Thursday, October 30, 2008

Check Vitamin D Levels this Winter

In this newsletter I have reported that low vitamin D levels are associated with increased risk for heart attacks, strokes, at least 17 different cancers, diabetes, autoimmune diseases, depression and osteoporosis. Adequate blood levels of vitamin D are thought to be over 75nmol/L. Researchers at the University of Toronto have now shown that in the winter, more than 93 percent of the people in Toronto have concentrations below 75 nmol/L, and 75 percent have concentrations below 50 nmol/L (BMC Public Health, September 26, 2008).

Only those with light skins had average vitamin D intakes exceeding the current Recommended Adequate Intake (RAI = 200 IU/day). Those with dark skin and/or excess weight had very low levels of vitamin D. Dark skin blocks ultraviolet light. Obesity sequesters vitamin D so it is not available for use. Aging also lowers vitamin D levels as the skin of older people doesn't make vitamin D as well as during younger years.

In the wintertime, I recommend getting a blood test called D3. If it is below 75 nmol/L, you need more sunlight or vitamin D pills. The blood test for the active form of vitamin D (1,25 dihydroxy-vitamin D) is of little value as it often is normal when a person has a severe deficiency. Lack of vitamin D causes the parathryroid gland to produce massive amounts of parathyroid hormone that causes these falsely high levels. More on vitamin D

Thursday, October 23, 2008

Stretching Pros and Cons

Researchers at the University of Sydney in Australia reviewed the world's literature and concluded that stretching does not prevent muscle soreness that follows vigorous exercise (1). Athletes train by taking a hard workout, feeling sore the next day, and then taking easy workouts for as many days as it takes for the soreness to go away. Since stretching does not reduce muscle soreness, it will not help you to recover faster from hard exercise. The best way to recover from exhausting competition is to move with little pressure on muscles, such as cycling on a stationary bicycle (2).

Stretching does not prevent injuries (3). Muscles and tendons tear when the force applied to them is greater than their inherent strength. Anything that makes a muscle stronger helps to prevent injuries, but stretching does not make muscles stronger or faster.

Even though most high school and college coaches have their athletes stretch before games or races (4), you should not stretch before competition because it decreases muscle strength (5) and impairs your ability to run fast (6).

However, stretching can make you a better athlete. Muscles attach to bones by long fibrous bands called tendons. Stretching lengthens tendons, and the longer the tendon, the greater the force a muscle can exert on a joint (7). So stretching a tendon to make it longer allows an athlete to exert more force around a joint to help him jump higher, run faster, lift heavier or throw further (8).

References: 1-Cochrane Database of Systematic Reviews 2007, Issue 4; 2-American Journal of Physical Medicine & Rehabilitation, June 2007; 3-Clinical Journal of Sport Medicine, March 2005; 4-Clinical Journal of Sports Medicine, May 2006; 5-Journal of Bodywork and Movement Therapies, April 2006; 6-Sports Science, May 2005; 7-Journal of Sports Science, February 2006; 8-The American Journal of Sports Medicine, February 2006. Fitness newsletter

Thursday, October 16, 2008

Broken Knee Cartilage is Forever

A team of researchers at the University of Western Ontario in London, Ontario have shown that arthroscopic removal of loose cartilage and trimming of knee cartilage is no better than doing no surgery at all (NEJM, September 11, 2008). The only other study that also used sham surgery was done at Baylor Medical School and showed the same results (New England Journal of Medicine 2002;347:81-8). The procedure is done when a surgeon inserts small tubes through the skin into the knee joint and trims the edges of cartilage and removes loose pieces of cartilage from the joint.

You hear about many athletes returning to the athletic field after breaking cartilage in their knees and having surgery. However, almost all will have pain in their knees for the rest of their lives and most will eventually have their knees replaced. When you break cartilage in your knee, it will never heal.

If you hurt your knee and the pain persists, your doctor will probably order an MRI. If it shows that you have a crack in your cartilage, you should never run or jump again. When you run, the force of your foot striking the ground is transmitted up to your knee and can extend the existing cracks. Running 6-minute miles exerts a force exceeding three times body weight. Landing from a jump exerts even greater force on your knee joint. You can usually ride a bike safely because you pedal in a smooth rotary motion that exerts little force on your knee joint. Swimming is also usually safe for your knees.

If you extend the cracks in your knee cartilage, you can have pain all the time. Then it is probably time for you to have knee replacement surgery. Surgery is also indicated for a torn anterior cruciate ligament. Your knee is really two sticks held together by four bands called ligaments. You can tear any one of three of these bands and usually do quite well. However if you tear the anterior cruciate ligament, the cartilage of your lower leg is allowed to slip backwards against that of your upper leg and shear off additional cartilage, eventually necessitating a knee replacement. So almost always doctors recommend replacing a torn anterior cruciate ligament.

Contact sports that require running and jumping, such as football and soccer, are the ones that put you at increased risk for knee damage. Once you crack cartilage in your knees, you probably should avoid all sports that require running and jumping. Most people can ride or even race on bicycles and not extend their knee damage.
More on arthroscopic knee surgery

Friday, October 10, 2008

Don't Regain Lost Weight

A new study shows that older people who diet without exercising lose huge amounts of muscle. When weight loss was combined with exercise, they did not lose muscle (Journal of Applied Physiology, October, 2008). Loss of muscle slows metabolism even further because larger muscles burn more calories at rest.

In this study, elderly sedentary people were placed in three groups: 1) Diet only, 2) exercise only, 3) diet and exercise. Those who dieted and exercised for four months lost more fat and less muscle than those who only dieted. Most of the exercisers chose to walk on a treadmill, which is not a very vigorous endeavor.

This also explains why losing weight repeatedly through dieting shortens a person's life span. Many people go on diets and lose weight, quickly regain their lost weight and then go on a diet again. These people then become fatter at the same weight because they have lost so much muscle. Therefore at the same weight, they have fuller fat cells. Full fat cells produce immune stimulant called cytokines that turn on a person's immunity continuously to cause inflammation, which increases risk for cancers, heart attacks, strokes, diabetes and other harmful diseases. More

Wednesday, October 08, 2008

Plastic Bottles and Containers: New Concerns

A study from Peninsula Medical School in Exeter, U.K. shows that high levels of urinary Bisphenol-A (BPA), a chemical compound commonly used in plastic packaging for food and beverages, is associated with heart attacks, strokes, diabetes and abnormal liver tests (JAMA, Sept 17, 2008). BPA can break down to form female hormones called estrogens that are linked to breast and uterine cancer in women, decreased testosterone levels in men, and may also cause birth defects.

You are exposed to BPA, primarily through food, drinking water, tooth sealants that you may receive in a dentist's office, and exposure through your skin and lungs from household dusts. Ninety percent of Americans have detectable levels of BPA in their urines.

Although the safety of BPA is still uncertain, you would be prudent to limit your exposure. The primary concerns are plastic water bottles and baby bottles. Each bottle is supposed to have a number in a circle stamped on the bottom. Try to avoid the following numbers:
#1 Most single-use water bottles are made from polyethylene terephthalate (PET or PETE).
#7 This is used for many colorful hard plastic lexan bottles made with polycarbonate plastics.
At a minimum, do not re-use bottles or containers with these numbers. Do not freeze or reheat foods or beverages in them.

Plastic products that bear the following numbers appear to be safe:
#2 HDPE, high-density polyethylene, the most widely recyced plastic,
#4 LDPE, low-density polyethylene) and
#5 PP, polypropylene.