By Dr. Mercola
One of the best parts of leading a healthy lifestyle is that it doesn't only affect one or two aspects of your health; it makes you healthier overall. Take eating vegetables, which is arguably one of the most important aspects of living healthy.
Vegetables contain many different antioxidants and other disease-fighting compounds that are very difficult to get anywhere else.
Plant chemicals called phytochemicals may reduce inflammation and eliminate carcinogens, while others regulate the rate at which your cells reproduce, get rid of old cells and maintain DNA.
Vegetables are also a primary dietary source of naturally occurring nitrates, which have multiple health benefits, including for your vision health.
Eating More Leafy Greens May Lower Your Glaucoma Risk
Glaucoma is a leading cause of blindness for people over 60. It's estimated that 3 million Americans suffer from it, but only about half of them know it. In the early stages, glaucoma has no symptoms, but it progresses slowly until vision loss becomes noticeable.
At this point, it may be too late, but if glaucoma is caught early your vision loss may be slowed or prevented. Even with treatment, however, about 10 percent of people with glaucoma will still lose their sight.1 Prevention is therefore the best strategy.
Glaucoma is caused by damage to your optic nerve, often due to abnormally high eye pressure. Impaired blood flow is also known to play a role, and this is where eating your veggies come in.
Green leafy vegetables are an excellent source of nitrates, which are converted into nitric oxide in your body. Nitric oxide, in turn, helps to relax and dilate your blood vessels, improving blood flow and lowering blood pressure (high blood pressure is a risk factor for glaucoma).
There's also some evidence that nitric oxide signaling may be involved in maintaining low eye pressure. Adding more nitrate-rich veggies to your diet may therefore be a simple way to lower your risk of glaucoma.
Indeed, when researchers analyzed data for more than 100,000 U.S. adults, those who consumed the most nitrate (primarily from leafy green vegetables like kale and spinach) had a 21 percent lower risk of developing open-angle glaucoma (the most common form) compared to those who ate the least.2
How Much Nitrate Per Day Was Protective?
Leafy greens were the richest source of nitrates in the study participants' diets. Those who ate the most leafy greens were 48 percent less likely to develop "paracentral" glaucoma, which is particularly associated with blood flow.
So how much nitrate appeared to be protective against glaucoma? Those who were on the high end of consumption consumed about 1.5 servings of greens daily, which contain about 240 milligrams (mg) of nitrate.
Those on the low-end of the spectrum consumed just one-third serving of leafy greens daily, which contained about 80 mg of nitrate. Overall, kale and collard greens appeared to be most beneficial. According to the researchers:3
"The only vegetable that was consistently inversely associated with POAG was kale or collard greens: 1 serving or more per month of kale or collard greens was significantly associated with 55% to 70% reduced odds of POAG [primary open-angle glaucoma]."
While many vegetables contain natural nitrates, some of the best sources include:
✓ Collard greens
✓ Green beans
Beyond Nitrates: Why Dark Leafy Greens Are Excellent for Vision Health
Data from the U.S. Centers for Disease Control and Prevention (CDC) revealed that 87 percent of Americans are not meeting vegetable intake recommendations and 76 percent are not eating the recommended amount of fruits.4
This means that many are missing out on the protective effects of green leafy vegetables, and this extends far beyond nitrates. For instance, the carotenoids lutein and zeaxanthin are primarily found in green leafy vegetables, with kale and spinach topping the list of lutein-rich foods.
Other healthy options include Swiss chard, collard greens, broccoli and Brussels sprouts. Lutein and zeaxanthin are both important nutrients for eye health,5 as both of them are found in high concentrations in your macula — the small central part of your retina responsible for detailed central vision.
More specifically, lutein is also found in your macular pigment — known for helping to protect your central vision and aid in blue light absorption — and zeaxanthin is found in your retina. Both have been linked to a lower risk of cataracts and advanced macular degeneration.
Microgreens Have Magnified Nutrition
While lettuce is typically listed as a healthy leafy green (and a good source of nitrates), there's a growing movement that suggests you should ditch your lettuce in favor of more nutritious options, like microgreens.
It's not that lettuce is bad, per se. It's just that, pound for pound, it doesn't really supply the concentration of nutrients that you could get from microgreens. Microgreens are basically very young vegetables, harvested at about 1 or 2 weeks when they're only a few inches tall.
Specifically, microgreens are "harvested when seed-leaves have fully expanded and before true leaves have emerged."6
The greens are snipped off above the root (in contrast to sprouts, in which you consume the whole thing — root, stem, seed and all) and can be enjoyed in place of lettuce or even as a vegetable side dish.
Research published in the Journal of Agricultural and Food Chemistry found microgreens may contain up to six times more vitamin C, vitamin E, beta carotene and other nutrients than mature greens.7
Red cabbage, cilantro, garnet amaranth, and green daikon radish were noted as particularly nutritious microgreens, but you may also want to try basil, broccoli, kale and sunflower microgreens.
They're pricey to buy at specialty markets, so your best bet (for your wallet and for freshness) is to simply grow your own at home.
Another Reason Why Healthy Diet (and Exercise) May Lower Glaucoma Risk: Insulin Resistance
A diet focused on processed foods (i.e. sugars, grains and unhealthy fats) sets the stage for developing insulin resistance, which in turn is associated with multiple chronic diseases, including glaucoma.
In fact, insulin resistance and related conditions, including diabetes, pre-diabetes and metabolic syndrome all increase glaucoma risk.8 The remedy, in part, is to simply eat real food, including plenty of vegetables. Vegetables are rich in vitamin K1, which increases insulin sensitivity.9
Dark green leafy vegetables are also a good source of magnesium, another nutrient that may play a key role in helping to prevent insulin resistance and diabetes, and therefore may affect your glaucoma risk.
Following my nutrition plan will automatically reduce, or eliminate, excess sugar and grain intake from your diet while helping you increase your vegetable intake and optimize your insulin levels. Aside from eating right, one of the most effective ways to lower your insulin levels is through exercise.
A regular exercise program consisting of high-intensity interval training (HIIT), strength training and more can go a long way toward reducing your insulin levels and thereby protecting your vision. Regular exercise may also help reduce eye pressure in open-angle glaucoma.10
This Green Drink Is a Real Pick-Me-Up
If you're looking for a different way to get more vegetables into your diet, try vegetable juicing. Raw juice can be likened to a "living broth," as it is teeming with micronutrients that many people are lacking. When you drink fresh-made green juice, it is almost like receiving an intravenous infusion of vitamins, minerals, and enzymes because they go straight into your system without having to be broken down.
Leafy greens lend themselves extremely well to juicing, too, although you can add virtually any combination of veggies that you enjoy. For a recipe that provides a perfect pick-me-up in the morning or during your afternoon slump, along with beneficial leafy greens and more, try this green drink recipe from Greatist. Look for organic ingredients if possible:11
Perk-Me-Up Green Drink
- 2 medium-size pears
- 1 cup spinach
- ¼ cucumber
- 1 cup cilantro
- 1 medium-size lime
- ½-inch ginger
- Remove the rind from the lime. (You can also leave it on, particularly if the lime is organic.)
- Push all ingredients through juicer, pour into two glasses, and stir.
What Else Can You Eat to Benefit Your Vision Health?
Vegetables are important for vision health, but they don't represent the whole picture. To protect your eyes from disease and maintain proper eyesight even as you age, be sure your diet includes plenty of the following foods for healthy vision:
✓ Organic Pastured Egg Yolks
Egg yolk is a source of both lutein and zeaxanthin along with healthy fat and protein, and while the total amount of carotenoids is lower than in many vegetables, they're in a highly absorbable, nearly ideal form. According to research,12 adding a couple of eggs to your salad can also increase the carotenoid absorption from the whole meal as much as ninefold.
Keep in mind that once you heat egg yolks (or spinach) the lutein and zeaxanthin become damaged, and will not perform as well in protecting your vision; so cook your eggs as little as possible, such as poached, soft-boiled, or raw.
✓ Wild-Caught Alaskan Salmon
Rich in omega-3s, the omega-3 fat DHA is concentrated in your eye's retina. It provides structural support to cell membranes that boost eye health and protect retinal function, and research suggests eating more foods rich in these fats may slow macular degeneration.
Those with the highest intake of animal-based omega-3 fats have a 60 percent lower risk of advanced macular degeneration compared to those who consume the least.13 A 2009 study also found that those with the highest consumption of omega-3 fats were 30 percent less likely to progress to the advanced form of the disease over a 12-year period.14
A second study published in 2009 found those with diets high in omega-3 fats, along with vitamin C, vitamin E, zinc, lutein and zeaxanthin, had a lower risk of macular degeneration.15 In addition to wild-caught Alaskan salmons, sardines and anchovies are other good sources of animal-based omega-3s.
Wild-caught Alaskan salmon is a good source of astaxanthin, but you may not be able to eat enough of it to reap optimal clinical results. Astaxanthin is produced only by the microalgae Haematococcus pluvialis when its water supply dries up, forcing it to protect itself from ultraviolet radiation.
Compelling evidence suggests this potent antioxidant may be among the most important nutrients for the prevention of blindness. It's a much more powerful antioxidant than both lutein and zeaxanthin and has been found to have protective benefits against a number of eye-related problems, including:
✓ Age-related macular degeneration (ARMD)
✓ Cystoid macular edema
✓ Diabetic retinopathy
✓ Inflammatory eye diseases (i.e., retinitis, iritis, keratitis, and scleritis)
✓ Retinal arterial occlusion
✓ Venous occlusion
Astaxanthin crosses the blood-brain barrier AND the blood-retinal barrier (beta carotene and lycopene do not), which brings antioxidant and anti-inflammatory protection right to your eyes.
Dr. Mark Tso,16 now of the Wilmer Eye Institute at Johns Hopkins University, but who was my boss when I worked at the University of Illinois Eyebank in the1970s, has demonstrated that astaxanthin easily crosses into the tissues of your eye and exerts its effects safely and with more potency than any of the other carotenoids, without adverse reactions.
Depending on your individual situation, you may want to take an astaxanthin supplement. I recommend starting with 4 milligrams (mg) per day. Krill oil also contains high-quality animal-based omega-3 fat in combination with naturally occurring astaxanthin, albeit at lower levels than what you'll get from an astaxanthin supplement.
✓ Black Currants
Black currants contain some of the highest levels of anthocyanins found in nature — approximately 190 to 270 milligrams per 100 grams — which is far more than that found in even bilberries. They're also rich in essential fatty acids, lending added support to their anti-inflammatory properties. Anthocyanins are flavonoids, and the health benefits of these antioxidants are extensive. As discussed in one 2004 scientific paper:17
"Anthocyanin isolates and anthocyanin-rich mixtures of bioflavonoids may provide protection from DNA cleavage, estrogenic activity (altering development of hormone-dependent disease symptoms), enzyme inhibition, boosting production of cytokines (thus regulating immune responses), anti-inflammatory activity, lipid peroxidation, decreasing capillary permeability and fragility, and membrane strengthening."
For medicinal purposes, many opt for using black currant seed oil, which is available in capsule form. But eating the whole food is always an option, especially when they're in season.