When you have a prescription filled at a pharmacy, you are entitled to an insert which provides among other information, a disclosure of all known side effects of the drug. You are entitled to this information by low. No such insert is provided when you purchase a supplement at the health food store or anywhere else. However, supplements can have side effects, too. Although they may be natural, that doesn’t mean they are safe. People have been known to die of natural causes. It is just as important to know the side effects of supplements as it is to know the side effects of drugs, first of all, in order to make informed decisions as to whether or not to take the supplement and, secondly, if a side effect should occur, to know its cause.

Glucosamine is reputed to be an effective natural therapy for osteoarthritis. Its pain relief is achieved without the side effects of analgesic drugs, which, as we saw in last week’s article, are formidable. However, glucosamine sulfate does have side effects of its own, which can be significant. It is, therefore, important to be aware of them.

The Side Effects of Glucosamine

Glucosamine can cause gastrointestinal problems, including nausea, heartburn, diarrhea, constipation, and indigestion. It can also cause drowsiness, skin reactions, and headache. I have a friend who has been taking glucosamine sulfate at the recommended dosage of 1,500 mg a day for the past five years and has found it effective for relief of her arthritis symptoms. When I told her of these side effects about a year and a half after she had started the supplement, one of them rang a bell – drowsiness. This symptom began about the same time she began taking glucosamine. Her doctor could find no physical cause and diagnosed depression. But this diagnosis did not seem right to my friend because she had no other symptoms of depression. She chalked it up to getting older and just lived with it. But knowing that this symptom is a possible side effect of glucosamine, she decided to change the timing of her dosages from 500 mg three times a day at breakfast, lunch, and dinner to 500 mg three times a day at lunch, dinner and again at 8 p.m. She found that this change made a difference in her energy level during the day. he now has energy during the day. She now has energy during the early part of the day when she wants to be active, and she winds down in the latter part of theday. This is a pattern she is comfortable with.

Glucosamine, Blood Sugar Levels, and Insulin Resistance

There have been anecdotal reports of poorer blood glucose control in people with diabetes who take glucosamine. Glucosamine is composed of glucose, a sugar, and the amino acid glutamine. Theoretically, glucosamine sulfate might exacerbate diabetes by increasing insulin resistance and/or decreasing insulin production, resulting in elevated blood glucose levels. Animal research with rats has raised concern that glucosamine desensitizes cell membranes to the effects of insulin. However, these animal studies involved intravenous infusion of glucosamine that results in higher serum concentrations than oral intake. Furthermore, in a large 3-year, placebo controlled trial, published in 1999 in the Lancet, blood glucose levels tended to decline slightly in patients treated with glucosamine; whereas glucose levels remained stable in those receiving a placebo. But to complicate matters further, in an unpublished study announced at the Experimental Biology 2000 conference, non-diabetic subjects taking glucosamine sulfate, 1500 mg per day for 12 weeks, had significantly increased insulin levels compared to those taking a placebo. Additional research to determine the effects of glucosamine on blood sugar levels and insulin is needed.

In the meantime, the possibility that long-term treatment with glucosamine could trigger or exacerbate insulin resistance or elevated blood sugar levels cannot be ruled out. Therefore, diabetics should consult their doctor before taking glucosamine sulfate and have their blood sugar levels monitored regularly if they do take the supplement. This is also something that non-diabetics should do as well. My friend is not a diabetic, but she has her blood tested on a regular basis as part of her medical check-ups. A complete blood count includes blood glucose levels. So far hers have been in the normal range. But she will be watchful to see if there is any rise in those levels from her base level.

Glucosamine and Shellfish Allergies

Glucosamine is derived from the shells of crab, lobster, or shrimp. There is, therefore, concern that glucosamine sulfate might cause reactions in people allergic to shellfish, even though glucosamine is not derived from the meaty portion of the shellfish, which is responsible for most allergies. Until more is known, use glucosamine sulfate with caution if you have a shellfish allergy. My friend has such an allergy. She breaks out in hives when she eats shellfish. Thus far, however, she has had no signs of an allergic reaction to glucosamine sulfate in the five years that she has been taking it.

She has decided to continue taking the supplement because she believes it has improved her symptoms through the promotion of cartilage synthesis and repair of damaged joints. She feels that her arthritis have improved rather than deteriorated in the five years she has been taking glucosamine sulfate. Her alternatives are the drugs commonly used to treat osteoarthritis, which suppress symptoms but do nothing to halt the disease process and whose side effects she considers more deleterious.

Next week’s article will be about chondroitin sulfate, another natural therapy reputed to be effective for osteoarthritis and of ten taken in conjunction with glucosamine sulfate. It, too, has side effects. The benefits and the side effects of chondroitin sulfate will be the subject of next week’s column.

Mary Lou Williams, M. Ed., is a lecturer and writer in the field of nutrition. She welcomes inquires. She can be reached at (239) 267-6480.