Tuesday, December 03, 2013

All Future Blog Posts will be at DrMirkin.com

Hello!
Thanks for reading my blog for the past several years.
I would love to have you continue as a reader, but you will need to go to
DrMirkin.com

If you would like to receive weekly emails with a digest of that week's news, please sign up for my free weekly newsletter ("Dr. Mirkin's Fitness and Health eZine")

You will find a box to enter your email address on any page of DrMirkin.com

Sincerely,
Dr. Gabe Mirkin
www.drmirkin.com


Tuesday, March 26, 2013

Most Running Shoes Slow You Down and Increase Risk of Injuries

Research presented at the Annual Meeting of the American Academy of Orthopedic Surgeons (March 19, 2013) and to be published next month (Journal of Strength & Conditioning Research, April 2013) shows that running shoes with thick heels can slow you down. They may also increase your chances of injuring yourself.

Adolescent competitive track athletes ran on a treadmill in heavily padded-at-the-heel sneakers, track shoes or barefoot, at four different speeds.

CHANGING FOOTWEAR CHANGES LANDING: Wearing cushioned heel sneakers caused the runners to land on their heel 70 percent of the time at all speeds. Wearing track shoes caused them to land on their heels less than 35 percent of the time. Running barefoot, they landed on their heels less than 30 percent of the time. Shoes with cushioned heels caused runners to land on their heels, while wearing track shoes or no shoes at all caused a forefoot or mid-foot landing.

HARM FROM HEEL STRIKE: Barefoot runners tend to land on their mid-foot or forefoot. Cushioned heels on running shoes tempt runners to take longer strides, so they land on their heels and smack the ground with a much greater force.

Landing on your heel causes the force of your heel striking the ground to be transmitted with more direct and greater force to your hips and knees. Running in flat-soled shoes that promote a forefoot strike transmits less foot-strike force up your leg to your back and helps to prevent hip and knee damage.

One study reports that running barefoot, in and of itself, is neither good nor bad. The key is to decrease the force of your foot hitting the ground. Running barefoot encourages you to take a shorter stride and hit the ground with less force (Journal of Strength and Conditioning Research, 2012; 26 (8): 2021).

WHY RUNNERS ARE INJURED SO FREQUENTLY: Harvard University evolutionary biologist Dan Lieberman claims that modern running shoes may explain why fifty percent of serious runners are injured at least once a year. He also believes that people with joint replacements of their lower extremities should not run (Nature, January, 2010).

LANDING ON YOUR HEELS: Modern running shoes have features that cause runners to land on their heels with forces of at least three times body weight at six-minute mile pace. The faster a runner runs, the greater the force, which causes stress fractures of the feet and lower legs, shin splints, tears in the fascia on the bottom of the feet, knee and hip pain, tendon and joint damage and more.

LANDING ON YOUR FOREFOOT: Hitting the ground with the heel first generates tremendous force because it stops the foot suddenly and temporarily. On the other hand, landing on the front of the foot allows the foot to keep on moving as the heel is lowered toward the ground to distribute the forces throughout the entire lower leg. For example, drop a pen on the tip of one end. It hits with tremendous force because it stops when it hits the ground and then falls forward. However if the pen were dropped on the side of one end, it would hit the ground with much less force because after hitting on the side of one end, the force would be distributed as the pen falls backward to the other end.

EXCESSIVE PRONATION: In the 1960s doctors thought that the high frequency of running injuries was caused by excessive pronation, a rolling inward of the foot after the heel strikes the ground. They felt that the foot rolled inward toward the arch to dissipate the tremendous heel strike forces.

This, in turn, caused the lower leg to twist inward and they blamed the frequent running injuries on the inward twisting motion of the leg after heel strike. They invented running shoes with special arch supports called orthotics to limit inward rolling and built running shoes with thick heels to cushion some of the shock of the heel hitting the ground. These features increase the likelihood that runners land on their heels. Today the standard treatment for many running injuries is special orthotics and padded heels to help heal running injuries. I have written about and prescribed these features for many of my patients with running injuries.

LESS FORCE WITH FOREFOOT LANDING: Dr. Lieberman felt that if the runners ran barefoot, they would be less likely to land on their heels and therefore would not need to wear shoes with padded heels and orthotics. He has shown in elegant experiments that landing on the front part of the foot reduces the force of the foot strike very significantly.

However, he has no data to show that running injuries can be prevented by running barefoot. He has shown only that modern running shoes tend to encourage a runner to land on his heels, and that heel strike generates more force than front foot strike. Also, many roads have stones and cut glass that can cause injuries, and most runners have such thin skin on the bottom of their feet that they couldn't possibly run barefoot or in thin soled shoes.

TODAY DOCTORS STILL PRESCRIBE ORTHOTICS: Most sports medicine doctors treat many running injuries with running shoes with orthotics and thick heels. Now we have running shoes with very thin soles and minimal heels (such as Vibram Five Fingers or Dunlop Volley). Indeed, Vibram supported Dr. Lieberman's studies.

Thursday, March 14, 2013

Who Gets High Blood Pressure from Salt?

Not everyone gets high blood pressure from taking in too much salt. The people who are most likely to get high blood pressure from taking in too much salt are those whose cells do not respond well to insulin (Hypertension, Jan 2013). People whose cells do not respond well to insulin are called "insulin resistant". On the other hand, those whose cells respond well to insulin are called "insulin sensitive". They can develop high blood pressure from not taking in enough salt.

SALT RESTRICTION ISN'T FOR EVERYONE. Thirty-five years ago, researchers first described people whose blood pressure and weight rise when they take in extra salt. They are called "salt sensitive". They gain weight because their kidneys cannot get rid of the extra salt. The extra weight is caused by retaining extra fluid. Eventually, taking too much salt can cause salt-sensitive people to suffer kidney damage as evidenced by leaking protein (albumin) into their urine. (Diabetes Res Clin Pract, April 1998;39 Suppl:S15-26). Those who do not develop high blood pressure when they take in large amounts of salt are called "salt insensitive".

DEFINITION OF INSULIN RESISTANCE: Most cases of high blood sugar in diabetics are caused by inability of cells to respond to insulin, not by lack of insulin. Before insulin can do its job of driving sugar from the bloodstream into cells, it must first attach to special hooks on the outer cell surface called insulin receptors. Anything that blocks insulin from attaching to its receptors on the surface of cells can cause high blood sugar levels and high blood pressure. People who respond normally to insulin usually do not get high blood pressure from taking in too much salt. Insulin receptors are blocked by eating red meat, eating animal saturated fat, lack of exercise, excess fat in fat cells, overweight, fat stored in the belly, not eating enough fruits and vegetables, and lack of vitamin D.

THIS STUDY: People who are salt sensitive and have high blood pressure are usually fatter, and have higher blood levels of creatinine, cholesterol, aldosterone, glucose and insulin (Hypertension, Jan 2013).
• Creatinine goes up when the kindeys are damaged.
• Aldosterone is secreted by the adrenal glands to cause the body to retain salt.
• Blood sugar goes up when insulin receptors are blocked.
• Insulin goes up when blood sugar levels rise.

SALT-SENSITIVE PEOPLE HAVE A HIGH RISE IN INSULIN WHEN THEY TAKE IN EXTRA SALT. Fasting blood sugar levels are usually normal and did not differ between salt sensitive and salt resistant people with high blood pressure regardless of how much salt they took in. However fasting blood levels of insulin increased in salt sensitive patients when they took in extra salt (Am J Hypertens, 1998 (Apr);11(4 Pt 1):397-402). . The extra salt causes high insulin levels which constrict arteries to raise blood pressure. People who have insulin resistance at low salt intake will have much more insulin resistance at a higher intake of salt. For them, a high salt intake increases blood pressure, insulin, and blood sugar.

HOW TO TELL IF YOU ARE INSULIN INSENSITIVE AND THEREFORE PROBABLY SHOULD RESTRICT SALT: People who are insulin insensitive usually have what is called metabolic syndrome. You have metabolic syndrome if you have any three of the following:
• storing fat primarily in your belly
• having small hips
• being overweight
• having blood triglycerides (>150)
• having blood HDL cholesterol (<40 br=""> • having a fatty liver
• having a fasting blood sugar >100 (HbA1c> 5.7)
• having high insulin levels
• having high blood pressure

EVERYONE SHOULD CHECK HIS OR HER BLOOD PRESSURE: Get a blood pressure cuff. Take your blood pressure just before you go to bed. If your systolic blood pressure is above 120 much of the time, you have high blood pressure and should check with your doctor to see if you are salt sensitive and therefore, should restrict salt (and make other lifestyle changes).

Monday, January 14, 2013

Being Overweight Does Not Prolong Lives

A recent meta-analysis of a hundred large studies showed that being a little bit overweight offers slight protection (a six percent decrease) from premature death (Journal of the American Medical Association, January 2, 2013). This study has been widely reported in the media, with headlines such as "Our Imaginary Weight Problem".

Instead of being told that overweight is beneficial, people should continue to hear that excess weight shortens lives, particularly if their fat is stored in the belly.

WHY THE REPORT IS FLAWED: People with wasting diseases usually lose weight long before they die. All chronic diseases that shorten lives have a tendency to make people lose weight. Heart diseases, cancers, late stages of diabetes, kidney failure, arthritis, and even aging itself, usually cause weight loss before death (J Cachexia Sarcopenia Muscle, 2012;3(1):1-4). Weight loss that precedes death can last as long as 10 to 20 years, so it is impossible to correct epidemiological studies for this effect.

As people with wasting diseases approach death, their rate of weight loss increases dramatically. Sicker people, and those closer to death, lose weight faster than people with wasting diseases whose immunities are successfully holding their diseases at bay. It is true that people who have diseases that will eventually kill them may live longer as long as they do not lose weight.

EVEN A LITTLE BIT OF FAT IN YOUR BELLY CAN KILL YOU. Not all fat is harmful. Fat stored on your hips and upper legs protects you from disease. It does not turn on your immunity or cause inflammation; and it helps to prevent diabetes and heart attacks.

However, fat located inside your belly and around your organs:
• turns on your immunity to cause inflammation that leads to cancers, heart attacks, strokes, diabetes, inflammatory types of arthritis and so forth; and
• blocks insulin receptors to raise blood sugar levels, leading to diabetes that can damage every cell in your body.

This large study should not make you believe that being overweight is beneficial. You should maintain a healthful weight and try to lose any excess fat that you have in your belly. Belly fat is harmful and shortens lives.

Thursday, August 30, 2012

Coconut Water Is Not a Special Sports Drink

The headline reads: "Coconut Water Is an Excellent Sports Drink" (Science Daily, August 20, 2012; presented at the 244th National Meeting & Exposition of the American Chemical Society (ACS) in Philadelphia). The author states: "Coconut water is a natural drink that has everything your average sports drink has and more. It has five times more potassium than Gatorade or Powerade. Whenever you get cramps in your muscles, potassium will help you to get rid of the cramps. It's a healthy drink that replenishes the nutrients that your body has lost during a moderate workout."

This flies in the face of everything I have learned about potassium:

• POTASSIUM DEFICIENCY IS NOT A PROBLEM IN HEALTHY EXERCISERS. In 1967, Dave Costill of Ball State University tried to create potassium deficiency in runners. He couldn't do it because potassium is found in all foods except refined sugar, and his athletes would not stay on a diet that consisted only of hard candy. The kidneys and sweat glands conserve potassium so well that you don't lose much. If an athlete develops potassium deficiency, it is usually caused by drugs, such as diuretics or corticosteroids, or by diarrhea or repeated vomiting. Some athletes try to control their weight by making themselves vomit. This is called bulemia, and the person usually denies vomiting. Their physicians can prove that they are vomiting by ordering blood and urine tests. If blood levels of potassium are low and urine levels are high, vomiting is the likely cause.

• POTASSIUM DEFICIENCY IS NOT A USUAL CAUSE OF CRAMPS OR TIREDNESS IN EXERCISERS. Tiredness and cramps in athletes can have many causes, but lack of potassium in the diet is not one of them. Athletes who are tired and suffer frequent muscle cramps need an evaluation for other causes of chronic tiredness. If none can be found, the athlete may be overtraining and should talk to the coach or a personal trainer about changing workouts.

• THE ONLY MINERAL THAT EXERCISERS NEED TO REPLACE IS SODIUM, COMMON TABLE SALT. The definitive studies on minerals and exercise were done during World War II. Dr. James Gamble of Harvard Medical School paid medical students to lie on rafts in his swimming pool, taking various amounts of fluids and salt and having blood drawn to measure salt and mineral levels. He showed that you have to take a lot of salt when you exercise for several hours, particularly in hot weather. For many years after that, students at Harvard Medical School heard Dr. Gamble give his lectures on minerals and exercise, and today, most serious students still read the Gamble lectures published in 1958 by The Harvard University Press. Now, more than sixty years later, nobody has improved on his research.

After Gamble published his studies, people who worked or exercised in hot weather were given salt tablets. Then doctors became concerned because they thought that a person could have his blood pressure raised by taking in too much salt, so they recommended restricting salt, causing many people to suffer heat stroke and dehydration during hot weather exercise. A low-salt diet does not lower high blood pressure for most people. A high-salt diet causes high blood pressure usually only in people with high blood insulin levels. Eating salty foods and drinks when you exercise for more than two hours is unlikely to raise blood pressure. We don't recommend salt tablets because they can cause nausea and vomiting, but you can use table salt or any salty food.

If you don't take salt and fluids during extended exercise in hot weather, you will tire earlier and increase your risk for heat stroke, dehydration and cramps. We eat heavily- salted potato chips or peanuts and drink fluids at least every 15 minutes when we ride in hot weather. Potassium deficiency doesn't occur in healthy athletes. The only mineral that athletes need to take when they exercise is salt.

If you like the taste of coconut water, it is a perfectly satisfactory fluid to take during exercise, but don't believe claims that it has any special benefits as a sports drink. If you use it during intense exercise, you will need other sources of sugar and salt.

Friday, June 15, 2012

Calcium Pills May Increase Heart Attack Risk

A German study followed 24,000 men and women, ages 35 to 64, for 11 years and found that those who took calcium supplements were 86 percent more likely to suffer heart attacks than those who do not (Heart, published online May 23, 2012). More than 60 percent of North American women over 60 take calcium supplements to help prevent bone fractures (U.S. Centers for Disease Control and Prevention's National Center for Health Statistics, 2011).

In the study from Germany, there was no significant difference in death from stroke or heart attack no matter how much calcium people got FROM FOODS. There was even a suggestion that increased calcium intake from foods was associated with increased heart attack risk. Other factors that increase heart attack risk were excluded from the study.

Another study showed that calcium pills may reduce fractures by 10 percent, but can INCREASE risk for heart attacks by 25 percent (British Medial Journal, published online July 2010). Thus if 1,000 people were given calcium for five years, there would be 26 fractures prevented but there would also be 14 heart attacks, 10 strokes and 13 deaths more than in people not taking calcium pills.

OTHER STUDIES SHOW THAT TOO MUCH CALCIUM FROM FOOD AND PILLS INCREASES HEART ATTACK RISK: Eight studies followed more than 10,000 patients, average age of 68 years, for an average 3.8 years, taking 500 to 1400 mg calcium daily. They had 1.3 times the chance of suffering a heart attack as people taking no calcium pills. Those taking more than 805 mg calcium per day from food without pills were 1.86 times more likely to suffer heart attacks (British Medical Journal, 2010;341:3691).

HOW TOO MUCH CALCIUM CAN CAUSE HEART ATTACKS: Calcium supplements raise blood calcium levels which increases chances of forming clots, a major cause of heart attacks and strokes (J Bone Miner Res. 1997;12:1959-70). Calcium supplements can thicken neck artery plaques (Atherosclerosis, 2007;194:426-32) and calcify main arteries (J Bone Miner Res, 2010;25:505-12). Taking calcium without also taking vitamin D increases heart attack risk even further, because calcium blocks the activation of vitamin D to cause a relative deficiency of that vitamin.

TOO MUCH VITAMIN D RAISES CALCIUM: Vitamin D markedly increases calcium absorption to raise blood calcium levels. Researchers at the University of Copenhagen followed almost 250,000 people and found that people with blood levels of hydroxy vitamin D below 10 nmol/L were 2.3 times more likely to die prematurely and those with levels above 140 nmol/L were 1.42 times more likely to die prematurely (Journal of Clinical Endocrinology and Metabolism, published online May 2012). So both low and high calcium levels are harmful.

GET YOUR CALCIUM FROM FOOD, NOT PILLS: Adult men and women need 1,000 to 1,200 milligrams of calcium daily, according to the National Institutes of Health. You get that amount from a cup of yogurt, a glass of milk and a slice of cheese. If you avoid dairy products, you could meet your calcium requirement with a bowl of enriched cereal, a glass of fortified orange juice, half a cup of tofu and a piece of salmon.

GET YOUR VITAMIN D FROM SUN OR PILLS: You cannot meet your needs for vitamin D from foods. You have to depend on the sun or pills. Get a blood test for hydroxy vitamin D. If it is above 75 nmol/L, you are fine. If it is above 140 nmol/L, you are taking overdoses of vitamin D and should reduce your intake of vitamin D pills.

If your blood level of hydroxy vitamin D is below 50 nmol/L, you need more sunlight or you can try taking up to 2000 IU of vitamin D per day for a month. Once blood levels of vitamin D are above 50 nmol/l, you should reduce your intake of the pills to 1000 IU per day or less.

Sunday, May 27, 2012

How to Recover from Muscle Soreness Caused by Intense Exercise

Muscle soreness should be part of every exercise program. If you don't exercise intensely enough on one day to have sore muscles on the next, you will not gain maximum fitness and you are also losing out on many of the health benefits of exercise. The benefits of exercise are much greater with intense exercise than with casual exercising.

You must damage your muscles to make them grow and become stronger. When muscles heal, they are stronger than they were before you damaged them. All athletes train by "stressing and recovering". On one day, they take a hard workout in which they feel their muscles burning. Eight to 24 hours after they finish this intense exercise, their muscles start to feel sore. This is called Delayed Onset Muscle Soreness (DOMS). Then they take easy workouts until the soreness is gone, which means that their muscles have healed.

DOMS IS CAUSED BY MUSCLE DAMAGE. Muscles are made up of fibers. The fibers are made up of a series of protein blocks called sarcomeres that are lined in a long chain. When you stretch a muscle, you stretch apart the sarcomeres in the chain. When sarcomeres are stretched too far, they tear. Your body treats these tears in the same way that it treats all injuries, by a process called inflammation. Eight to 24 hours after an intense workout, you suffer swelling, stiffness and pain. The most beneficial intense exercise program is:

• severe enough to cause muscle pain on the next day, and
• usually allows you to recover almost completely within 48 hours.

ACTIVE, NOT PASSIVE, RECOVERY: When athletes feel soreness in their muscles, they rarely take days off. Neither should you. Keeping sore muscles moving makes them more fibrous and tougher when they heal, so you can withstand greater forces and more intense workouts on your hard days. Plan to go at low intensity for as many days as it takes for the soreness to go away. Most athletes try to work out just hard enough so that they recover and are ready for their next hard workout in 48 hours.

TIMING MEALS TO RECOVER FASTER: You do not need to load extra food to recover faster. Taking in too much food fills your muscle cells with fat, and extra fat in cells blocks the cell's ability to take in and use sugar. Sugar is the main source of energy for your muscles during intense exercise. Using sugar to drive your muscles helps them to move faster and with more strength.

Timing of meals is more important than how much food you eat. Eating protein- and carbohydrate-containing foods helps you recover faster, and the best time to start eating is as soon as you finish a hard workout.

At rest, muscles are inactive. Almost no sugar enters the resting muscle cell from the bloodstream (J. Clin. Invest. 1971; 50: 2715-2725). Almost all cells in your body usually require insulin to drive sugar into their cells. However during exercise your muscles (and your brain) can take sugar into their cells without needing insulin. Exercising muscles are also incredibly sensitive to insulin and take up sugar into their cells at a rapid rate. This effect lasts maximally for up to an hour after you finish exercising and disappears almost completely in around 17 hours. The best time to eat for recovery is when your cells are maximally responsive to insulin, and that is within a short time after you finish exercising.

Not only does insulin drive sugar into muscle cells, it also drives in protein building blocks, called amino acids. The sugar replaces the fuel for muscle cells. The protein hastens repair of damaged muscle. Waiting to eat for more than an hour after finishing an intense workout delays recovery.

WHAT TO EAT AFTER YOUR INTENSE WORKOUTS: Fatigue is caused by low levels of sugar, protein, water and salt. You can replace all of these with ordinary foods and drinks. If you are a vegetarian, you can replace your protein with combinations of grains and beans. You can replace carbohydrates by eating virtually any fruits, vegetables, whole grains, beans, seeds and nuts.

A recovery meal for a vegetarian could include corn, beans, water, bread, and fruits, nuts and vegetables. If you prefer animal tissue, you can get your protein from fish, poultry or meat. Special sports drinks and sports supplements are made from ordinary foods and therefore offer no advantage whatever over regular foods.

BODY MASSAGE: Many older studies have shown that massage does not help you recover faster from DOMS. Recently, researchers at McMaster University in Hamilton, Ontario showed that deep massage after an intense workout causes muscles to enlarge and grow new mitochondria (Science Translational Medicine, published online Feb, 2012). This is amazing. Enlarging and adding mitochondria can help you run faster, lift heavier weights, and even prevent heart attacks and certain cancers. See http://www.drmirkin.com/public/ezine021212.html (second article).

NSAIDS DELAY DOMS RECOVERY: Non-steroidal anti-inflammatory drugs (NSAIDS), such as ibuprofen, may help relieve pain, but they also can block muscle repair and delay healing. See http://www.drmirkin.com/public/ezine090609.html

HOT BATHS: Most research shows that a hot bath is not much better than doing nothing in helping muscles recover from exercise (European Journal of Applied Physiology, March 2006),

COLD OR ICE BATHS: A recent review of 17 small trials, involving 366 participants, showed a minor decrease in DOMS with ice water baths. They found "little quality research" on the subject and "no consistent method of cold water immersion" (Cochrane Library, published online February 15, 2012). Cold water immersion can reduce swelling associated with injury, but has not been proven to speed the healing of DOMS.