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To Supplement or Not to Supplement

It is often said that nutrition is the fourth discipline of triathlon. Indeed, we’ve all heard about how important it is to eat a balanced diet that includes all the nutrients we need to support our training and recovery. This time of year, many athletes are starting to ramp up their training and clean up their nutrition habits accordingly – so I start to get a lot of questions about supplements that promise to make up for less-than-perfect diets or improve athletic performance. To help separate fact from advertising fluff, I sat down with Axes sports dietitian Janet Carter for guidance, and she had three key messages to share.

First, intake of any nutrient above the Recommended Daily Allowance can in the least be unnecessary and a waste of money, but at worst can be dangerous. While there are certain types of people who may be more susceptible to certain nutrient deficiencies, it is important to have bloodwork and/or a dietary assessment to determine your nutritional status.

Second, even though each vitamin or mineral has particular functions in the body, supplementation does not “supercharge” those functions. For example, iron’s function is to transport oxygen though the blood, but taking iron supplements does not equal EXTRA oxygenation of the blood. (Bummer, right?)

Third, you are almost always better off getting your vitamins and minerals through your diet rather than a pill. There are synergistic properties of the healthy foods we consume that benefit us in ways that even science doesn’t fully understand yet.

With that background in mind, let’s take a closer look at some common vitamins and minerals that I get asked about the most.

B vitamins

This group of vitamins helps with metabolism and releasing energy, which are critical to athletic performance. Deficiencies can cause fatigue and weakness. Vegetarians, vegans, older adults, and people with GI issues can be at particular risk for deficiencies. Supplementation would only affect athletic performance if the athlete was deficient to begin with.

Food sources: Beef, poultry, salmon, eggs, milk, leafy greens, yogurt, legumes


This mineral carries oxygen (via the blood) throughout the body, so it’s important to working muscles. Women are more at risk for low iron, which can cause fatigue and hamper performance. Too much iron can be toxic, however, so it is critical to have a blood test to determine whether you need supplementation.

Food sources: Red meat, poultry, seafood, legumes, spinach, broccoli, nuts


In addition to building teeth and bone, calcium is important to muscle contraction and also helps stimulate fat metabolism – so it’s of particular importance to endurance athletes. Children and teens (who are still growing), adults over 50 (particularly women, who are at higher risk for osteoporosis), vegans, and endurance athletes are all groups at higher risk for calcium deficiency. A blood test and dietary analysis can help you determine your need for supplementation.

Food sources: Milk, cheese, yogurt, legumes, leafy greens, almonds

Fish oil

The omega-3 fatty acids contained in fish oil are essential fatty acids, which means we must obtain them from our diet; our bodies do not make them. Studies show numerous health benefits, including heart health, brain health, and reduced inflammation. Additionally, some preliminary studies have found improvements in muscle recovery after exercise. Research shows that benefits are greater from food sources over supplements, but there is no evidence of any detrimental effects of supplementation except at very high doses. So this is one that wouldn’t hurt to add, especially if you don’t eat much seafood.

Food sources: Fatty (cold-water) fish, flaxseed, chia seeds, walnuts, grass-fed beef, spinach

Vitamin D

In addition to getting it from food sources, vitamin D is produced in your body when your skin absorbs sunlight. Deficiency is extremely common, especially in the elderly and people with darker skin, and many athletes are deficient as well. Vitamin D regulates the absorption of calcium and phosphorus, so deficiency puts you at risk for stress fractures and muscle weakness. There can be serious side effects from excessive Vitamin D supplementation, but not when it comes from sun exposure or dietary sources.

Food sources: Cheese, egg yolks, mushrooms, salmon, canned tuna

Overall, there is no substitute for a balanced diet rich in a variety of healthy foods that provide important nutrients. Sufficient levels of vitamins and minerals can help your body stay healthy and functioning at its best. If you notice a change in your energy levels or you suspect you may have a deficiency, consider consulting your doctor or a dietitian to investigate. While there is no silver bullet supplement that will improve your performance by itself, if you do have a deficiency, supplementing may be helpful to you.

If you have questions about nutrition for training or would like to set up a consultation with one of our sports dietitians, reach me at


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