Can Nutrients Really Help Prevent Eye Diseases?
Many conditions of the eye that are considered a normal part of aging can be helped by a healthy diet and by supplementation of nutrients. The Age-Related Eye Disease Study (AREDS) was a major clinical trial sponsored by the National Eye Institute that enrolled a total of 3640 participants from the age 55 to 80 years old. This landmark study provided strong evidence that nutrients in the form of supplements could delay the progression of macular degeneration by 25%.
Lutein and Zeaxanthin
23 million people worldwide have age-related macular degeneration (AMD) or cataracts. Macular degeneration is the leading cause of blindness of people over 55 and the incidence is supposed to triple by 2025. Researchers know that proper nutrition is essential for good vision and to reduce the risk of eye diseases. Studies have shown that antioxidant vitamins and minerals reduce the risk of AMD by 25%.
Lutein and Zeaxanthin are nutrients that are naturally found together in green leafy vegetables such as spinach and kale and in bright orange/yellow vegetables like orange/yellow peppers.
Lutein is a major pigment that is deposited in the macula of the eye. It protects the macula by absorbing damaging UV radiation and also serving as an antioxidant. It is also deposited in the lens of the eye.
Zeaxanthin is also an antioxidant and a photo-protectant. Low levels of zeaxanthin are associated with an increased risk of AMD. Because it is found in low levels in the normal diet it almost always needs to supplemented. Zeaxanthin is deposited in the very center of the macula, the fovea - the part of the eye most sensitive to sharp vision and responsible for your ability to see 20/20 (assuming your eyes are focused with the proper glasses or contact lenses).
Levels of lutein and zeaxanthin can be measured with a test called the macular pigment optical density (MPOD) test. Individuals with higher MPOD levels have a greater tolerance for the intensity of glaring light and recover more quickly from glare. This recovery time can be measured with the macular photostress stress. Shortened recovery time from glare can be critical for night driving.
Higher levels of lutein and zeaxanthin in the macula also improve contrast sensitivity - the ability to see objects more clearly in dim light and faded, low contrast situations.
Omega 3 (fish oils)
No dietary interventions have been validated as much as supplementation with the Omega 3 oils. Not only are they beneficial for optimal health of your heart, joints and brain but are extremely beneficial for your eyes. The retina of the eye has the highest concentration of omega 3 oils in the entire body and therefore a deficit of these oils effects the function of the retina. Fish oils are also beneficial for dry eyes.
Unless you consume several servings as week of cold water fish (salmon, herring, tuna) you are likely to be deficient in omega 3 oils. Another problem is that the omega 3 oils are in "competition" with the other unsaturated fats in your diet, the omega 6 oils which are typically consumed the most (such as corn, soybean, safflower and canola oils). Too much of the omega 6 oils can prevent the omega 3's from having their full effect.
It has been estimated that our ancestors has a ratio of about 1:1 or maybe even as high as 4:1 of omega 6 to omega 3 in their diet. The typical American diet may be as high as 20:1 - a grossly imbalanced amount of omega 6 to omega 3 oils. (The lower the amount of omega 6 in relation to omega 3 the better.) Omega 9 oils, such as olive oil, are not a problem in inhibiting the effects of Omega 3 oils. It is recommended that our ratio be no higher than 4:1.
The two major components of the omega 3 oils are EPA and DHA. DHA is now added to most all baby formulas because of its known effect of boosting optimal brain development in the newborn child. Because the retina of the eye and the brain are virtually the same type of tissue it also aids in the proper development of the retina.
The reason omega 3 oils are beneficial to your health- and to your eyes- is because they are anti-inflammatory. Most of the diseases of modern civilization are inflammatory in nature and therefore many medications are anti-inflammatory. The non-steroidal anti-inflammatory agents are aspirin, Tylenol, and Aleve or prescription drugs like Celebrex. The steroidal anti-inflammatory agents are cortisone and its cousins prednisone and prednisolone. As you know, these all have major unpleasant side effects.
Omega 3 oils suppress the inflammatory signaling molecules in your body that turn on the "inflammatory cascade" (the beginning of the events that cause inflammation). Keep in mind that anything that is beneficial for your health in general is good for your eyes.
Benefits of Omega 3 oils (EPA/DHA)
- • Interleukin 1-beta (IL-1beta) - DHA suppresses the action of this cytokine (inflammatory signaling molecule) which activates adhesion factors that cause cholesterol and other substances to stick to the lining of the blood vessels. This contributes to atherosclerosis, a problem of the heart, brain and the eyes.
- • Cyclooxygenase-2 (COX-2) - Both EPA and DHA prevent the gene expression of cyclooxygenase which produces prostaglandins that cause chronic inflammation. The human body has approximately 30,000 genes in every cell of the body, but in order for them to carry out their function they must be "expressed" or turned on. Cyclooxygenase turns the genes on that cause inflammation. (In some cases it is beneficial to turn on these genes to fight infection; only in a chronic state is it unwarranted.)
- • Leukotriene B4 (LTB4) - This cytokine is synthesized by the omega-6 product arachidonic acid and 5-lipooxygenase. DHA prevents the arachidonic acid from getting into the cells and causing inflammation.
- • Tumor necrosis factor - alpha (TNF-alpha) - This cytokine causes inflammation throughout the body. It causes the blood vessels to narrow resulting in high blood pressure and damage to the tissues. Both EPA and DHA suppress the effect of TNA-alpha.
- • Thromboxane (TxB2) - This is synthesized from omega 6 fatty acids. (Another reason to keep the consumption of the omega 3 oils down) It can cause high blood pressure and blood clot formation. EPA/DHA helps to keep TxB2 in check.
How Much Omega 3 fish oil is enough?
It is generally recommended that at least 1,000 mg a day or more of the active ingredients of fish oil (DHA/EPA) be consumed. (A typical formulation per fish oil capsule is 180mg EPA and 120mg/DHA with a total of 300. Therefore 3 of these capsules would give 900 mg of the active ingredients). Better formulations have a higher percentage of omega 3 oils and are also more bio-available. They are more readily absorbable into the body and utilized.
Vitamin C - 500mg/day
Vitamin C is a major antioxidant found in fruits and vegetables. All cells of the body depend upon it and it is concentrated in the tissues of the eye. It is found at an extremely high concentration in the aqueous humor of the eye - 15 times greater than in the blood. It gives strength to the blood vessels and is required for the synthesis of collagen, the intercellular cement which holds the tissues of the body together including the sclera and cornea of the eye. It helps the body resist infections.
When taken in combination with other nutrients it can slow the progression of macular degeneration by 25% and visual acuity loss by 19%. Some studies show that women taking a vitamin C supplement for ten years or more experienced a 64% reduction in developing cataracts.
Vitamin E - 200 IU/day.
A recently discovered member of the Vitamin E family that is emerging as having additional health benefits over "conventional" vitamin E is delta tocotrienol. Several research groups have shown that it may be beneficial for pre-diabetics and diabetics. One benefit is that it helps to prevent "angiogenesis" - that "out-of-control" growth of unwanted blood capillaries in the retina.
Vitamin E is found in 8 different forms. (alpha, beta, gamma and delta tocopherol and alpha, beta, gamma and delta tocopherol) Historically vitamin E in the form of alpha tocopherol has been the most studied and researched and studies conducted with Vitamin E almost always use the alpha tocopherol form. New research is emerging showing the superiority of the delta tocotrienol form.
Both tocopherols and tocotrienols are antioxidants but only delta tocotrienol has been shown to reduce cholesterol, inhibit cancer and manage diabetes, the leading cause of blindness for working age adults. However, too much of the alpha tocopherol form can block the absorption of the delta tocotrienol form.
Delta tocotrienol specifically has been shown to be beneficial in helping ameliorate diabetic retinopathy, macular degeneration, glaucoma, cataract, and trachoma.
Additionally, in animal studies, scientists have seen a significant beneficial overall effect of increased insulin sensitivity, lower triglycerides, and lower LDL (bad cholesterol) levels. It keeps cholesterol from sticking to the artery wall which causes hardening of the arteries.
Vitamin E is an antioxidant especially effective for fatty tissues such as the retina of the eye. It is the only antioxidant that can protect the cell membrane. It strengthens the blood vessels helping prevent wet macular degeneration and also by being an anti-inflammatory agent and by being anti-angiogenic.
The risk of developing the leading cause of blindness in older people - age-related macular degeneration (AMD) - was reduced by 34 percent in women taking a combination of vitamins B6 and B12 and folic acid. The risk of visually significant AMD was 41 percent lower. There were no men in the study.
Recent studies have drawn a connection between AMD and blood levels of homocysteine, an amino acid. High levels of homocysteine are associated with dysfunction of the blood vessel lining, whereas treatment with vitamin B6, vitamin B12 and folic acid appears to reduce homocysteine levels and may reverse this blood vessel dysfunction.
William G. Christen, Sc.D., of Brigham and Women's Hospital and Harvard Medical School, Boston, and colleagues conducted a randomized, double-blind clinical trial involving 5,442 women age 40 and older who already had heart disease or at least three risk factors.
Of these 5,205 did not have AMD at the beginning of the study. In April 1998 these women were randomly assigned to take a placebo or a combination of folic acid (2.5 milligrams per day), pyridoxine hydrochloride (vitamin B6, 50 milligrams per day) and cyanocobalamin (vitamin B12, 1 milligram per day).
Participants continued the therapy through July 2005 and were tracked for the development of AMD through November 2005. Over an average of 7.3 years of treatment and follow-up, 137 new cases of AMD were documented, including 70 cases that were visually significant (resulting in a visual acuity of 20/30 or worse).
Of these, 55 AMD cases, 26 visually significant, occurred in the 2,607 women in the active treatment group, whereas 82 of the 2,598 women in the placebo group developed AMD, 44 cases of which were visually significant.
Women taking the supplements had a 34 percent lower risk of any AMD and a 41 percent lower risk of visually significant AMD.
"The beneficial effect of treatment began to emerge at approximately two years of follow-up and persisted throughout the trial," the authors write.
"The trial findings reported herein are the strongest evidence to date in support of a possible beneficial effect of folic acid and B vitamin supplements in AMD prevention," the authors write.
Because they apply to the early stages of disease development, they appear to represent the first identified way-other than not smoking-to reduce the risk of AMD in individuals at an average risk.
"From a public health perspective, this is particularly important because persons with early AMD are at increased risk of developing advanced AMD, the leading cause of severe, irreversible vision loss in older Americans," they add.
"Beyond lowering homocysteine levels, potential mechanisms for the effectiveness of B vitamins and folic acid in preventing AMD include antioxidant effects and improved function of blood vessels in the eye, they note."
Zinc (40 mg/day)
Zinc is a mineral that is involved in more than a hundred functions in the body. It helps Vitamin A to move from the liver to the retina and produce melanin, a protective pigment in the eye. Deficiencies have been linked to poor night vision.
A recent article in the Kansas City Star has highlighted that in the past year a test that checks vitamin D levels in the blood has surged in popularity among doctors. The article continues on . . .
"If you have symptoms that include fatigue and muscle aches and pains, don't be surprised if your doctor suggests a vitamin D blood test at your next visit. Because of widespread deficiencies, some doctors won't need any symptoms to suggest it.
"Vitamin D is important to bone and muscle health for certain, but vitamin D experts worry that D deficiency is implicated in cancers, autoimmune diseases, heart disease, diabetes, high blood pressure, infections and depression, to name but a few ailments.
"Carla Aamodt, an internal medicine doctor with St. Luke's Health System, said about half the patients she was testing were vitamin D deficient, with many more "borderline." Michael Kennedy, a family physician at the University of Kansas Hospital, said a third to a half of the patients he tested in the past year have been deficient. Cardiologist James O'Keefe said general population statistics were worse. Lack of sun exposure, the natural way the body makes vitamin D, helps explain the deficiencies.
"If a patient is deficient, levels usually can be increased with vitamin D supplements, typically in pill form. Food sources of vitamin D, such as ocean fish and fortified milk, typically can't be consumed in enough quantities to do the trick.
"For borderline and slight deficiencies, doctors often recommend an over-the-counter supplement containing 1,000 IU or more of vitamin D3 (cholecalciferol), taken daily. Most multivitamins contain 400 IU of vitamin D. Up to 2,000 IU in a daily vitamin D supplement is considered safe for most people without worry of toxicity. Severe deficiencies may require a prescription."
If there is any single nutrient that holds the potential for enormous health and performance gains it is Vitamin D. Vitamin D suppresses the growth of abnormal retinal blood vessels. It helps to keep the immune system under control and enhances the function of the pancreas which makes insulin. It also lowers insulin resistance.
Alpha Lipoic Acid - Works synergistically with C and E as an antioxidant fighting free radicals that can cause vision loss.