Published on Enhanced Fitness and Performance (http://enhancedfp.com)

Vitamin A can Inhibit The Benefits Of Vitamin D

By DMorgan
Created 03/16/2010 - 11:18am

Even Low Amounts of Vitamin A Can Negate Benefits of Vitamin D

Given that cancer, heart disease and diabetes are three of the top causes of death in the United States, ensuring that you are getting enough of this crucial vitamin should be a top priority.

A study by Dr. William Grant, Ph.D., another internationally recognized research scientist and vitamin D expert, found that about 30 percent of cancer deaths [1] -- which amounts to 2 million worldwide and 200,000 in the United States -- could be prevented each year with higher levels of vitamin D.

Knowing this, it’s clearly important to avoid anything that might hamper your vitamin D production, and it appears vitamin A supplementation may indeed have this effect.

I highly recommend you read Dr. Cannell’s article [2] about this latest BMJ study, in its entirety, as he explains quite well how even the researchers themselves seem to have missed this crucial connection.

He writes:

“Dr. Mazda Jenab and his 45 colleagues from the International Agency for Research on Cancer confirmed that low vitamin D levels are a risk for colon cancer in a dose response manner; those with the highest levels were about twice as less likely to develop colon cancer compared to those with the highest levels.

However, hidden on page eight is one sentence and a small table, which shows that the benefits of vitamin D are almost entirely negated in those with the highest vitamin A intake. And the retinol intake did not have to be that high in these older adults to begin to negate vitamin D's effects, about 3,000 IU/day.

Remember, young autistic children often take 3,500 IU of retinol a day in their powdered multivitamins, which doesn't count any additional vitamin A given in high single doses.

This is the largest study to date showing vitamin A blocks vitamin D's effect and explains some of the anomalies in other papers on vitamin D and cancer.”

The Synergistic Effects of Vitamin A on Vitamin D

It’s highly unfortunate, but many people in developed countries are potentially sabotaging the multitude of health benefits they could receive from adequate vitamin D by taking excessive amounts of vitamin A, either in the form of multi-vitamins or cod liver oil.

I spent many hours reviewing this issue in the latter part of 2008, and as a result, I issued a revision of my long held recommendation for cod liver oil [3]. If you missed that important update, please take the time to review it now.

I had recommended cod liver oil as a source of vitamin D for quite some time, prior to this revision. My stance was based on the fact that cod liver oil contains vitamins D and A in addition to healthy omega-3 fats.

These vitamins are essential for most everyone who cannot get regular sun exposure year-round.

However, as I began reviewing the latest research, I realized there was compelling evidence that the ratios of these two vitamins may be of paramount importance in order to extract optimal health benefits. And this latest study appears to confirm that theory.

It’s important to understand that vitamin A is essential for your immune system and a precursor to active hormones that regulate the expression of your genes just like vitamin D, and the two work in tandem.

For example, there is evidence that without vitamin D, vitamin A can be ineffective or even toxic. But if you’re deficient in vitamin A, vitamin D cannot function properly either.

So proper balance of these two vitamins is essential. Too much or too little of either may create negative consequences.

Unfortunately, we do not yet know the optimal ratios between these two vitamins, but it is clear that nearly all cod liver oil products supply them in levels that do not appear to be ideal.

You also need to discern between various forms of vitamin A.

It is the retinoic acid (retinol) form of vitamin A that is problematic. Not beta carotene.

Beta carotene is not a concern because it is PRE-vitamin A. Your body will simply not over-convert beta carotene to excessive levels of vitamin A. So taking beta carotene supplements is not going to interfere with your vitamin D.

How Can You Ensure Proper Ratios of Vitamins A and D?

As Dr. Cannell has stated in earlier writings on this topic, the ideal way to obtain the proper vitamin A to D ratio is to obtain it the way your body was designed to obtain it:

Source URL: