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Metabolic Syndrome Increases Salt's Effect on Blood Pressure

Most doctors recommend salt restriction for all their patients, even though many will not develop high blood pressure from high-salt intake and some may even be harmed if they restrict salt. Heavy exercisers lose so much salt that they have to take in lots of salt just to replace what they lose through sweat.

A study from China shows that people with metabolic syndrome are the ones who are most likely to develop high blood pressure from a high-salt diet and that high levels of insulin may cause the rise of blood pressure that is associated with increased salt intake (Lancet, published online March 2, 2009). Metabolic syndrome occurs when a person's cells lose their ability to respond adequately to insulin and blood levels of sugar rise too high. It is caused by eating too much refined carbohydrates, being overweight, not exercising, and lacking vitamin D and is characterized by storing fat primarily in the belly, having a thick neck, high blood triglycerides, low blood good HDL cholesterol, high blood sugar, and eventually liver damage and all the side effects of diabetes. People with metabolic syndrome had a greater rise in blood pressure with increased salt intake and drop in blood pressure with salt restriction. The more risk factors for metabolic syndrome a person had, the greater the rise and fall of blood pressure with changes in salt intake.

If you are concerned about your blood pressure, you can buy an inexpensive wrist cuff and check your blood pressure at bedtime. If it is below 120, you do not need to restrict salt. If you store fat primarily in your belly rather than your hips, your HDL is below 40, your triglycerides are above 175, or you have a blood sugar above 100 two hours after a meal or an HBA1C above 5.9, you probably should restrict salt and definitely should work to correct the causes of metabolic syndrome (described above).

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Follow-up on the controversy about bone loss in cyclists:

Last week I quoted a study that concluded: "Sprint cyclists, and to a lesser extent distance cyclists, had greater tibia and radius bone strength surrogates than the controls, with tibial bone measures being well preserved with age in all groups. This suggests that competition-based cycling and the associated training regimen is beneficial in preserving average or above-average bone strength surrogates into old age in men" (Medicine & Science in Sports & Exercise, March 2009).

Several readers responded, quoting other studies that showed competitive cyclists have lower bone mineral density in their spines than moderately-active, aged-matched men (Medicine & Science in Sports & Exercise, February 2009; Osteoporosis International Reports, August 2003). These studies have been interpreted to mean that cycling increases risk for bone fractures beyond what you would expect from just falling off the bike.

I cannot find any studies showing that cycling weakens bones to increase fracture risk. Bone density is associated with bone strength, but does not measure it. The only way to measure bone strength is to see how much force it takes at break a bone. For example, birds have strong bones that are not very dense.

The theory that the act of cycling weakens bones flies in the face of our current understanding of bone metabolism. If indeed cyclists suffer from weak bones (and I do not believe that they do), the cause would be something other than riding a bicycle. Bones are constantly remodeling. Cells called osteoblasts bring in calcium to bones while cells called osteoclasts take calcium out. Any force on bones increases, and lack of force decreases, the rate of bone formation. Astronauts in space lose bone because lack of force blocks their ability to respond to Insulin Like Growth Factor-1 that stimulates bone growth (Journal of Bone and Mineral Research, March 2004). All competitive cyclists know that hammering on the pedals while pulling up on their handle bars puts tremendous force on every muscle and bone in their bodies, and this should stimulate bone growth.

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Reports from drmirkin.com

Osteoporosis and salt
Exercise for arthritis
Treatment of low back pain

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Recipe of the Week:

Mushroom Nibbles

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June 22nd, 2013
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
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