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.
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.
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
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
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.
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.
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
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.
Practical suggestions to help you optimise your vitamin D status.
· 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 vitamin products or fortified foods
· The best form of vitamin D as a supplement is vitamin D3 because this is identical to the kind your own body makes in your skin.
SAFE SUN EXPOSURE
It’s thought that one of the contributing factors to low Vitamin D status is that people are covering themselves up and using sunscreen to protect against skin cancer. We know that we make Vitamin D via sun exposure – ideally expose face, legs and forearms to sunlight (between 10am and 2pm) for ten minutes without sun protection on as many days as possible through the summer. Ensuring that the skin does not burn or redden. The 10 minutes is the advice for fair skinned people. Darker skinned people will require a longer period.
The Vitamin D Society suggest approximate sun exposure times for maximum daily vitamin D production for different skin types –
· 10 mins – Very light skinned Caucasian
· 20 mins – Mediterranean
· 30 mins – Middle Eastern
· 40 mins – Southern Asian
· 60 mins – African (dark-skinned)
Vitamin D Society https://www.vitamindsociety.org/
Our tip would be to build your Vitamin D reserve over the summer months with regular exposure and wear sunscreen/clothes after 10 mins or longer depending on your skin colour.
FOOD SOURCES OF VITAMIN D
It’s estimated we may get around 10% of our Vit D requirements from food, so it’s a good idea to contain some of these foods in your weekly menu.
VITAMIN D3 – EGGS, BUTTER, OILY FISH
EGGS - have eggs once or twice a week – we shared some other nutritional information about eggs in Episode 55 – we talked about the protein, fat, choline and B12 content in eggs. 1 egg contains approx. 40iu of Vitamin D mostly from the yolk.
Ideas for egg meals would be the simple dishes like scrambled, poached, boiled eggs, omelets, egg muffins, frittata, and dishes like Turkish eggs.
OILY FISH – 75g of salmon contains approx. 400iu of Vit D, 75g of canned tuna in water contains approx. 40iu, 2 sardines in oil is approx. 40iu. We’d suggest eating oily fish 1-2 times per week.
VITAMIN D2 – MUSHROOMS AND FORTIFIED MILKS E.G. SOYA AND ALMOND
Mushrooms – the D2 type – ½ cup white mushrooms exposed to UV light contains 366iu compared to a 1/2 of portabello mushrooms only having 4iu (presumably not exposed to UV light). The message is that we need to store mushrooms on a sunny window ledge to maximise Vitamin D content!
It’s also important to have adequate supplies of other nutrients in your food plan to work as co factors alongside Vitamin D – they are:
· Magnesium – eat lots of dark green leafy vegetables, whole grains and nuts and seeds
· Calcium – examples are milk and cheese, small fish such as sardines, apricots, blueberries, chickpeas, kidney beans, fortified tofu
· Boron – is a trace element found in in leafy green vegetables like kale and spinach. It can also be found in grains, prunes, raisins, non citrus fruits, and nuts
· Vitamin K – dark green leafy vegetables, vegetable oils, and grains – you only require 1mcg per day so eating a variety of fresh foods should support you
· Vitamin A – eat orange vegetables like squash, sweet potato, carrots and fruits such as mango, dried apricots and cantaloupe melon, you’ll also find Vitamin A in liver, beans, spinach and broccoli
· We advise if you eat a rainbow with lots of variety you will get a wide range of nutrients.
1. 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.
2. 10% of your Vit D requirement may come from food
a. Vitamin D3 form is available from foods e.g. oily fish, butter, eggs.
b. Vitamin D2 found in plant-based foods e.g. mushrooms, fortified soya milk and almond milk
3. Factors contributing to low Vitamin D status include
a. Living in the Northern hemisphere
b. Covering up with clothes and sunscreen
c. Living/working/playing/exercising indoors so having less sun exposure
4. Some groups of people are at risk of a low Vitamin D status
a. People with dark skins (the ability to absorb UV light is reduced with darker skin)
b. 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
c. Ageing – decreases the capacity of skin to produce vitamin D3 be as much as 50%
d. People who are overweight/obese – Vitamin D is stored in body fat making it less bioavailable
5. Our suggested approach to attaining Optimal Vitamin D status is
a. SAFE Sun Exposure so you are optimising your opportunity to make vitamin D naturally with sunshine
b. Eat vitamin D Rich Foods
c. Know your vitamin D status – get tested – GP or private test
d. Use supplements with guidance from a health professional based on your Vit D status results – reach optimal – then maintain.
6. As a Runner an optimal Vitamin D status will
· Promote and protect bone health and minimise the risk of stress fractures
· Promote muscle function, repair and recovery
· Support the immune system and minimise/prevent COLDS/FLU/UPPER RESPIRATORY TRACT INFECTIONS which are a common complaint of runners during the colder months.
· Promote vasodilation – vital for blood flow and the delivery of extra oxygen and nutrients to the muscles during exercise.
The suggestions we make during this episode are for guidance and
advice only, and are not a substitute for medical advice or treatment.
If you have any concerns regarding your health, please contact
your healthcare professional for advice as soon as possible.
Aileen Smith and Karen Campbell met at as nutrition students (Institute for Optimum Nutrition, London) and became lifelong friends and nutritional buddies! Both have a love of running and a passion for nutrition, delicious food and healthy living.
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