Special Diet for Parkinson's Disease

Note: If you're taking Sinemet or the generic equivalent you need to watch your diet in order to give it a chance to work.

The following article was written about Parkinson's Disease but many of the recommendations would apply also to those with PSP who are on Sinemet or levodopa.

A special diet for Parkinson's disease has evolved out of the knowledge that diet can interfere with the effectiveness of levodopa. Therefore this section pertains only to those people on Sinemet who are experiencing fluctuations in their mobility (the terms levodopa and Sinemet will be used interchangeably).

Why are there interactions between levodopa (Sinemet) and diet?

First we must understand some special features of levodopa:

1. Levodopa has a very short plasma half-life. This means that levodopa rapidly disappears from the blood. This takes from 60 to 90 minutes. Therefore the blood levels of the drug bounce up and down. It is easy to imagine that anything that would delay levodopa from entering the blood would also delay how much levodopa gets to the brain and consequently would effect how well the medication works.
2. Levodopa is not absorbed from the stomach, but from the small bowel. Therefore anything that delays the emptying of the stomach contents into the small bowel can decrease absorption of the drug.
3. Levodopa is a type of amino acid called a large neutral amino acid (LNAA). To be absorbed, levodopa must attach itself to carrier molecules in the wall of the intestine which then carry it across the intestinal wall to the blood. This same mechanism is present to move levodopa from blood to brain. Therefore, anything that also uses this carrier system can compete with levodopa and potentially interfere with the ability of levodopa getting to the brain.

What factors interfere with the absorption of levodopa?

Since levodopa is not absorbed from the stomach, the stomach's role is simply to deliver the medication to the place where it is absorbed, which is the small bowel. Because of this, the contents of the stomach and the rate at which they are digested become very important. Another consideration is that there are enzymes in the stomach lining which play a role in metabolizing the drug. Therefore, the longer levodopa stays in the stomach, the more it will be metabolized and less drug will be available for absorption.

There are many dietary factors which affect how rapidly the stomach empties its contents. In regard to the food groups, fat takes the longest to be digested, followed by protein and then carbohydrates. Dietary fiber also slows the emptying of the stomach. Other factors, such as increased stomach acidity and certain medications (e.g. anticholinergics) have been shown to slow the rate of stomach emptying.

Experiments to see if decreasing stomach acidity with antacids improves the absorption of levodopa are helpful in a few patients. It should also be noted that stomach or bowel diseases, as well as constipation can effect the rate of absorption.

Research has compared the absorption of levodopa when it is given on an empty stomach versus when it is given with a meal. This clearly demonstrates that, in some people, taking levodopa with a meal can dramatically delay the absorption of the drug.

What is the recommendation for timing of medication?

Sinemet should be taken 15 to 30 minutes before meals to assure the most predictable absorption. There are two exceptions to this rule:

1. If Sinemet produces nausea, the medication should be taken with a light low protein snack such as crackers and juice or, if necessary, with the meal. If this does not help, a drug called Domperidone** can block the nausea side-effects and enhance the absorption of levodopa.
2. The second exception is if a person experiences too much dyskinesia or involuntary movement after taking the drug. Dyskinesia may be improved by slowing the absorption of the drug by taking it with meals.

What dietary factors affect levodopa getting from blood to brain?

Once levodopa gets from the stomach to the small bowel it is absorbed into the blood stream. As mentioned earlier, to get across the intestinal wall, levodopa must be transported by attaching to carrier molecules. This carrier system is present from intestine to blood and from blood to brain. It can be likened to seats on a train. There are a limited number of seats and when these seats are filled no more levodopa can be transported. At the level of the intestine this is not a problem since the "train" has a large carrying capacity, but at the level of the brain the "train" is much smaller. Other large neutral amino acids (LNAA) found in the diet use the same carrier system as levodopa. These amino acids are isoleucine, leucine, valine, phenylalanine, tryptophan and tyrosine. Meals high in protein and therefore high in LNAAs can interfere with the ability of levodopa getting into the brain by taking up the seats on the train.

Research has substantiated this idea. Patients have been given a constant infusion of levodopa by vein. This allowed for a constant blood level of levodopa. Since most fluctuations in mobility are directly related to the fluctuating level of levodopa in the blood, a constant blood level of levodopa assures a constant state of mobility. This implies that levodopa is entering the brain at a constant rate. Patients were then asked to drink a solution of one of the competitive amino acids. In spite of a constant infusion of levodopa, these patients turned "off" or their mobility declined. This clearly demonstrated that LNAAs are competitive with levodopa and can block the drug from entering the brain. The same result was seen with a high protein meal. These studies suggested that a low protein diet improved the response to levodopa.

Who should try the low protein diet?

Consideration should be given to the severity of the disease. If a person has motor fluctuations that interfere with activities or has noticed that food seems to interfere with how well Sinemet works, a reduced protein diet may help these problems.

How much protein should be eaten?

People who need to lower the protein in their diet should reduce it to recommended daily allowance of protein. Most Americans eat far more than this on a daily basis. The RDA for protein is .8 g/kg (.36 gab) body weight.

How should the protein be distributed throughout the day?

Restricting protein to the RDA compared to the typical American consumption of protein clearly improves the time a person is mobile throughout the day. Restricting the majority of the protein to the evening meal, compared to evenly distributing it throughout the day, further improves the amount of time a person is mobile. The decision between these two methods of distribution depends on the severity of the disease and the person's life style needs.

For the person who has moderate motor fluctuations, a diet with protein spread evenly throughout the day will reduce the likelihood of high levels of amino acids and improve the amount of mobile time. For the person with marked motor fluctuations, a diet with protein restricted to the evening meal will allow for even a more predictable response. The drawback to this diet is a less mobile evening. If this is compatible with the life style of the patient, this diet is best for the person who has marked fluctuations in mobility.

Do carbohydrates play a role in the parkinsonian diet?

It has been shown that increased carbohydrates result in increased insulin secretion which lowers LNAAs circulating in the blood. Therefore, increased carbohydrates plus a decreased protein intake may further enhance the delivery of levodopa to the brain by lowering the competition with other LNAAs. The therapeutic role of carbohydrates in the parkinsonian diet needs further investigation.

What are the recommendations for carbohydrate use in the parkinsonian diet?

If weight is lost when protein is lowered in the diet, carbohydrates should be increased to maintain ideal body weight. The amount should be determined with the help of a dietician. If excessive but predictable dyskinesia results from the increased carbohydrates and lowered dietary protein, it may be helpful to try to evenly distribute carbohydrate intake throughout the day as well as reduce the levodopa dose.

Practical Guidelines for a Well-Balanced Diet in Parkinson's Disease

1. Eat a daily diet which has a balance of all food groups. This should include 2-3 servings from the meat group, 4-5 from fruit and vegetables, 2-3 from the milk group and at least 6 from the bread and cereal group. An average man may need eleven or more servings from the bread and cereal group to provide enough calories to maintain weight.
2. On an average, calorie intake should be maintained at 25 to 30 calories per kilogram of body weight. If dyskinesia is present, additional calories should be added to prevent weight loss. Monitor weight on a weekly basis. Weight loss is the best sign of under nutrition.
3. Fiber and adequate fluids are important in the control of constipation and prevention of bowel disease. Fiber can be found in whole grains, fruits and vegetables. If necessary, unprocessed bran can be added. To avoid gas, start with one teaspoon daily and increase by one teaspoon per day to a total of one tablespoon, twice daily. In addition, adequate amounts of fluid are essential. This should be equivalent to six to eight glasses of water per day.
4. An effort should be made to eat a diet low in saturated fats and low in cholesterol. Cholesterol consumption should be approximately 300 mg per day. If calories are needed in the Parkinson's diet, they are best added in the form of complex carbohydrates and unsaturated fats.
5. The need for vitamin supplements remains controversial. Although most people should be able to get adequate vitamins from a balanced diet, most elderly people with a chronic illness have enough nutritional risk factors to warrant taking a multivitamin. On the other hand, vitamins are drugs and overuse of some can cause toxicity. High doses of vitamin C and E used in the hope of slowing the progression of Parkinson's disease have minimal toxicity, however, their true benefit is still unclear.
6. Pyridoxine (B6) does not worsen Parkinson's disease if used in the recommended amount of 2 mg per day. If supplemental vitamins are used, intake should not exceed 5 mg. Pyridoxine-free multivitamins are only needed if a person is taking levodopa rather than Sinemet.
7. Elderly people have many risk factors for decreased calcium intake which can contribute to osteoporosis and increased risk of broken bones. In Parkinson's disease, decreased calcium intake may occur when protein is restricted in the form of dairy products. Careful attention should be given to assure daily calcium intake of 1000 to 1500 milligrams.
8. Vitamin D is important in calcium balance. If exposure to sun is inadequate, or chronic use of sunscreen products necessary, supplements of 200 to 400 I.U. of vitamin D should be given daily.
9. Iron is essential in the formation of hemoglobin which carries oxygen to the cells. If iron supplements are needed, they should be separated from the time Sinemet is taken to reduce interference with the effectiveness of Sinemet.
10. Take Sinemet 15 to 20 minutes before meals to assure more predictable absorption.
11. Avoid high protein meals.
12. For people on Sinemet who are noticing fluctuations in their mobility, protein manipulation may be helpful. The following steps should be followed:
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    1. Your health care provider should determine if an evenly distributed or restricted protein diet would be best. This is decided by disease severity and life style needs. Referral is then made to the dietician.
    2. The dietician establishes current dietary intakes of calories, protein and calcium. A nutritional care-plan is then established with appropriate instruction regarding reduction of protein and how it should be distributed throughout the day.
    3. Protein should be reduced to meet the recommended daily allowance of .8 g/kg (.36 g/lb) of body weight.
    4. If protein is to be evenly distributed, it should be equally divided between three meals. For example: a man who is 170 pounds, weighs 77 kilograms. He would require 62 grams of protein per day which is approximately 21 grams per meal.
    5. If protein is to be restricted, the protein in breakfast and lunch together, should equal approximately 10 grams of high quality protein. The rest of the protein (i.e. 52 grams for the 170 lb man) should be eaten from dinner to bedtime.
    6. Calorie intake should be calculated to provide adequate calories to prevent weight loss. Decreased calories from protein reduction may need to be replaced by increasing carbohydrates or unsaturated fats.
    7. Calcium intake should be monitored to assure 1000 to 1500 mg per day.
    8. This diet should be tried for 2 to 4 weeks. The improvement in response to Sinemet should be evident within a few days. At this time, reevaluation of the benefits should be made by your healthcare provider. Evaluation of proper use of the diet should be made by the dietician.

This article was written under a grant agreement for the American Parkinson Disease Association by:

Julie H. Carter, RN, MN
Adult Nurse Practitioner
Department of Neurology
Oregon Health Sciences University
Portland, Oregon

Sponsor:

American Parkinson Disease Association, Inc.
1250 Hylan Boulevard
Staten Island, NY 10305
Tel: 1-800-223-2732