For The Love of Food

Welcome to Friday’s For The Love of Food, Summer Tomato’s weekly link roundup.

This week low-fat diets get the boot, calorie restricted monkeys are vindicated, and morning sunshine keeps you slim.

Want to see all my favorite links? (There’s lots more). Be sure to follow me on on Delicious. I also share links on Twitter @summertomato,  Google+ and the Summer Tomato Facebook page. I’m very active on all these sites and would love to connect with you. (And yes, I took that pepper heart pic myself).
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For The Love of Food

Welcome to Friday’s For The Love of Food, Summer Tomato’s weekly link roundup.

In case you missed it, here’s the archive of my appearance on Dead to the World with David Gans (KPFA radio) from Wednesday night. One of my longest discussions of Foodist to date. It will only be available until May 29:

http://www.kpfa.org/archive/id/91603

UPDATE: Here’s a more permanent version if you want to listen after the KPFA archive expires.

This week around the interwebz the salt police take a blow, chili peppers reduce Parkinson’s risk, and why sunshine is important for more than just vitamin D.

Want to see all my favorite links? (There’s lots more). Be sure to follow me on on Delicious. I also share links on Twitter @summertomato,  Google+ and the Summer Tomato Facebook page. I’m very active on all these sites and would love to connect with you. (And yes, I took that pepper heart pic myself).

Read the rest of this story »

Vitamin D

Both environmental and genetic factors seem to play a role in the development of multiple sclerosis (MS), but determining an exact cause of the disease has been elusive. Now new evidence suggests that vitamin D may play a direct role in regulating a gene known to be associated with MS. This finding helps bridge the gap between environmental and genetic risk factors, and strengthens the hypothesis that vitamin D could be instrumental in MS prevention.

MS is an autoimmune disease that attacks myelin, a component of the nervous system essential for the conduction of neural impulses. Onset of MS usually occurs between the ages 18 and 35, and is more prevalent in females than males.

One of the most interesting epidemiological findings associated with MS is that it is more common in regions farthest from the equator, with a few notable exceptions. Climate, sunlight and vitamin D are all suspected candidates in the occurrence of MS, as are genetics and diet. Importantly, the relationship between geographical location and MS risk seems to be most significant in early childhood years. After age 15, risk of MS for immigrants is closer to that of their home country than to that of their new country.

Sunshine is the most common source of vitamin D for humans. Vitamin D is created when ultraviolet B (UVB) light contacts skin. Dietary vitamin D is rare, though it can be obtained at significant levels with certain foods, particularly oily fish (e.g. sardines and salmon). Notably, Norway and many Asian countries have relatively low prevalence of MS. It has been suggested that fish consumption is the reason for these regional discrepancies that cannot be explained by sun exposure. This makes vitamin D a particularly strong candidate for MS prevention.

In addition to environmental factors, certain genetic risks are linked to MS. In particular, proteins associated with the body’s immune cells are mutated in many MS cases. Mutations in these proteins disrupt the ability of immune cells to determine which particles in the body are foreign and which are “self.” When this happens, the cells get confused and begin to attack their own body’s tissues.

A new article published last week in PLoS Genetics investigated the relationship between vitamin D and the genetic variants associated with MS. They found that vitamin D directly interacts with these genes at a molecular level, providing insight into the mechanism by which vitamin D may affect the disease. Though it is still not clear what specific role vitamin D plays in its interaction with MS genes, a new avenue of exploration has opened up into MS etiology.

The tie between vitamin D and MS is still vague, but it is a good idea to ensure your vitamin D levels are adequate. People living at latitudes greater than 40 degrees from the equator (San Francisco is on the border) should be taking vitamin D supplements. This is true for many reasons; MS is not the only disease that is linked to low vitamin D levels.

Vitamin D pills are now easy to find, and can be obtained at both Trader Joe’s and Whole Foods. Take one or two oil-based 1000IU vitamin D supplements daily. Men should avoid vitamin D supplements that contain calcium, because excess calcium increases risk of prostate cancer.

Do you take vitamin D supplements?

UPDATE: This article can also be found in Synapse.

Vitamin D

For the past several years the data in support of increasing vitamin D intake for every living human has been mounting. This week the American Journal of Clinical Nutrition features a collection of new research articles addressing the trends in vitamin D status and optimal dose recommendations.

This week’s take home lesson: While current research indicates we should be getting more vitamin D than is presently recommended, as a whole our vitamin D levels appear to have decreased in the past 15 years. The best way to combat this deficiency is with vitamin D supplements.

Vitamin D is a fat-soluble prohormone and essential nutrient produced when ultraviolet radiation (UVB) contacts our skin. It is probably best known for its role in bone metabolism (it has been shown to be more important than calcium for maintaining bone health), however recent studies indicate that vitamin D is essential for other physiological process as well.

Low blood levels of vitamin D have now been associated with many different chronic diseases including cancer, coronary heart disease, multiple sclerosis, Alzheimer’s disease, tuberculosis, depression, hypertension, periodontal disease, schizophrenia, seasonal affective disorder and type 1 diabetes.

In light of these findings, many nutrition researchers have argued for increasing recommended levels of vitamin D intake, but making population-wide recommendations have proved difficult for world health agencies because of large variability and uncertainty in vitamin D requirements.

There are several things to consider when evaluating vitamin D status in an individual. Latitude (sun exposure) is probably the single best predictor of vitamin D status. Anyone living in San Francisco or further north cannot get enough sun exposure to achieve sufficient vitamin D status, particularly during the winter months.

Because vitamin D is fat-soluble, it is retained in body tissues for several months after sun exposure. For this reason, people living at far north latitudes are particularly vulnerable to vitamin D deficiency because they frequently do not store up sufficient vitamin D during the summer to sustain their needs during the winter.

To further complicate matters, it is incredibly difficult to obtain vitamin D through dietary sources. Fatty fish and eggs are the only natural sources of vitamin D, though they are probably insufficient to achieve optimal status. Milk and soy products are typically fortified with vitamin D, as are some juices.

Skin pigmentation, sun avoidance and body composition (high body fat) are all associated with vitamin D deficiency. Darker skin tones do not convert sunlight to vitamin D as easily as lighter skin tones. Sunscreen blocks virtually all vitamin D synthesis. Body fat reduces bioavailability of vitamin D tissue stores.

This week’s study by Anne Looker et al, suggests that increased body mass as well as awareness of skin cancer risk and use of sunscreen have contributed to a significant decline in vitamin D levels in north America in the past decade.

The good news is that supplementation does appear to be effective at improving vitamin D status. Though there is still some disagreement on what the optimum blood levels of vitamin D are, it is generally agreed that they are much higher than currently recommended by any world health organization. One of the principle motivations of the present studies is to inform new vitamin D recommendations.

Kevin Cashman et al offers estimations of dietary requirements of vitamin D for healthy adults. They performed a randomized, placebo-controlled study testing the effects of different vitamin D doses and how they effect blood vitamin D levels.

The absolute minimum amount of vitamin D supplementation recommended by the study is 8.7 ug/day, or approximately 400 IU. This was to maintain blood serum levels greater than 25 nmol/L, and is double the current FDA recommendation for people under age 50. However, this suggestion is only sufficient to avoid deficiencies associated with bone loss and not other chronic diseases.

“The data from the present study clearly show that vitamin D tissue stores, developed during summer via exposure of skin to sunshine, were not sufficient to maintain serum 25(OH)D concentrations of greater than 25 nmol/L in most of the population [during winter], and that dietary vitamin D is an absolute requirement to maintain status above this minimum threshold.”

But the recommendations do not stop here. To maintain blood serum levels of greater than 50 nmol/L–a range more consistent with lowering risk of chronic disease–the study recommends 28 ug/day or 1100 IU of vitamin D. To keep blood serum above 80 nmol/L (from all I have read this is what I would recommend), 41 ug/day or 1650 IU is needed.

Remember this is most important if you are overweight, live north of San Francisco, get little sun exposure or have darker skin. Very rarely do I recommend vitamin supplements (they are not usually effective and are sometimes dangerous), but in this case the evidence is unequivocal.

Vitamin D supplements are easier to find than in the past, but they are usually packaged with calcium and are insufficient in dosage. Men should be wary of excess calcium supplementation since it is associated with an increased risk of prostate cancer.

I will continue looking for a good vitamin D supplement and will post when I find one I am happy with. If you have any recommendations, please share them with us.

Look for supplements where vitamin D is in the form of cholecalciferol, or vitamin D3.