I've heard it suggested that you should wait 15-30 minutes to let the vitamin D on the skin absorb.

Does Vitamin D wash away while you're swimming?

I would think so. Water is water. OTOH, maybe it requires scrubbing to detach?

Rule of thumb... avoid showering or water exposure for as long as is reasonably possible post sunlight exposure to maximize D.

Now, that just ruins the beach for me!

Do you think applying coconut oil to your skin before going swimming would help you retain some Vitamin D?

If the vitamin d is in an oil, seems to me you'd need soap or at least rubbing to remove it!

if you spend the afternoon at the beach, taking occasional dips in the water, you must be retaining some vitamin d. i can't believe it's being washed away. and if it's true that in 15-30 minutes it's being absorbed, then the time you are soaking up the sun, you will also be absorbing the vitamin. so although you might wash away some in the water, i'd imagine you're keeping quite a bit. my drive home from the beach is about 20 minutes, so if i just wait a little longer before i shower, hopefully i'll be keeping as much as possible (i also ride home in a topless jeep!).

I thought this was interesting.

I wonder if this has some relation to the effects of sunlight/sunlight deprivation?

Diurnal variation of the human adipose transcriptome and the link to metabolic disease.Loboda A, Kraft WK, Fine B, Joseph J, Nebozhyn M, Zhang C, He Y, Yang X, Wright C, Morris M, Chalikonda I, Ferguson M, Emilsson V, Leonardson A, Lamb J, Dai H, Schadt E, Greenberg HE, Lum PY.
Rosetta Inpharmatics, LLC (A wholly-owned subsidiary of Merck & Co,, Inc,), 401 Terry Ave N,, Seattle, WA 98109, USA. pek_lum~merck.com.

ABSTRACT: BACKGROUND: Circadian (diurnal) rhythm is an integral part of the physiology of the body; specifically, sleep, feeding behavior and metabolism are tightly linked to the light-dark cycle dictated by earth's rotation. METHODS: The present study examines the effect of diurnal rhythm on gene expression in the subcutaneous adipose tissue of overweight to mildly obese, healthy individuals. In this well-controlled clinical study, adipose biopsies were taken in the morning, afternoon and evening from individuals in three study arms: treatment with the weight loss drug sibutramine/fasted, placebo/fed and placebo/fasted. RESULTS: The results indicated that diurnal rhythm was the most significant driver of gene expression variation in the human adipose tissue, with at least 25% of the genes having had significant changes in their expression levels during the course of the day. The mRNA expression levels of core clock genes at a specific time of day were consistent across multiple subjects on different days in all three arms, indicating robust diurnal regulation irrespective of potential confounding factors. The genes essential for energy metabolism and tissue physiology were part of the diurnal signature. We hypothesize that the diurnal transition of the expression of energy metabolism genes reflects the shift in the adipose tissue from an energy-expending state in the morning to an energy-storing state in the evening. Consistent with this hypothesis, the diurnal transition was delayed by fasting and treatment with sibutramine. Finally, an in silico comparison of the diurnal signature with data from the publicly-available Connectivity Map demonstrated a significant association with transcripts that were repressed by mTOR inhibitors, suggesting a possible link between mTOR signaling, diurnal gene expression and metabolic regulation. CONCLUSION: Diurnal rhythm plays an important role in the physiology and regulation of energy metabolism in the adipose tissue and should be considered in the selection of novel targets for the treatment of obesity and other metabolic disorders.


http://www.ncbi.nlm.nih.gov/pubmed/...Pubmed_RVDocSum

I wonder if sun light on one's stomach would affect belly fat?

It has huge implications on metabolic research particularly if you look at other research in Diurnal rhythm
Such as Diurnal rhythm of active calcium transport in rat intestine
THE RHYTHM OF DIGESTION: KEEPING TIME IN THE GASTRO-INTESTINAL TRACT.
Racial Differences in the Human Endogenous Circadian Period

I've grumbled before that when you look at metabolic research you don't see them starting with a level Vitamin D3 playing field. They don't make any effort to ensure that everyone on the trial has equivalent 25(OH)d status even though we know that influences lots of factors.

Now they really are going to have to think about ensuring the time of each experiment is equivalent. So if you consume xg of carbohydrate/fat/protein at
the point where the body's diurnal rhythm is in storing mode it will have a different impact on the same xg of exactly the same food when the body is in spending mode. I haven't noticed in the full text of any paper so far that the time of day of the experiment was conducted. (it's as rare to see season mentioned in Vitamin D research as if anyone didn't know Vit d varied seasonally. let alone any mention of latitude)

Makes you wonder about the validity of much rat research on metabolism given rats are nocturnal and most humans aren't.

I've always do my blood pressure at the same time of day as I assumed that varied according to circadian rhythm but I wonder if other things also vary like inflammatory status. It's funny how you take these things for granted without ever questioning why. I'd not thought about shift work and metabolic syndrome before but I now see others have thought of this and found out it does have an adverse impact
I wonder what effect street lighting at night has on metabolic rhythm.

It does have an effect. Have you ever read Lights Out: Sleep, Sugar and Survival by T.S. Wiley?



There's also a very good thread about it here: http://forum.lowcarber.org/showthread.php?t=196014

No but I've been suggesting try to improve sleep hygiene and just recently, because of the heat I've started using an eye mask so we can have the windows/curtains open but my eyes are tricked into thinking the room is darker than it is in fact. I do think it helps get a better quality sleep.


Thanks there is so much going on here it's very easy to miss the goodies.

From The Sunday Times
July 12, 2009

Okay, I know I'm looking for the easy way here - but I need recommendation of specifically what kind of Vit. D to order. Also calcium, magnesium, potassium and anything else I should have. And I know someone has posted a discount code for iHerb. I'd really appreciate having that again. I HAVE to get some stuff ordered & usually it seems I already have things (usually the wrong kind) on hand when I see these posts. So this time, I'm asking before ordering.
Thanks so much.

Shame on you, Cats!

Vitamin D3 from Bio-tech

I personally take Country Life's Total Mins as my primary mineral supplement (it has phosphorus & calcium as hydroxyapatite, and some silica, among many other minerals), although I also take additional magnesium glycinate. My only complaint is that it is in tablet form, so I have to break it down into little pieces before swallowing to ensure proper breakdown and availability.. Would love for it to be in capsule form (making personal note to e-mail the company).

I have been buying these Vitamin D softgels from iHerb, but am thinking of switching to these, which are recommended by The Vitamin D Council on their website.