InsideTracker is a service that analyzes an athlete’s biomarkers to offer personalized guidance on nutrition, supplementation, and tweaks to training that is backed by science.
Whether you’re a competitive athlete, weekend warrior, or fitness fanatic, chances are you’ve played the numbers game. With such a wide array of apps and devices dedicated to logging heart rate variability, power to mass ratio, miles per week, minutes per mile, or calories per day, the numbers game is a fun (albeit addictive) way to monitor and improve athletic performance.
We get it. That’s why earlier this year GU and InsideTracker partnered up to take a look under the hood of some of our top competitive athletes. We had 12 athletes pick an important event or race they were training for and then provided four testing opportunities for them (two before, two after) to see what effect nutrition and exercise had on over 40 health and performance related biomarkers.
The results were surprising, but they gave us an opportunity to implement science-based recommendations for training, nutrition, and supplementation to optimize overall health and performance. Here were some of the most common issues we found and how to fix them:
Measured as serum 25(OH)D
Findings: Vitamin D was one of the most common micronutrient deficiencies.
Why It Matters: Vitamin D is important for bone metabolism and calcium handling, muscle health and recovery, cognitive and immune function.
What Causes It: Vitamin D is known as the “sunshine vitamin” because it can be produced in the body with adequate sun exposure. Outdoor athletes may think they are getting plenty of vitamin D because they spend so much time outdoors, but they often still fall short. Sunscreen, protective clothing, darker pigmented skin, and living in northern latitudes (where the sun is less intense) all impair vitamin D production, which can lead to deficiency despite ample sun exposure.
- Muscle pain/weakness
- Frequent stress fractures
The Fix: Increase sun exposure, 15-30 minutes daily in the midday sun (less if more fair-skinned). Increase intake of vitamin D containing foods, which include:
- Fatty fish (salmon, sardines, mackerel, tuna)
- Eggs (with the yolk)
In some cases, athletes might still need to supplement with vitamin D for several weeks or more, particularly during winter. Doses typically range from 1,000-5,000 IU depending on the severity of the deficiency. D3 (cholecalciferol) is the preferred supplemental form (as opposed to D2, or ergocalciferol), since this form is more effective at raising blood levels. Taking supplements daily with fat-containing meals enables optimal absorption.
Measured as hemoglobin, hematocrit, serum iron, ferritin, transferrin saturation, total iron binding capacity
Findings: Serum ferritin (the body’s iron storage form) tended to be less than optimal for many of our athletes. Serum ferritin levels are often overlooked with standard blood tests that may only look at hemoglobin or blood iron levels. These levels can show up as normal even though serum ferritin levels are low.
Why It Matters: High training volumes—and running in particular—can deplete stored iron in order to facilitate red blood cell turnover, as well as aerobic energy production. It can also be diet related, particularly in vegetarian and vegan athletes who aren’t consuming iron-rich foods, such as red meat, that provide better absorption rates than plant based sources of iron.
- Shortness of breath
The Fix: Steak and spinach salad, anyone? Athletes should first increase dietary sources of heme (animal derived) and non-heme (plant derived) iron taken alongside vitamin C rich foods, as vitamin C helps boost absorption. Supplementation should only be considered in cases of a diagnosed deficiency and under the guidance of a qualified physician or nutrition professional. The body has a hard time eliminating excess amounts of iron, and toxicity is possible even at moderate supplemental doses. This can ultimately damage vital organs.
Here’s a list of foods that are a good source of iron:
- Lean red meat
- Lean pork
- Dark chocolate >70% cacao
- Dark leafy greens
Cooking in a cast iron skillet is another way to incorporate more iron into meals. If taking supplemental iron, it is best taken on an empty stomach, preferably not in close proximity to exercise, which can interfere with absorption.