A new study has shown that eating vegetable nitrates, found mainly in green leafy vegetables and beetroot, could help reduce your risk of developing early-stage age-related macular degeneration (AMD).
Researchers at the Westmead Institute for Medical Research interviewed more than 2,000 Australian adults aged over 49 and followed them over a 15-year period.
The research showed that people who ate between 100 to 142 mgs of vegetable nitrates each day had a 35% lower risk of developing early AMD than people who ate less than 69mgs of vegetable nitrates each day.
Lead Researcher Associate Professor Bamini Gopinath from the Westmead Institute and the University of Sydney said the link between vegetable nitrates and macular degeneration could have important implications.
“This is the first time the effects of dietary nitrates on macular degeneration risk has been measured.
“Essentially we found that people who ate 100 to 142 mgs of vegetable nitrates every day had a reduced risk of developing early signs of macular degeneration compared with people who ate fewer nitrates.
“If our findings are confirmed, incorporating a range of foods rich in dietary nitrates—like green leafy vegetables and beetroot—could be a simple strategy to reduce the risk of early macular degeneration,” Associate Professor Gopinath said.
Spinach has approximately 20mg of nitrate per 100g, while beetroot has nearly 15mg of nitrate per 100g.
The research did not show any additional benefits for people who exceeded 142mgs of dietary nitrate each day. It also did not show any significant connections between vegetable nitrates and late stage AMD, or between non-vegetable nitrates and AMD risk.
One in seven Australians over 50 have some signs of macular degeneration.
Age is the strongest known risk factor and the disease is more likely to occur after the age of 50.
There is currently no cure for the disease.
The research compiled data from the Blue Mountains Eye Study, a benchmark population-based study that started in 1992.
It is one of the world’s largest epidemiology studies, measuring diet and lifestyle factors against health outcomes and a range of chronic diseases.
“Our research aims to understand why eye diseases occur, as well as the genetic and environmental conditions that may threaten vision,” Associate Professor Gopinath concluded.
11 Steps To Help Prevent Macular Degeneration
Here is a list of 11 steps you can take to prevent or slow the progression of macular degeneration, followed by a brief discussion of each step:
- Don’t smoke.
- Eat plenty of dark, leafy green vegetables, such as raw spinach.
- Take a balanced multivitamin/multimineral supplement, such as Centrum Silver, unless your doctor advises otherwise.
- If you already have AMD, ask your doctor about one of the AREDS formulations or other supplements specially formulated for macular health, such as I-Caps AREDS 2 (Alcon), PreserVision AREDS 2 (Bausch + Lomb), Eyepex Macula (Eyepex Formulas) or MacularProtect Complete AREDS2 (ScienceBased Health).
- Eat fish or take a fish oil supplement.
- Exercise regularly, and maintain a healthy weight.
- Eat fruit and nuts daily.
- Limit your intake of refined carbohydrates (high-glycemic index foods).
- Keep your blood pressure and cholesterol under control.
- Wear sunglasses outdoors to block UV and blue light that may cause eye damage.
- Have regular eye exams.
Step One: Stop Smoking
Probably the number one way to prevent AMD is to stop smoking or not smoke in the first place. Consider findings from these studies:
- Smokers are up to four times more likely than non-smokers to have macular degeneration, public health experts at the University of Manchester said in a British Medical Journal report. In Great Britain, an estimated 53,900 people older than 69 have AMD attributed to smoking. Of that number, 17,900 are legally blind.
- Another study from the Massachusetts Eye and Ear Infirmary showed that current and past smokers had a 1.9- and 1.7-fold greater risk, respectively, of AMD compared with non-smokers.
Step Two: Eat Plenty Of Greens To Prevent AMD
Eating plenty of dark, leafy greens may help with macular degeneration prevention.
A study published by researchers at the Massachusetts Eye and Ear Infirmary reported that people who consumed the most vegetables rich in carotenoids (lutein and zeaxanthin) had a 43 percent lower risk of AMD than those who ate these foods the least.
Carotenoid-rich vegetables include dark, leafy greens, especially raw spinach, kale and collard greens.
“In particular, a higher frequency of intake of spinach or collard greens was associated with a substantially lower risk for AMD,” researchers said.
The authors concluded that “consumption of foods rich in certain carotenoids, in particular dark green, leafy vegetables, may decrease the risk of developing advanced or exudative (‘wet’) AMD, the most visually disabling form of macular degeneration among older people.”
Step Three: Take Multivitamins/Multiminerals
Taking vitamins and minerals in the form of from a trusted source may be a good idea for many reasons, including general eye health.
Particularly for an older person, it may be difficult to obtain all the nutrients you need from diet alone. Ask your doctor for advice about which supplements might work best for you based on your specific health needs.
Step Four: Consider An AREDS Nutritional Supplement
Two large clinical trials sponsored by the National Eye Institute (NEI) have suggested certain nutritional supplements can slow the progression of AMD among people with early and intermediate stages of macular degeneration.
AREDS1. The antioxidant vitamin formula used in the first AREDS study contained the following ingredients:
- vitamin C – 500 mg
- vitamin E – 400 IU
- beta-carotene – 15 mg
- zinc – 80 mg (as zinc oxide)
- copper – 2 mg (as cupric oxide)
The results of AREDS1, published in 2001, revealed patients at high risk of progressive AMD who took the daily antioxidant and zinc supplement had up to a 25 percent reduced risk of their macular degeneration progressing to an advanced stage (depending on the degree of AMD present at the start of the trial), compared to matched participants who took a daily placebo pill.
It should be noted, though, that among study participants who had either no AMD or only early AMD, the supplement did not provide any apparent benefit. Also, the antioxidant formula in the study did not have any significant effect on the development or progression of cataracts.
Still, because of the demonstrated protective effect of the supplement used in the AREDS1 study against AMD progression among high-risk patients, many pharmaceutical companies have developed “AREDS formula” supplements sold as eye vitamins.
Popular AREDS-formula eye vitamins include I-Caps (Alcon), Ocuvite PreserVision (Bausch + Lomb) and MacularProtect Complete (ScienceBased Health). Variations of these products and eye vitamins from other manufacturers also may contain lutein and zeaxanthin and/or omega-3 fatty acids.
Since the results of AREDS1 were published, researchers have found that supplements containing beta-carotene, a vitamin A precursor, may increase the risk of lung cancer among smokers and previous smokers. (Eating foods containing beta-carotene, however, does not appear to cause a similar risk, and may in fact be protective against certain cancers.)
Due to these findings, many health professionals are advising smokers and previous smokers to avoid beta-carotene found in nutritional supplements.
AREDS2. Based on the positive outcome of the original AREDS study, the NEI began a second round of clinical trials in 2006 — called AREDS2 — to see if the AREDS-formula supplement could be improved and provide added eye benefits.
AREDS2, a five-year study with more than 4,000 participants who had varying stages of AMD at the time of enrollment, evaluated the effect of adding lutein (10 mg) and zeaxanthin (2 mg) and/or omega-3 fatty acids (350 mg DHA and 650 mg EPA) to the original AREDS formula. These nutrients were chosen because they have demonstrated eye benefits in other studies.
The AREDS2 researchers also investigated the effect of eliminating beta-carotene and reducing the zinc dosage of the original formula.
Results of the AREDS2 study were published in May 2013. The outcomes revealed that study participants taking the modified AREDS formula with added lutein and zeaxanthin had a 10 to 25 percent reduction in the risk of AMD progression. Those participants with the lowest dietary intake of foods containing these carotenoids experienced the greatest benefit.
Another important finding was that patients who were randomly assigned to take the original AREDS formula containing 15 mg beta-carotene had a greater risk of lung cancer during the course of the AREDS2 study, compared with those who were randomly assigned to take the revised formula without beta-carotene. Most of the participants who developed lung cancer during the study were former smokers.
A finding that was a surprise to many eye care professionals was that the addition of omega-3 fatty acids to the AREDS formula did not significantly reduce the risk of AMD progressing to advanced stages.
Based on the AREDS2 results, the study authors concluded that adding lutein and zeaxanthin to the original AREDS formula and removing beta-carotene from the supplement may increase its safety and effectiveness in preventing the progression of macular degeneration among certain people with high risk of vision loss from AMD.
Step Five: Prevent AMD By Eating More Fish
Research also has shown the benefits of eating fish for macular degeneration prevention:
- A study at the Massachusetts Eye and Ear Infirmary showed that senior men with the highest levels of fish consumption (more than two servings weekly) were 45 percent less likely to have AMD than those who ate the least amount of fish (less than one serving per week).
- Brian Chua and researchers at the University of Sydney demonstrated similar findings. They evaluated 2,900 people aged 49 or older. Participants who ate fish at least once a week were 40 percent less likely to have beginning-stage AMD develop than those who reported eating fish less than once a month or not at all. Those who ate fish at least three times weekly were less likely to have late-stage AMD.
Step Six: Exercise Regularly And Maintain A Healthy Weight
Regular exercise reduces macular degeneration risk, according to a study in the British Journal of Ophthalmology.
In this study, 4,000 people ages 43 to 86 were monitored for 15 years. After considering other risk factors such as weight, cholesterol levels and age, researchers found that people who led an active lifestyle were 70 percent less likely to have AMD develop during the follow-up period.
To be included in the active group, participants must have walked at least two miles a day, three times weekly, or the equivalent.
Step Seven: Eat Fruit And Nuts Daily
Eating fruits and nuts can help reduce your risk of macular degeneration:
- A 2004 study at Harvard Medical School showed that participants who ate three or more servings of fruit daily had a substantially lower risk of “wet” or advanced AMD.
- Another study from the Massachusetts Eye and Ear Infirmary demonstrated that eating nuts helped deter progression of early or intermediate AMD to more advanced stages.
Step Eight: Reduce Refined Carbs In Your Diet
Diets high in refined carbohydrates increase the risk of AMD, which was confirmed in a study published in the American Journal of Clinical Nutrition. Highly refined foods have a high glycemic index, causing a rapid increase in blood sugar and insulin release.
Examples of refined carbohydrates include white bread, white rolls, baked white potatoes, donuts and pretzels. Low glycemic index foods include most fruits, brown rice, multi-grain and whole grain breads, apple juice and carrot juice.
Be careful, though, when considering the glycemic index of foods. The glycemic index (GI) was developed in 1981 by researchers at the University of Toronto. It is a value from 1 to 100 that indicates a food’s effect on a person’s blood sugar level, with a value of 100 being equivalent to the change caused by the same amount of pure glucose. A food with a high glycemic index increased blood sugar level more severely than foods with lower GI values.
But glycemic index values do not take into account the available carbohydrate (total carbohydrate minus fiber) in a food, and does not reflect the actual amount of carbohydrate in a typical serving of the food. So a food that may at first seem like “bad” food because it has a high glycemic index may in fact be very healthful due to other components (other than available carbohydrate) in the food and the actual amount of carbohydrate consumed in a typical serving.
To avoid “good” foods seeming “bad” because of misleading GI values, researchers at Harvard later came up with a measure called the “glycemic load.” The glycemic load of a serving of food can be calculated as its carbohydrate content measured in grams (g), multiplied by the food’s glycemic index, and divided by 100. For one serving of a food, a glycemic load (GL) greater than 20 is considered high, a GL of 11-19 is considered medium, and a GL of 10 or less is considered low. Foods that have a low GL in a typical serving size almost always have a low GI — but not always!
For example, watermelon has a high glycemic index (72). So if we judged it by its glycemic index alone, we might consider watermelon a “bad” food that could increase your risk of macular degeneration. But watermelon contains a very high amount of water, along with healthful vitamin C and lycopene (a substance that has been shown to be helpful for heart health), and the amount of available carbohydrate in a slice of watermelon is quite low (only 5 percent, based on weight) due to its high water content.
If you calculate the glycemic load of watermelon, these factors result in it having a GL value of only 3.6! So, as you might have guessed even without all this math, watermelon is a healthful food despite its high glycemic index. Eat as much as you want! And, when possible, consider the glycemic load (GL), not the glycemic index (GI), of foods you eat when evaluating your dietary risk factors for AMD.
Step Nine: Control Blood Pressure And Cholesterol
Some evidence indicates that controlling cholesterol can protect you from macular degeneration. Cholesterol is a fatty substance that can build up in blood vessels, inhibiting blood flow necessary for maintaining health of eye tissue.
Also, blood pressure control may be important for macular degeneration prevention. Major investigations including the Framingham Heart and Eye Studies and Beaver Dam Eye Study indicate a significant link between high blood pressure and development of advanced, potentially blinding forms of macular degeneration.
Step Ten: Wear Sunglasses With UV & Blue Light Protection
Major studies show no conclusive evidence that overexposure to the sun directly causes macular degeneration. But some findings suggest at least an association between AMD and cumulative eye damage from overexposure to both UV and high energy visible (HEV) or “blue” light.
As an example, a recent major study found that people who consumed too few antioxidants, in combination with overexposure to blue light, were four times more likely to develop advanced or “wet” AMD. For this reason, it is a good idea to wear sunglasses that protect against both UV and HEV light outdoors.
Step Eleven: Have Regular Eye Exams
Last but not least, have regular eye exams. The American Academy of Ophthalmology recommends a dilated eye exam at least every two to three years if you’re between 45 and 60 and every year after the age of 60.
By following these steps, you’ll know you’ve done everything you can to prevent AMD. But if you’re strongly genetically predisposed to develop macular degeneration, it still may develop and worsen.
Regular eye exams can help your eye doctor detect AMD and monitor it so that you can receive proper AMD treatment, if appropriate, beyond these preventive measures.
More information: Bamini Gopinath et al, Association of Dietary Nitrate Intake with the 15-Year Incidence of Age-Related Macular Degeneration, Journal of the Academy of Nutrition and Dietetics(2018). DOI: 10.1016/j.jand.2018.07.012
Journal reference: Journal of the Academy of Nutrition and Dietetics
Provided by: Westmead Institute for Medical Research