Vitamin B6 and B12 help prevent depression in older folk

Our elders have a higher risk of diseases. I would suggest that this risk is in part due to the poor diet that elder people can have. It would appear that there are a number of factors that influence the poor diet. Things that spring to mind are the cost of a healthy diet, running out of energy and enthusiasm for cooking/preparing a wholesome meal and a loss of appetite.

Therefore there are a lot of studies that show older people don't eat their RDI let alone a ODA. A study looked at intake of vitamin B6 and B12, and incidence of depression. This study looks at peoples diet (by questionnaire, which means errors could be high as people often answer these as they think they should be, not as they are actually eating).


They found that for every 10 mg increase in vitamin B6 and 10 microg increase in vitamin B12 resulted in a 2% decrease in risk of depression. The abstract is a bit ambiguous, however I think it means a 10mg increase in vitamin B6 results in a 2% decrease, and likewise for B12. 

To put this number in perspective the elderly RDI is B6 is 1.7mg and B12 - 6.0 micro grams. So 10mg increase is approximately 5 times the RDI for B6 and twice RDI for B12.

Now this increase isn't trivial. A quick google revels that a cup of green veges has between 0.25 -0.5 mg vitamin B6. Thus to eat 10mg you are looking at 20 cups of veges! B6 is also    

Vitamin B12 is found in animal products and half a fish fillet is 2 micro grams and about this for 50 grams of red meat. So an increase of 6 micro grams is again significant. 

This raises the question of how did the elderly people consume enough food to make the statistics significant ie eat enough so that they had 10 mg  / micro g higher than others.

My only logical conclusion is that they supplemented. So lets make sure our parents and elders have a vitamin B supplement to keep them on the safe side.

Reference: Kimberly A Skarupski, Christine Tangney, Hong Li, Bichun Ouyang, Denis A Evans and Martha Clare Morris  Longitudinal association of vitamin B-6, folate, and vitamin B-12 with depressive symptoms among older adults over time  American Journal of Clinical Nutrition, doi:10.3945/ajcn.2010.29413 Vol. 92, No. 2, 330-335, August 2010

Vegetable vending machine

Very cunning vending machine. Put your fresh produce in it at the "farm" gate and allow people to purchase it when they pass your gate. Brilliant way to get locally grown fresh produce into the community. This has many options. Wonder how it could work in New Zealand 

We all know - but how do we do?

Walk up to anyone you know and ask them this question: What do you need to do to become more healthy? Or what should you do to decrease risk of Western degenerative diseases?

The answer you all most guarantee is "eat more fruit and veges and exercise more"

Then if we know the answer - why don't we do it? 

I guess if I had the answer to this I would be charging a billizion dollars and transforming peoples lives with a simple magic wand. If there ever was an example of knowing what to do - and not doing it - it would have to be our family. I know huge volumes - and we struggle to live a healthy life. People often say it is healthier than their lives, which might be true, but I know what the high standard is, as we are not doing it (yet). I think we can conclude:

Knowledge and wisdom are therefore clearly different things and the natural state of humans is to eat poorly, high fat, high sugar. It takes discipline to have a healthy lifestyle. 

Blueberries decrease risk of heart disease - if you eat enough

Berries are good for you - I would be very surprised if this was news to you! However do you know how many you need to eat to obtain this cardio-protective role.

Lastly year I blogged that you needed one and half cups of strawberries, daily for four weeks, to reduce cholesterol and oxidation stress levels.

Well in the latest Journal of Nutrition they feed freeze dried blueberries and found over a 8 week period that blood pressure dropped, oxidation of cholesterol was reduced along with others markers of oxidation stress. So blueberries are great for you. The question that remains was how many were they taking.

They were taking 50 grams of freeze dried blueberries. This is equivalent to 200 grams of "fresh" blueberries. Apparently there is 80 grams of blueberries in a 200 ml cup. So 2 and 1/2 cups of fresh blueberries are needed daily. By fresh, this can mean frozen blueberries, as lose of nutrients between freeze drying and normal freezing is likely to be approximately the same. Or to put it another way this is 3kg of blueberries every two weeks.


Now do you eat this amount? 

Reference: Arpita Basu Mei Du, Misti J. Leyva, Karah Sanchez, Nancy M. Betts, Mingyuan Wu, Christopher E. Aston and Timothy J. Lyons Blueberries Decrease Cardiovascular Risk Factors in Obese Men and Women with Metabolic Syndrome J. Nutr. (July 21, 2010). doi:10.3945/jn.110.124701

Just encase you thought we knew everything

One of the fascinating parts of bio-chemistry nutrition is that people are always finding out more things that vitamins do in our bodies.

It has always stuck me as odd that people (in general thinking about doctors, dietitians and medical folk) as so certain that the RDI's are acceptable. Yet scientists working on the cutting edge are continually uncovering new things that vitamins are involved in. How can one be certain about what level to taken, when we don't even know all the things that they do.

Such is the case with riboflavin (B2). They have just found a new human transporter of riboflavin. This transporter is located in the brain and saliva glands. They believe that this transporter may control the levels of riboflavin in the brain.

Even though we know so much, we really know very little about how the body really operates, hence I try and have an open mind about nutritional topics.

Reference: Yoshiaki Yao, Atsushi Yonezawa, Hiroki Yoshimatsu, Satohiro Masuda, Toshiya Katsura and Ken-ichi Inui Identification and Comparative Functional Characterization of a New Human Riboflavin Transporter hRFT3 Expressed in the Brain. Journal of Nutrition, doi:10.3945/jn.110.122911 Vol. 140, No. 7, 1220-1226, July 2010

Lead in calcium supplements - how is NZ going?

Lead in food and drink is disturbingly frequent. However the level is normally under the "safe" limits. This lead comes from historical leaded petrol, lead in solder in old water pipes..... Anyway lead is also naturally found in limestone/calcium deposits. Lead can also be bio acculuated in the shells of filter feeders such as oysters.

This is relevant because calcium supplements are often made either from limestone (calcium carbondate) or from oyster shells, which are a waste product in the seafood industry.

About 15 years ago I had of a study that had found lead in calcium supplements. Came across a paper today that was in my read/file pile. It is a 2000 paper that found:

• Four of the seven oyster shell supplements had lead in them.This being of the approximate level of 1 µg/ supplement pill (800 µg dose). Any lead intake is unhealthy. However any level below 3 µg per 800 µg tablet.   
• Four of the 14 limestone supplements had lead in them.With an average of 1.5 µg per 800 µg dose.    

So clearly you want to have a supplement with zero levels of lead, not just meeting the high standard. Which products on NZ shelves have lead in them? That is a very good question. I will email the suppliers and keep you posted. Please contact me if you would like your brand questioned, as there are a lot of brands in NZ and I'm not aware of all of them.

Lastly remember it is not just your calcium intake that builds strong bones. You MUST have a high vitamin D level as well. 

Reference Edward A. Ross; Nancy J. Szabo, PhD; Ian R. Tebbett, Lead Content of Calcium Supplements JAMA. 2000;284:1425-1429. :

Bin Inn Peanut butter - low trans fats

I love bin inn's, health food shops, "ethnic" shops hmmmm wonderful looking products, great smells and always something tempting to try. However I have never had a specific reason to purchase stuff regularly. However this has changed.

Very disappointed to find out a year or so ago that peanut butter really is peanut margarine. Yup that's right. Ever wonder how they could take peanuts and oil and make the smooth creamy paste that is neither runny or solid? It is peanut marg!

This was disappointing as we used it quite a bit as a quick sandwich filler when in a rush in the morning. Got to be better than a high sweet product such as a jam. Anyway you local Bin Inn has a machine that grinds up peanuts (shelled) straight into peanut butter. Apparently they use a special type of peanuts, that typical shop ones don't have enough oil to make the paste.

Visit your local Bin Inn to purchase healthy peanut butter.

Busting the cold and flu myths - busted !

A newspaper article today lists cold and flu "myths". In typical journalism style that have taken a complex issue and dumbed it down to the point where they are propagating myths themselves. Nearly every myth they state, there is evidence that shows it isn't a complete myth. I will just tackle one of them:

Myth 7: Vitamins can help to kick a cold.
Verdict: Many people swear by vitamin C or echinacea as a preventive measure. However, Dr Hampson says there's no conclusive evidence that taking vitamins will prevent colds or substantially reduce their duration.

O some many things wrong. Number one is that echinacea is NOT a vitamin. Dooh. It is a herb. And there is plenty of evidence that if you use the right part of the herb, with the right bioactive, with the right dose that echinacea helps you overcome a cold. However you need a high quality product so goto a herbal shop (or an Amway distributor who selle Nutriway/Nutrlilite). Anything you purchase at a supermarket or chemist is unlikely to have the high levels of the active ingredients. I do take note that they don't even talk about echinacea in the discussion point!

Vitamin C. The bad news is once you get a cold vitamin C doesn't help you. However if you are taking grams of it before you "catch" the cold it speeds your recover time. So no you can't take vitamin C like medication and expect it to work. However if you have a regular high intake your length of cold time is decreased.

Most of the other myths actually have evidence pointing to it being correct....... so it really is a poor article.

. 

Don't take Avandia for diabetes

Avandia is a non subsidized diabetic medication. That means it is only taken by a few hundred NZ'ers. This is good news as it increases your risk for  heart attacks. For the full story see Bad Science blog who writes about the safety debacle and how it shouldn't be available to consume.

Sleep disorders in NZ

25% that is the magic number. That is right a quarter of NZ suffer from CHRONIC sleep problems. That is a huge number - and would have a massive effect on families.

Reference: Paine SJ, Gander PH, Harris RB, Reid P. Prevalence and consequences of insomnia in New Zealand: disparities between Maori and non-Maori. Aust N Z J Public Health. 2005 Feb;29(1):22-8.


Also see here about weight issues and sleep apnea

Good news on the cancer front (well at least in the USA)

The media tend to paint a negative picture of stuff, and as humans we seem to have an inbuilt mechanism that remembers bad stuff. Well here is some good news about cancer rates in the USA. First up we have total incidence and death rates for both male and female. The spike around 1990 is very intriguing. Take note that from mid 90's both the cancer rate and death rate are dropping.

Have a look at break down of selected cancer diagnosis rates. You can now see where the 1990 spike came from, prostrate cancers. I wonder if this was due to better detection methods picking up a backlog of prostrate issues, then the spike. Lung cancers are down in males, likely due to less smoking. Colon and rectum cancers are also down. This could be due to a improved diet - less processed meats and more fiber intake. I find it interesting that for both male and female skin cancers are increasing.

The male death rates of the same cancers as above is below, however the graph below goes to the 1930's, instead of 1975 like above. The spike in prostrate death rates is smaller than the diagnoses spike. Therefore indicating that the spike in diagnosis was due to backlog of cancers just starting ie spike caused by better detection. Again mostly good news. Cancers deaths down for lung, prostrate, colon, stomach and slight decreases for pancreas and leukemia and slight increase in liver cancer deaths.

The womens cancer rates are shown below. First note that the left scale is the same between the male and female death rates. The female death rate is significantly lower than the male death rate! The increase in lung death rate is likely due to females starting smoking later than males. Breast cancer death rates are down as are colon, uterus, stomach. Ovary and pancreas have leveled off. I find it very interesting that there is similarities between both sexes.

So the good news in summary is that cancer rates have leveled off and appear to be decreasing. Also death rates have significantly reduced over the last few decades. Very good news. There is only one assumption, that the USA statistics are reflected in your countries statistics.

Reference: Ahmedin Jemal, Rebecca Siegel, Jiaquan Xu, Elizabeth Ward, Cancer Statistics, 2010. Published Online: 7 Jul 2010

It hurts just reading about it - peoples amazing ability to be proffesional

As I have already mentioned I receive email updates from International Journal of Impotence Research: The Journal of Sexual Medicine. If I read these paper updates it is almost guaranteed to make me cringe. All these papers about chopping, applying vacuum, repairs, operations etc. It is a great incentive to look after ones body so that that very important part of the male anatomy stays in good health. 

I find it amazing that doctors can be so professional about things such as this. To the point when they don't cringe when they are explaining their latest chop and repair strategy's. I can't imagine having a job "repairing" penises all day long. 

I used to get heaps from my co workers when I went to breast feeding conferences. Surrounded by women talking about breasts. I could understand where they were coming from..... it sounds great but in real life breasts are not that sexy, especially when they have infections and hay breast feeding, the breast isn't very exposed. So I found it easy to be professional and very quickly breast in the context of breastfeeding became  just another part of the natural cycle of life.

I guess that this is what the above mentioned doctors do. I have up-most respect for these doctors (well actually all specialists) who have trained for so long, and help men recover their manhood. I just hope and plan never to see them!

Vitamin K and cystic fibrosis

One of the key elements of cystic fibrosis is fibrosis (scaring) of the pancreas. I'm not so sure of the connection between pancreas and vitamin K. This is not to surprising as vitamin K is one of the vitamins and most people, myself included, have a poor knowledge about.

A study that took children and adolescents who had cystic fibrosis and tried the following three levels of supplementation (explained further after the list):

<150 µg/d (low; multivitamins/no supplement)
150–999 µg/d (middle; CF-specific vitamins) 
1000 µg/d

So the first level was a low daily intake from food and/or a typical multivitamin. The second level was subjects taking multivitamin designed for cystic fibrosis. The last group took high levels of vitamin K.   

Comparing the blood levels of vitamin K to "healthy" children and adolescent (so not necessary optional vitamin K status, just "normal") the only group to achieve these normal levels was the high group with 1000 µg/d.

What I found amazing is that this research wasn't undertaken till this year. I would have naively assumed that before a multivitamin preparation was advertised as a specific cystic fibrosis multi they would have undertaken these tests to determine what level to use. Clearly not.


Reference: Kelly A Dougherty, Joan I Schall and Virginia A Stallings Suboptimal vitamin K status despite supplementation in children and young adults with cystic fibrosis Am J Clin Nutr (June 16, 2010). doi:10.3945/ajcn.2010.29350

Enhance your parents/grandparents lives - purchase them some zinc supplements

We all love our elders and want them to live healthy for as long as possible. There are a number of issues with elderly diets. Firstly as there food intake is low they are at risk for sub optimal nutrition. Then there are the issues of spreading a low income over a range of activities resulting in less income for healthy foods through to lack of  appetite etc. supplementation is something that can help elderly keep in good health.

Studies looked at zinc supplementation (I would recommend a multi, not just a zinc supplement).

Study one gave elderly 45 mg/day (quite a high dose) for 12 months. Compared to the placebo group the zinc group:

the incidence of infections was significantly lower

Another study with 20 mg of zinc per day for 2 years concludes:

Low-dose supplementation of zinc and selenium provides significant improvement in elderly patients by increasing the humoral response after vaccination and could have considerable public health importance by reducing morbidity from respiratory tract infections

The next study was a "1-y randomized, double-blind, and placebo-controlled vitamin E supplementation trial; all were given daily doses of 50% of the recommended dietary allowance of essential vitamins and "minerals, including zinc." This equates to 7.5 mg of zinc per day. They measured zinc levels in the blood before and after the study. Those who had healthy zinc levels (>70µg/dL) :

in nursing home elderly are associated with a decreased incidence and duration of pneumonia, a decreased number of new antibiotic prescriptions, and a decrease in the days of antibiotic use. Zinc supplementation to maintain normal serum zinc concentrations in the elderly may help reduce the incidence of pneumonia and associated morbidity

Yet another study with healthy elderly supplemented 45mg/day for 6 months. What they found was a decrease in a bunch of inflammatory markers when compared to the placebo group. Because heart disease is a inflammatory disease they concluded with:

These findings suggest that zinc may have a protective effect in atherosclerosis because of its antiinflammatory and antioxidant functions

I could go on. This is not a comprehensive review of zinc supplementation and elderly. How many paper and studies will it take for people to determine that zinc supplementation preferable via multi mineral (and vitamin) supplement is a good thing. When will the medical profession start to acknowledge that zinc (and other) supplementation is a key part of looking after our elderly. 

You can to take control of your own life, and the lives around you because no one else cares as much about your family as you!


References:
Ananda S Prasad et al  Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress. American Journal of Clinical Nutrition, Vol. 85, No. 3, 837-844, March 2007  
François Girodon Impact of Trace Elements and Vitamin Supplementation on Immunity and Infections in Institutionalized Elderly Patients
Arch Intern Med. 1999;159:748-754
Simin N Meydani, Junaidah B Barnett, et al Serum zinc and pneumonia in nursing home elderly. American Journal of Clinical Nutrition, Vol. 86, No. 4, 1167-1173, October 2007
Bin Bao, Ananda S Prasad, et al Zinc decreases C-reactive protein, lipid peroxidation, and inflammatory cytokines in elderly subjects: a potential implication of zinc as an atheroprotective agent American Journal of Clinical Nutrition, doi:10.3945/ajcn.2009.28836 Vol. 91, No. 6, 1634-1641, June 2010

Vitamin D: ODA and how to get it

Returning to the graph I have previously posted (click to enlarge)

"Safe" cutoff 
The "safe" cut off of 100 ng/ml is conservative. This is because no harmful effects were noted in a study which kept peoples vitamin D blood levels above 100 ng/ml, therefore it must be ok. However no further studies have been done at levels above this. Hence > 100 ng/ml is termed toxicity, as it is unknown, but potentially not toxic.

Lower cutoff
The lower cutoff of 32 ng/ml is for at least two reasons. Firstly as previous graph shows a minimum of 32 ng/ml is needed to insure healthy bone density in all skin types. I do note that for white and lightly tanned people this number could be considerably larger.

Secondly elderly are at risk of developing secondary hyperparathyroidism. This is where you get kidney failure, pains in joints and bones and possible deformed limbs. The risk for this is dramatically increased with blood vitamin D levels of less than 32ng/ml.

Supplementation with RDI for children

Now when 400 IU vitamin D dose raises the blood vitamin D levels in young children. It raises the blood levels to 32 - 80 ng/ml. This puts then in repletion range of the graph. Hence this is a good level to supplement kids with in winter, and possibly summer as well.

Supplementation for adults
However when 400 IU is taken by an adult, (the adults RDI) there is virtually no change in blood vitamin D levels. Hence this isn't enough. It takes 90 days for blood vitamin D levels to stabilize when taking supplements. The table below shows the increase in vitamin D blood levels are various levels of supplementation:

Supplement - change in blood levels (ng/ml)

     200          decreased(!)

     400            2.8       

  1 000            7.0

  5 000          28

10 000          70

 
Repeating we want to obtain a blood level higher than 32 ng/ml, but less than 100 ng/ml. This corresponds to a theoretically intake of  4 500 - 15 000 IU/day.

However what is our individual blood levels? Well we could pay for a kit to measure them, or next time you visit a doctor you can get your blood tested for vitamin D (in NZ).

However if you don't have access to vitamin D levels in your own blood, one could look at papers studying the population of your area:

• Christchurch adults are estimated to receive from the sun 1 200 IU / day in summer and only 60 IU / day in winter. This results in theoretical blood levels of 8.4 and  0.42 ng/ml respectively. Therefore supplementation of at least 5 000 IU is needed in summer, and more than this in winter
• Elderly Dunedin-its approximately 25% and 70% have vitamin D levels below 16 ng/ml. So again high levels of supplementation are needed.   

Hope that this series has been helpful - it sure has been insightful for me!

RDI of vitamin D (again)

Vitamin D RDI - I have already covered this in my book, and in a previous post. Why am I discussing it again? Because new material has come to light - and if I had this paper that I am currently reviewing - it would have saved me a lot of work in my book! So here are some other little known facts about the RDI:

The British were notorious for arguing for low RDI's. This is because UK struggled to feed itself, in WWII they almost lost the war because they couldn't ship in enough food to feed the population. With the unlocking of magnetic mines, which my Grandfather worked on, and better convoy's to beat the submarines they just scrapped through.

Apparently they set their adult RDI at 100 IU of vitamin D a day. This is because seven adult women who had abnormal bone softening which is called osteomalacia in adults or rickets in children. A x-ray of a child with rickets is shown below. At the top of the picture is the end of the thigh and the knee joint. Then comes the shine bones connecting to the ankle and heal. The shin bones should be straight, yet they are curved at an appalling angle! So back to the seven women with this type of bone problem - When they were feed 100 IU of vitamin D who were cured of the bone softening with this dose.

However the accepted RDI became 400 IU. This was due to 400 IU being the approximate amount of vitamin D in a teaspoon of cod liver oil. Cod liver oil used to be feed to children and adults at one teaspoon to keep them healthy. Children and parents on this dose didn't have rickets or osteomalacia so clearly this was an adequate dose.

However in 1997 the RDI yet again changed to 200 IU. This was due to adoption of American standard as an international standard. The 200 IU was described as "a generous allowance"

All of these figures were determined before it was possible to measure the concentration of vitamin D in the blood stream! Now we can...... and I will cover this tomorrow and hopefully it will wrap up this very long series on vitamin D. 

Don't leave your iodized exposed to the air.

A quick aside from the vitamin D posts. I have just found out that exposing iodized salt to air causes the iodine salt to become oxidized. This then evaporates away! Hence store your salt in a air tight container !

In our multi supplements we receive iodine (if yours doesn't change brands). Also we apply both seaweed extract and fish extracts to our garden. Hence we should also be getting iodine from our fruits and vegetables. Some also say that iodized salt also has a aluminum based chemical additive that makes it flow well. They also say that they processing to get it white takes away minerals. Again I don't know if this is true. The colors in raw sea salt are due to the organisms that grow in the warm and salty water as it is evaporated..... do the colors themselves don't actually add any nutritional value to the salt.

For the record we use "raw" sea salt and grind it up as we go. However for larger amounts eg for removal of fluid from vegetables before processing or with preserved lemons.... we use the commercial iodized salt as it is simpler and easier.

Blood vitamin D levels are very strongly linked to bone density

There is an amazingly accurate correlation between vitamin D levels and bone density. Given my previous post about how "messy" correlations are in human studies, these results are dramatically and miraculously correlated. So basically put your bone density depends on your vitamin D levels which depend upon how much you expose your torso and legs to the sun.

This study took thousands of participants and measured their vitamin D blood levels and bone densities. Each person created a data point on the graph below. The top line is for European light skinned people, middle line for Latino skinned people which have a medium skin pigment with the lower line being black Americans.

Update: The paper changed units on me without noticing. My previous optimal vitamin D post stated that repletion zone was 30 - 100 ng/ml, where this graph the white zone is approximately 20 - 100 nmol/L. So they were close enough for me to be tricked! Since all other vitamin D posts are in ng/ml I will convert this graph into these units. This is done by dividing the numbers below by 2.5. This results in the white band starting at approximately 8 and ending at 40, with the end of the graph being 72 ng/ml.

Vitamin D: Optimal blood levels - picture says a thousand words

As the old saying goes- a picture is worth a thousand words. This graph is worth at least 10 thousand words. It is both simple and obvious.... that you want to be at least in the repletion stage:































Two logical questions then follow on. Firstly where in the repletion stage should you be and secondly how much sunlight (or supplements) should you be getting to maintain this optimal repletion stage. These two very important questions will be answered in further upcoming posts.

Ridicules slow level of vitamin D in supplements compared to sunlight

There is a term in vitamin D research called a MED. This stands for minimal erythemic dose. Doesn't make any more sense?! What this means in reality is the dose of "sunlight" (actually UV B lamps) that is just at or below your burn time. This "sunlight" is shone on a test subject who is only clothed in swim wear. It produces the maximum vitamin D levels in the blood. The vitamin D levels are measured in the blood 24 hours after exposure and this is used to calculate how much vitamin D the body created.

The interesting thing that a unit of MED is the same across all the five different melanin (skin pigment) types. Say for someone like me that has a whiter than a ghost skin a MED in summer is 10 - 15 minutes. Where as someone with Asian or Indian genetics it would be about 30 minutes where as a dark skinned person of African genetics a MED could be up to 120 minutes.

Therefore the amount of sunlight you need to generate a MED is very dependent on skin pigmentation.

The next question is how much vitamin D does a MED produce? The answer is 10 - 20 000 IU's of vitamin D. Now go to your multi supplement and see how much it contains. The answer is likely to be about 400 IU or less. Even at 500 IU this is only 2.5 - 5.0 % of how much your body can produce in a day! I am very disturbed that the supplement levels are so low.... yet we think they are high as the RDI is only 200IU. This is silly, people get upset about mega doses of vitamins yet the body can make a hundred times the RDI of vitamin D.    

Reference: Symposium: Vitamin D Insufficiency: A Significant Risk Factor in Chronic Diseases and Potential Disease-Specific Biomarkers of Vitamin D Sufficiency. Circulating 25-Hydroxyvitamin D Levels Indicative of Vitamin D Sufficiency: Implications for Establishing a New Effective Dietary Intake Recommendation for Vitamin D1. Bruce W. Hollis. 2005 American Society for Nutritional Sciences.

Vitamin D: Get your belly out

One might assume that all parts of the skin produce the same level of vitamin D when exposed to sunlight. Well it turns out this assumption is not valid. The following graph illustrates this. The first column is completely covered in sunscreen. The next is head and neck not covered in sunscreen and the third arms not covered in sun screen. These first three columns are not statistically different from each other. This means that head/neck and arms don't produce enough vitamin D to make a difference to vitamin D levels. What this also means is that you can put lots of sunscreen on your neck, face and arms and not worry about reducing your vitamin D levels, cause they were not going to rise anyway.   

The trunk and the legs body area produced maximum vitamin D levels, just like having on sunscreen on at all. This means that you want to expose your stomach/back/trunk area, or your legs to the sun. This is very important in winter because vitamin D levels are low.

So go find yourself a warm, sunny and sheltered area where you can strip down in the winter sun. hmmm  topless sunbathing should be encouraged :) and for those who would like to see a topless car wash should check out this link (LOL and SFW)

Vitamin D: Can your body make it in NZ wintertime ? who knows!

We all know that exposure of skin to sunlight makes vitamin D. Today it is time to challenge this assumption. The first thing the realize is that not all colors (wavelengths) of sunlight works the magic of vitamin D creation. The more blue a wavelength the more energy it has. This is why you get sunburn from UV light because it has more energy than the other light. This is shown dramatically in the following two illustrations. "Figure 7" is on a log scale. The line starts at "1" and ends at 0.00001 (which is 10(-4) in science speak).  

The figure below  shows what your eyes typically perceive. You can note that the eye's ability to see starts at just over 400nm. And at 400nm in the above "figure 7" is where the wavelength no longer produces any vitamin D.

Therefore we can conclude that it is the invisible UV radiation that gives our body the ability to make vitamin D.

Now the reason that this UV light is needed is because this has enough energy to provide the chemical reaction of making vitamin D to occur. Now this UV light needs to be "bright" enough to have enough energy to create the reaction. This is similar to taking a plant that needs bright light and planting it in area of dim light. The plant either struggles or dies because there is not enough energy in the sunlight to allow it grow via photosynthesis.

On a sphere (the earth) the parts by the poles receive weaker sunlight than the equator. This is illustrated in the following figure:  

So the question is at what latitude can/cannot make vitamin D in exposing your skin. The effect of latitude is much more significant than one would expect. This is shown in the table below. 20 degrees or less there is lots of UV radiation. NZ is approximately 40 degrees..... and has the complicating factor that our UV radiation is higher than Europe.   

In the UK which is approximately 50 degrees north and

in the UK it is likely there is insufficient ambient UVB during the winter to synthesize vitamin D3 

So winter 50 degrees is not good..... how about us???? I assume that in NZ we can generate vitamin D from the sunlight, as NIWA's web site states we should be able to.as they have a  UV sunlight table.

So how long - and how much of our body do we need to expose to generate enough vitamin D. Very good question - I don't know. I am having trouble interpreting the table... hopefully over the next few days I can answer this.

References: Figure "7" Diffey, B. L. 1991. Solar ultraviolet radiation effects on biological systems. Review in Physics in Medicine and Biology 36 (3): 299-328.
Figure "2" Wikipedia: Visible spectrum
Figure 3: SDUSD Teacher Professional Development - 6th Grade - Earth Science. March 18th, 2009, Mission Bay High School. Presenter - Memorie Yasuda
Table 1, Diffey etc. 
Quote ibad
NIWA table: Balancing risks and benefits of UV radiation. Richard McKenzie, Ben Liley, and Paul Johnston