DEAR DR. ROACH: I am a 23-year-old woman. Recently, my friend experienced a problem with high blood pressure, and for about five days, I followed her diet, which consisted of no added salt or sugar. While taking care of her, I checked my blood pressure once or twice, and it was normal. However, after almost five days, I measured it again and noticed that the diastolic number was consistently below 60 mm Hg. This prompted me to monitor my blood pressure more regularly to see if this was just a temporary issue. Despite reintroducing salt and sugar and increasing my water intake, the diastolic number continued to stay below 60 mm Hg most of the time.

The ongoing low blood pressure readings have led me to consider some past events. In 2022, I experienced my first fainting episode during the summer, followed by another fainting spell during the next summer. I am unsure if it is related, but my last blood test in 2022 showed borderline-low hemoglobin levels, with everything else being normal.

Should I be worried about these consistently low blood pressure readings, especially since I do not have any clear symptoms? Also, can you please provide me with advice concerning my diet? — B.A.N.

ANSWER: A low-salt and low-sugar diet is considered a healthy diet. We do need some salt in our diet, but it is highly unusual for a young person to consume such little sodium that they have adverse health effects. Low blood pressure is very common in young women, with readings of 90/60 mm Hg or lower not unheard of. Although fainting is a bit more likely in people with blood pressure this low, there is the benefit of a much lower risk of heart attack and stroke.

Low hemoglobin levels can also predispose people to fainting, but the most common cause is iron loss due to menstrual bleeding, which has nothing to do with salt or sugar. Iron deficiency is a hypothesis, though, not a diagnosis, and it should be tested by checking iron levels prior to treatment.

The effect of increasing salt in most people is usually a very modest increase in blood pressure by just a few points. A small subset of people have blood pressure that is very responsive to dietary salt, to the point that salt restriction can keep them from needing medication. But most people have kidneys that just get rid of the excess salt, so the blood pressure stays very near to its set point.

DEAR DR. ROACH: After a recent bone density scan, I was told to increase my vitamins C and D and to stop consuming caffeine. What does caffeine do to the bones? — L.

ANSWER: Caffeine causes a small amount of calcium and magnesium loss through the kidneys for a few hours after consumption, which has led some experts to recommend against excess caffeine intake. In fact, the amount of caffeine necessary to cause this effect is higher than most coffee drinkers get in a day. More importantly, a study found that coffee drinkers who are women had somewhat of a lesser risk of osteoporosis than non-coffee drinkers.

I’ve lived long enough to know that many people don’t take well to advice about stopping coffee, so I am very circumspect about doing so. In the case of low bone density or osteoporosis, I recommend increasing dietary calcium rather than stopping coffee.

Vitamin D is appropriate for people who have low vitamin D levels and have or are at risk for osteoporosis, but vitamin C supplementation is only necessary for very rare cases of vitamin C deficiency.