Vitamin D

A quick internet search will tell you that vitamin D is “a fat-soluble vitamin that help(s) the body absorb and retain calcium and phosphorus; both are critical for building bone. Also… vitamin D can reduce cancer cell growth, help control infections and reduce inflammation.”

Vitamin D has many tasks within the body and is essential for keeping us as healthy as possible through protein synthesis, muscle function, cardiovascular function, cell growth, musculoskeletal regulation, inflammatory response, and also for supporting immunity.

But why is it called the “sunshine vitamin’?

I don’t want to get into too much vitamin D chemistry and its formation (it’s actually a pro-hormone and not a vitamin at all), but here’s a very brief explanation. During exposure to sunlight our skin produces vitamin D3. Which is awesome – free healthy stuff from the sun! This sun induced vitamin D synthesis can, however, be greatly influenced by the seasons, time of day, latitude, altitude, air pollution, skin pigmentation, sunscreen use, whether the sunlight is passing through glass and plastic, as well as good old fashioned ageing. And during this time of year, which for us in the UK is autumn and winter, UV levels from the sun are not strong enough for us to make our own vitamin D.

A 2021 survey commissioned by the British Nutrition Foundation found that almost half of British adults are not aware of the Government’s recommendation to consider taking vitamin D supplements to stave off any deficiency in this vital nutrient. And apparently around 1 in 6 adults in the UK have low enough levels of vitamin D to cause rickets, bone pain and disabilities (Department of Health & Social Care, April 2022).

Other symptoms of a deficiency in vitamin D can include:

• Muscle pain (often diagnosed as fibromyalgia or chronic fatigue syndrome)
• Increased sensitivity to pain
• A tingly, “pins-and-needles” sensation in the hands or feet
• Muscle weakness in body parts near the core of the body, such as the upper arms or thighs
• Waddling while walking, due to muscle weakness in the hips or legs
• Osteoporosis and/or a history of broken bones
• Muscle twitches or tremors, or even spasms
• Low sex drive
• Low testosterone

As well as these symptoms, there’s a direct association between vitamin D deficiency and mortality rates from health conditions like cancer, cardiovascular disease, and diabetes and a long list of other undesirable things, including hypertension, increased blood pressure, endothelial dysfunction, and sudden cardiac death syndrome. As a result Public Health England has responded to growing concerns around low vitamin D levels by recommending that everyone should consider supplementing their diet with daily vitamin D all year round, not just in the autumn and winter months.

While there’s no definitive way to tell if you’re deficient in vitamin D without getting a blood test, (and even if you did get a blood test, there’s a broad range of medical opinions as to what’s “normal”), supplementing with vitamin D, in my opinion, is a must.

When we have the correct levels of vitamin D, we perform better physically, build strength easier and have fewer injuries. It regulates our muscles by activating the expression of genes that modulate muscle growth and differentiation, particularly that of Type II muscle fibres. When there’s a deficiency of vitamin D, Type II fibres are scrawny little things. Put them on supplementation and they get bigger. Vitamin D also strengthens the interaction between the two muscle cell proteins, myosin and actin, making muscle contractions stronger. So broadly speaking, having optimal levels of vitamin D increases your overall capacity to perform aerobic and anaerobic exercise.

Optimum levels of vitamin D also ensures healthy lung structure, capacity, optimal oxygen exchange, and the ability to finish a task without wheezing like an old steam engine. The vitamin also has direct effects on serotonin and dopamine levels, which are vital to muscular coordination and avoiding fatigue.

Having better levels of this crucial vitamin can increase circulating levels of the key hormones estradiol, testosterone, FSH, LH, and DHEA in women in general. Similarly, vitamin D supplementation has been shown, in at least one study, to significantly increase testosterone levels in men.

All that sounds amazing! So how much should I have?

Public Health England’s guidelines issued in 2016 say that everyone over the age of 1 year should have 400 international units (IU) of vitamin D per day. In the US the RDA is higher and varies between 600 IU of vitamin D all the way up to 2200 IU. However, all of those figures are pretty much based on guesswork and may still be a little too conservative.

It should be noted that it can be possible to take too much vitamin D. Possible negative side effects of vitamin D “intoxication” include anorexia, frequent urination, nausea, thirst, vomiting, and possibly altered mental status as well as kidney failure, but you’d have to take a massive amount of vitamin D to have these things happen.

As with most aspects of health and fitness, the story isn’t quite as simple as taking vitamin D and good things happening. If you choose to supplement with vitamin D, you also need to consume in your food, or take in supplement form, vitamin K2. And there are some good reasons why this is important.

Vitamin K2 works together with Vitamin D3 making sure that calcium is deposited in the bones and not elsewhere such as the arteries. Research has found the combined use of vitamin K2 & D3 to be more effective than either nutrient alone for preventing bone loss and for improving bone mineral density.

Vitamin D3 and vitamin K2 also work together to produce and activate a substance called Matrix GLA Protein (MGP), found around the elastic fibres of your arterial lining. MGP helps to protect against arterial calcification.

So there you have it. Vitamin D is absolutely essential for your body’s good health. If you’d like some advice about supplementation please ask.