Remember the old joke:
Q: How do you know carrots are good for your eyes?
A: Well, have you ever seen a rabbit with glasses?
It’s not a terribly convincing scientific proof for anyone over age 5 or so, but actually, diet and lifestyle really can affect your eyesight. Hunter-gatherers don’t get myopia (nearsightedness), but in the United States, at least ⅓ of the population has it, and that’s not even counting other eye problems like age-related vision loss or complications of diabetes. So what are we doing wrong in the modern world, and how can we address it with diet and lifestyle changes?
Vision and Metabolism
One reason why Paleo is relevant to eye health is the connection between vision and metabolic health. If you have diabetes or know someone who has it, you’re probably familiar with diabetic retinopathy: blurry or distorted vision, spots in front of your eyes, or related problems caused by long-term diabetes. It’s one of the primary causes of vision problems in adults, and it’s ultimately caused by constant and uncontrolled high blood sugar damaging blood vessels in the eye.
Not all patients with diabetes get diabetic retinopathy, but it’s a very common complication, especially among people who have had the disease for a while. And what’s more, this study found that there’s no clear cutoff for the point when complications start:
“Our results show a more gradual increase of retinopathy prevalence with [fasting blood glucose levels], and strongly suggest a continuous relationship.”
In other words, damage to the microvascular structure of the eyes doesn’t start when you officially “have diabetes;” it’s a more basic problem of consistently high blood sugar.
Diabetic retinopathy is one thing, but there’s another common diabetic eye problem: myopia, or nearsightedness. Plenty of people without diabetes have myopia, but this study found that diabetic subjects were much more likely to have myopia than the general population, and the authors concluded that being nearsighted was likely a metabolic consequence of poor blood sugar regulation. This study confirmed the association in another population.
Another connection between vision and metabolism comes from a different hormonal disease: PCOS. PCOS involves changes to the sex hormones, but it’s typically accompanied by insulin resistance and other metabolic symptoms as well. And women with PCOS also have unusually high rates of eye problems, including dry or itchy eyes. It’s not clear how PCOS causes eye problems, but the researchers pointed out that the sex hormone and insulin dysregulation problems in PCOS are related, so it may very well be both.
A third connection between high blood sugar and vision problems is the association of refined carbohydrates with Age-related Macular Degeneration (AMD). AMD is the most common cause of vision loss in the industrialized world, and as the name suggests, it typically hits people when they’re older – it’s the most common cause of people just “losing their eyesight” as they age when there’s no other reason for the problem.
Epidemiological studies in the US and in Australia indicate that an overall Western dietary pattern is bad news, and a study that tried to tease out all the different components of diet found that a high intake of refined carbohydrates is associated with increased risk of AMD.
Put all these things together, and you end up with the conclusion that maintaining stable blood sugar levels and healthy insulin metabolism, plus a diet low in refined carbs, can help keep your eyes healthy especially as you age. Diabetes and PCOS are the extreme end of the scale, where we can see the chickens coming home to roost, but they point to a more basic problem with the modern diet: way too much sugar, way too many refined carbohydrates, and the damage to metabolic and sex hormones that ensues.
Micronutrients and Vision: Dietary Patterns Beat Supplements
That was the carbs; now it’s time to look at other nutrients. Surprisingly enough, Vitamin A isn’t actually all that important – it’s dangerous to have a deficiency, but most people in the industrialized world aren’t at any risk for that, and eating a huge overload isn’t likely to do any good.
Studies on AMD have found that high intake of fish/Omega-3 fats, nuts, Vitamin D, and certain carotenoids (lutein and zeaxanthin) are associated with lower rates of the disease, but bear in mind that these are associations and don’t necessarily prove causation. Vitamin A had surprisingly little association with anything at all, and the data for Vitamins C and E were conflicting. (And in case you were wondering, they couldn’t find much at all for total fat or saturated fat)
It also seems like diet beats supplements in this case. It’s not clear, that supplements can re-create those dietary patterns (for example, there’s very little evidence that Omega-3 supplements have any of the same benefits of a dietary pattern naturally high in Omega-3 fats). There’s some evidence that antioxidant supplements can help delay the progression of AMD once problems have already started, but studies haven’t found a preventative benefit for healthy people.
Then there’s the case of Vitamin D. This study found a relationship between low Vitamin D levels and nearsightedness, but the authors were very careful to note that it’s not totally clear whether this is an effect of the Vitamin D or sun exposure generally. In fact, there’s a fair amount of evidence that sun exposure may be good for your eyes, especially for preventing nearsightedness.
In other words, we have a bunch of potentially protective factors (Omega-3 fats, antioxidants, Vitamin D), plus evidence that they work much better as part of an overall dietary pattern and lifestyle than as isolated supplements. That’s exactly the premise of the Paleo approach: instead of continuing to eat junk food and taking a bunch of pills, embrace the bigger picture of nutrient-dense foods and healthy lifestyle patterns that provide your body with all the things it needs for good health.
Don’t Forget Lifestyle!
The importance of sun exposure for Vitamin D (and potentially for other things as well) brings up a bigger point: health isn’t just about what you eat; it’s also about the other inputs that you give your body in the form of exercise, light exposure, sleep, stress, and other factors. And it’s probably not that shocking to learn that these things also have an effect on vision. Just to name a few effects:
- Sleep, stress management, and exercise are three powerful ways to improve your insulin sensitivity and carbohydrate metabolism regardless of what you eat.
- Exercise outside can be a double benefit: you get the insulin-sensitizing effects and a healthy dose of sun on your skin for the Vitamin D.
It’s not that you’re going to head out for a long walk with 20/30 vision and come back with 20/20. But all of these lifestyle factors are good for eye health in the long run – not to mention everything else!
Summing it Up
Not all eye problems are caused by diet. And carrots might be very tasty, but they aren’t actually an eye-health superfood, especially not in isolation.
Instead of looking at this or that individual food, it makes more sense to look at overall dietary patterns that contribute to good eye health. A good diet for maintaining healthy vision would be…
- One that doesn’t cause chronically high blood sugar, insulin metabolism problems, or other metabolic issues – it should be low in highly refined carbs (although not necessarily low in all carbohydrates!)
- One that provides generous amounts of micronutrients.
- One adequate in Omega-3 fats.
In terms of lifestyle, an eye-healthy lifestyle would include healthy sun exposure and at least some regular movement (and remember that walking is intense enough for insulin purposes). Paleo is a perfect example of a diet and lifestyle that fits this mold. It’s not the only conceivable diet that does, but it’s a great starting point.