A leading cardiac expert who personally has helped an estimated 1,000 patients replenish their vitamin D blood levels says that we need a lot more vitamin D than most people think, and that recommendations cannot be generalized but must be tailored for every different individual.

Dr. William Davis, a Milwaukee-based heart disease specialist, wrote the comments in an article entitled, “Vitamin D + You: Not a Vitamin, and Not One Size Fits All” that appears on the health web site www.MyHeartCentral.com.

“The media are quick to say such things as ‘Take the recommended daily allowance of 400 units per day,’ or ‘Perhaps intake of vitamin D should be higher, maybe 2000 units per day’ or ‘Be sure to get your 15 minutes of midday sun.'” Davis wrote. “The Food and Nutrition Board of the Institute of Medicine has been struggling with this question, also. They have tried to make broad pronouncements on American requirements for various nutrients by recommending Recommended Daily Allowances (RDA). The Food and Nutrition Board break vitamin D requirements down by age and sex, little better than a one-size-fits-all approach. Nonsense.”

He continued, “First of all, much of the confusion over dosing stems from the fact that vitamin D should not be called a ‘vitamin.’ We think of vitamins as nutrients our bodies were meant to obtain from foods. But, outside of oily fish, there is very little naturally-occurring vitamin D in food. (Even in fish, there is generally no more than 400 units per 4 oz. serving.) Sure, there’s 20 units in an egg yolk, 100 units per 8 oz of milk because the USDA mandates it, and you can activate the vitamin D in a shiitake mushroom by exposing it to ultraviolet radiation, but those sources hardly help at all. Vitamin D is better regarded as a hormone, not a vitamin. Vitamin D exerts potent effects in tiny quantities with hormone-like action in cells. It is the only hormone that is meant to be activated by sun exposure of the skin, not obtained through diet. As with any other hormone, such as thyroid hormone, doses should be individualized.”

Davis points out that people with low thyroid condition, for example, are not treated with one-size-fits-all recommendations. “Would you accept that you should take the same dose of thyroid hormone as every other man or woman your age, regardless of your body size, proportion of body fat, metabolism, genetics, race, dietary habits, and other factors that influence thyroid hormone levels? Of course you wouldn’t. Then why would anyone insist that vitamin D be applied in a one-size-fits-all fashion?”

He continued, “In truth, the ideal replacement dose of thyroid hormone can range widely from one person to another. Some people require 25 mcg per day; others require 800% greater doses. Likewise, vitamin D requirements can range widely. I have used anywhere from 1000 units per day, all the way up to 16,000 units per day before desirable blood levels were achieved.”

A full-body tanning session is estimated to produce 10,000 to 25,000 units of vitamin D naturally — more than 100 times what an 8-ounce glass of whole milk produces.

His bottom-line recommendation: “There’s only one way to truly individualize your need for vitamin D and thereby determine your dose: Measure a blood level.”

Davis recommends vitamin D blood levels of 60-70 nanograms per milliliter as measured by a calcidiol test.

“I would rank normalizing vitamin D as among the most important things you can do for your health. It should never be too much bother,” he wrote. “And if your doctor refuses to at least discuss why he/she won’t measure it, then it’s time for a new doctor.”