The Triathletes Ultimate Vitamin D Guide

The Triathletes Ultimate Vitamin D Guide

Are you getting up enough Vitamin D? If you’re not sure how Vitamin D impacts your performance, then read this article to understand the importance of Vitamin D and how it affects your health.


Why is Vitamin D important?

Vitamin D boosts your immune system, positively impacts your cells’ health and function, enhances your recovery, eases muscle aches, increases bone strength and minimises inflammation—all of which are crucial to preventing illness and injury.

Why is Vitamin-D really important for athletes?

Jo Scott-Dalgleish BSc (Hons) is a registered BANT nutritionist specialising in working with endurance athletes. She has revealed that the small number of scientific studies conducted on endurance athletes have all suggested that they do not necessarily have adequate vitamin D levels.

Further studies have shown that vitamin D deficiency is linked to increased stress fracture risk, inflammation, impaired muscle function and viral respiratory tract infections and reduced musculo-skeletal performance.

Where do we get Vitamin D?

Us athletes in the norther hemisphere are enjoying the slow pace of the off-season and bracing ourselves for the eminent winter. Cyclist tan lines, open water swims and warm runs are a distant memory, and we are now spending the majority of our time in the gym or swimming pool.


The lack of daylight and cold weather isn’t just affecting our mood and how we train, but also our levels of Vitamin D. The main source of Vitamin D is sunlight – we only absorb a small amount from our food.


Research into this fat-soluble vitamin, which acts as a hormone within our bodies, has revealed linked Vitamin D with undesirable ailments, from fatigue, high blood pressure, heart disease and depression to fibromyalgia, bone loss, and autoimmune diseases. Whereas, research has shown optimal levels of Vitamin D keep us happy and healthy.


However, research has also shown that even when exposed to lots of sunlight, Vitamin D deficiency can still be present and that winter days only exasperates the problem. Vitamin D deficiency also increases with age and is more common among women then men. You are also at an increased risk of deficiency if you have a history of bone fractures or impaired absorptions (such as Crohns or Celiac disease). Some medications can also effect Vitamin D levels. This is why it’s so important to discuss Vitamin D levels with your doctor.


What’s the optimal level of Vitamin D?

The UK government recommends just 400 IU or 10 micrograms a day. This is the amount you need to prevent rickets, a disease caused by vitamin D deficiency. But how much Vitamin D do we need for OPTIMAL health and performance?

Research by vitamin D pioneer Dr. Michael Holick, Professor of Medicine, Physiology, and Dermatology at Boston University School of Medicine, recommends Vitamin D intakes of up to 2,000 IU a day — or enough to keep blood levels of 25 hydroxy vitamin D at between 75 to 125 nmol/L (nanomoles per liter). That may sound high, but it’s still safe: Lifeguards have levels of 250 nmol/L without toxicity.


What foods are high in Vitamin-D?

There are a number of foods you can add or increase in your diet to boost your levels of Vitamin D, the key ones are:

  • Fish liver oils, such as Krill oil and cod liver oil. One tablespoon (15 ml) of cod liver oil = 1,360 IU of vitamin D
  • Cooked wild salmon. (3.5) ounces = 360 IU of vitamin D
  • Cooked mackerel (3.5) ounces = 345 IU of vitamin D
  • One whole egg = (20) IU of vitamin D


Do I need to supplement?

It’s challenging to attain the amount of Vitamin D you require to get your blood levels to the optimal range from food and sunlight alone. The levels you need is also personal and differs person to person (or triathlete to triathlete). However, once you reach the optimal levels, the results will surprise you.

You need to be careful with the brand of supplement you take. This is because the only active form of vitamin D is vitamin D3 (cholecalciferol) and many vitamins and prescriptions of vitamin D have vitamin D2 – which is not biologically active.



We highly recommend talking to a health expert for a supplement recommendation and guidance on your Vitamin D levels.

Have you experienced any performance benefits by optimising your levels of vitamin D?

Please leave your thoughts by adding a comment below – but remember, we can’t offer personal medical advice online.