什麼是玉米黃素?

Zeaxanthin Benefits

Zeaxanthin is a carotenoid molecule found in eye cells . Zeaxanthin has two important functions:

  • It forms a yellow pigment barrier that protects eye cells from the harmful effects of certain light sources, such as the sun.
  • It protects the eyes from dangerous free radicals and unstable molecules that steal electrons from healthy cells and cause damage (known as oxidation).
  • Once inside the body, zeaxanthin is attracted to the eyes. It enters the lens, the clear, curved structure toward the front of the eye, and the macula and fovea, the two parts of the retina or tissue that lines the back of the eye.

The macula is the most sensitive part of the retina and has the most photoreceptors. These special cells convert light into signals that the brain can interpret. Therefore, the macula is where the sharpest vision occurs. It is also responsible for your ability to perceive color.

Zeaxanthin and another carotenoid called lutein are the only dietary carotenoids that accumulate in the retina. Since zeaxanthin and lutein are present in large amounts in the macula, they are called macular pigments.

Meso-zeaxanthin is thought to be produced when your body breaks down other carotenoids, and you don't typically get it from your diet

Zeaxanthin uses

Research shows that zeaxanthin may help slow or prevent the progression of eye diseases such as cataracts and age-related macular degeneration (AMD), which are the leading causes of visual impairment and acquired blindness in the United States.

Supplement use should be individualized and reviewed by a healthcare professional. No supplement is intended to treat, cure, or prevent disease.

Age-related macular degeneration (AMD)

Some dietary sources of zeaxanthin have been studied as protective factors for AMD, which affects people 65 years and older.

A 2012 meta-analysis found that a diet rich in lutein and zeaxanthin reduced the risk of early-stage AMD developing into late-stage AMD by 26%. It also helps reduce the risk of early AMD by about 4%.
Likewise, a 2017 review found that lutein and zeaxanthin obtained through dietary sources and supplements may protect eyes against the progression of AMD.

A more severe form of macular degeneration, called wet macular degeneration, occurs when blood vessels in the macula grow and leak fluid. Dry AMD is one of the risk factors for wet AMD, but there are other risk factors, such as high blood pressure.

According to the American Academy of Ophthalmology, zeaxanthin may help prevent the progression of both types of AMD.

cataract

Consuming zeaxanthin and lutein may slow the formation of cataracts, which can cause blurred vision.
American Optometric Association. Lutein and Zeaxanthin – Nutrients beneficial to the eyes.

A 2017 review found that higher blood concentrations of lutein and zeaxanthin were associated with a reduced risk of nuclear cataracts, although evidence that lutein and zeaxanthin help reduce the risk of other types of cataracts is currently weak.

uveitis

Uveitis is inflammation or swelling of the uvea of ​​the eye. The uvea is located in the center of the eye and is responsible for supplying blood to the retina. Lutein and zeaxanthin may help slow this inflammatory process.

A 2015 in vitro study found that lutein and zeaxanthin have anti-inflammatory effects on human uveal cells. But it's worth noting that this study was conducted on cells in the laboratory, so it's impossible to know whether these effects would also occur in humans.

More high-quality studies in humans are needed before further conclusions can be drawn about the effectiveness of lutein and zeaxanthin in uveitis.

diabetic retinopathy

Diabetic retinopathy is a complication of diabetes in which uncontrolled blood sugar causes damage to blood vessels in the retina. Lutein and zeaxanthin reduce the oxidative processes that damage the eyes in this way.

A 2015 review looked at a series of animal studies that evaluated the effects of lutein and zeaxanthin in diabetic mice and rats. It was concluded that lutein and zeaxanthin have a protective effect against diabetes-related retinal changes.

However, because these studies were conducted in rodents, there is no evidence that these effects occur in humans.

What are the side effects of zeaxanthin?

Researchers found no side effects or negative interactions with zeaxanthin.
American Optometric Association. Lutein and Zeaxanthin – Nutrients beneficial to the eyes.

However, people with fair skin may experience yellowing of the skin if the maximum recommended daily dose for adults (10 mg) is exceeded.

Precaution

There does not appear to be a risk in consuming too much lutein and zeaxanthin on a daily basis through supplements or diet.

While zeaxanthin supplements have not been found to cause any adverse side effects, their long-term use has not been studied. In fact, researchers are not sure whether taking synthetic forms of zeaxanthin lasts longer than five years.
Bright Focus Foundation. Lutein and zeaxanthin prevent macular degeneration.

Therefore, zeaxanthin supplements are only recommended for those who are very concerned about worsening vision loss.

If you're looking for a decades-long plan to support eye health, focus on eating fruits and vegetables every day.

Dosage: How much zea yellow should I take?

Always check with your healthcare provider before taking supplements to make sure the supplement and dosage are appropriate for your individual needs.

Generally speaking, health experts recommend that adults eat five servings of fruits and vegetables each day, which should provide about 5 milligrams of carotenoids (including zeaxanthin and lutein).

Currently, there is no recommended daily intake of zeaxanthin. However, taking at least 2 mg appears to have health benefits.

Research shows that when people consume 5-6 mg of zeaxanthin per day, the risk of AMD is lowest and cataract growth is slowed.

Through diet alone, you can get 5-10 mg of zeaxanthin and lutein from a variety of whole foods.

Zeaxanthin and lutein can be taken at any time of day, but mealtimes are usually best. As a fat-soluble antioxidant, zeaxanthin requires some fat to be absorbed properly.

Try spraying your vegetables with olive oil to help ensure you're getting the most out of the zeaxanthin they contain. Or, if taking a supplement, take it with food.

Sources and Precautions of Zeaxanthin

If you haven't been diagnosed with macular degeneration, health experts recommend increasing your zeaxanthin intake by eating foods rich in this micronutrient. This recommendation includes people who may be at risk for AMD, such as family members of diagnosed patients or smokers, who are four times more likely to develop AMD than people who have never smoked.

Macular Association. Smoking and vision loss. According to the American Optometric Association, broadening your diet to include foods rich in carotenoids is a promising way to protect your eyes from disease.

Food sources of zeaxanthin

Zeaxanthin occurs naturally in a variety of fruits and vegetables. Dark leafy green vegetables are especially rich in zeaxanthin. Because they contain the highest content of carotenoids. In fact, zeaxanthin is responsible for the rich color of these foods, as it modulates light energy and keeps chlorophyll at the proper levels during photosynthesis. The chlorophyll in dark green vegetables actually masks the pigments lutein and zeaxanthin, giving the vegetables their recognizable green color.

Scientific information often lists foods containing zeaxanthin and lutein as one category, rather than listing them separately. This may be because lutein can be converted to the carotenoid meso-zeaxanthin in the eye, but also because zeaxanthin is low in the human diet.

But you shouldn't just eat a few vegetables. In addition to green vegetables, eggs and brightly colored fruits and vegetables are good sources of zeaxanthin and lutein.

Foods that provide the carotenoids needed for eye health include:

  • Egg
  • kale
  • spinach
  • Swiss Chard
  • lettuce
  • mustard
  • Radish leaf vegetables
  • kale
  • Watercress
  • Haricot vert
  • squash
  • pumpkin

Zeaxanthin Supplements

Zeaxanthin-containing supplements and eye health supplements are becoming more and more popular.

Studies show that taking zeaxanthin increases the density of macular pigment in the eyes.

One study had people take zeaxanthin supplements for 6 to 24 months. Studies have found that 36-95% of humans have increased macular pigment density. Interestingly, this reaction varies from person to person.

Higher macular pigment density is associated with a lower risk of AMD.

Note that the FDA does not regulate dietary supplements to the same extent as pharmaceuticals, except that it prohibits unsubstantiated health claims. The FDA or the European Food Safety Authority (EFSA) have not approved any health claims for zeaxanthin supplements.

generalize

Zeaxanthin is a carotenoid, a pigment that gives orange and yellow fruits and vegetables their bright colors. Along with the carotenoid lutein, zeaxanthin can help slow or even prevent the progression of cataracts and age-related macular degeneration. If you have been diagnosed with vision loss and are unable to get between 6 mg and 10 mg of both carotenoids in your diet, consider taking supplements to fill the gap.

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