Keeping up-to-date on the latest research is no easy task.
Science works like this: we have a question, research is conducted and results analyzed. More studies are done and overtime the totality of those results will start to reveal a clearer answer.
The more evidence there is, and the more that evidence ‘lands’ on a particular answer, our confidence of those results strengthens.
The challenge nowadays is that we are inundated with study results left, right and center. Every day it seems like some new study is on the news or being talked about.
To make matters worse, each study seems to contradict another.
As the saying goes, we can’t lose sight of the forest for the trees.
Vitamin D. To take or not to take?
The results of a recent large study that was supposed to be the final answer as to whether or not taking vitamin D supplements could help with bone health and support muscular strength (which helps to prevent falls, and therefore reduce the risk for fractures) were revealed.
The author’s concluded that vitamin D supplements don’t make bones stronger.
The researchers conducted a meta-analysis, a research word meaning they grouped together, and analyzed the results a bunch of studies (81 in this case) that met certain criteria. They included studies where subjects had some kind of fracture, had experienced a fall and studies which had information on bone density for about 54,000 people.
In the end, they claimed vitamin D had no benefit.
The devil is in the details
It’s beyond the scope of this article to highlight all of the problems with this particular study.
A major limitation in meta-analyses is that there can be significant differences between the studies that are included. The dose of vitamin D, how vitamin D was taken (e.g. one large dose once every 2 months versus smaller daily doses), the subjects’ blood levels of vitamin D at the start of the study and at the end, and how long vitamin D supplements were taken can all be different.
This might not seem important, but it influences how the results are interpreted.
You don’t need to be a scientist to know that 400 IU of vitamin D is not the same amount as 800 IU or 2000 IU. Different doses will result in different blood levels of vitamin D and blood levels influence how the body absorbs and manages the minerals needed for bone health.
Would you expect 200 mg of ibuprofen to be as effective as 1600 mg when it comes to pain relief? Of course not, but this is the approach that is typically taken with supplement studies.
An arbitrary dose is given which doesn’t lead to a positive benefit and then the nutrient in question is categorically dismissed. With vitamin D, blood levels DO matter.
Synergy is the foundation of nutrients’ role
There is another issue with how nutrient research has historically been done. In the gold standard double-blind, placebo-controlled studies, researchers always want to control anything that will influence the study results.
If you were testing ASA for pain relief, you’d want to make sure subjects weren’t using any other pain relievers otherwise any pain relief provided by ASA would be ‘down played’ because some of the pain relief would be coming from another analgesic if subjects were in fact taking them. Fair enough.
This drug-model study design is used all the time with nutrient research. To see the effects of vitamin D and vitamin D only, other nutrients that work with vitamin D3 would typically not be considered or at least not included as supplements. Otherwise researchers wouldn’t feel confident in the results.
They’d be concerned that some of the positive results would be attributed to the other nutrients. The irony of course is, that’s how nutrients and biology work. Nutrients work together and enhance the effects of each other.
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This meta-analysis did not consider this, and so yes, giving vitamin D at any dose, without considering blood levels of vitamin D and not considering if supporting nutrients are optimized will likely not provide sufficient bone and muscular benefits.
Despite these limitations, there are several well designed studies that have shown a meaningful benefit with bone and muscular health when vitamin D3 is used alone.
The key of course is using an appropriate dose that will raise blood levels of vitamin D to a known minimum beneficial level. The amount needed varies from person to person which is why testing is the only way to know if you’re “good to go”.
There isn’t one dose for everyone. A crucial fact the vast majority of studies have ignored including those in this ‘definitive’ meta-analysis.
What foods are high in vitamin D?
Vitamin D is not found easily in the food supply. Best foods include:
- Milk
- Fatty fish like salmon, herring, sardines, trout, herring
- Beef liver
- Egg yolks
- Cod liver oil
- Shrimp
A few vitamin D fun facts:
- In Canada, you can only make vitamin D from the sun in a meaningful way from about April to the end of September (sorry, winter sunshine doesn’t cut it).
- Is vitamin D the same as D3? Yes, but with the increased use of D2 in vegan foods, we know now refer to vitamin as D3 to avoid confusion
- You can’t store enough vitamin D made in the summer to last throughout the fall and winter.
- Adequate safe sun exposure (UVB index of a least 3) is needed for your skin to produce it. No, you’re not making any when the sun is up at 7 am or is still around at 7 pm in the evening (UVB isn’t strong enough).
- Do you get vitamin D from tanning beds? Yes, caution is advised though.
- The skin’s ability to make vitamin D declines with age.
- There are very few natural food sources of vitamin D which is why supplements are typically needed year round.
- Optimal calcium absorption occurs with a vitamin D blood level of 75-80 nmol/L.
- Clinical deficiency is defined as <25 nmol/L; most Canadians’ levels are 25-35 nmol/L by January.
- There’s no one right dose for everyone; genetics plays a big role when it comes to personal dose.
Vitamin D alone may not directly boost bone mineral density as much as we once thought but to dismiss it out right defies basic biology and physiology. Furthermore, ensuring you get all the nutrients needed for bone health is crucial to get the most from vitamin D’s seemingly countless health benefits, including bone health.
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Other nutrients to focus on include:
- Calcium: needed to build strong bone mineral.
- Magnesium: also needed for bone mineral development and to activate vitamin D into its active form.
- Vitamin K2: not to be confused with K1. K2 is needed to keep calcium out of soft tissues like your blood vessels and ensure it gets into your bones and teeth.
- Vitamin C: is needed to help make collagen, the main protein that bone is made of.
- Zinc: helps vitamin D work inside your cells, including bone cells where it helps to strengthen them.
- Boron: helps your body use other minerals such as calcium and magnesium properly.
So, it’s a vitamin DO for vitamin D in Canada
Doug Cook RDN is a Toronto based dietitian and functional dietitian with a focus on digestive, gut, mental health. Follow me on Facebook, Instagram and Twitter.