Supps Uncategorized

The dangers of too much vitamin D

Many of us are deficient in vitamin D but aggressive supplementation may cause more problems than it solves, says Dr John Berardi

Dr John Berardi is a nutrition and exercise coach, sport scientist, author, and a founder of Precision Nutrition. He is based in Toronto, Canada.

itamin D supplementation has achieved almost mythical status for its perceived ability to act as a panacea to many ailments, much like fish oil once was.

What we do know is that nearly everyone we test is low in vitamin D, and that adequate levels are essential for a whole host of positive health outcomes. Getting back up to optimal levels is therefore very important, which is why you’ve probably either supplemented with vitamin D at some point, or it has been recommend to you by a fitness professional.

The latest trend is to take high to very high dosages, as much as 4,000 to even 6,000 IU per day, or even a once-a-week dosage of 50,000 IU. I’ve heard all kinds of recommendations.

Overly-aggressive supplementation protocols scare me. We simply do not know at this stage how many nutrients interact – either positively or negatively – with others.

Think about it: if you are deficient in vitamin D you are likely deficient in other nutrients too. So just topping up vitamin D levels, and ignoring any other deficiencies, may well make those other deficiencies worse, or make a physiological problem associated to a particular deficiency even worse.

Nutrient interaction
Let’s take vitamin K as an example. You may know that vitamin D consumption increases calcium levels in the body. You may not know that vitamin K helps dispose of this excess calcium appropriately. You don’t want it deposited on the walls of your arteries: that’s arteriosclerotic plaque build-up in action.

If you are taking lots of vitamin D but deficient in vitamin K, you will be getting all the associated benefits, but will have increased calcium levels that could – over time – result in a serious health problem.

Vitamin D also interacts with vitamin A. They raise or lower each other’s status in the body so you need to ensure your intake of both is balanced. Magnesium is another nutrient we know of that interacts with vitamin D too.

These are just the few examples we actually have data on right now. There are likely to be many more nutrients that closely interact with vitamin D, but we just haven’t done the research yet to find out which.

Diet comes first
I do supplement with vitamin D, but I monitor my levels with regular blood tests and take the appropriate dose to bring my levels back up into the healthy range. I also supplement with vitamin K, and I try to mitigate some of the other issues that might occur, such as taking a multivitamin alongside vitamin D.

It’s another reason why a good natural diet is so important. You’re not going to get enough vitamin D from foods, we know that, but if you eat a varied diet with fruits, vegetables, meat, nuts and seeds, you are very likely to have sufficient levels of all the other essential vitamins and minerals your body needs.

For more tips and advice tap here or go to