CYCLING PERFORMANCE TIPS
I have taken a daily multivitamin for years. And a B with C (often called stress tabs). Do they help? My rationale was that as long as they were not mega doses (which can be harmful with the fat soluble vitamins A and D) my only real risk was to my wallet. And it was insurance to cover me if my diet was lacking. I saw a recent on line article suggesting athletes could benefit from a list of vitamin and mineral supplements. So it got me thinking about what I do, and what the data might be. So the question on the table - "do you short change yourself if you don't use supplements (assuming a normal, well balanced diet)?"
Coenzyme Q-10 (COQ10)
Coenzyme Q-10 (ubiquinone or CoQ10) is not one of the traditional vitamins, but is often marketed in multi-vitamin preparations. It is fat-soluble and is found in particularly high levels in the mitochondria of muscles (which are the power houses of muscle activity). Which suggests that supplements might improve athletic performance.
Although athletes taking coenzyme Q-10 have higher blood levels of that enzyme, they do not improve their aerobic performance or endurance. To quote from Dr. Mirkin.com (where references are available), "...all studies showing that CoQ10 improves performance are weak, uncontrolled, supported by special interest groups, and/or have two few subjects to show improvement in performance. Of six placebo-controlled studies, one showed that cross country skiers raced faster after taking coenzyme Q-10 pills, but the other five showed no improvement in muscle energy metabolism, muscle fatigue, endurance, or maximal ability to take in and use oxygen (VO2 max)."
Vitamin is best known for its role in night vision (why your mom told you to eat your carrots), and may play a role in preventing infections. It plays no role in energy metabolism or muscle function.
"Evidence of vitamin A and E deficiencies in athletic individuals is lacking apparently because body storage is appreciable.
"Studies on ...fat-soluble vitamin A deficiency have noted no decrease of endurance capacity."
Bottom line: There is no physiologic rational for vitamin A deficiency and poor performance, and actual clinical investigations have demonstrated no benefit of supplements. Even more important, as a fat soluble vitamin which can build up over time in fatty tissue, megadoses pose a definite risk. Aside from the use of a general multivitamin once a day, leave vitamin A out of your training regimen.
The literature suggests that athletes (just like non athletes) tend to be Vitamin D deficient, but Vitamin D deficiency is such a frequent diagnosis these days ( "..over 77% of the general population (are) considered vitamin D insufficient") that I wonder if our normal values used in testing are really valid. But even if the number is a lower than 77%, the fact remains that vitamin D deficiency is real and common, more common in the winter (sunlight is required to produce Vitamin D) and more common in the summer if sunscreen is used (using sunscreen cuts skin vitamin D production by 95%. - So athletes "...in higher latitudes, in winter and early spring seasons, and for indoor sport activities" are those at most risk of vitamin D deficiency.
What are the risks of Vitamin D deficiency? Musculoskeletal injury has been suggested, but a meta analysis found "...(injury) association with vitamin D status is unclear."
How about performance? The data is slim. There has been speculation that Vitamin D is important in muscle cell health but no studies demonstrating decreased performance (or improvement with supplementation). From 2013: "There are few studies to date that have examined the relationship between vitamin D status and performance."
So how do I rate Vitamin D?
Iron is an essential component of many cellular enzymes as well as hemoglobin (the protein which is found in red blood cells and carries oxygen throughout the body). If you do not absorb enough iron (problems with the lining of the small intestine such as celiac disease, gastric weight loss surgery, a change in diet) or are losing blood (menstrual blood loss, intestinal bleeding), you can become iron deficient. And iron deficiency can occur before your blood count begins to fall.
This has led to speculation that a low total body iron state without anemia may contribute to poor performance. In this scenario, the serum ferritin (a measure of body iron levels) would be low, but the blood count may not yet have started to drop. In addition, it has been suggested that these borderline low iron cases might be athletes with a ferritin at the low end of what is defined as the "normal" range.
There was a recent article that suggested that iron might be of benefit for those competing at altitude. But if you read the detail, it really is about iron helping the performance of anyone who is iron deficient. So unless you are iron deficient (have a low ferritin and low blood count), iron will not help your performance (at altitude or sea level), and if you have adequate total body iron stores, there are definite risks of iron overload and toxicity with unneeded supplements.
There is no data that zinc is beneficial in exercise performance, and several studies that indicate it is harmful at higher doses. This article by Dr. Mirkin is a nice summary.
Zinc supplements are most commonly taken for their reported benefit to improve sexuality and sexual function. Zinc is concentrated in the prostate and the assumption was that "..if a little is good, more must be better." There is no evidence that zinc supplements have a positive effect on prostate infections, impotence, enlarged prostate or any other prostate disorders. And those taking zinc supplements have an increased rate of prostate cancer.
There is no study data to support a positive effect on athletic performance with the last data base search in 2012 failing to show any benefits for zinc supplementation. The conclusion of one of an earlier studies from 1994 is as valid today as it was then: "There is no conclusive evidence that supplementation with any of these trace minerals (including zinc) will enhance performance. A diet containing foods rich in micronutrients is recommended. However, for those athletes concerned that their diets may not be sufficient, a multivitamin/mineral supplement containing no more than the RDA may be advised."