Low Vitamin D levels are very likely limiting your running performance, and may compromise your health.
As runners, we want to do everything possible to perform well and have a great season. We are meticulous about our training schedules, hydration, sleeping habits, etc. Yet many times we fall short when it comes to nutrition.
In the summer of 2008, I started to feel rather lethargic during workouts and I struggled to maintain my normal training paces. My recovery from my harder efforts and long runs took longer than usual. I immediately and incorrectly assumed I had low serum ferritin levels indicating iron deficiency anemia.
One colleague to whom I lamented about my chronic fatigue asked me if I had checked my Vitamin D levels. “Vitamin D levels?” I exclaimed. I live in California, it is summer, and I am outside way more than the recommended 20 to 30 minutes a day. There is no way I could be Vitamin D deficient, especially since in addition to being exposed to sun most days, I eat a very balanced diet that includes a daily multivitamin supplement. However, a visit to my doctor confirmed that my serum 25–hydroxy-Vitamin D (25(OH)D) value was dangerously low (18 ng/ml). Normal levels are between 40-70 ng/ml. And for those with chronic diseases such as cancer, heart disease, diabetes, and multiple sclerosis, normal blood levels should be between 55-70 ng/ml. I was shocked.
I immediately started daily supplementation with 1,000 IU of vitamin D (Vitamin D3). After eight weeks, my 25 (OH)D level had improved somewhat (28 ng/ml). I did feel slightly better, but I wanted to recover completely, so I upped my dosage to 2,000 IU daily. A few weeks later my levels were within the normal range (56 ng/ml). I felt noticeably stronger and was able to hit my usual paces during training. And in October 2008, I set a half-marathon personal record.
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