For many years, doctors have told patients who have high blood pressure to restrict their intake of salt. A recent study from Japan confirms that a low-fat diet is far more effective than a low-salt diet in lowering high blood pressure.
Having high blood pressure increases your chances of a stroke or a heart attack. Doctors recommended restricting salt because it causes your body to retain extra water, which expands blood volume and raises blood pressure. So, it appeared logical that restricting salt would decrease blood volume and therefore lower blood pressure. However, we now know that salt restriction rarely lowers high blood pressure.
More recent studies show that low-fat diets are far more effective in lowering blood pressure than salt manipulation. The mechanism remains obscure, but the most likely answer is that low-fat diets help you to lose weight, and weight loss lowers high blood pressure.
Q: My job requires a physical fitness test that includes 100 sit-ups. What can I do to get myself ready in just two months?
A: To train for endurance, you need to follow two principles of training: One is stressing and recovering, and the other is interval sets. All athletic training is done by taking a hard workout and then allowing enough time for your body to recover before you stress your body again. Training for most sports is done by choosing workouts that are hard enough to require 48 hours for your muscles to recover. On one day you do a hard workout, and on the next, you do an easy one or take the day off.
The same principles of training apply to all sports. If each day, you tried to do as many sit-ups as you could, lift the heaviest weights you could or run as fast as you could, you would not improve maximally and you would probably injure yourself.
You can do far more work by using intervals: Do a few sit-ups, rest and then do a few more.
Q: Every summer I worry about catching some disease at our community pool. What can I do to protect myself?
A: The chance of getting AIDS or herpes from your local swimming pool is extremely remote, but you can get warts on the bottom of your feet if you walk around barefoot.
You get AIDS only from infected blood, semen, breast milk and possibly vaginal fluid. You get herpes only from placing the herpes virus on broken skin or mucous membranes. There's no evidence that you can get AIDS or herpes from chlorinated or brominated swimming pools. Studies done at the National Institutes of Health showed that the herpes and AIDS viruses are killed almost immediately by chlorinated water.
You can be infected with herpes by sitting with broken skin on an infected seat or on the side of a pool. The herpes virus can survive up to 4 1/2 hours on spa benches, seats and the sides of a pool. The chance of getting herpes from these areas is not great, but you can protect yourself by placing a towel underneath yourself when you sit on the side of a pool.
You can acquire painful plantar warts on the bottom of your feet by walking barefoot at the pool. You can prevent this by wearing sandals when you get out of the water.
Contaminated water in unchlorinated hot tubs can cause pseudomonas folliculitis: small, itchy blisters and red spots around some of the body's hair follicles.
Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.