By Dr. Mercola
Eating plenty of dark leafy greens, rich in carotenoids like lutein, can go a long way toward maintaining healthy vision and keeping cognitively fit into old age. Lutein, which you have to get from your diet as your body cannot manufacture it, is well-known for its vision-enhancing properties.
Along with zeaxanthin, it's found in high concentrations in your macular pigment and macula lutea,1 the small central part of your retina responsible for detailed central vision.
High levels of these carotenoids help stave off age-related eye diseases such as cataracts and macular degeneration, the latter of which is the No. 1 cause of blindness among the elderly. However, more recent research notes lutein also plays an important role in brain health, and may help prevent cognitive decline.
Lutein-Rich Diet Helps Keep You Cognitively Fit
According to recent research,2,3,4,5,6,7 which involved 60 adults between the ages of 25 and 45, those with higher levels of lutein in middle-age had more youthful neural responses than those with lower levels. Carotenoid status was assessed by measuring macular pigment optical density, which is known to be highly correlated with the lutein status in your brain.
Most studies have focused on the effects of diet after cognitive decline has already set in. Here, they wanted to evaluate whether lutein might have a protective effect, as the process of cognitive decline has been shown to begin far earlier than typically expected. According to these researchers, you can start seeing cognitive deterioration as early as your 30s. Indeed, the results suggest your diet, and in this case lutein-rich foods, does help keep your brain young.
"Now there's an additional reason to eat nutrient-rich foods such as green leafy vegetables, eggs and avocados. We know these foods are related to other health benefits, but these data indicate that there may be cognitive benefits as well," said Naiman Khan, professor of kinesiology and community health at the University of Illinois.
How Diet Affects Your Vision
Your diet can also influence your risk for nearsightedness and healthy vision in general. According to Loren Cordain, an evolutionary biologist at the Colorado State University in Fort Collins, elevated insulin levels affect the development of your eyeball, making it abnormally long, thereby causing near-sightedness.8
Cordain found that when hunter-gatherer societies change their lifestyles and introduce grains and carbohydrates, they rapidly develop myopia rates that equal or exceed those in western societies — often within a single generation.
The reason for this is because high insulin levels from excess carbohydrates can increase insulin resistance and disturb the delicate choreography that normally coordinates eyeball lengthening and lens growth. When your eyeball elongates, the lens can no longer flatten itself enough to focus a sharp image on your retina.
This theory is consistent with observations that you're more likely to develop myopia if you are overweight or have Type 2 diabetes, both of which involve elevated insulin levels. Following my nutrition plan will help normalize your insulin level by reducing, or eliminating, excess sugar and processed grains from your diet. To learn more about which foods can help safeguard your vision, please see my previous articles, "Eat Right to Protect Your Eyesight," and "The Best Foods for Healthy Eyes."
Other Health Benefits of Lutein
Lutein has also been found to promote health in other ways, beside optimizing vision and cognition. For example, studies have found:9
- Diets rich in the carotenoids beta-carotene, lutein and lycopene resulted in greater resistance against oxidation of low-density lipoprotein (LDL) cholesterol. Carotenoid supplements did not increase LDL oxidation resistance. Higher plasma concentration of carotenoids was also associated with lower DNA damage10
- Lutein and zeaxanthin in combination with vitamin E appears to improve lung function11
- Plasma levels of antioxidants such as lutein, zeaxanthin, vitamin E, beta-cryptoxanthin, lycopene and alpha- and beta-carotene are inversely correlated with congestive heart failure severity12
- Plasma carotenoid levels are also inversely correlated with prostate cancer13
Lutein is primarily found in green leafy vegetables, with kale and spinach topping the list of lutein-rich foods. You'll also find it in orange- and yellow-colored fruits and vegetables. The word lutein actually comes from the Latin word "luteus," which means "yellow." As a general rule, anywhere from 15 to 47 percent of the total carotenoid content in dark green leafy vegetables is lutein.14
Following is a list of foods that are particularly rich in lutein.15,16,17 Ideally, you'll want to buy the whole food and consume these foods as close to raw as possible, as the lutein (and other carotenoids such as zeaxanthin) are easily damaged by heat. Accessory micronutrients in the foods that enhance their action also tend to get easily damaged.
Red and yellow peppers
Raspberries and cherries
While there's no recommended daily intake for lutein or zeaxanthin, studies have found health benefits for lutein at a dose of 10 milligrams (mg) per day and at 2 mg/day for zeaxanthin.
How to Optimize Lutein Absorption
Lutein and other carotenoids are fat-soluble, so to optimize absorption, be sure to add a little bit of healthy fat to your meal. For example, research21,22 shows that adding a couple of eggs — which contain both lutein and healthy fats — to your salad can increase the carotenoid absorption from the whole meal as much as nine-fold.
Ideally, opt for organically-raised, free-range pastured eggs. Not only do they tend to have a better nutritional profile, by opting for pastured eggs you'll also avoid pesticide exposure and genetically modified organisms.
The vast majority of commercially available eggs come from concentrated animal feeding operations (CAFOs), where the hens are not permitted to forage on pasture. Instead, they're typically fed a diet of corn and soy, the vast majority of which are genetically engineered. CAFO eggs are also far more prone to cause foodborne illness caused by salmonella contamination
If you live in an urban area, visiting a local health food store is typically the quickest route to finding high-quality local egg sources. Your local farmers market is another source for fresh free-range eggs. Cornucopia.org also offers a helpful organic egg scorecard23 that rates egg manufacturers based on 22 criteria that are important for organic consumers.
You can often tell the eggs are free-range by the color of the egg yolk. Foraged hens produce eggs with bright orange yolks, indicative of higher amounts of lutein and zeaxanthin. Dull, pale yellow yolks are a sure sign you're getting eggs from caged hens that are not allowed to forage for their natural diet. Another way to boost absorption of lutein from your vegetables is to add some raw organic butter or healthy oil such as olive or coconut oil to your salad.
Other Valuable Brain Nutrients
Clearly, your brain health is not dependent on any single nutrient (although a strong case could be made for the omega-3 fat DHA, as DHA is actually a component of every cell in your body and most of the omega-3 fat found in your brain is DHA). Cognitive decline can have many underlying factors, but addressing your diet is often a good place to start.
Not only can nutritional deficiencies wreak havoc with your brain function, your gut health also plays an important role, and toxic exposures from your diet or environment can also contribute. Ideally, you'd want to address all of these issues. I've written extensively about all of them. As for nutritional deficiencies, animal-based omega-3, vitamin D and B vitamins appear to be particularly important.
As a general rule, I recommend getting most if not all of your nutrition from REAL FOOD, ideally organic to avoid toxic pesticides, and locally grown. Depending on your situation and condition, however, you may need one or more supplements. Following is a listing of foods containing nutrients that are particularly important for healthy brain function. If you find that you rarely or never eat foods rich in one or more of these nutrients, you may want to consider taking a high-quality, ideally food-based supplement.
|Nutrient||Dietary Sources||Supplement Recommendations|
Animal-based omega-3 fats, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)
Cold-water, fatty fish such as sardines, anchovies, herring, mackerel and wild-caught Alaskan salmon.
|Fish oil or krill oil. There is no set recommended standard dose of omega-3 fats, but some health organizations recommend a daily dose of 250 to 500 mg of DHA and EPA for healthy adults. |
The omega-3 index test can be an enormously important health screen, and it's commercially available.
As with vitamin D, getting your level tested is the best way to customize your dosage, as your requirements for omega-3 will vary depending on your lifestyle; your intake of fatty fish, for example, and your level of physical activity.
Your index should ideally be above 8 percent. So, to customize your dosage, get your level measured and then adjust your dosage until you reach 8 percent.
The ideal way to optimize your vitamin D level is through sensible sun exposure, not food.
|To ascertain whether you might need a vitamin D3 supplement, be sure to check your vitamin D level at least twice a year, and take whatever dosage needed to maintain a level of 40 to 60 ng/mL year-round. |
When taking a supplement, keep in mind you may also need to increase your intake of vitamin K2, and keep an eye on your magnesium-to-calcium ratio, as all of these nutrients work in tandem.
Liver, chicken, veal, peanuts, chili powder, bacon and sun-dried tomatoes have some of the highest amounts of niacin per gram.26
Other niacin-rich foods include baker's yeast, paprika, espresso coffee, anchovies, spirulina, duck, shiitake mushrooms and soy sauce.27
|The dietary reference intake established by the Food and Nutrition Board ranges from 14 to 18 mg per day for adults. |
Higher amounts are recommended depending on your condition. For a list of recommended dosages, see the Mayo Clinic's website.28
For pellagra, discussed above, doses range from 50 to 1,000 mg daily.
|Nutritional yeast is an excellent source of B vitamins, especially B6.31 One serving (2 tablespoons) contains nearly 10 mg of vitamin B6. |
Not to be confused with Brewer's yeast or other active yeasts, nutritional yeast is made from an organism grown on molasses, which is then harvested and dried to deactivate the yeast.
It has a pleasant cheesy flavor and can be added to a number of different dishes.
Meat, egg yolks, fish, liver, poultry, nuts and legumes.32
|B8 is not recognized as an essential nutrient and no recommended daily intake has been set. |
That said, it's believed you need about 300 mcg per day. Vitamin B8 is sometimes listed as biotin on supplements.
Brewer's yeast is a natural supplemental source.33
Fresh, raw, organic leafy green vegetables, especially broccoli, asparagus, spinach and turnip greens, and a wide variety of beans, especially lentils, but also pinto beans, garbanzo beans, kidney beans, navy and black beans.34
|Folic acid is a synthetic type of B vitamin used in supplements; folate is the natural form found in foods. (Think: folate comes from foliage, edible leafy plants.) |
For folic acid to be of use, it must first be activated into its biologically active form (L-5-MTHF).
This is the form able to cross the blood-brain barrier to give you the brain benefits noted.
Nearly half of the population has difficulty converting folic acid into the bioactive form due to a genetic reduction in enzyme activity.
For this reason, if you take a B-vitamin supplement, make sure it contains natural folate rather than synthetic folic acid. Nutritional yeast is an excellent source.35
Vitamin B12 is found almost exclusively in animal tissues, including foods like beef and beef liver, lamb, snapper, venison, salmon, shrimp, scallops, poultry, eggs and dairy products.
The few plant foods that are sources of B12 are actually B12 analogs that block the uptake of true B12.
|Nutritional yeast is also high in B12, and is highly recommended for vegetarians and vegans. |
One serving (2 tbsp.) provides nearly 8 mcg of natural vitamin B12.36
Sublingual (under-the-tongue) fine mist spray or vitamin B12 injections are also effective, as they allow the large B12 molecule to be absorbed directly into your bloodstream.