Q. I was rushed to the emergency department a few weeks ago because of low sodium. I have always been careful to eat a healthy diet low in salt. I’ve also made it a habit to drink a lot of water to stay well hydrated.

As a consequence of my fluid intake and low-sodium diet, I actually ended up with hyponatremia. The doctor advised me not to drink too much water because it can lead to an imbalance of electrolytes. I’d like to warn others of this danger.

A. Hyponatremia is a life-threatening shortage of sodium in the bloodstream. Elite athletes sometimes end up with this condition if they drink too much water and don’t replace electrolytes.

A low-salt diet rarely results in hyponatremia by itself, but some people may not do well on a strict regimen. One reader shared this story:

“My uncle Jim followed a low-salt diet and suffered from dizziness to the point of vertigo. To keep his balance while walking, he had to hold onto the walls or furniture. He suffered for many months and consulted several physicians. Finally one suggested that he increase his sodium intake. This immediately cured his problem.”

Q. How good is green coffee bean extract for weight loss?

A. A meta-analysis of research on green coffee bean extract as a weight-loss aid suggests that it helps people lose about two pounds a month (Gastroenterology Research and Practice online, Aug. 31, 2010). Consumerlab.com has found that pills containing green coffee bean extract are of variable quality, however.