Dispelling nutrition myths, ranting, and occasionally, raving


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The vitamin D debate: Won’t someone please think of the children?!

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The latest “study” on vitamin D reached the conclusion that vitamin D does nothing to prevent myriad medical conditions. You may be wondering why I placed study in quotation marks. That’s because it’s not actually a new study. It’s an analysis of the results from a number of randomized controlled trials of vitamin D supplements.

Of course, there are the usual issues with meta-analyses. We don’t know for certain if the authors cherry-picked the studies they chose to look at. We don’t know (without spending substantial amounts of our own time, and probably money) if the original studies were flawed. It’s a good thing that it’s good that this analysis looked at studies using a randomized control model. This avoids the obvious potential confounding factors seen with observational studies. However, I have some doubts that these studies would have been conducted over long enough time-spans to accurately assess the use of vitamin D supplements. After all, they were looking at the effects of vitamin D supplementation on myocardial infarction or ischaemic heart disease, stroke or cerebrovascular disease, cancer, total fracture, hip fracture, and mortality. To truly determine the effects of vitamin D supplementation on these conditions supplementation would have had to begin in childhood and continue until death (or at least very old age).

The authors found that vitamin D did not affect outcomes by more than 15% for any of the above conditions, aside from hip fractures in institutionalized seniors.

I’m inclined to think that we may be expecting far too much from vitamins and minerals. Just because vitamin D probably doesn’t prevent cancer or heart disease doesn’t mean that there aren’t any benefits to be obtained from taking it as a supplement. Perhaps it may prove to be beneficial in mood regulation, cold prevention, or something else less earth shattering than these studies looked at.

Perhaps there is no benefit to taking vitamin D supplements. However, I’m not quite ready to toss my bottle. I know that I can’t meet the currently recommended amount of vitamin D through diet alone. And I’m certainly not getting any from sun exposure this time of year. I don’t think that we should dispose of the current vitamin D recommendations on the basis of one meta-analysis. I’m certainly open to changing my mind but for now I’d like to hedge my bets. I’d rather risk taking a “useless” vitamin D supplement than risk experiencing adverse health consequences from not consuming sufficient vitamin D.

In addition, I worry that research such as this may lead to new parents neglecting to supplement their infants with vitamin D and causing a resurgence in rickets. Just because there’s uncertainty about the long-term outcomes of vitamin D supplementation doesn’t mean that we don’t know the benefits in early childhood.


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Strong bones

Last week a US government advisory group announced that there is no benefit for healthy “older” women to take low-dose calcium or vitamin D supplements. These conclusions were based on findings that these supplements do not appear to reduce the risk of broken bones.

There are a few important things to note about this pronouncement: 1. This message applies only to healthy older women. Women who are suffering from certain illnesses may require more of some nutrients and should consult with their doctor before stopping (or starting) any supplement regimen. 2. The advisory group did not look at higher supplement doses. There may be benefits (or risks) to consuming higher supplemental doses. 3. The announcement was based on risk of broken bones in comparison to risk of kidney stones. The advisory group did not look at any benefits of supplementation other than bone health. There may be additional benefits to vitamin D supplementation (again, or risks) we just don’t have sufficient research to advise on this basis yet.

I think that the most important lesson we can take away from this study is that many illnesses that befall us when we’re elderly are a result of exposures and lifestyle during our youth. As I remember learning in school: osteoporosis is a pediatric disease with geriatric consequences. We can’t mistreat or neglect our bodies when we’re young and then expect to make up for it when we’re elderly. To ensure strong healthy bones as seniors we need to ensure that children and young adults consume healthy balanced diets; including adequate vitamin D (which may require supplementation) and calcium. Children also need to engage in regular physical activity and we need to continue to exercise throughout our lives to maintain muscle mass and strong bones.

While it’s never too late to start leading a healthy life, it’s also never too early.


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Is the sun setting on vitamin D?

Researchers in Germany recently found that higher maternal levels of vitamin D during pregnancy translated to higher in utero levels of vitamin D for their babies. This in turn, was associated with greater likelihood of developing a food allergy by age two. This is interesting because vitamin D is one of the few supplements I advise pretty much everyone to take, at least during the winter months, as it’s highly unlikely that most of us are meeting the current recommendations via food consumption.

Looking at the original journal article, I couldn’t find any listed source of funding. Always the first thing I check when I’m looking for legitimacy of research. Next I checked to see how many participants there were, and how they were selected. There were 629 mother-child pairs, not too shabby. Participants were recruited from an existing cohort study entitled LINA (Lifestyle and environmental factors and their Influence on Newborns Allergy risk). I’m not sure how participants were recruited from the study, nor am I sure how participants for the original study were recruited. I can’t help but wonder if they were volunteers if there might be some selection bias that would skew the results. However, further along in the methods, the researchers state that the vitamin D levels were tested for 378 mother-child pairs. This is still not a bad sample size, but not nearly as good as it initially appeared.

Getting into the statistical analysis makes me wish I had cared more about learning and retaining statistical ability when I was in school. It’s interesting to note that vitamin D levels were strongly correlated with season. Maternal and cord blood levels of vitamin D peaked in August and were lowest in March. Also, only seven of the mothers took vitamin D supplements during pregnancy. 44% of the mothers were deficient in vitamin D, 26% were insufficient, and 30% had optimal levels. 50% of newborns had deficient levels of vitamin D.

Results were analysed by dividing the mother-child pairs into quartiles based on the mothers’ vitamin D levels. I find this a little suspicious. There are no details provided as to how many mother-child pairs were in each category, nor what the cut-off were for each quartile, and I’m not sure how fair it is to draw comparisons between the quartiles if the distribution (as was mentioned in the analysis) was not equal. The results do show significantly more diagnosed food allergies among children born to mothers in the 3rd and 4th quartiles (i.e. those with the highest blood levels of vitamin D during pregnancy). However, there were still only six in the 4th quartile and five in the 3rd, compared to three in the 2nd and one in the 1st. It’s also important to note that the “diagnosed” food allergy was reported by the mother on a questionnaire; diagnosis was not actually obtained by the researchers. This introduces an additional element of bias.

In the discussion the researchers acknowledge that there was a high level of participation from allergy sufferers which may mean that the results can’t be generalised to the entire population.

Because vitamin D levels were so strongly correlated with the seasons I wonder if there is some other seasonal factor which may be causing the increased rate of food allergies among the children. There may also be some other commonality among the mothers with higher levels of vitamin D which is leading to increased rates of food allergies among their offspring.

I do think that this research is interesting and warrants further investigation. However, I worry that studies like this may actually cause more harm than good. Vitamin D supplements for infants are important to avoid the development of rickets. I wouldn’t want any potential parents, or new parents, to interpret these findings as an indication that they shouldn’t be providing these supplements to their babies.

 

Thanks to one of my loyal readers for sharing the news article with me and for one of my twitter friends for hooking me up with the original journal article.


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Follow Friday: Vitamin D

I’m not going to lie; when I clicked on the link in the tweet from @fitocracy I was hoping to find some fodder for a blog rant. The tweet read: “Vitamin D: 3 Things You Probably Know, 3 Things You Probably Didn’t”. Fortunately, I was pleasantly surprised by a seemingly accurate article about vitamin D written by the founders of the website examine.ca which is a science-based site about supplements and nutrition.

If you’re interested in learning more about vitamin D, or just curious to find out if you already know it all, you should check out this article.


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Got fortified cow beverage?

I’m getting caught-up on my nutrition article reading. You may have seen headlines all over the news a few weeks ago about how many children are drinking too much milk.

I think that many parents have been convinced, dare I say by the dairy industry (under the guise of Canada’s Food Guide), that children need lots and lots of milk to have strong teeth and bones. Unfortunately for all of us milk loathers who suffered through the dreaded milk program in grade school, this is not true. Yes, milk is a good source of protein (8 grams per cup), calcium (30% of our daily needs as adults), and vitamin D (45% DV – although it’s important to point out that cow’s milk is fortified with vitamin D so I don’t really think it should be praised for that). The thing is, there are plenty of other foods that contain these nutrients. If your child suffers from lactose intolerance or a milk allergy they are not going to develop rickets or osteoporosis (yes, it’s a pediatric disease with adult consequences) as long as they obtain enough of these nutrients from other sources. If you’re child just doesn’t like milk, or you choose not to serve them milk for whatever reason, they can still live healthy and productive lives.

One of the reasons that excessive milk consumption in children is an issue is that it tends to lead to insufficient consumption of other nutrients, specifically iron. Iron deficiency can lead to anemia which can be indicated by paleness, fatigue, decreased immune function. There is also the potential for poor growth and development as a result.

Good food sources of iron include: oat bran cereal, clams, spinach, beans and lentils, tofu, egg yolks, beef, and baked potatoes. Using uncoated cast iron cookware (especially to cook acidic foods such as tomato sauce) can also increase iron consumption. Consuming vitamin C containing foods (such as citrus fruits, peppers, and tomatoes) with iron-containing foods can also increase the amount of iron absorbed.

Good food sources of protein include: tuna (and other fish), poultry, meat, beans, legumes, yoghurt, tofu, nuts, eggs, even grains.

Good food sources of calcium include: yoghurt, fortified orange juice, many cheeses, spinach and other dark leafy greens (kale, broccoli, asparagus), tinned salmon (with bones) and sardines, fortified cereals, and tofu.

Good food sources of vitamin D include: egg yolks, fatty fish (herring, eel, salmon, sardines, tuna), and fortified cereals.

There is a huge proliferation of “milks” on the market these days. You’re no longer limited to cow’s milk or soy milk. There’s almond milk, coconut milk, sunflower milk, quinoa milk, hemp milk, rice milk… The choices can be overwhelming. The first thing you should check for is added sugar. No need to consume any more sugar than we already do. Next, check your labels to ensure your “milk” is fortified. Finally, check for unwanted ingredients like added oils. Beyond those tips, go for what you (or your child) actually likes. With all the options available you should be able to find one that will be both pleasing to your palate and provide the nutrients you need.