Topping up your vitamin D tank

Now that my vitamin D replacement experience dates back nearly 5 years, I've been witnessing an unusual phenomenon:

The longer you take vitamin D, the less you need.

Let me explain. You take 10,000 units D3 in gelcap form. 25-hydroxy vitamin D levels, checked every 6 months, have remained consistently between 60 and 70 ng/ml. Three years into your vitamin D experience and 25-hydroxy vitamin D level rises to 98 ng/ml--an apparent need for less vitamin D.

So we cut your intake from 10,000 units per day to 8000 units per day. Another 25-hydroxy vitamin D level 6 months later: 94 ng/ml. We cut dose again to 6000 units, followed by another 25-hydroxy vitamin D level of 66 ng/ml.

This has now happened in approximately 20% of the people who have been taking vitamin D for 3 or more years. I know of no formal analysis of this effect, what I call the "topping up" phenomenon. Reasoned simply, it seems to me that, once your vitamin D "tank" is topped up (i.e., tissue stores have been replenished), it requires less to keep it full.

No one has experienced any adverse consequence of this topping up effect though it has potential for some people to develop toxic levels if 25-hydroxy vitamin D levels are not monitored long-term. In my office, I measure 25-hydroxy vitamin D levels every 6 months.

It means that long-term monitoring of 25-hydroxy vitamin D is crucial to maintain favorable and safe levels.

Comments (17) -

  • brian

    1/22/2011 3:02:39 PM |

    I deleted my own comment - should have previewed it first (grammar was horrible). Moving on... Smile

    I bet one reason for less D3 has a lot to do with the removal of change agents, namely wheat, sugar and vegetable oils.


  • Henry Lahore

    1/22/2011 3:06:38 PM |

    Have not heard of "topping off" before, and I have read over 3,000 articles on vitamin D. Like to have some more detail: out of how many people, what age, what weight, what skin color, what health, what other supplements, what kind of vitamin D, what latitude, etc.  Admininstrator for vitaminDwiki dot com

  • Might-o'chondri-AL

    1/22/2011 5:26:29 PM |

    Looks like vitamin D clearance 1/2 life shifts to longer cycle -it hangs in there more. I wonder how many of us have genetic vit. D 1/2 life variation to begin with.

  • qualia

    1/22/2011 7:09:38 PM |

    yep, how about healing of the villi after going off gluten per your recommendation? the average healing time for damaged villi is about 1-3y.

    are those 20% also the ones who had the lowest D level at the beginning? or did they just need a higher dosage to reach the target level, but were not more deficient on average than the steady 80%?

    if it is the storage and top-up effect, they theoretically should have been lower statistically speaking at the beginning.

  • Dr. William Davis

    1/22/2011 8:12:36 PM |

    Henry and Qualia--

    This is just an informal observation I have not tried to characterize.

    However, I have not noticed any specific patterns to the phenomenon.

    The majority of people in the office are Caucasian, so I am uncertain how race enters into the equation.

  • Anonymous

    1/23/2011 1:17:09 AM |

    What are some natural sources of vit D?

  • Paul

    1/23/2011 3:09:14 AM |

    "What are some natural sources of vit D?"

    Other than the sun, there are not many.

    The best, modern day, natural dietary source of cholecalciferol (D3) is fatty fish (wild caught sardines, salmon, catfish, and mackerel.)  they can provide 300-400iu per 3oz. serving.  You'd have to eat a whole lot of fish to get 5000-10000iu of D3 a day.

    Cod liver oil is another source, but almost all the cheaper commercially available brands of CLO have had all the "natural vitamins" striped out in the distillation process.  The synthetic forms of Vitamins A and D are only then added back into the formulations.  In addition, its usually done in extremely unbalanced ratios that may cause Vitamin A toxicity. This is why cheap brands of CLO are not a recommended source of D3.

    Mushrooms are often said to be a good source of vitamin D, but they only contain the plant form - ergocalciferol (D2) - which doesn't help us vertebrates.

  • moblogs

    1/23/2011 9:57:09 AM |

    This has happened to me. I started with 5000IU but needed way more, so I took 10,000IU, however when I took 7000IU a year later, my optimal level was as it was on 10,000IU. I'm of South Asian heritage.
    At the moment I'm experimenting with 12,500IU out of curiosity, but this is certainly not a dose I'll take permanently.

  • Geoffrey Levens

    1/23/2011 3:52:34 PM |

    Always the odd man out, has not happened to me.  Probably 5 or 6 years at least and I still need the same amount, about 8000iu/day to hold even at around 50ng/ml. Pretty interesting though...

  • Steve

    1/23/2011 7:16:13 PM |

    First, thanks for the blog & all this info -- very helpful for me. A question: I'm finishing a jar of "dry" (not oil suspended) Vitamin D3 capsules and taking them, as you recommended, with oil, in this case Sam's Member's Mark Fish Oil that is enteric coated. Will the enteric coating prevent the fish oil from helping the "dry" D3 absorption?

  • Davide Palmer

    1/23/2011 8:02:18 PM |

    I wonder if this principle applies to other supplements like fish oil. I know it can take months for omega 3's to be stored in tissues in adequate amounts.

  • Catherine/Santa Fe

    1/23/2011 8:48:30 PM |

    Yes, this happened to BOTH my husband and I, but in only 18 months time.

    Both our levels went up quickly from 32ng to 68mg in only 8 weeks on 5,500IU of D3.  And we maintained those levels for about a year on above dosage. But then our test stared showing higher levels (80 and 98) with same dosage/same name brand, so we lowered it to 3,000 a day and last test showed 70 and 78. But since reading this article, I am going to keep tabs more closely.

  • Travis Culp

    1/24/2011 7:42:49 PM |

    Well, my theory would be that this occurs in people who are supplementing D3 and have a concomitant weight loss, and are thus in need of less D3 due to a reduction in body mass, especially adipose tissue. That's just a gut feeling though, so to speak.

  • Anonymous

    1/24/2011 8:13:21 PM |

    Couldn't an increase in sun exposure change your vitamin D levels - maybe a sunnier year, or a new habit of walking outside, for instance?

  • Anonymous

    1/25/2011 6:16:22 PM |

    I was wandering about that mysel, whether sun exposure during the summer months along with steady suplementation wouldn't cause seasonal variations in D levels.  Could that possibly be affecting the results in your patients tests? In other words, have you noticed any possible correlations between high numbers and time of the year?

  • Patricia D.

    2/10/2011 8:14:26 PM |

    Regarding where to aim at for optimal benefit with individual blood serum levels of VD3:

    Dr. Cannell of the Vitamin D Council ( recommends blood serum levels between 50-80ng/ml.  

    He recommends between 90-100 for all cancer survivors.

    We heard a VD3 expert interviewed on "The People's Pharmacy" radio show (I'm sorry I don't have the name - but I could get it) ... His recommendation for optimal levels  was between 60-90 ng/ml.

    My personal goal is 90 ng/ml because I have an autoimmune condition.  I pay good attention to the VD3 co-factors including magnesium.

  • paul

    4/29/2011 8:46:50 AM |

    Vitamin D is vital for our health. It's important not to take too little or too much of it. I suggest you stay under the sun for at least 10 - 15 minutes.

    Vitamins Canada