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No Evidence Cycling Weakens Bones

No data exists in the scientific literature showing that any type of exercise weakens bones. Bone growth depends on the forces exerted on them by gravity and contracting muscles. So any activity or exercise that causes you to contract your muscles will strengthen bones (Medicine & Science in Sports & Exercise, November 2009).

Previous studies showed that world class cyclists had reduced bone densities in their spines. However, bone density tests do not measure bones strength. They measure how much bones block X-rays that try to pass through them. The only way to measure bone strength is to see how much force it takes to break a bone.

The most likely explanations for broken bones in cyclists are high-impact crashes and/or lack of vitamin D. I recommend that all cyclists get a blood test called Vitamin D3 in December or January. If it is below 75 nmol/L, they are deficient in vitamin D and at increased risk for breaking bones. To prevent fractures, they should do winter training in the southern sunbelt or take at least 800 IU of Vitamin D3 per day.

A recent review of 12 blinded, controlled scientific studies showed that oral vitamin D reduced non-vertebral and hip fractures in patients over 65 years of age (Evidence-Based Medicine, October 2009). Blood levels of vitamin D below 75 nmol/L cause parathyroid hormone levels to rise too high, which causes osteoporosis. A main function of vitamin D is to increase calcium absorption from the intestines into the bloodstream. When blood levels of vitamin D fall below 75 nmol/L, levels of ionizable calcium drop. This causes the parathyroid gland to produce large amounts of its hormone. Higher than normal blood parathyroid hormone levels take calcium out of bones to cause osteoporosis.


Reports from

Enzyme pills
Canker sores
Inherited susceptibility to diabetes


Dear Dr. Mirkin: Are artificial sweeteners dangerous?

1) The National Cancer Institute of the US states that no data associate reasonable doses of any of the artificial sweeteners on the market with cancer.

2) Recent data show that artificial sweeteners may stimulate the hunger centers in the brain to make you hungrier so that you may eat more. That is the worst that you can say.

3) Too much sugar and other refined carbohydrates can lead to heart attacks and diabetes. A high rise in blood sugar causes sugar to stick on the surface of cell membranes. Once there, it cannot get off and eventually destroys the cells. In both diabetics and non-diabetics, this can cause heart attacks, strokes, blindness, deafness and all of the other side effects of diabetes. So if artificial sweeteners help you to avoid sugar without increasing your hunger, they are probably beneficial for you.

Fact sheets on artificial sweeteners
Saccharin regulation by the US Congress


Dear Dr. Mirkin: Is it healthful to eat only raw foods?

Eating plenty of raw fruits, vegetables and seeds is very healthful, but it would be difficult, if not impossible, to get all of the calories and nutrients you need from a long-term diet of all-raw foods.

Several years ago I reported on the work of Dr. Richard Wrangham, an anthropologist at Harvard who believes that the ability to cook food virtually shaped the human species. Since cooking allowed humans to eat both plants and meat, and to get more calories from many plants than are available when they are eaten raw, humans had access to more food than all other animals. This advantage appears to explain why humans evolved with larger brains, which allowed them to dominate their environment wherever they went. Now Dr. Wrangham has written a fascinating book, "Catching Fire: How Cooking Made Us Human". He explains how our species benefited from the ability to cook foods and why we are no longer adapted to the raw diet consumed by all other animals. "Catching Fire" can be found at or your local bookstore. Highly recommended!


Recipe of the Week:

It's time for Diana's famous . . .
Three Sisters Soup!

You'll find lots of recipes and helpful tips in The Good Food Book - it's FREE

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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