food-ascorbic acid, food-folate, food pyridoxine, food thiamine (vitamin B1), and glucose-tolerance-factor chromium – all the essential factors for the metabolism of sugars found in fruits.

Type 2 (non-insulin-dependent) diabetics, depending on the severity of their condition, may not be able initially to handle a markedly increased intake of fruit. However, they may benefit from a gradual increase in fresh fruit, if monitoring blood sugars, and especially from increased intake of fresh, raw vegetable salads without dressings.

At the minimum, introduction of daily raw salads as a complementary therapy improves the effectiveness of oral supplements. It appears likely that DES oral supplements that include vitamins B6, B9, and C will demonstrate enhanced ability to turn around DES. The key message is that a simple dietary therapy is the best alternative treatment for DES. It has resulted in a high recovery rate for all patients, regardless of the severity of their DES.

More on the web at: www.NutriOptom.com.

Dr. Lane is Director of the Nutritional Optometry Institute and a Fellow of the American College of Nutrition. For further info or correspondence, see http://www.nutrioptom.com.