When it comes to eye health, particularly in preventing age-related macular degeneration (AMD), the Age-Related Eye Disease Study (AREDS) and its successor, AREDS2, have made significant contributions to our understanding of dietary supplementation for eye health. That being said, the AREDS formulas aren't without their share of controversy, especially concerning the dosage of zinc.
Rethinking Zinc in the AREDS Formulas
The original AREDS formula contains 80 mg of zinc oxide, a level that has been criticized as being excessive. The AREDS2 study, responding to concerns about the potential toxicity of higher zinc levels, reduced the amount of zinc to 40 mg. However, follow-up AREDS research showed that 25 mg of zinc is just as efficacious as 80 mg. It's safer and equally as effective, so there's no reason an AREDS formula should contain a zinc dose above approximately 25 mg.
Another concern around the AREDS study involves the simultaneous intake of multivitamins by study participants. In AREDS, two-thirds of participants took multivitamins along with the AREDS formulation, and in AREDS2, this number was almost nine out of ten. Given that multivitamins often contain additional zinc, this introduces potential variability in total zinc intake, further supporting the rationale for limiting the zinc content in AREDS formulas to 25 mg.
Building a Case for Full-Spectrum Carotenoids
Both AREDS formulas include carotenoids, but their usage of isolated forms has provoked criticism. The first AREDS formula contained β-carotene, which was removed in AREDS2 due to increased lung cancer risk among smokers consuming it in its isolated form. (This risk was not observed with food-based carotenoids.) Despite the elimination of β-carotene, the use of other isolated carotenoids in the AREDS formulas remains controversial.
I assert that carotenoids, as they naturally occur together in many fruits and vegetables, should be consumed in a full-spectrum approach to maximize their health benefits and ensure safety.
Interestingly, high β-carotene intake from foods does not increase lung cancer risk, even in smokers, whereas isolated β-carotene does. This contrast could arise due to a disproportional intake of β-carotene compared to other carotenoids like β-cryptoxanthin, or that high intake of β-carotene may prevent the absorption of other carotenoids. This competition for absorption is exemplified by evidence showing that higher intakes of lutein and zeaxanthin can decrease β-carotene absorption (van Het Hof et al., 2000).
Moreover, the role of β-cryptoxanthin, another dietary carotenoid, highlights the safety of the full spectrum approach. A study showed high dietary intake of β-cryptoxanthin is associated with a lower risk of lung disease in smokers, contrasting with the effects of isolated β-carotene (PubMed 36771049). People who consume more β-carotene from food automatically obtain more of the other carotenoids, including β-cryptoxanthin.
Further supporting the advantages of the full spectrum approach, recent studies show lycopene, a carotenoid not found in the macula but rich in tomatoes, may protect lutein and zeaxanthin en route to the macula (Antioxidants 2020, 9, 264; Antioxidants 2019, 8, x). This research implies that protection against AMD could extend beyond lutein and zeaxanthin supplementation and towards a broader dietary carotenoid intake.
Another carotenoid source worth noting is the golden spice, saffron. Saffron is a rich source of many carotenoids, but two are particularly relevant to AMD: crocin and crocetin. Clinical research indicates that daily supplementation with 30 mg of saffron for six months can significantly improve retinal function in patients with AMD (PMID: 28289690).
There are over 600 carotenoids that naturally occur in foods, each with potentially unique and beneficial properties. This rich diversity further supports the need for a full-spectrum carotenoid approach in both our diets and supplementation practices.
Studies tend to focus on isolated nutrients. The reason is not that isolated nutrients are superior, but rather than conducting studies and analyzing results is easier. Therefore, we don't have many studies looking at the advantages of the "full spectrum" approach, but it is a conservative approach that could potentially offer more benefits and fewer risks. The idea is based on the premise that in nature, nutrients typically work synergistically, providing more significant health benefits when consumed together than individually.
Where Do We Go from Here?
Despite their drawbacks, the AREDS and AREDS2 supplements remain some of the most widely recommended in ophthalmology practices. These formulas have significantly advanced our understanding of nutritional intervention for eye health. However, like all areas of medical science, there's always room for improvement and refinement.
The concerns around zinc dosage and carotenoid selection in the AREDS formulas highlight the need for continued research and improved formulas. As we strive for improved eye health, we must continue to explore and refine these formulas, keeping up with new scientific discoveries and the evolving understanding of nutritional science.
There's a growing consensus favoring a full-spectrum approach to carotenoids over isolated forms. The complexity and diversity of carotenoids in nature seem to hint at a sophistication that we are just beginning to comprehend.
The ultimate goal of these efforts is to create a supplement that is maximally effective, yet closer to nature. While we may not be there yet, my research is focused on formulating the next generation of supplements that reflects the complexity and richness of nature itself.
In the meantime, if you are taking the AREDS formula with 80mg of zinc, consider switching to something else. The AREDS2 formula is a better choice due to the reduced amount of zinc, but the dose remains high enough that, at a minimum, most of us should avoid simultaneously consuming other supplements that contain zinc.
Another consideration is the consumption of isolated carotenoids. If you are consuming any isolated carotenoids, take care to ensure that you also consume plenty of "full spectrum" carotenoids from foods and, optionally, from a concentrated natural carotene source such as saffron or some of the herbs and spices listed below:
Parsley: It contains a variety of carotenoids, including β-carotene, lutein, and zeaxanthin.
Basil: Both sweet and holy varieties of basil are rich in β-carotene, lutein, and zeaxanthin.
Saffron: As mentioned above, saffron contains two carotenoids important to eye health, crocin and crocetin, which give it its vibrant color.
Coriander: Coriander, also known as cilantro, is rich in β-carotene, lutein, and zeaxanthin.
Chili Powder: Chili powder contains a variety of carotenoids, including lutein, zeaxanthin, and β-carotene.
Paprika: Paprika is made from ground bell peppers and is a good source of β-carotene and other carotenoids.
Rosemary: It contains carotenoids including β-carotene, lutein, and zeaxanthin.
Tarragon: This herb is another good source of β-carotene.
Oregano: It also contains carotenoids, including β-carotene.
Marigold: Marigold (specifically the species Tagetes erecta) is rich in lutein and zeaxanthin and is commonly used to produce lutein supplements.
Cayenne Pepper: Cayenne pepper contains carotenoids, including capsanthin, capsorubin, and β-carotene.
Dill, Parsley, and Thyme: These are good sources of carotenoids, especially β-carotene.
Peppermint: Peppermint contains β-carotene among other carotenoids.
Sage: This herb is known to contain carotenoids, including β-carotene and lutein.
These herbs and spices should complement a balanced and varied diet rich in fruits and vegetables. Furthermore, you can leverage knowledge from traditional medical systems, such as Ayurveda and TCM, to fine-tune your personal selection of healing herbs and spices.
Always remember to check the latest research for the most accurate information.