Vitamin D is often described as the SUNSHINE VITAMIN as it’s produced when skin is exposed to sunshine, or rather, the ultraviolet B (UV-B) radiation that the sun emits – produces Vitamin D3.

You may get small amounts of Vitamin D from your diet – it’s thought about 10% of your requirement may come from food. Vitamin D3 form is available from foods e.g. oily fish, butter, eggs.

Vitamin D2 found in plant-based foods e.g. mushrooms, fortified soya milk and almond milk, however D2 needs to be converted to D3 by the body and Vitamin D3 converted to its active form (Calcitriol) by the liver and kidneys.

We’ll talk about:

Why an optimal Vitamin D status is important for runners

How do you test for Vitamin D and what is an optimal Vitamin D status?

Practical suggestions to help you optimise Vitamin D status.

SHOW NOTES

05:34)

Why is Vitamin D important for optimal health and especially for runners?

Vitamin D is important for everyone and especially for runners. Vitamin D has wide ranging functions across the whole body. Vitamin D Receptors (VDRs), which mediate the biological functions of Vitamin D are found across the body in the cells of most organs and tissues e.g. brain, heart, skin, intestines, pancreas, bone, kidneys, prostate and breast, which demonstrates just how widely Vitamin D is utilised.

· Runners need to protect their BONES – we want to retain a healthy bone mineral density and protect against fractures E.g. stress fractures or fractures as a result of accidents. Vitamin D has a key role to play in the absorption and utilisation of calcium for strong bones

· MUSCLE function is very important for runners – Vit D has a role in muscle repair and remodelling which will help protect against injury and support performance and recovery.

· To keep up with training schedules and competition throughout the year it’s important to minimise/prevent COLDS/FLU/UPPER RESPIRATORY TRACT INFECTIONS which are a common complaint of runners during the colder months. It’s thought that Vitamin D supports the immune system by inhibiting viral replication and microbial entry into lungs.

· Vitamin D supports the CARDIOVASCULAR SYSTEM for heart structure and function – remember the heart is a large muscle!! Vitamin D promotes vasodilation – vital for blood flow and the delivery of extra oxygen and nutrients to the muscles during exercise.

(09:52)

Is there is any evidence to suggest that Vitamin D improves running performance?

· Low vitamin D status could negatively impact the health and training efficiency of athletes – for all the reasons we’ve mentioned earlier

· There doesn’t seem to be clear evidence to support maintaining Vitamin D level at “supranormal levels” i.e. >100–125 nmol/L, in order to achieve an improved athletic performance – it appears that optimal status of 75-100nmol/L is recommended for optimal health and good sporting performance

(11:45)

As runners spend a lot of time outdoors you’d imagine that their Vitamin D status would be good – is this the case?

Evidence suggests that trends in Vitamin D deficiency in global populations are similar in athletic populations. That’s because of the risk factors and barriers for a low Vitamin D status.

We know that optimal sun exposure is key for Vitamin D production so location and lifestyle will play a factor:

· Living in the Northern hemisphere – generally less sun exposure

· Covering up with clothes and sunscreen – limiting sun exposure – protection against skin cancer

· People who live/work/play/exercise indoors will have less sun exposure

There are some other issues to consider:

· People with dark skins (the ability to absorb UV light is reduced with darker skin)

· Genetics – some people have polymorphism of VDR gene which results in reduced vitamin D binding – those people may require higher dose supplementation and more regular testing

· Ageing – decreases the capacity of skin to produce vitamin D3 be as much as 50%

· People who are overweight/obese – Vitamin D is stored in body fat making it less bioavailable

(16:24)

Are there any FEMALE FACTORS to consider regarding Vitamin D status?

The 2 main female factors to consider are:

· Pregnant/breast feeding women may be prone to deficiency due to increased nutrient requirements

· Menopausal and post-menopausal women are at risk of loss of bone mineral density which may lead to the development of osteoporosis and risk of fractures. An optimal Vitamin D status will support your body in absorption of calcium and phosphorus, key minerals for bone health and it also supports a downward regulatory effect on parathyroid hormone level resulting in reduced bone loss. The International Osteoporosis Foundation, say that 1 in 3 women over the age of 50 years will experience osteoporotic fractures in their lifetime.

(19:18)

Deciding when to test for Vitamin D Status and types of tests available

We think it is good practice to test vitamin D routinely i.e. twice a year.

As runners, if you notice symptoms of any chronic injury, poor recovery, or recurring stress fractures, then it may be is a time to think about having a vitamin D test. Also consider if your exposure to sunlight is optimal. For example, if you tend to run early in the morning, or late in the evenings, or maybe you do indoor running and training, it might be that your sun exposure is more limited than you think it is.

2 types of tests –a home skin prick test – usually a home test kit and the other involves a blood draw. We briefly talk through the 2 types of tests.

(25:04)

Understanding your test results

If you do a home test kit you’ll probably receive a guidance sheet from the testing company explaining the results and suggesting some actions. They are usually quite simple to read, they’ll detail the standard reference range that your results are being measured against. Reference ranges do vary amongst labs but generally you’ll find a colour coded sheet with results graded from deficient to optimal typically the ranges will be

• OPTIMAL – greater than 100 with a safe upper limit of 220 nmol/L

• Sufficient – 50-100 nmol/L

• Insufficient – 25-50 nmol/L

• Deficient – less than 25 nmol/L

Our suggested testing companies

https://betteryou.com/products/vitamin-d-test-kit

https://medichecks.com/products/vitamin-d-25-oh-blood-test

(27:16)

Is it possible to have too much Vitamin D?

Vitamin D toxicity is rare. Common symptoms/conditions associated with Vit D toxicity are hypercalcaemia (a high calcium level in the blood serum) and polyuria (condition where the body urinates more than usual and passes excessive or abnormally large amounts of urine each time you urinate, more than 3L per day) and symptoms such as thirst and constipation. If your test result was in the high range of 250 nmol/L you should consult with your medical practitioner. Toxicity may occur if a person supplements with huge doses per day for several weeks or months.

(34:30)

Practical suggestions to help you optimise your vitamin D status.

SUPPLEMENTS

· Depending on your test result and Vitamin D Status you may require either a therapeutic dose or a maintenance dose of Vitamin D.

· Vitamin D Supplements usually measured in iu e.g. 1000iu – 10,000iu – a maintenance dose is usually between 1000-4000iu per day. The European Food Safety Authority (EFSA) have set the Tolerable Upper Level at 4000iu/day for adults and pregnant women. A therapeutic dose may range from 5000- 10,000 iu/day. In certain cases of deficiency a higher dose may be prescribed medically.

· It’s important to take professional advice if your result shows that you are deficient, your medical practitioner may prescribe a very high dose under medical supervision to support you in gaining an optimal result in a timely fashion whilst also investigating the underlying reasons for a deficient Vitamin D status.

· High dose vitamin D3 should be taken alongside vitamin K2 (to support calcium homeostasis by directing calcium into bone away from arteries)

· Retest after 1-3 months then reduce dose to maintenance

· Various types of supplements – tablets/sprays/drops – sometimes Vitamin D is included in multi...