hi all

as far as i know
any mention here of sweet drinks helping the absorption of sinemet
has been purely anecdotal

this (second last question below, marked with *****)
is the first 'official' mention that i have come across
that makes a connection between levodopa absorption and insulin


janet



"http://parkinsonswellness.org/nut.html"

A Special Diet for Parkinson's Disease

"A special diet for Parkinson's disease has evolved out of the knowledge that diet can interfere with the effectiveness of levodopa. Therefore, this pertains only to those people receiving levodopa who are experiencing fluctuations in their mobility"

Why are there interactions between levodopa 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 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 it from entering the blood would also delay how much gets to the brain and, consequently, would affect 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 (LNNA). To be absorbed, it 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 its ability to get to the brain.

What factors interfere with the absorption of levodopa?

Since levodopa is not absorbed into the blood stream,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, the rate at which they are digested, and the rate at which the stomach empties into the small bowel became very important.

Another consideration is that there are enzymes in the stomach lining that play a role in metabolizing the drug. Therefore, the longer the drug stays in the stomach, the more it will be chemically broken down and less drug will be available for absorption.

There are many dietary factors that 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 (eg, anticholinergics) have been shown to slow the rate of stomach emptying.

Experiments are being done to see if decreasing stomach acidity with antacids might improve the absorption or the drug in a few patients. It should also be noted that stomach or bowel diseases, as well as constipation, can affect 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 the drug with a meal can dramatically delay the absorption or the drug.

What is the recommendation for timing of medication?

Sinemet should be taken 15 to 30 minutes before meals to ensure the most predictable absorption. (The same recommendation would apply for Sinemet CR, although it is not thought to be as critical for its absorption.)

There are two exceptions to this rule:

1. If this drug produces nausea, the medication should be taken with a light, low-protein snack such as crackers and juice or, if necessary, with a meal.

2. The second exception is if a person experiences too much diskinesia or involuntary movement after taking the drug. Diskinesia 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 transports the drug from intestine to the blood stream and from the blood stream to the 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 LNAAs 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.

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 their medication 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 the recommended daily allowance of protein. Most Americans eat far more than this on a daily basis The RDA for protein is 0.8 g/kg (0.36 g/lb) body weight.

How should the protein be distributed throughout the day?

Restricting protein to the RDA, compared with 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 with evenly distributing it throughout the day, further improves the amount or 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 an even 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 dosage of the medication.


janet paterson
53 now / 41 dx pd / 37 onset pd / 44 dx cd / 43 onset cd
tel: 613 256 8340 url: "http://www.geocities.com/janet313/"
email: "[log in to unmask]" smail: PO Box 171 Almonte Ontario K0A 1A0 Canada