A reader reports that L-lysine helps stave off mouth sores. Can it help prevent dementia too?

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Q: Whenever I feel a cold sore coming on (the telltale “tingly feeling”), I take L-lysine tablets. When I take 1,000 milligrams a day, often the cold sore will never develop. If it got a head start, it disappears several days sooner than it would otherwise.

I read your article about herpes and cold sores being linked to Alzheimer’s disease. Is there anything in L-lysine that could be helpful in preventing dementia? I’m going to start taking it every day, maybe 500 mg a day.

A: There are few well-controlled long-term studies of using the amino acid L-lysine to prevent or treat cold sores (HSV-1 or herpes labialis). A review in the dermatology journal Cutis (July 2005) concluded that L-lysine benefits are unclear. It might help prevent recurrences in selected patients. That said, many readers report success like yours.

There is growing evidence to suggest a link between herpes infection and the risk of developing Alzheimer’s disease (Frontiers in Genetics, Sept. 10, 2018). A study from Taiwan found that people taking antiviral medicines for herpes were significantly less likely to develop dementia (Neurotherapeutics, April 2018). Whether L-lysine would be beneficial remains to be determined.

Q: I’ve read in your column that grape juice and pectin may help relieve arthritis pain. I would like to try it, but I have diabetes. Grape juice has a lot of sugar. Does any lower-sugar liquid seem to work?

A: Other readers also have shared your concern about the sugar in grape juice. One recommended low-sugar grape juice. Others have suggested pomegranate juice or tart cherry juice as alternatives. Neither is low in sugar, but they do have fewer calories than Concord grape juice.

You may be interested in other arthritis remedies that are less likely to affect your blood sugar. They include unflavored Knox gelatin, bromelain, boswellia, curcumin, ginger, ashwagandha and stinging nettle. You can learn more about these options in our book “Alternatives for Arthritis.” To purchase a copy, please send $12.95 plus $3 shipping and handling to: Graedons’ People’s Pharmacy, Dept. AFA, P.O. Box 52027, Durham, NC 27717-2027. It also can be ordered at www.PeoplesPharmacy.com.

Q: I recently learned of a 2005 Danish study that showed a correlation between atrial fibrillation and fish oil. My wife stopped taking 1.2 grams of fish oil daily and stopped fibrillating. On her doctor’s advice, she no longer has to take a drug for this problem.

Do you have any information that you can add to support a correlation between fish oil and fibrillation?

A: Your question intrigued us because research so far has looked at fish oil for preventing rather than causing atrial fibrillation. Most of the fish-oil trials have been either inconclusive or shown no benefit for this dangerous heart-rhythm abnormality.

The Danish study you cited (American Journal of Clinical Nutrition, January 2005) concluded that fish consumption did not reduce the risk of atrial fibrillation. A more recent Danish study reported that people getting a moderate amount of fish oil from their diets were less likely to experience atrial fibrillation than those eating more or less fish (Europace, November 2014). The best dose provided about half as much omega-3 fats as your wife was taking.