Lutein and its isomers zeaxanthin and meso-zeaxanthin are macular pigments that accumulate in the human retina
They cannot be synthesized in mammals and must be obtained from the diet and then distributed to various tissues, especially the retina, and have the following physiological functions:
- The most important antioxidant in the macula of the retina, the area that produces the most essential area of vision, inhibits free radicals formed by photosensitive processes
- Formation of macular pigment that filters harmful short-wave blue light (absorbs 40% to 90% of incoming blue light)
- Improve visual function (achieved by reducing chromatic aberration and improving color contrast), improve glare incapacitation and photostimulation recovery period
In empirical medicine, what are the benefits (benefits) of taking lutein? Are there any side effects or contraindications? See text analysis for details
What is Lutein?
Lutein is a fat-soluble pigment that belongs to the Carotenoids family, and there are more than 600 carotenoids in nature, of which 30-50 are part of the normal human diet.
Carotenoids can be divided into two main groups: non-polar carotenes (such as β-carotene and lycopene) and polar luteins (xanthophylls, such as lutein and zeaxanthin).
Since lutein biosynthesis occurs only in plants, algae, bacteria, and certain fungi, the main intake of human lutein depends on diet or supplements.
Studies have shown that for every 10% increase in dietary lutein intake, serum lutein concentrations increase by 2% to 4%.
Lutein is mainly distributed in the human body in other parts of the human body, including the skin, cervix, brain and breast, such as the eyes (retina, rod-shaped outer segment, lens).
What are the recommended empirical benefits of lutein?
1. Lutein is beneficial to blood lipid regulation
Dyslipidemia is a controllable risk factor for the development of cardiovascular disease and is characterized by elevated plasma triglycerides, total cholesterol, or LDL cholesterol concentrations, and decreased HDL cholesterol concentrations.
Dyslipidemia alone or in combination with other modifiable risk factors such as diabetes, hypertension, obesity, low physical activity, and smoking significantly increases the risk of cardiovascular events such as myocardial infarction, ischaemic stroke, or coronary death.
A meta-analysis (7 randomized controlled trials) suggested that lutein/zeaxanthin supplementation significantly increased high-density lipoprotein cholesterol (HDL-C) levels in older adults (aged ≥ 60 years). Note 1
*Conclusion: Lutein supplementation may have a positive effect on blood lipid regulation in the elderly, but limited by the small sample size, more studies are still needed for further verification
2. Lutein is beneficial to the brain health of the elderly
Aging alters the cellular, blood vessels, and structural characteristics of the brain, leading to cognitive function, attention span, and memory decline, as well as delays in cognitive information processing.
Structurally, brain volume or brain weight declines at a rate of 40% every 10 years starting at age 5, and the actual rate of decline may increase with age, especially over 70.
A systematic review (9 studies) noted that in healthy older adults, three MRI-using intervention studies showed positive effects on brain activity in terms of learning, resting state connectivity, and gray matter volume. Note 1
Another 4 cross-sectional studies using MRI showed that lutein was positively correlated with brain structure and neural efficiency in cognitive tasks.
*Conclusion: Lutein may have beneficial effects on brain health in healthy older adults.
3. Lutein is beneficial to retinopathy of prematurity
Retinopathy of prematurity is defined as a progressive disease, a multifactorial retinal disease characterized by abnormal retinal vascular development.
In addition to causing blindness and severe visual impairment, retinopathy of prematurity often occurs with other neonatal conditions such as neurological dysfunction, brain dysplasia, necrotizing enterocolitis, ventricular hemorrhage, and bronchopulmonary dysplasia.
A meta-analysis (3 randomized controlled trials of 406 preterm infants younger than 32 weeks) noted that oral lutein/zeaxanthin failed to reduce the incidence of retinopathy of prematurity, nor did it reduce the risk of bronchopulmonary dysplasia, sepsis, necrotising enterocolitis, and mortality. Note 1
*Conclusion: For retinopathy of prematurity, oral lutein does not reduce the incidence
4. Lutein is beneficial for cognitive function
As people age, many aspects change, both physical and psychological. Some changes may be good and some are not.
Changes in cognitive functions as a normal aging process have been well documented in the scientific literature.
Some cognitive abilities, such as vocabulary, are resilient to brain aging and may even improve with age. Other abilities, such as conceptual reasoning, memory, and processing speed, decline over time.
A systematic review (5 randomized controlled trials) found that lutein supplementation (10 mg daily for 12 months) improved some measures of cognitive function, such as visual episodic memory and inhibition. Note 1
*Conclusion: Lutein supplementation has a positive effect on cognitive function in different age groups, but more large trials are needed to support the results.
5. Lutein is beneficial for age-related macular degeneration
Age-related macular degeneration is a progressive visual impairment associated with retinal pigment-photoreceptor cell neurodegeneration, with the common symptoms being blurred central vision, deformation, and decreased vision.
In developed countries, age-related macular degeneration is the leading cause of central vision loss, and age is the strongest predictor, and although it rarely occurs in people under 50 years of age, the risk of developing the disease in patients over 65 years of age more than triples compared to patients aged 74 to 75 years.
A meta-analysis (9 randomized controlled trials, 855 patients with macular degeneration) suggested that supplementation with lutein or related combinations (10 or 20 mg per day for more than 6 months) helped increase macular pigment density (MPOD) and improve visual acuity and contrast sensitivity. Note 1
*Conclusion: Lutein supplementation or related combinations have a positive effect on macular degeneration, but due to high heterogeneity between studies, more long-term large-scale trials are needed
6. Lutein is good for bone health
Skeleton is a dynamic tissue with structural and metabolic functions. Structurally, bones protect vital organs from mechanical forces, provide levers to transmit force from one area of the body to another, and provide attachment positions for muscle-driven movements.
From a metabolic point of view, bones contain a large number of blood cell types and are the largest calcium reservoir in the body.
Adequate nutrition, mechanical load, hormonal status, and genetics are required to maintain bone homeostasis, and disruption of any of these factors can have harmful consequences.
An observational study of 63 healthy adults showed that while serum lutein and zeaxanthin concentrations were not associated with bone mass, macular pigment density (MPOD) was significantly associated with bone density in the proximal femur and lumbar spine. Note 2
*Conclusion: Long-term intake of lutein-rich diets is strongly associated with better bone status and may reduce the likelihood of clinical outcomes such as osteoporosis and fracture risk.
7. Lutein improves dark adaptability
Dark adaptation refers to the process by which the eye becomes more sensitive to light when light is reduced.
For example, entering a dark area from a well-lit place (for example, going to the movies) will be dark at first, but it will only begin to see clearly after a while.
Clinically, dark adaptation is a method of measuring visual function and has been shown to be one of the symptoms of retinal diseases (such as macular degeneration, macular edema, retinitis pigmentosa, diabetes and hypertensive retinopathy), as well as vitamin A deficiency, light, smoking, aging, tissue hypoxia can also cause reduced dark adaptation.
Two observational studies found that macular pigment concentration was related to dark adaptation, and those with higher concentrations had significantly better dark adaptation. Note 1, Note 2
*Conclusion: Higher macular pigment levels help to enhance visual function in low light conditions (while ingesting lutein can enhance macular pigment)
8. Lutein increases the frequency of physical activity
Physical activity is defined as any physical activity produced by skeletal muscle that results in energy expenditure, and the American College of Sports Medicine recommends that to promote and maintain health, all healthy adults need at least 5 minutes of moderate-intensity aerobic activity 30 days a week, or at least 3 minutes of high-intensity aerobic activity 20 days a week.
Physical inactivity is a modifiable risk factor for cardiovascular disease and a variety of chronic diseases, including diabetes, cancer (colon and breast cancer), obesity, high blood pressure, osteoarticular disease (osteoporosis and osteoarthritis), and depression.
A systematic review (17 studies) suggests that higher lutein levels may be associated with more frequent physical activity, which may help improve physical activity and reduce the risk of chronic disease. Note 1
The mechanism behind it may be related to the fact that lutein crosses the blood-brain barrier, regulates the functional properties of neurons, and affects the communication between neurons.
*Conclusion: Lutein levels were positively correlated with the frequency of physical activity, and those with higher levels also participated in more frequent physical activities
9. Lutein is beneficial for diabetic retinopathy
Diabetic retinopathy is currently the number one cause of blindness in people aged 20 to 60, and during the 10 years of the onset of diabetes, the probability of developing retinopathy in diabetic type I and type II patients is 100% and 60%, and the blindness rate is 20 times that of the general population.
Although early detection, blood glucose/blood pressure and lipid control can reduce the risk of morbidity, it is often difficult to achieve clinically.
One randomized, double-blind, placebo-controlled trial (31 weeks in 31 patients with nonproliferative diabetic retinopathy) noted that lutein supplementation had an effect on visual function (particularly contrast sensitivity at low spatial frequencies) compared with placebo. Note 1
*Conclusion: Lutein supplementation may improve visual function in diabetic retinopathy, but more research is needed to confirm the feasibility of add-on therapy
10. Lutein improves stress resistance
Psychological stress refers to the physical and psychological reactions triggered by all external stimuli, although benign stress brings growth, but extreme or recurring stress events are often associated with cardiovascular disease, immune diseases, mental disorders and cancer.
A randomized, double-blind controlled study (12-month, 59 healthy adults) showed that intake of lutein and zeaxanthin helped improve psychological stress, serum cortisol, and Suboptimal Health Status Questionnaire values. Note 1
*Comment: Oral lutein may have the effect of reducing psychological stress and improving physical and emotional health, but more research is needed due to sample size
11. Lutein reduces the incidence of cancer
About 30% of cancers are associated with 5 major behavioral and dietary risks, such as: high body mass index, low fruit and vegetable intake, physical inactivity, smoking, and alcohol consumption.
Asians are 25 times less likely to develop prostate cancer and 10 times less likely to develop breast cancer than residents of Western countries, but the incidence of these cancers has increased significantly as lifestyles have become Westernized.
A case-control study (521 women) reported that higher blood concentrations of carotenoids (α-carotene, β-carotene, lycopene, lutein/zeaxanthin) were associated with lower rates of breast cancer. Note 3
Another meta-analysis (including 10 studies, 1958 cases of esophageal cancer and 4529 cases of control group) pointed out that the higher the intake of carotenoids (beta-carotene, alpha-carotene, lycopene, beta-cryptoxanthin, lutein and zeaxanthin), the lower the risk of esophageal cancer. Note 4
Another case-control study (1993 colorectal cancer patients and 2410 control groups) showed that consuming more lutein-rich foods (including spinach, broccoli, lettuce, tomatoes, oranges and orange juice, carrots, celery and green vegetables) significantly reduced the risk of colorectal cancer. Note 5
*Conclusion: Higher intake of lutein from food is associated with lower cancer rates, but the effectiveness of additional supplementation remains to be confirmed
12. Lutein improves visual adaptation
Disability glare refers to the temporary loss of visual accuracy caused by uncontrolled light such as high intensity in the visual range, glare not only easy to cause eye fatigue, affect reading and learning, but also may cause traffic accidents.
In addition, photostress recovery means that it takes a while for the eyes to return to normal vision after encountering strong light, and aging and abnormal visual cells may lead to increased recovery time.
Several studies have found that supplementation with lutein and zeaxanthin (12 mg daily for 6-12 months) can significantly increase macular pigment density, in addition to improving transient glare disabling caused by bright light, and helping to reduce the time required for photostimulation recovery. Note 1-2
13. Lutein is beneficial for intellectual performance
There are many definitions of intelligence, including but not limited to abstract thinking, understanding, self-awareness, communication, reasoning, learning, emotional knowledge, and the ability to plan and solve problems.
And intelligence is not just used to learn book knowledge, academic skills, or exam skills, it reflects a broader and deeper ability to make sense of our surroundings.
The ability of the intellect to grasp or understand things, or figure out what to do, is also often seen as a predictor of academic achievement, job performance, and income.
An observational study (114 adults with a BMI ≥ 25 kg/m²) showed that subjects with higher density of macular pigment (lutein molecules in the retina) had significantly better intelligence (as measured by the Kaufman Brief Intelligence Test), regardless of body fat percentage. Note 1
In addition, the study further found that the effect of macular pigment on intelligence level is most significant in improving fluid intelligence.
*Fluid intelligence: refers to the ability to solve, create, and flexibly respond to challenges in new situations without prior knowledge
*Conclusion: Macular pigment density can be regarded as an independent indicator of intelligence, and higher people have better intellectual performance
14. Lutein reduces the incidence of cataracts
Cataract is a disease caused by protein degeneration at the lens site, which causes the originally clear water lens to turn cloudy, which in turn affects the entry of light into the retina, causing vision loss.
Compared to other eye diseases (such as glaucoma, macular degeneration, diabetic retinopathy), cataracts are the leading cause of blindness in people over 40 years old in Asia.
A meta-analysis (including 8 population observations) showed that higher blood concentrations of lutein and zeaxanthin helped reduce the risk of nuclear cataract (27% and 37%, respectively), but there was no obvious association with other forms of cataracts (such as cortical and subcapsular cataracts). Note 1
In addition, a meta-analysis of the literature on dose response also pointed out (meta-analysis, including 6 prospective generation studies, 41,999 participants) that dietary intake of more lutein and zeaxanthin can reduce the incidence of nuclear cataract by 25%. Note 2
The mechanism behind it is related to the antioxidant properties of lutein, which can remove peroxides, hydroxyl radicals, lipofuscin, and protect cell membranes from ultraviolet rays and blue light.
*Nuclear cataract is the most common type of senile cataract.
*Conclusion: Moderate intake of lutein can help reduce the incidence of some types of cataracts, but considering the possible confounding and bias of the included studies, further confirmation is needed in more controlled intervention studies
15. Lutein prevents cardiovascular and metabolic diseases
Cardiovascular and related metabolic abnormalities can be said to be the bulk of various health problems, and those with metabolic abnormalities are 3 times more likely to suffer from cardiovascular disease than ordinary people, and the associated cardiovascular risk factors include, hypertension, high cholesterol, and high blood sugar.
A large systematic review (71 studies with a sample size of 387,000 people) and meta-analysis showed that higher intake of leaf yolk or higher blood lutein concentrations contributed to the following states (data were found after mathematical analysis).Note 1
- Reduce the risk of coronary heart disease (a cardiovascular atherosclerotic disease that causes angina pectoris and myocardial infarction) by 12%.
- Reduce the risk of stroke by 18%.
- Reduce the risk of metabolic syndrome (a health problem including obesity, blood pressure, blood sugar, dyslipidemia) by 25%
The mechanism behind it is believed to be related to the antioxidant and anti-inflammatory effects of lutein, which are one of the main causes of cardiovascular disease and metabolic disease.
16. Lutein improves visual recognition function
Modern people have a high dependence on 3C, often causing premature aging of the eyes, if the following phenomena occur, it may be typical visual aging, such as narrow field of view, slower response to visual information, difficult to adjust focus, poor light adaptability, etc
In a recent controlled study, it was found that taking lutein and zeaxanthin can increase visual processing ability (especially the ability to distinguish between objects and light sources) by 20%, which is significantly helpful for driving safety, reading speed, sports performance, and cognitive performanceNote 1
17. Lutein improves skin aging
Skin aging is a complex physiological process, currently known to be mainly divided into endogenous aging (genetically related), usually irreversible, the second is exogenous aging, mainly related to ultraviolet radiation damage, also known as photoaging.
Even though these two aging processes are independent of each other, the molecular mechanism is the same, i.e. reactive oxygen species damage (which are naturally produced by cell metabolism), often resulting in collagen degradation or reduced synthesis.Note 2
There is no shortcut or panacea for anti-aging, the best strategy is through a good lifestyle and antioxidant foods.
A double-blind controlled study has shown that lutein and zeaxanthin can help improve overall skin tone and brightness, but also increase the Minimal Erythema Dose, which may have whitening and improving skin condition.Note 1
The mechanism behind it is related to the antioxidant properties and photoprotective activity of lutein and zeazanthine, which can reduce melanin formation and reduce harmful light damage.
18. Lutein relieves visual fatigue
Modern people often can’t do without the computer, in addition to leisure mobile phones and tablets are also on the side, so the eyes often appear sore, numbness, swelling, pain and other discomfort, these symptoms represent the eyes sent out for help, so every focus on the eyes after 30 minutes, please rest 5 to 10 minutes, so as not to cause accelerated aging of the eyes.
In a study of visual fatigue, it was found that taking lutein combination (in the experiment, subjects were asked to do 2 hours of text proofreading and observe the reaction after taking lutein) did reduce fatigue, discomfort and stress index caused by frequent eye useNote 8
Are there any side effects of lutein?
In the known scientific literature, lutein in moderation is extremely safe, and in a 5-year large-scale study of AREDS2 at a daily dose of 10 mg, no toxicity or adverse effects were found with taking Lutein and zeaxanthin. Note 6
The only confirmed side effect is yellowing of the skin of the hands and feet (caused by long-term large doses or overdose, also known as caroteneemia), the cause is that the constitution is more sensitive to lutein, and the metabolism is not enough to cause yellowing of the skin, and the uninformed think it is jaundice.
Caroteneemia is harmless to the human body, as long as the intake is reduced, the yellowing of the skin will gradually subside, so do not worry too much.
Safety precautions
1. The safety of lutein in pregnant women and lactation is unknown, so it is recommended to consume more vegetables and fruits
2. Patients with cystic fibrosis often cannot absorb carotenoids from food or supplements, so care should be taken when using lutein products
3. Eating snacks containing alternative oils (Olestra) or using other carotenoid supplements may reduce lutein absorption
4. A case study found that a woman with glaucoma had taken lutein (20 mg daily for 8 years, with a high-lutein diet) for a long time, resulting in cases of retinal crystal deposits, which did not affect the patient’s vision, and the crystals had partially disappeared after discontinuation. Note 7
5. Smokers taking high-dose lutein supplements (greater than 10 mg per day) may be associated with a higher risk of lung cancer, so caution should be exercised before use. Note 8
What is the best food source of lutein? Which is the most bioavailable?
According to the current available research, the bioavailability of lutein intake from egg yolk is the highest, and the absorption efficiency is several times that of health preparations and vegetables (corbage), and the mechanism behind it may be related to the fat composition therein. Note 1
Eating one egg a day for 5 weeks can increase the concentration of lutein and zeaxanthin in the blood, by 26% and 38% respectively. Note 2
Another study found that intake of lutein-rich eggs (1 mg daily) for 90 consecutive days had the same effect on increasing blood lutein concentrations as using 5 mg of health food. Note 3
*The lutein content in egg yolks varies greatly depending on the chicken feeding style and feed, usually containing 0.41 mg to 1.764 mg of Lutein per 100 grams. Note 4
Natural food source of lutein
Many foods contain lutein, such as dark green leafy vegetables and fruits: Brussels sprouts, spinach, kale, broccoli, peas, kiwifruit, grapes, oranges are rich in lutein, if you can take 1 bowl of spinach or kale per day to reach the recommended amount of 6 mg of lutein per day, but note that these foods should not be cooked for too long, as long as they are cooked, because long-term cooking will cause the loss of nutrients.
Recommended dosage of lutein supplementation (how to eat)
If you do not often eat the vegetables, fruits and eggs mentioned above, or if you often eat outside, you can choose a nutritional health food containing lutein to supplement.
As for the amount of supplements, it has been found in many studies that in order to help vision, the average person needs to consume 6~10 mg of lutein daily, but not more than 20 mg.
What are the 3 main factors that affect the absorption of lutein and zeaxanthin?
1. Properties of food: For example, cooked or raw food, although cooked to reduce the content of lutein, it increases the bioavailability of lutein compared to uncooked sources
2. Amount of dietary fat: Adding an appropriate amount of fat when cooking, or taking it with meals (using health supplements) can improve the absorption rate
3. Plant-derived dietary fiber: Simultaneous intake of foods containing pectin, guar gum, alginate, cellulose or wheat bran has been shown to reduce the absorption of lutein molecules