TABLE OF CONTENTS
There is a song that I use to sing in Sunday School as a child and it goes something like this – watch your eyes, watch your eyes what they see – don’t see! Thinking back on it now, I know it does have some spiritual connotations, particularly, the part that says – ‘Don’t see!’ However, as I thought through this post, the song did come to mind, as we want to see, and very well at best, as we age.
According to research, more than One (1) billion people suffer from some form of vision impairment or blindness, globally (Assi et al. 2021). Further, research contends that most of these may be preventable or even corrected. As such, quality of life will play an important role as it relates to one’s overall health and ocular health (eye health) is a critical component. In this article, we are going to explore Five (5) nutrients that are a ‘must-have’ in your diet for eye health, both for now and in the future. Let’s discuss!
Our diet plays a significant role in our overall health and ocular health is no exception. According to research, over Twenty (20) million people suffer from some form of vision issue, globally (Flaxman et al. 2020). Most of the causes of eye issues include cataracts, glaucoma, diabetic retinopathy, and age-related macular degeneration (AMD). Many of these conditions have been mostly associated with adults and are expected to increase exponentially in years to come (Flaxman et al. 2020).
While several mechanisms and therapies exist to manage, treat, or resolve eye issues, the interest in nutrition, especially as it relates to dietary antioxidants and certain vitamins and minerals is becoming a growing one. These alternative therapies are seen as more cost-effective strategies for preventing and controlling ocular issues (Weikel et al. 2012; Loskutova et al. 2019; Li et al. 2017).
A major eye concern is that of age-related macular degeneration (AMD). AMD is defined as a disease of the eye that blurs one’s central vision (National Institutes of Health.gov). Therefore, AMD causes one to lose central vision. However, the peripheral or what is called the ‘side vision’ will still be functional (American Academy of Ophthalmology). This condition usually occurs as we get older, and aging causes the macular to become damaged. The macular is that section of the eye that is responsible for sharp straight-ahead vision and is located in the retina (National Institutes of Health.gov). On the other hand, the retina is the tissue that is located at the back of the eye and is very sensitive to light (National Institutes of Health.gov).
Research has shown that certain nutrients may be able to prevent or delay particular eye conditions and help with overall ocular health. This was observed in one of the most advanced studies having to do with the eyes – Age-Related Eye Disease Study or AREDs for short. This randomized study of over Three Thousand, Six Hundred and Forty (3,640) individuals with AMD purported that daily, long-term intake of supplements with vitamin C (500 mg), vitamin E (400 IU), beta-carotene (15 mg), Zinc (80 mg – zinc oxide) and copper (2mg, as cupric oxide) reduced the risk of the progression to late stages of AMD (Tanvetyanon, and Bepler,2008). Other oxidants such as lutein and zeaxanthin were also shown to be useful for AMD when they are not combined with beta-carotene. Nonetheless, further research is recommended (Chew et al. 2014).
In this article, we will be exploring five (5) of the most potent nutrients which have been proven to be able to assist with particular eye diseases or just with the overall health of the eyes both in the short and long term. These include zeaxanthin, lutein, astaxanthin, omega 3 and vitamin C.
Five (5) Best Nutrients for Eye Health:
- Omega 3
- Vitamin C
Zeaxanthin and Eye Health
Zeaxanthin is a non-provitamin-A carotenoid that belongs to the xanthophyll family (Murillo and Fernandez, 2019). It is considered one of the two (2) major carotenoids in the macula and retina of the human eye (Sommerburg et al. 1998). The next major carotenoid is Lutein. Like lutein, it has been shown by research to be beneficial to the eyes and human health in general (Murillo and Fernandez, 2019). It must be noted that carotenoids in general are significant sources of vitamin A. However, non-provitamin A carotenoids are those that do not display any vitamin A activity but have been associated with many health benefits (i.e., lutein, lycopene, astaxanthin and of course, zeaxanthin) (National Institutes of Health.gov).
Zeaxanthin is found in plant sources such as leafy greens, carrots, papaya, orange, and peaches (Sparrow and Kim, 2009). For leafy green vegetables, the concentration of zeaxanthin is about 40mg per 100g. On the other hand, for yellow and orange fruits and vegetables, the concentration is reportedly a little less, at one (1) gram or less per 100 g (Sparrow and Kim, 2009). Zeaxanthin is also found in animal products such as egg yolks and cheese (Sparrow and Kim, 2009). Research also denotes that this nutrient is usually more bioavailable in animal products due to its fat content (Sparrow and Kim, 2009). The only source of carotenoids for humans is food (Sommerburg et al. 1998). As such, while supplements are now available, the first recommendation to ensure that you are fueling your body with this nutrient is your diet.
Both zeaxanthin and lutein are accumulated in the peripheral part of the retina of the eyes and gradually increase in concentration to the center of the macula with zeaxanthin being more dominant than lutein, which is mostly concentrated in the macular and retina of the eye (Billsten et al. 2003). As such, they play a significant role in the overall health of the eyes. This is because they help to protect the eyes against age-related macular degeneration (AMD) (Mozaffarieh et al. 2003) as well as cataracts (Ribaya-Mercado and Blumberg, 2004). Research also shows that zeaxanthin can protect against oxidative stress as well as inflammation on a structural level (Murillo et al 2019). Carotenoids in general have been proven to play an essential role in protecting cellular membranes and lipoproteins against oxidative stress (Sies and Stahl, 1995).
According to both vitro and in vivo studies, zeaxanthin as well as lutein was found to protect against chronic eye diseases. It was also found to protect against cardiovascular diseases, which include AMD, cataracts, coronary heart disease as well as stroke (Ribaya-Mercado and Blumberg, 2004). Research in vitro study also shows that zeaxanthin along with lutein was able to significantly reduce the accumulation of lipofuscin (Sundelin and Nilsson, 2001). Lipofuscin or aging pigment is a brownish pigment that forms due to the breakdown as well as the absorption of blood cells that have been damaged (medlineplus.gov/medical encyclopedia). Lipofuscin or aging pigment is usually found in the heart muscles, liver, retina, nerve cells etc.
Research also shows that zeaxanthin can serve as a blue light filter, which can reduce the intensity at which blue light reaches the retina of the eye (Bone et al. 2001). Exposure to light, especially blue light is said to be a risk factor for AMD. According to Taylor et al. (1992), individuals with advanced AMD were said to have a higher exposure to blue light, especially over a duration of Twenty (20) years. As such, zeaxanthin may be able to reduce one’s risk in the development of AMD. Further, according to Barker et al. (2011), the supplementation of pure zeaxanthin (12.2 kg/d) for Twenty-two (22) weeks, greatly reduced the area of lesion that caused the exposure to blue light. It must be noted that the researchers used fovea Monkeys for this study and not humans.
Lutein and Eye Health
Lutein is a carotenoid which reportedly has anti-inflammatory properties as well as many benefits for eye health (Buscemi et al. 2018). Apart from eye health, some of the other benefits of lutein include improving cognitive function and cardiovascular health. It also purportedly may be able to help decrease one’s risk of developing cancer (Buscemi et al. 2018). Nonetheless, more studies on these effects are still recommended.
However, for this post, we will focus on its benefits for the eyes. This is because research contends that it may be able to improve or prevent age-related macular disease (AMD). A disease that can lead to blindness or other forms of vision impairment (Buscemi et al. 2018).
Research suggests that AMD is the main cause of blindness and vision impairment in developed countries (Wong, et al. 2014, Lim et al. 2012). One of the main reasons for this, as reported, is the low consumption of green leafy vegetables and fruits (Abdel-Aal, et al. 2013). Several studies have observed the positive effect of lutein as it relates to its ability to improve macular visual acuity (Richer et al. 2004, Stringham et al. 2016, etc.), its ability to improve macular pigment optical density levels (Richer et al. 2004, Murray et al. 2013, Stringham et al. 2016, etc.) which is an important measure of vision health. It was also found to improve what is known as ‘contrast sensitivity’ (Richer et al. 2004, Huang et al. 2015, etc.) all leading to improved eye health.
One of the earliest original studies of lutein benefits for the eye dates to the early 1990s. In a case-control study with Four Hundred and Twenty-one (421) individuals as well as Six Hundred and fifteen (615) individuals in a control group. The case study group of Four Hundred and Twenty-one (421) individuals had a condition known as ‘neovascular AMD. Neovascular AMD is a progressive retinal degenerative macular disease that gradually causes vision impairment. The condition is said to mostly affect the elderly population (National Institutes of Health.gov).
The study found that the highest concentration of Lutein produced an odd ratio of 0.3 risk of developing AMD. On the other hand, there was a negative relationship between the lowest concentration of lutein and the risk of developing AMD (Eye Disease Case-Control Study Group, 1993). The odd finds led to further research into the supplementation of lutein for AMD called the ‘Lutein Antioxidant Supplementation Trial or (LAST)’.
This study, of Ninety (90) participants with atrophic AMD (a disorder of the central retina), showed that the supplementation of 10 mg/day lutein alone or with another antioxidant for One (1) year improved atrophic AMD, Macular Pigment Optical Density (MPOD) (Richer et al. 2004) as well as visual acuity (VA) and contrast sensitivity (CS). It was also purportedly beneficial for glare sensitivity of participants (Parisi, et al. 2008).
Additionally, another study also showed that the supplementation of lutein of 20 mg/day for three (3) months, followed by a reduced supplementation of 10 mg/d for another three (3) months was observed to significantly increase macular pigment optical density (MPOD) by about Twenty-eight (28%) percent when compared to placebo participants with AMD (Weigert, et al. 2011). Further, the supplementation of lutein of 10 mg/day was shown to greatly improve the aging retina of over Seventy-two (72) patients with AMD (Murray et al. 2013).
Importantly, it was found that large doses of lutein may not necessarily produce better results as most studies found that lutein supplementation of 20mg/day was not more effective than a dose of 10mg/day to improve visual health (Stringham, et al. 2016; Huang et al. 2015, etc.). Furthermore, those whose dietary intake of lutein (median consumption) was low but supplemented with lutein (0.7mg/d), experienced the most positive results from the supplementation of lutein (Age-Related Eye Disease Study 2 (AREDS2) Research Group, 2014).
As per toxicity, to date, no study has shown any adverse effects of lutein supplementation, particularly at established upper limits in research (European Food Safety Authority, 2010). Most research used a Lutein limit of Twenty (20) mg/day as per some of those mentioned in this article. However, excessive carotenoid supplementation may lead to toxicity under certain conditions (i.e., oxidative stress and mitochondrial dysfunction (200). Additionally, according to Landrum et al (1997) and Dagnelie et al (2000), an intake of Thirty (30) and Forty (40) mg per day was demonstrated to be safe.
You can find lutein in foods such as spinach, kale, basil, parsley, collards, turnip greens, lettuce, squash, peas, pumpkin, broccoli, egg yolk, etc.
Astaxanthin and Eye Health
Astaxanthin is a naturally occurring carotenoid that is red in pigment and belongs to the xanthophyll family (Giannaccare et al. 2020). It is usually found in marine environments, particularly in seafood such as shrimp, lobster, salmon, and microalgae (Giannaccare et al. 2020). In addition to its purported health benefits due to its antioxidant and anti-apoptotic properties, growing research suggests that it may be beneficial for the management of ocular diseases. Ocular diseases refer to any condition that interferes with the proper functioning of the eyes, particularly visual clarity. As such, it characterizes common eye disorders such as cataracts, glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy etc. (CDC.gov).
Research shows that astaxanthin in combination with lutein or zeaxanthin was able to significantly improve one’s visual acuity, contrast sensitivity and vision-related functions (Piermarocchi et al. 2012). Additionally, astaxanthin which reportedly has a stronger antioxidant activity than zeaxanthin and lutein, was able to address the risk factors of AMD (Dryja, 2016). Astaxanthin was also found to exert neuroprotective effects in experimental models of diabetic retinopathy. This it does, by reducing oxidative stress and lessening the effects of certain inflammatory factors (Benlarbi-Ben et al. 2019; Yeh et al. 2016, etc.)
This was observed by Yeh and Colleagues with Fifty (50) female participants who were induced with diabetes. The participants received 0.6 mg/kg astaxanthin, 3 mg/kg astaxanthin and 0.5mg/kg lutein. The participants who were treated with astaxanthin showed the preservation of outcomes (histological and functional) of diabetes retinopathy. They also experienced reduced oxidative stress and inflammation (Yeh et al. 2016). Additionally, it was shown that it may help with the management of glaucoma (Floriani et al. 2016) but may not necessarily be sufficient to thwart the progression of the disease (Kimur et al. 2017).
Astaxanthin was also purported to be able to prevent the development of cataracts (Ishikawa et al. 2015). Cataract is denoted as a major cause of blindness and as such, usually requires surgery to help with restored vision (Scorcia et al. 2020). Nonetheless, a recent study with diabetic mouse models found that the supplementation of astaxanthin delayed both the development and progression of metabolic cataracts. This was done by the astaxanthin preventing mostly oxidative stress. However, more studies are needed where this is concerned, especially studies involving humans.
Omega-3 Fatty-acids and Eye Health
Diet plays a major role in eye health. As such, research has shown that a diet rich in omega-3 fatty acids, that is obtained from both food sources and supplementation may be able to help with ocular health (Zhang et al. 2020).
There are two (2) types of omega-3 fatty acids – short and long-chain. Short-chain fatty-acid – Alpha-linoleic acid (ALA) is found in foods such as flaxseed and chia seeds etc. while long-chain – docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA) can be obtained from marine life such as oily fish. However, researchers recommend the direct intake of long-chain omega-3 fatty acids as preferable for eye health (Nettleton, 1991). Additionally, research contends that diets that are enriched with long-chain omega-3 fatty acids have been purported to have long-term benefits for many chronic ocular conditions such as dry eye disease (DED) as well as Age-related macular degeneration (AMD) (Rand and Asbell, 2011; SanGiovanni, 2005).
Further, research contends that women with a low intake of omega-3 fatty acids tend to have higher incidences of dry eye disease (DED). This was observed for women in the United States in a study entitled ‘The United States Women Health Study’ (Miljanovic et. al 2005). However, the overall effect of long-chain fatty acids in food or supplementation effects on DED, still requires further studies. Additionally, diets rich in polyunsaturated fatty acids may help to improve the cellular retina response to situations such as ischemic (heart issues caused by the narrowing of the arteries which can lead to heart attack), oxidative stress and inflammatory damage, particularly as it relates to AMD (Reme et al. 1994; Simón et al. 2016 etc.).
These effects were observed in animal models. Further, epidemiology studies have linked the dietary intake of long-chain omega-3 fatty acids intake with a reduced risk of developing early stages of AMD (Tan et al. 2009). It also reportedly may be able to reduce the risk of the progression of the disease (Wu et al. 2017). Conversely, the supplementation of long-chain fatty acids does not have similar effects where the development of AMD is concerned, as such, food sources would provide more beneficial effects (Lawrenson and Evans, 2017). This is because the consumption of whole foods may have a more synergistic effect of fatty acids with other nutrients that are present in whole foods (Merle et al. 2018).
The therapeutic dosages of One Thousand (1000) mg to Three Thousand (3000) mg EPA/DHA per day is the usual recommendation for daily omega-3 intake (Flock et al. 2013; de Groot et al. 2019). One Thousand (1000) mg of fish oil is said to have about 300 mg of both EPA and DHA (nih.gov). However, the generally recommended daily intake (RDI) of EPA and DHA is usually 250 – 500 mg (Zhang et al. 2018). If you do not eat enough food with omega-3 fatty acids, then it would be difficult to get enough EPA/DHA. As such, supplementation may be your best option. Additionally, most food sources of omega-3 are available in Alpha-linoleic acid (ALA) forms and as such, may not provide the optimal effects for ocular care. Therefore, all three (3) DHA, EPA and Alpha-linoleic fatty (ALA) acids may be the best option, which may only be available via supplementation (Simopoulos, 2002).
According to research, most Western diets have more omega-6 fatty acids than omega-3. However, the excessive consumption of foods high in omega-6 fatty acids can lead to the development of diseases such as cardiovascular diseases, cancer, and autoimmune diseases (Simopoulos, 2002). On the other hand, a high consumption of omega-3 to omega-6 may have a suppressive effect where these diseases are concerned (Simopolous, 2002). As such, a lower ratio of omega-6 to omega-3 fatty acids is more desirable in reducing the risk of many chronic diseases (Simopoulos, 2002, Simopoulos, 2016).
Vitamin C and Eye Health
Vitamin C or L-Ascorbate/L-ascorbic acid is found in the lens of the eyes, the part surrounding the ocular humors. This nutrient is known to bathe the lens of the eyes (Shui et al. 2009; Senthilkumari et al. 2014) and is said to act as a physiological sunscreen for the eyes, protecting the lens from ultraviolet light (UV). It also helps to regenerate Vitamin E and glutathione which further helps to increase the body’s antioxidant abilities.
However, as we age, the vitamin C levels in the lens decrease. Research contents that a decrease in Vitamin C in the lens is usually linked to cataracts or the severity of cataracts (Tessier et al. 1998). Cataracts, which are described as the clouding of the lens of the eyes, are reportedly the leading cause of blindness (World Health Organization, 2020). In fact, research suggests that cataract is responsible for at least Fifty-One (51%) percent of blindness, globally (World Health Organization, 2020) with age reportedly being a major risk factor for the development of the disease (Hodge, et al. 1995; Age-Related Eye Disease Group, 2001).
Therefore, the increased consumption of vitamin C may help to increase the concentration of vitamin C in the lens of the eyes (Taylor et al. 1991). As such, a low plasma concentration of vitamin C is observed in individuals with cataracts (Taylor et al. 1991). To this extent, the supplementation of Vitamin C may help to both replenish and restore Vitamin C levels, as we get older and thus protect against the development of cataracts.
While many studies have shown the protective effect of Vitamin C on the lens of the eyes, there are those studies that indicate that it may stimulate the progression of cataracts (Lim et al. 2020). However, studies have indicated that the maintenance of vitamin C levels is critical for eye health. Nonetheless, excess intake may cause the formation of cataracts. The way in which vitamin C may contribute to the progression of cataracts in this regard is stated to be complex.
As such, the silo of nutrients is usually not recommended, but instead, a combination of nutrients can have a more synergistic effect on the eye and overall health. However, more studies are recommended to evaluate regular intake of vitamin C and the value of higher or excess intake levels (Braakhuis et al. 2019; Donaldson et al, 2017). Notwithstanding, animal studies have shown the benefits of vitamin C supplementation for the prevention or delaying of ocular diseases, particularly, cataracts (Lim et al. 2020).
Vitamin C can be found in foods such as citrus fruits (oranges, lemon, grapefruit, kiwi etc.), strawberries, bell peppers, tomatoes, and cruciferous vegetables such as broccoli, brussels sprouts, cabbage, and cauliflower. Vitamin C is also found in abundance in Irish potatoes (white potato), spinach, papaya, cantaloupe etc.
According to the National Institutes of Health, the adequate intake of vitamin C is at least Ninety (90) mg per day for adult men and Seventy-five (75) mg per day for adult females. The Recommended Daily Intake (RDI) for infants to those up to Eighteen (18) years old ranges from Fifteen (15) mg to Seventy-five (75) mg per day (Institute of Medicine, 2000). However, people who smoke require at least Thirty-five (35) mg of Vitamin C daily (Institute of Medicine, 2000).
Here is an illustrative summary of the Five (5) ‘must-have’ nutrients for Impeccable Eye Health!
Let’s Sum Up!
The eyes are considered the windows of the soul. As such, it is in our best interest to take care of them, especially as we age.
Diet has been proven time and time again to be paramount to overall health and eye health is no exception. As such, carotenoids such as zeaxanthin and lutein, astaxanthin, plus other nutrients like Omega-3 and vitamin C, have been proven by research to be beneficial for ocular health (eyes). As such, these nutrients may help to reduce the risk or delay the onset of certain diseases of the eyes such as cataracts and other ocular health issues, particularly as we age.
While it might be challenging at times to get all the necessary nutrients via our diet, supplementation in most cases has been proven to be equally beneficial.
So, now that we are aware of the five (5) best nutrients for eye health. What will you do or continue to do to ensure that your eyes remain healthy, especially as you age? Watch your eyes!
You can read more about Omega-3, dietary fats, Vitamin C and vitamins and minerals in general in these articles:
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