Preserve your vision: prevent (or reverse) diabetes

Diabetes is a serious disease that poses considerable risks to the vascular system, particularly to the crucial and delicate blood vessels of the eyes.  

Diabetes is the leading cause of blindness in adults.1

Nonrefractive visual impairment refers to a visual defect that cannot be corrected with glasses, and diabetic retinopathy is a common cause of nonrefractive visual impairment. Retinopathy is quite common among diabetics; about one-third of diabetics over the age of 40 have diabetic retinopathy.2 Retinopathy can lead to serious vision loss, preventing sufferers from driving and living independently.

A new study has uncovered an alarming upward trend in nonrefractive visual impairment, and provides evidence that the diabetes epidemic is likely the cause.

Photo of an eye

Nonrefractive visual impairment increased by 21% among adults between 1999 and 2008 – a dramatic increase in a short period of time. When broken down by age, the largest increase in prevalence occurred in younger people – 20 to 39 years of age, compared to older age groups. This is a stark finding that predicts climbing rates of disability among middle-aged and younger adults in the near future.

The researchers then looked to the risk factors for this type of visual impairment to find the potential underlying causes.  The risk factors include older age, poverty, lower education level, lack of health insurance, and diabetes. Diabetes rates increased by 22% among U.S. adults from 1999 to 2008, and the other risk factors remained relatively stable, suggesting that the increase in visual impairment was due to the increase in diabetes.

Once diabetes is diagnosed, the damage to the body progresses over time, and the risk of complications progressively rises. Having diabetes for at least 10 years was linked to greater risk of nonrefractive visual impairment, and a greater proportion of the population had been living with diabetes for at least 10 years in 2008 compared to 1999; in adults younger than 40, this proportion doubled. 2 Type 2 diabetes is becoming more common in younger populations, and therefore diabetes is beginning to do its damage earlier in life, bringing dangerous complications, such as vision impairment, earlier in life.

This is alarming data that begs for action; it indicates that medical advances toward better glucose control are not preventing vision loss due to diabetes. Managing glucose with drugs is not enough – we must get rid of diabetes to get rid of the risk.

Preventing and reversing diabetes

For type 1 and type 2 diabetics, the risk of vision-related complications can be eliminated with a nutritarian eating style plus frequent exercise.  The vegetable-based dietary program described in my book The End of Diabetes  is the most effective dietary approach for those with diabetes and is much more effective than drugs. For a Type 2 diabetic, this approach results in complete reversal of the diabetic condition for the majority of patients. For a Type 1 diabetic it eliminates the excessive highs and lows, dramatically reduces insulin requirements and prevents the degenerative diseases common in later life in those with type 1 diabetes.  Both type 1 and type 2 diabetics can maintain excellent health, proper eyesight and quality of life into old age.   Now is the time for us individually and collectively to utilize modern nutritional science to save our vision and save lives. 

References:

1. American Diabetes Association: Diabetes statistics [http://www.diabetes.org/diabetes-basics/diabetes-statistics/]
2. Ko F, Vitale S, Chou CF, et al: Prevalence of nonrefractive visual impairment in US adults and associated risk factors, 1999-2002 and 2005-2008. JAMA 2012, 308:2361-2368.

Eat leafy greens to see clearly

 

Carotenoids are pigments present in fruits and vegetables. An interesting fact about carotenoids is that carotenoids exert their beneficial effects by traveling to and then concentrating in specific tissues in the body. For example, lycopene, a carotenoid found in tomatoes, travels to the prostate, where it has potent anti-cancer effects

Lutein and zeaxanthin, which are found in leafy greens like kale, travel to the central area of the retina (called the macula), and are the only known carotenoids located in the human visual system. Previous research has shown that these pigments are protective against age-related macular degeneration. Scientists now have evidence that these macular pigments also play important roles in visual performance.

Since our bodies can’t produce these pigments, levels of lutein and zeaxanthin in the retina depend on the amounts consumed in the diet. 

Light must pass through lutein and zeaxanthin before being transmitted to photoreceptor cells that will produce a message from the light to send to the brain. As light passes through, some short wavelength (blue) light is absorbed by the macular pigments. For this reason, there was a theory that macular pigments have a light-filtering function in vision.

An analysis of several studies on the subject of macular pigments and visual performance confirms this theory. The authors evaluated the evidence and concluded that lutein and zeaxanthin likely improve the following visual functions by acting as light filters:

  • Discomfort glare – For example, experiencing bright light after being in a dark room. The wavelengths that macular pigments are capable of absorbing produce the least discomfort, suggesting that macular pigments protect the eye from this overstimulation by filtering the light.
  • Disability glare – Subjects with higher levels of macular pigment show improved visibility of objects in the presence of glare.
  • Photostress recovery – Elevated macular pigment values decrease the time necessary to recover vision following exposure to bright light.
  • Contrast – Macular pigments increase visibility and edge definition of objects in the atmosphere, possibly by absorbing blue sky light.

Rich sources of lutein and zeaxanthin include kale, spinach, turnip greens, swiss chard, and collards.


Reference:

Stringham JM et al. The Influence of Dietary Lutein and Zeaxanthin on Visual Performance. Journal of Food Science 2009

 

High fat intake - especially saturated fat - is associated with macular degeneration

 

Age-related macular degeneration (AMD) is the leading cause of vision loss in Americans over 60 years of age. This disease involves cell death in the macula of the eye, which has a high density of cone cells and is responsible for central vision.1 

A recent study published in the Archives of Ophthalmology2 investigated the relationship between fat intake and the presence of intermediate AMD 4-7 years later in over 1700 women, and found that some fats may benefit eye health while others may be damaging.

Total fat.Women aged 50-75 who consumed the highest proportion of calories from fat (43%) had the greatest risk of AMD – 70% higher odds than those with the lowest proportion of calories from fat (21%). As the authors stated,

"High-fat diets might be a marker for diets that are poor in many micronutrients that could protect against age-related macular degeneration.”3

They then looked further into the associations between specific types of dietary fat and AMD.

Saturated fats are detrimental when it comes to heart disease and cancer, so these results are no surprise - saturated fats showed the greatest association with AMD – 60% increased odds of AMD in women who consumed the greatest amounts. Monounsaturated fats, which are present in nuts, seeds, and avocados, were associated with a lower prevalence of the disease.

The associations between polyunsaturated fats and AMD are more difficult to interpret – the authors reported that both omega-3 and omega-6 polyunsaturated fatty acids were associated with a two-fold risk of AMD. But don’t overreact and throw away your walnuts and flaxseeds - the intakes of omega-3 and -6 in this study were highly correlated to one another, making it difficult to discern the effects of one from the other. Also, a 12-year study in the American Journal of Clinical Nutrition last month found that people at high risk for AMD were less likely to develop the disease if they had a greater intake of omega-3 fats.4 The authors of the current study hypothesized that excessive omega-6 fatty acid intake may influence AMD by promoting inflammation that can contribute to retinal damage. Vegetable oils, processed foods, and animal products contain high levels of omega-6 fats – with that in mind, the authors also stress that the associations that they found likely do not represent effects of only the types of fat, but the cumulative effects of the all the compounds in the foods that contain each type of fat.3

The evidence is overwhelming that a Nutritarian diet-style, with raw seeds and nuts as the major fat source, and the high exposure to phytochemicals and carotenoids is the healthiest way to eat. Can you imagine all the personal medical tragedies that could be prevented?   It would sure put a lot of drug companies and doctors out of business.

 

References:

1. http://www.nlm.nih.gov/medlineplus/maculardegeneration.html

2. Parekh N et al. Association Between Dietary Fat Intake and Age-Related Macular Degeneration in the Carotenoids in Age-Related Eye Disease Study (CAREDS). An Ancillary Study of the Women's Health Initiative. Arch Ophthalmol. 2009;127(11):1483-1493.

3. http://www.medpagetoday.com/Ophthalmology/GeneralOphthalmology/16950

4. Sangiovanni JP et al. {omega}-3 Long-chain polyunsaturated fatty acid intake and 12-y incidence of neovascular age-related macular degeneration and central geographic atrophy: a prospective cohort study from the Age-Related Eye Disease Study. Am J Clin Nutr. 2009 Oct 7. [Epub ahead of print]