Oh, sure, my times on 'Angie' might look impressive but it doesn't reflect the number of times I slide off the pull-up bar. If I didn't have the tenacity of Wile E. Coyote (not to mention the colorful expletives of Yosemite Sam), Angie would own me. It's my grip.
You'd think I'd have 'crushing hands of death', too. After all, I have five years of experience grappling almost exclusively with a Gi - exceptions for spontaneous bouts in the lobby of CrossFit Eastside where the absence of hand-holds is much less troubling than the rug burn and the bruising from geometric miscalculations around furniture (a challenge for me even if I wasn't in mid-air at velocity).
when I read the following study* initially, it took me about three days before it registered that this data might help. First, the study was done on a 60-plus population which didn't exactly scream 'max pull-ups' at first. For another thing, researchers happened to test grip strength as a measure but wasn't specifically looking for grip improvement. I think I was driving mid-span on the 520 bridge when it dawned on me that it doesn't matter if the study was specific to grip strength as long as it improves it and that a layer of dust that thick on my dashboard could actually affect gas mileage as well as grow wild, organic root vegetables.
"For the current study, researchers analyzed data from the InCHIANTI study, which evaluated factors contributing to the decline of mobility in late life. The study involved 976 people who were 65 years and older from two towns in the Chianti area of Italy. The mean age of participants was 74.8 years. Data were collected from Sept. 1998 through March 2000. "
Again, I was thrown by the age group initially but since the study revealed that a Vitamin D deficiency may be the culprit, anyone is susceptible especially those of us living under near constant cloud cover who don't drink fortified milk or juice. As I discussed this article with my friend Tamim, a native of Kenya, he pointed out that some forms of rickets are still diagnosed in children from his country simply by grip strength (They may do that here but the code number on your bill makes it sound far more complex and the procedure costs a few hundred dollars ).
The researchers found that physical performance and grip strength were about five to 10 percent lower in those who had low levels of vitamin D. After looking at other variables that could influence the results, such as body mass index, physical activity, the season of the year, mental abilities, health conditions and anemia, the results held true.
Five to ten percent matters when your 75 pull-ups deep and your callouses are about to mutiny and drop you to the ground.
The study wasn't designed to evaluate whether low vitamin D levels actually cause poor physical performance, but the results suggest the need for additional research in this area, said Houston. She said vitamin D plays an important role in muscle function, so it is plausible that low levels of the vitamin could result in lower muscle strength and physical performance." But it's also possible that those with poor physical performance had less exposure to sunlight resulting in low vitamin D levels," she said.
This is one of the few times I've seen a research paper acknowledge the possibility that the results could be backward engineered.
Current recommendations call for people from age 50 to 69 to get 400 international units (IUs) of vitamin D per day and for those over age 70 to get 600 IUs. Many researchers, however, suggest that higher amounts may be needed." Higher amounts of vitamin D may be needed for the preservation of muscle strength and physical function as well as other conditions such as cancer prevention," said Houston. "The current recommendations are based primarily on vitamin D's effects on bone health."
The Linus Pauling Institute makes a similar recommendation for dosage though many experts agree the number is conservative. The issue ultimately is toxicity.
Vitamin D toxicity (hypervitaminosis D) induces abnormally high serum calcium levels (hypercalcemia), which could result in bone loss, kidney stones, and calcification of organs like the heart and kidneys if untreated over a long period of time. When the Food and Nutrition Board of the Institute of Medicine established the tolerable upper intake level (UL) for vitamin D, published studies that adequately documented the lowest intake levels of vitamin D that induced hypercalcemia were very limited. Because the consequences of hypercalcemia are severe, the Food and Nutrition Board established a very conservative UL of 2,000 IU/day (50 mcg/day) for children and adults. Research published since 1997 suggests that the UL for adults is likely overly conservative and that vitamin D toxicity is very unlikely in healthy people at intake levels lower than 10,000 IU/day. Vitamin D toxicity has not been observed to result from sun exposure.
Obviously avoiding toxicity would be as easy as ensuring that all your RDA was met basking in beautiful sunlight but it's unlikely that our jobs or our weather patterns will allow that to happen any day soon and certainly not consistently. The Linus Pauling institute goes on the explain the recommendations for sunlight to provide an optimum dosage naturally:
Sunlight exposure provides most people with their entire vitamin D requirement. Children and young adults who spend a short time outside two or three times a week will generally synthesize all the vitamin D they need. The elderly have diminished capacity to synthesize vitamin D from sunlight exposure and frequently use sunscreen or protective clothing in order to prevent skin cancer and sun damage. The application of sunscreen with an SPF factor of 8 reduces production of vitamin D by 95%. In latitudes around 40 degrees north or 40 degrees south (Boston is 42 degrees north), there is insufficient UVB radiation available for vitamin D synthesis from November to early March. Ten degrees farther north or south (Edmonton, Canada) this “vitamin D winter” extends from mid October to mid March. According to Dr. Michael Holick, as little as 5-10 minutes of sun exposure on arms and legs or face and arms three times weekly between 11:00 am and 2:00 pm during the spring, summer, and fall at 42 degrees latitude should provide a light-skinned individual with adequate vitamin D and allow for storage of any excess for use during the winter with minimal risk of skin damage.
Situated in those sparsely sunlit latitudes, sits Scandanavian mothers who dutifully force feed spoonfuls of cod liver oil to their brood as if they naturally knew that Vitamin D would be in short supply over the winter. Cod liver oil is one of the very few dietery sources other than unnaturally fortified foods.
Vitamin D is found naturally in very few foods. Foods containing vitamin D include some fatty fish (mackerel, salmon, sardines), fish liver oils, and eggs from hens that have been fed vitamin D. In the U.S., milk and infant formula are fortified with vitamin D so that they contain 400 IU (10 mcg) per quart. However, other dairy products such as cheese and yogurt are not always fortified with vitamin D. Some cereals and breads are also fortified with vitamin D. Recently, orange juice fortified with vitamin D has been made available in the U.S. Accurate estimates of average dietary intakes of vitamin D are difficult because of the high variability of the vitamin D content of fortified foods. Vitamin D contents of some vitamin D-rich foods are listed in the table below in both international units (IU) and micrograms (mcg). For more information on the nutrient content of foods you eat frequently, search the USDA food composition database.
One last curious point had me thinking of my winters here in Seattle. I've often found it harder to avoid the munchies here during fowl weather and I assumed it was boredom, comfort or some other psychological silliness I inflict on myself sometimes. The following statement, also from Linus Pauling, had me curious if perhaps the lower Vitamin D may be at the root of the issue.
The vitamin D receptor is expressed by insulin secreting cells of the pancreas, and the results of animal studies suggest that 1,25(OH)2D plays a role in insulin secretion under conditions of increased insulin demand. Limited data in humans suggests that insufficient vitamin D levels may have an adverse effect on insulin secretion and glucose tolerance in type 2 diabetes (noninsulin-dependent diabetes mellitus; NIDDM) (10-12).
*The research is supported by the Italian Ministry of Health and in part by the National Institute on Aging. Co-researchers were Gary Schwartz, Ph.D., and Stephen Kritchevsky, Ph.D., both with Wake Forest, Matteo Cesari, M.D., Ph.D, with the University of Florida, Luigi Ferrucci, M.D., Ph.D., with the National Institute on Aging, Dario Maggio, M.D., and Antonio Cherubini, M.D., Ph.D, both with the University of Perugia in Italy, Mary Ann Johnson, Ph.D., with the University of Georgia, and Benedetta Bartali, R.D., with Cornell University.