Sunday, May 30, 2010

Nuts Prevent Heart Attacks

A review of 25 studies shows that eating nuts (including peanuts) lowers cholesterol to help prevent heart attacks (Archives of Internal Medicine, May 10, 2010). Eating an average of 2.5 ounces of nuts per day lowers total cholesterol 5.1 percent, LDL (the bad cholesterol) 7.4 percent, and triglycerides 10.2 percent. It even lowers Lp(a), a genetic component of cholesterol that increases risk for strokes and heart attacks in young people. The more nuts a person eats, the lower the cholesterol. Those with the highest bad LDL cholesterol had the greatest lowering when they ate nuts.

An earlier review of five large epidemiologic studies and 11 clinical studies showed that eating nuts reduces risk for heart attacks (Nutrition Reviews, May 8, 2001). The most improvement came from eating two ounces (four tablespoons) of nuts five or more times a week. Eating an ounce of nuts more than five times a week can result in a 25 to 39 percent reduction in heart attack risk.

Nuts are a rich source of monounsaturated fatty acids. Before the bad LDL cholesterol can form plaques in arteries, it must be converted to oxidized LDL. LDL formed from monounsaturated fat is highly resistant to oxidation, so the LDL is less likely to be converted to its form that damages arteries. The nuts in these studies included almonds, brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pistachios, walnuts, and peanuts. Among Americans, peanuts account for approximately half of all nuts consumed.

Thursday, May 27, 2010

Strenuous Exercise Prolongs the Lives of Cells

Italian researchers showed that after running a marathon, a person's lymphocytes live longer (BMC Physiology, May 2010). This could help to explain why exercisers live more than 12 years longer than those who do not exercise (British Journal of Sports Medicine, March 2008).

Every cell in your body has a programmable cell death called apoptosis. For example, skin cells live 28 days and then die. Cells lining the inside of your mouth and intestines live 48 hours, and your red blood cells live 120 days. When cells become cancerous, they live forever. They lose apoptosis and forget to die. Cancer cells then transfer to other tissues to prevent them from functioning. For example, breast cancer cells become so abundant that they may travel to your liver and damage it so you lose liver function. They travel to your brain and you lose brain function. Cancer cells kill by preventing other tissues from functioning in your body.

What would happen if your cells lived longer than they are supposed to, but still retained apoptosis and died, only later than they normally do? Perhaps you would live longer. This study shows that running a marathon prolongs the life of cells by increasing many of the messenger chemicals associated with delayed apoptosis, including SIRT1 (an enzyme that contributes to longevity).

Shortened telomeres (chromosome caps) represent aging. An earlier study showed that fifty-year-old competitive marathon runners have telomeres that were almost the same length as those of 20-year-old runners on the German National Team, and more than 40 percent longer than those or inactive men of the same age (Circulation, December 2009; reported in the February 10 eZine)

Thursday, May 20, 2010

Bicycle Riding Posture

Recreational bicycle riders probably should not try to tuck their heads down in the form of racers. A study from Trinity College in Dublin, Ireland shows that "aerodynamic position" (with the head down near the handlebars) causes bicycle riders to tire earlier when they ride fast (European Journal of Applied Physiology, March 2010 and January 2006). Researchers compared how quickly cyclists tired during high-intensity cycling at constant speed in upright and supine postures. During the fatigue tests, riders performed a 10-second all-out effort followed by riding at a fast speed for 50 seconds. They repeated the all-out, 10-second bursts every minute until they couldn't go fast any more. Riding supine caused a drop in power and fatigue earlier than riding upright.

Riding bent over can reduce lung capacity in cyclists who have not trained in an aero position and adapted to it. The limiting factor in how fast a person can ride is the time it takes to move oxygen from the air you breathe into your muscles. If your lung volume is diminished, you take in less oxygen and tire earlier.

Then why do virtually all bicycle racers try to ride lower and lower? Because air resistance slows you down and the lower and narrower you ride, the less air pushes against your body. When you pedal on level ground with no wind blowing, 60 percent of your energy is directed to overcome air resistance against your body. Ed Pavelka, a world-class endurance bicycle racer, says: "The fastest speeds in cycling are obtained on aero bikes with the handlebar well below the height of the saddle. Fatigue is caused by the duration and intensity of effort, and reducing the work you have to do against air resistance is more important than anything else."

If you are not a bicycle racer, you will probably be more comfortable and ride longer if you don't try to get as low as possible. To receive Ed Pavelka's free weekly newsletter, with great information for racers and recreational riders, go to http://www.roadbikerider.com/newsletter.htm

Saturday, May 15, 2010

Muscles: Incredible Health Benefits

Almost all people should do some form of strength training as they age. Aging causes loss of muscles which increases your risk for metabolic syndrome, diabetes, obesity, heart attacks and premature death (Sports Medicine, May 2010). Contracting muscles remove sugar from the bloodstream to prevent high blood sugar levels which damage every cell in your body.

The authors reviewed the world's literature and found 13 placebo-controlled studies of the effect of lifting weights on health in later life. Weight lifting reduced HbA1c (a measure of cell damage caused by sugar stuck on cells), body fat, and systolic blood pressure. It did not affect diastolic blood pressure, triglycerides, HDL, LDL or total cholesterol.

The only way you can enlarge muscles is to exercise them against progressive resistance. However, a recent report explains why middle-aged people are at such high risk for injury when they start a weightlifting program (American Journal of Lifestyle Medicine, May 2010). To enlarge muscles, you have to lift weights heavy enough to cause pain while you lift. This damages muscle fibers. Your immunity responds to this cell damage as it responds to an infection: with pain, swelling, and increases in white blood cells, cytokines and blood flow. You usually recover within hours or days. However, if you repeat a heavy workout before you recover from the previous one, it takes longer to recover and the tissue weakens, rather than being given time to heal and become stronger. You develop a condition called inflammation in which your immunity stays active all the time and attacks your own body (in the same way that it attacks invading germs) to prevent healing. Older people have exaggerated changes of inflammation in their muscles (American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, April 2010). If you continue to take stress and recover workouts over many months and years, your muscles become stronger and heal faster so you can lift heavier weights to grow larger muscles.

If you are a middle-aged person who wants to start a weight lifting program to gain the incredible health benefits of being stronger and having larger muscles, and at the same time, avoid the extremely high rate of injury in older weight lifters, you should avoid lifting heavy weights when your muscles feel sore and are still damaged from your previous intense workout. Check with your doctor to see if you have any condition that could be aggravated by lifting weights.

The first rule is that beginners should lift light for several months before they try to lift heavy. Join a gym and use 10 to 20 machines every day. Pick the heaviest weight that you can lift 10 times in a row comfortably without hurting, and do this every day. If you feel sore, take a day or more off. As it becomes easier to lift a weight, increase the repetitions until you can lift that weight 25 times in a row without discomfort.

After you have followed this program for several months, you are probably ready to lift heavier weights that cause pain while you lift them. Unfortunately, the correct way to grow muscles also puts you at increased risk for injuring yourself. Pain is necessary for the muscle damage to grow larger and stronger muscles. I recommend getting special instruction on how to perform multiple sets that hurt, using proper form to minimize the risk of injury. Many lifters pick the heaviest weight that they can lift 10 times in a row, do three sets of 10 and feel very sore in their last set. After an intense workout, you should not lift heavy again until the soreness goes away. More

Tuesday, May 11, 2010

Salt for Warm Weather Exercise

This month, two major reports in medical journals claim that getting people to reduce their intake of salt will save lives, prevent heart attacks and markedly reduce health costs (Annals of Internal Medicine, April 2010; NEJM, April 22, 2010). That may be true for many people who do not exercise, but for heavy exercisers and athletes, particularly those who are also vegetarians, it can cause cramps, fatigue, injuries and even death.

During World War II, Dr. James Gamble of Harvard Medical School showed that salt (sodium) is the only mineral that people need to be concerned about when they work or exercise for long periods in hot weather. After Gamble published his studies, people who work in the heat were given salt tablets, which is such a concentrated form of salt that they can cause nausea and stomach irritation. In the 1960s, doctors became concerned that too much salt can cause high blood pressure, so they started recommending low-salt diets.

Excessive intake of salt causes high blood pressure in some, but not all, people. High blood pressure increases risk for heart attacks, strokes, and kidney damage. Many middle-aged people who start an exercise program lose their tendency to develop high blood pressure when they take in extra salt (Journal of Human Hypertension, May 2006).

Not taking in salt when you exercise for more than two to four hours can prevent you from retaining the water that you drink. It can also block thirst, so you may not know that you are dehydrated. Thirst is a late sign of dehydration. You lose water during exercise primarily through sweating, and sweat contains a far lower concentration of salt than blood. So during exercise, you lose far more water than salt, causing the concentration of salt in the blood to rise. A person will not feel thirsty until the concentration of salt in the blood rises high enough to trip off thirst osmoreceptors in the brain, and it takes a loss of two to four pints of fluid to do that.

You need salt to retain the fluid you drink while exercising. In one study, female competitive distance runners took in drinks with different concentration of salt during a four- hour run (British Journal of Sports Medicine, August 2003). Ninety-two percent of those who took in plain water with no additional salt developed low blood levels of salt. Taking in fluid without also taking in adequate amounts of salt dilutes the bloodstream, so that the concentration of salt in the blood is lower than that in brain cells. This causes fluid to move from the low-salt blood into the high-salt brain, causing the brain to swell which can cause seizures and death. However, the low salt syndrome, hyponatremia, that can kill athletes is usually caused by taking in far too much fluid, rather than from not taking in enough salt. Taking extra salt just prior to competition can help you exercise longer and harder (Medicine and Science in Sports and Exercise, January 2007; Clinical Journal of Sport Medicine, January 2007). Athletes who took the extra salt had larger blood volumes and greater endurance. Salt makes you thirsty earlier so you drink more, and salt in your body holds water so you have more water available to meet your needs. Salty drinks taste bad, so it is easier to meet your needs with salted foods. If you plan to exercise for more than a couple hours in hot weather, drink one or two cups of the liquid of your choice each hour and eat a salty food such as salted peanuts.

Taking extra salt during prolonged exercise increases thirst so you drink more fluids, and prevents blood salt levels from dropping so low that you can become tired, develop muscle cramps, and even die. You can keep yourself fresh during extended exercise by eating foods with salt and drinking frequently, before you feel hungry or thirsty. Once you feel hungry or thirsty, you will find it very difficult to regain your strength. Commercial sports drinks help increase endurance by their caffeine, sugar, salt, and to a lesser degree, protein content. It is unlikely that any other component improves performance (The Physician and Sportsmedicine, April 2010).

What exercisers and athletes should do: I recommend that you buy a blood pressure cuff and take your blood pressure a few times a week before you go to bed. If your blood pressure remains above 120 systolic, you have high blood pressure and should check with your doctor. The amount of salt people need varies greatly from person to person. If you exercise regularly for more than a couple hours, particularly in hot weather, you need extra salt. You also need more sugar in hot weather to increase endurance. When you run out of sugar stored in muscles (glycogen), your oxygen requirements rise significantly and you have to slow down. We drink Pepsi and eat salted peanuts on long rides in the summer. You may prefer pretzels or any other salty snack.

Tuesday, May 04, 2010

Preventing Senility

A study from Columbia University in New York shows that those least likely to develop Alzheimer's disease eat a diet rich in omega-3 fatty acids, omega-6 fatty acids, vitamin E, vitamin B12 and folate, in foods such as nuts, fish, tomatoes, olive oil, poultry, broccoli and other cruciferous vegetables, fruits, and dark green leafy vegetables. They eat less red meat, organ meats and high-fat dairy products (Archives of Neurology, April 2010).

Alzheimer's disease is associated with an overactive immunity called inflammation. Your immunity is good for you because it prevents germs from invading your body. However if your immunity is overactive, it uses the same chemicals that it uses to destroy invading bacteria to punch holes in your arteries and damage your brain (Nature Medicine, August 2009). The foods recommended in the Columbia study reduce inflammation, while red meat and high fat dairy products may increase inflammation. Being overweight also increases risk for Alzheimer's disease because full fat cells release hormones that cause inflammation (Biochimica et Biophysica Acta, May 2009). More on Alzheimer's