Bone Health, Vitamin D and the Question of Supplementation

I broke my foot nearly 12 weeks ago in the middle of January. I slipped, caving my ankle inward sharply, as I jogged down a steep set of wooden stairs in the foggy mist. My ankle bone made brief contact with the stairs – so fast you wouldn’t have seen it happen had you been there – and then I bounced back up only to be met with excruciating pain on the outer side of my foot.

Long story short, I managed to fracture my 5th metatarsal – a clean break that fell along the line of a tuberosity avulsion fracture and a Jones fracture (the latter of which isn’t known to heal well). This put me in an air cast and obviously meant absolutely no running. Or for that matter no any activity of any sort for a solid 8 weeks, at which point I was finally allowed to be free from the air cast and walk, cycle and hike. Still no running though.

Truthfully I’d never given much deep thought to bone health before this. Certainly I practiced the basics and knew what was required in order to build strong bones. I knew that a lack of bone-building nutrients can predispose active individuals to stress fractures (such as this 2012 study outlines). I also knew that poor bone health results in osteopenia (low bone density – continued bone loss may result in osteoporosis) and osteoporosis (very low bone density – increases risk of fractures and breaks).

But I’ll admit there’s nothing like something personally affecting you to dive ever so much deeper into the research. While I was told my bone density looks just fine by my orthopaedic doctor, I still wanted to nourish my body best possible for optimal bone healing. And of all the important nutrients required, I find the most fascinating one to be vitamin D – because we’re evolved to get it from the sun, not food. In fact of the very few food sources there are, most are pretty poor⁽¹⁾.

Most people automatically equate bone health with adequate calcium intake. And certainly when it comes to bone health, calcium is definitely important. But here’s the thing – it’s imperative to maintain an optimal vitamin D blood concentration to maximize calcium absorption. Without that optimal vitamin D level, we can’t form enough calcitriol (a hormone known as the active form of vitamin D) and subsequently, there is insufficient calcium absorption from the food we eat. In other words, you might eat all the calcium-rich foods⁽²⁾ or take all the calcium supplements you want, but if your levels of vitamin D are low you can still become deficient in calcium anyway.

Inadequate vitamin D is obviously a bad situation destined to only get worse. In the absence of enough vitamin D the body will take calcium from its bones, which it sees as calcium reserves, in order to perform other key functions (such muscle growth, muscle contraction and nerve transmission). Eventually the existing bone will become weakened. Meanwhile, continued low vitamin D status prevents any new bone from forming.

Risk Factors for Low Vitamin D Status

There are a number of reasons why someone might end up with unfavourable vitamin D concentrations, including:

• Where in the world you live. If you live north of the 37th northern parallel (or south of the 37th southern parallel), the winter months mean no vitamin D from sun exposure. To visualize this, if you live in any of the greyed out portions of the map below (and zoomed in map of US below that), you are in a risk zone.

• If you train mainly indoors and/or spend little time outdoors in the summer months and/or always wear sunscreen when you do get out in the sun. Vitamin D is known as the sunshine vitamin for good reason – it’s produced in the body from sun exposure.
• Your training schedule is intense. Just as athletes require more of all other vitamins and minerals (which they can get from consuming the extra calories they also require), due to the increase in enzymatic activity from exercise, vitamin D is also required in greater amounts by those who train hard.
• How old you are. Your ability to convert vitamin D into the active form decreases with age. The average 65-year-old is producing only a quarter of what they did when they were 25 years of age.
• What your skin colour is. Those with darker skin typically have lower levels of vitamin D compared those with light skin (or in other words, they need more sun exposure to gain similar levels, about twice as much).
• Difficulties with absorption. Certain health conditions such as IBD (inflammatory bowel disease), celiac disease, liver disease and cystic fibrosis, can mean trouble when it comes to absorbing vitamin D.
• Overweight. A BMI (body mass index) above 30 means vitamin D gets tied up in fat stores making less of it available for use in the body.

Optimal Vitamin D Status

It’s clear the body must have optimal levels of vitamin D in order to absorb calcium and build a healthy skeleton. But how do you know if you have these ‘optimal levels’? What are they? This chart helps break it down:

While many negative consequences have been associated with levels that range from severely deficient to inadequate and with excess, most studies (such as this 2015 review points out) agree that the optimal serum level of vitamin D an athlete should target is 75-100 nmol/L (30-40 ng/ml). Therefore, the best way to know if you have optimal levels of vitamin D is to find out where you fall in the spectrum. And that is done via a blood test.

The Question of Vitamin D Supplementation

High dose supplementation is a controversial area and scientific opinion is divided when it comes to ideal supplementation amounts. Generally before recommendations are made, a simple blood test needs to be done to determine ones 25(OH)D status (serum 25-hydroxyvitamin D3 – a precursor to the active form of vitamin D) – in fact it’s a good idea to have this blood test be a part of your routine annual exam. Once levels are assessed, supplementation requirements can be properly determined.

Conservative supplementation recommendations fall between 400-1,000 IU daily. This amount is generally fine to begin taking without a blood test if you qualify under any of the risk factors listed above. For example, it might be ideal for someone who is currently within the optimal level of 75-100 nmol/L (30-40 ng/ml) and finds themselves without access to sun (such as during the winter months in areas north of the 37th parallel) and wishing to prevent current levels from dropping below optimal. However this amount is unlikely enough for an individual to recover from a vitamin D deficiency.

The more controversial recommendations of 2,000-10,000 IU daily may be used short-term in cases of deficiency – the more deficient one is, the greater the vitamin D dosage recommended. Doses higher than 10,000 IU require frequent monitoring via blood tests, to ensure blood serum levels don’t go beyond optimal levels into excess.

If you do require supplementation, the type of vitamin D you choose to take does appear to make a difference. It’s been found in studies, such as this 2013 one, that daily supplementation of vitamin D3 is more effective than D2. Additionally, it generally appears that liquid forms of vitamin D produce better results than pill versions do.

The Ideal Vitamin D Source

Ideally, year-round for those in southern latitudes and in the summer for those in northern latitudes, you get your vitamin D from exposing yourself to the sun. Get outside midday on sunny days (without sunscreen, because sunscreen blocks the synthesis of vitamin D) for at least 10-30 minutes – of course, the more skin exposed the better. It’s been shown that just 15 minutes of UVB exposure in the summer (in a bathing suit) can produce 10,000 to 20,000 IU of vitamin D3. Our bodies can store vitamin D in the liver (to a limit however), so getting all the sun in the summer months may last into the winter months.

Of course, to this day, we continue to hear advise to use sun screen and avoid direct sun exposure. Unfortunately it appears to be to the detriment of many people and likely one of the reasons many studies suggest vitamin D deficiency is now widespread – the avoidance of all direct sun exposure increases the risk of vitamin D deficiency. While excess sun exposure has indeed been shown to lead to skin cancer, no sun exposure is not better. There must be some regular sun exposure for optimal health. The minimum required to avoid vitamin D deficiency is only 5-10 minutes of exposure to the arms and legs (or to the hands, arms and face) 2 to 3 times per week.

So for lack of access to the sun, I’ve been taking liquid vitamin D3 these past few months – along with eating all the calcium-rich foods⁽²⁾, all the leafy greens and at least 1 scoop daily of greens powder (best source of vitamin K, also imperative to calcium absorption and needs to be in balance with vitamin D), plenty of dark chocolate and pumpkin seeds (fantastic sources of magnesium, yet another nutrient essential to calcium absorption and bone health) and lots of salmon, halibut and hemp hearts (excellent sources of omega-3 rich foods which are anti-inflammatory, therefore helpful in healing).

And today, after reviewing my x-rays, my orthopaedic doctor told me I can start running again. I can run again! Now just bring on the summer sun please 🙂

To deliciously healthy food and stronger faster running (or really, just being able to run, ha)… Cheers,

Sarah Cuff, R.H.N.
Holistic Sports Nutritionist
Founder Eat 2 Run Sports Nutrition
CSNN Sports Nutrition Instructor

1. As referred to in paragraph 4, here is a list of food sources of vitamin D (fortified foods not included):

2. As referred to paragraph 5, here is a list of calcium-rich foods:

*Yes, milk is a good source of calcium but you don’t see it listed here as I do not recommend the consumption of pasteurized milk (only grass-fed, full-fat unsweetened yogurt, kefir, and hard cheese) – if you do have access to fresh, raw, grass-fed milk, it contains 290mg calcium per cup.