Keep Your Eyes Fit With Good Nutrition

Most Americans are overweight or obese because of lack of exercise and an improper diet. In addition to increasing the risk of diabetes, heart attack and stroke, inactivity and obesity have also been shown to be risk factors for cataracts, glaucoma, and age-related macular degeneration (AMD).1

Increasing your physical activity and maintaining a well-balanced diet will improve the quality of your life and help preserve your vision.

A Balanced Diet

The three major sources of fuel found in foods are carbohydrates, proteins, and fats. We need all three to supply our body with the nutrients it needs to stay healthy. The key is understanding the characteristics of each food group and knowing the amount and proportions of carbohydrates, protein, and fats that make up a healthy diet.

Carbohydrates

Carbohydrates (frequently called “carbs”) are ring-like structures of varying complexity that contain carbon, hydrogen, and oxygen in similar proportions. The primary function of carbohydrates is to provide energy for the body, especially the brain and nervous system.

    • The most basic carbohydrate is called glucose. Glucose is a simple sugar, or monosaccharide. Other monosaccharides include fructose (fruit sugar) and galactose (milk sugar).
  • Slightly larger simple carbohydrates are called disaccharides. Disaccharides include maltose (found in beer), sucrose (found in cane sugar), and lactose (found in milk).

 

  • Complex carbohydrates are found in starchy vegetables, breads, cereals, rice, legumes, and pasta. The liver is the organ in our body that breaks down complex carbohydrates into glucose in order to provide energy for the body.

 

The glycemic index (GI) of a particular complex carbohydrate refers to how quickly it is broken down in the liver and raises blood sugar levels in the body. Carbohydrates with a high glycemic index promote weight gain in many people and increase the risk of Type 2 diabetes and diabetic retinopathy.

Table 1 lists common high and low glycemic index carbohydrates. Though it’s not necessary to eliminate high GI carbohydrates for a healthy diet, you should limit your consumption of these and balance them with low GI foods.

Table 1: Glycemic Index (GI) of Carbohydrates


High GI Carbs (Limit These)


Low GI Carbs (Better For You)

 

Potatoes

Beans

 


Corn


Peas

 


Carrots


Peanuts

 


Bananas


Apples

 


White bread


Sourdough and rye breads

 


White rice


Brown rice

 


Overcooked pasta


Protein-enriched pasta

 


Honey and jams


Skim milk products

 


Sugary breakfast cereals


Whole grain cereals

 


Soft drinks


Oranges

 


Candy


Apricots

 


High fructose corn syrup


Natural fruit sugar (fructose)

 

Most nutrition experts agree that in a balanced diet, 50 to 60 percent of calories should come from carbohydrates – with as much as possible coming from low GI carbohydrates. Highly processed foods and refined sugars should be reduced or eliminated.

Proteins

Proteins are complex organic compounds consisting of a chain of amino acids that contain carbon, hydrogen, oxygen, and nitrogen. The presence of nitrogen differentiates proteins from carbohydrates and fats.

Protein is the main component of our muscles, organs and glands. Every living cell and nearly all body fluids (including the tears that moisten our eyes) contain protein. Protein is required to maintain muscles, tendons, and ligaments. Children require adequate protein for growth and development.

We require approximately 22 different amino acids for our bodies to develop properly and stay healthy. Our bodies can produce some of these amino acids. The amino acids our bodies can produce are called nonessential amino acids because we do not need to get them from our food. However, there are nine amino acids that are not made in the body and must be obtained from our food. These are called essential amino acids.

If a food protein contains enough essential amino acids, it is called a complete protein. Sources of complete protein include beef, lamb, pork, poultry, fish, shellfish, eggs, milk, and milk products.

Protein found in fruits, vegetables, and grains usually lack one or more essential amino acids and are therefore incomplete proteins. However, plant-derived proteins can be combined to provide all essential amino acids and therefore act as a complete protein. Examples of such combinations include rice and beans or corn and beans. Therefore, vegetarians can obtain all essential amino acids by eating the proper combinations of foods.

In a nutritionally balanced diet, approximately 20% of the total daily calories should come from protein. The best protein sources are fish, poultry without skin, lean meat, beans, and lentils. These protein sources are the lowest in fat.

Lipids (fats)

Lipids are fats or fat-like substances found in animals and plants.

It is widely understood that too much fat in our diet is associated with heart disease and other health problems. However, the subject of fats is a complicated one, as there are both beneficial and harmful types of fats.

Saturated vs. Unsaturated fats

All fats and oils found in foods are made of chains of carbon-containing molecules called fatty acids. These fatty acids can be either saturated or unsaturated, based on how they are bound together by hydrogen atoms.

In general, the harder a fat, the more saturated it is. Fats found in meats and dairy products are typically saturated fats. Consuming saturated fats is strongly associated with higher blood cholesterol levels.

Liquid oils are usually unsaturated fats. Examples include olive and canola oils (monounsaturated fats) and corn, safflower, and soybean oils (polyunsaturated fats). Exceptions to this rule are coconut and palm oils, which are highly saturated fats.

There is some evidence that certain fatty acids contained in monounsaturated and polyunsaturated fats provide health benefits to the body. One category in particular is omega-3 fatty acids, which are found in olive oil, canola oil, flaxseed, soybeans, and many nuts and seeds). Studies are suggesting that omega-3 fatty acids may help lower cholesterol levels and blood pressure.

Trans-fatty acids

Trans-fatty acids (like saturated fats) are dangerous to the heart. They may also increase the risk for certain cancers. These compounds are produced during the processing (or hydrogenation) of polyunsaturated oils to keep them from getting rancid and to keep them solid at room temperature. Trans-fatty acids are found in stick margarine, shortenings, many fast foods, snack foods, and baked goods (including many commercially-produced white breads).

Trans-fatty acids may be even more dangerous that saturated fats because they increase LDL (“bad cholesterol”) and decrease HDL (“good cholesterol”) and may damage the lining of arteries. A study of 80,000 female nurses found that those women whose diets were high in trans-fatty acids had a 53% increased risk of heart attack compared to those who consumed the least of those fats.2

Trans-fatty acids have been shown to reduce the number and sensitivity of insulin receptors in the body, contributing to an increase in diabetes.3 They are also implicated as having harmful effects on our cardiovascular system, immune system, reproductive system, energy metabolism, and liver function.4,5

Cholesterol

Cholesterol is an essential lipid that our bodies need to repair cell membranes and manufacture hormones such as estrogen and testosterone. We get some cholesterol from our diet, but our liver manufactures two-thirds of the cholesterol in our bodies. Production of cholesterol by the liver is stimulated by the consumption of saturated fat.

Food cholesterol is found only in animal products, including beef, pork, chicken, fish, eggs, and high-fat dairy products. Many of these food items are also high in saturated fat. Therefore, consuming them both adds cholesterol to the body and stimulates the production of more cholesterol by the liver.

The body transports cholesterol and fat in the bloodstream by coating them with a water-soluble “bubble” of protein. This protein-cholesterol-fat compound is called a lipoprotein.6

Lipoproteins are classified as high-density lipoproteins and low-density lipoproteins:

  • High-density lipoproteins (HDLs) remove cholesterol from the walls of arteries and return it to the liver, where it can be processed and excreted. This is “good cholesterol” – higher HDL levels lower your risk for heart disease.

  • Low-density lipoproteins (LDLs) transport about 75 percent of the blood’s cholesterol to body cells. This is “bad cholesterol”, since elevated LDL levels are linked to increased risk for heart disease.

Triglycerides

Triglycerides are the fat molecules packed along with cholesterol within lipoproteins. High triglyceride levels displace HDL (“good cholesterol”) and may be responsible for the development of blood clots that can block arteries and cause heart attacks.

Recommended Cholesterol Levels

In addition to maintaining a proper diet and exercising frequently, have your blood cholesterol levels checked periodically as recommended by your physician. To maintain a healthy heart and cardiovascular system, the American Heart Association recommends the following guidelines for HDL, LDL and total cholesterol levels:7

Table 2: Recommended Cholesterol and Triglyceride Levels


Type of Lipid (Fat)

 


Recommended Blood Level

 


HDL (“good cholesterol”)

 


40 mg/dL or higher



LDL  (“bad cholesterol”)

 


Less than 130 mg/dL

 


Total cholesterol

 


Less than 200 mg/dL

 


Triglycerides

 


Less than 150 mg/dL

 

Some researchers believe LDL, total cholesterol, and triglyceride levels should be even lower. Consult with your physician to determine what levels are acceptable for you.

Studies Show Diet Affects Vision

Anything that affects the health of the cardiovascular system has the potential for causing damage to our eyes and vision. Arteriosclerotic changes can cause the blood supply to the eye to become blocked, resulting in sudden loss of vision. Type 2 diabetes from an improper diet and lack of exercise can lead to diabetic retinopathy and vision loss.

New research is confirming the connection between diet and eye health:

  • One recent study indicates that fats found that vegetable fats found in french fries and many other snack foods are associated with a higher risk of age-related macular degeneration (AMD). In contrast, subjects who had diets that were low in vegetable fats and high in omega-3 fatty acids, such as fish oils, appear to have a lower than normal risk of AMD8

  • In a study of 17,000 male physicians, Harvard researchers found that those with abdominal obesity were 31% more likely to develop cataracts than those without “love handles”.9
  • Another recent study indicates obesity is a likely risk factor in AMD, reducing the level of lutein available to the eye.10

A Diet for Good Vision

To maintain healthy eyes, follow the diet recommendations below and lead an active lifestyle. Also, consider taking nutritional supplements to assure that you are receiving adequate amounts of micronutrients that are important to maintaining eye health.

    1. Maintain a well-balanced diet of approximately 50 to 60 percent complex carbohydrates (mainly low GI type), 20 to 25 percent proteins, and 20 to 25 percent fats (mainly unsaturated fats containing omega-3 fatty acids).

  • Eat less fat, especially saturated fat.

 

  • Eat plenty of fruits and vegetables.

 

  • Limit your intake of fatty meats and dairy products.

 

  • Avoid fast food and snack foods. They are high in harmful saturated fats and trans-fatty acids.

  • Avoid soft drinks, candy, and other foods containing high amounts of refined sugars.

 

  • Drink a minimum of eight to ten large glasses of water daily.

 

  • Supplement your diet with a daily (antioxidant formula) multiple vitamin to make sure you’re getting the micronutrients you need for healthy vision.

 


References

1Richer S. Nutrition acts: Diet, science, and the eye. Review of Optom 2001; 138(9):76-87.
2WebMD. What are the major food components in a diabetes diet. http://my.webmd.com/content/article/1680.53090.
3Salmeron J et al. Unknown dietary fat intake and risk of type 2 diabetes in women. Am Journ Clin Nutrition 2001;73:1001-2;1019-26.
4Simopoulos AP, Robinson J. The Omega Diet. New York: Harper Perennial 1999:382.
5Erasmus U. Fats that Heal, Fats that Kill. Burnaby, B.C.: Alive Books, 1993:456.
6WebMD. Facts about cholesterol. http://mywebmd.com/content/article/1671.50422.
7American Heart Association. Cholesterol levels. http://www.americanheart.org/presenter.jhtml?identifier=4500.
8Seddon JM, et al. Dietary fat and risk for advanced age-related macular degeneration. Arch Ophthalmol 2001 Aug;119(8):1191-9.
9Schaumberg D, et al. Relations of fat distribution and height with cataract in men. Am J Clin Nutrition 2000; 72:1417-8.
10Hammond B, Snodderly D. Reduced macular pigment in people with high body fat. Ft. Lauderdale: Vision Science Lab, Univ of Georgia, Athens, Ga. 2001.

Leave a Reply

Your email address will not be published. Required fields are marked *