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“Diet for the Athlete, Workaholic, and Everyone in Between” Athlete, Workaholic, and Everyone in Between”

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Thus far in my blogs, I have discussed endurance activity using carbohydrate as the primary fuel source. In the last three weeks we outlined the protocol for pre, during and post workout fueling. While our body does prioritize carbohydrate as the primary fuel source for activity and brain function, many endurance athletes agree that carb-centered fueling is both frustrating and time consuming. In recent years, the ketogenic diet has emerged as a popular choice among extreme endurance athletes for a couple key reasons. Today’s post will discuss an introduction to ketogenic dieting, what it means, the potential benefits, as well as potential concerns and obstacles. This post will not discuss the physiology of the process in detail. For those interested in a greater level of detail, I have posted links to some of my favorite resources on ketogenic dieting.

Simply stated, the ketogenic diet is built for those interested in running on fat. As mentioned repeatedly in this blog, our body will use carbohydrates for activity first when they are available. Since they are such a common part of our diet, many go through life never considering another way to eat. But what happens when our body has no carbohydrate stores left, and none are in the diet? Our body adapts to use a fuel that is always available, fat. When the body has no carbohydrate, and does not have enough protein to make carbohydrate from, the body will begin to adopt fatty acids as the primary energy source. Metabolism of fat in the body produces a group of compounds called ketones, which can be used by all systems in our body, including the brain. As I may have eluded to above, it takes quite a bit of time to enter ketosis, and is not done without resistance from the body. Once in ketosis, most people report a return in energy and mental clarity, and our body runs on ketones without any significant problems.

The application and interest in this diet with runners is fairly straightforward. The average person has enough carbohydrate stored to fuel activity for approximately 2hrs, or 15 miles (give or take 10 miles). To compare, the same person has enough fat to fuel activity for 500-700miles. We reserve and store fat very efficiently, and can readily use it when needed. As you reflect on the pre-, during- and post- training protocols from the last 3 weeks, it becomes obvious that our body does not have a great deal of carbohydrate stores. You are constantly taking in glucose from food during the entire training and event to keep stores available. Runners on the ketogenic diet don’t use carbohydrate, and therefore do not have to eat anything before or during their event unless they choose to (except water and electrolytes). For an avid athlete running long distances on a regular basis, this has a great deal of appeal. It becomes more enticing when they learn that not only are feedings surrounding exercise optional, there is no need to time meals or eat every 3 hours. Since your body is not using sugar, no insulin is being produced, and blood sugar levels are stabilized by a compound called glycerol, which is abundant as a result of breaking down triglycerides into fatty acids for oxidation. With no need to manage blood glucose, and muscle glycogen out of the conversation, keto-dieters can eat when they please with no impact on performance.

In addition to endurance athletes, this diet has potential application with individuals who have compromised glucose utilization. For pre-diabetics, non-insulin dependent diabetics, and others deemed insulin resistant, the ketogenic diet has the potential to serve as an alternative to carb management and medication. As noted above, the body does not use insulin, and blood glucose is maintained with glycerol. Instead of trying to manage the compromised system, many diabetics are choosing a different energy path, one that “skips using what is broken”. In the short-term this seems to have success in many individuals. Unfortunately, we have never witnessed individuals in our culture and time maintain ketosis for a life time. More research and time is needed to better understand what the long-term effects of this diet are. My personal interest lies within extreme endurance athletes and diabetics. Extreme endurance athletes are often training so intensely their body must rely on an enormous amount of sugar, which strains the pancreas. Any organ used in this fashion will wear down over time. Just from observation I have noticed many endurance athletes in their 60’s are pre-diabetic. Low body fat, great muscle mass, but struggling with this issue despite it all. What if instead of demanding such constant insulin production, they were able to use fat. While fat also demands function from the pancreas, the amount of fat needed for caloric balance is less than half that of carbohydrate. All of this is speculation, but I look forward to watching this area of science grow.

At this point it seems like this diet would have great application to the populations discussed. With all this potential, what is the catch? Why isn’t everyone doing this? Are there any concerns? While there is a tremendous amount of potential, there are certainly a number of issues that complicate the ketogenic diet as a viable option for many individuals.

The first obstacle for most is the transition into ketosis. Our body does not like to switch to fat as our primary fuel source. Traditionally this switch implied starvation. Our body stores energy very efficiently, and body fat is meant to be a reserve kept for dire circumstances. As our body reaches the end of its carbohydrate reserves, most experience extreme fatigue, dizziness, headaches, changes in bowel regularity and consistency, shakiness, muscle cramping, disruptions in sleep, a temporary dip in thyroid hormones, and even an increase in kidney stone formation. That long list of symptoms is intimidating to type let alone experience, so it comes as no surprise many cannot handle this during training, working and activities of daily life. It is important to note that these are temporary, often lasting from 1-3 weeks depending on rate of carbohydrate depletion.

Once in ketosis, the biggest issue becomes the sustainability of the diet. Maintaining nutritional ketosis for extended periods is a very different diet than we are used to, and does not resemble most other low carb diets. Carbohydrate intake is supposed to be nonexistent, so it is essentially restricted to the 2.5 cups of dark green, non-starchy vegetables per day, and 1-2 servings of nuts. The rest of the diet is protein and fat. The most difficult part of this plan is the protein limitation. As mentioned before excess protein will be turned into carbohydrate, so protein has a restriction in ketosis, which is the main way this diet differs from an Atkins or South Beach. This results in a plan that has a lot more fat than protein, which means foods that are exclusively fat must take a leading role. Things such as grass-fed butter, vegetable oils, coconut oil and MCT oil are often consumed at every meal. An example meal plan for a 5’9” 155lb male triathlete is below:

Example Day:                    2400 kcal              200g Fat               120g Protein                      30g CHO

Meal 1: (60g Fat, 30g Protein)

4 slices Bacon (14g Fat, 12g Protein) Pan fried in 1 Tbsp Coconut Oil (14g Fat)

3 eggs (18g Protein, 12g Fat) cooked in 1.5 Tbsp Grass-fed Butter (18g Fat)

8oz Unsweetened Almond Milk (2.5g Fat, 1g CHO, 1g Protein) *For Calcium

Meal 2: (49g Fat, 33g Protein, 10g CHO)

6oz 75/25 Grassfed Ground Beef (42g Fat, 26g Protein)

1oz Cheese (7g Protein, 7g Fat)

2 cups mixed Greens (lettuce, romaine, spinach etc) (10g CHO)

Meal 3: (35g Fat, 15g Protein, 15g CHO)

½ cup Almonds

Meal 4: (56g Fat, 38g Protein, 5g CHO)

6oz Salmon Filet (22g Fat, 35g Protein) cooked in 1 Tbsp Olive Oil (14g Fat)

1 cup Asparagus (5g CHO, 3g Protein) add 1.5 Tbsp Grass-fed Butter (18g Fat)

8oz Unsweetened Almond Milk (2.5g Fat, 1g CHO, 1g Protein) *For Calcium

*Use ¾ teaspoon of Himalayan Sea Salt with food daily (Sodium and trace minerals)

*Use ¾ teaspoon of Salt Substitute with food daily (Potassium)

*Drink 130 ounces of fluids daily before accounting for exercise

Notice how much pure fat there is in the diet? While some enjoy it, others find it unappealing and cannot stick with it. In addition to fat as a barrier, vitamins and minerals pose a problem. Many of our micronutrients come from fruits, vegetables, dairy and grains. While we can do our best to maximize some of them in the 2 servings of vegetables and serving of nuts, we are still left without adequate micronutrients. To achieve balance many keto-dieters will use bone broth. It is very hard to assure adequate intake with broth, so supplements are commonly used. As noted above, this individual used unsweetened almond milk as a calcium supplement, salt for sodium, and salt substitute for potassium. This individual also consumes a mineral and vitamin complex that is spread throughout the day to maximize absorption and provide key vitamins and minerals that are lacking.

While quite a few websites now boast recipes and options for keto-dieters, many people still struggle with the lack of variety, and miss certain foods. As a Dietitian, my job is to help people maximize their health. For me, health is a balance of quality and quantity of life. It varies for most individuals, and that is our right. The clients I have who maintain the ketogenic diet are those who do not have strong social and emotional ties to food. While in many ways this is a positive attribute, it is a rare one in our culture. The ability to look at food as simply “energy to perform and sustain life”, will usually result in successful ketosis, but may also restrict certain social ties to food that many would argue impact quality of life.

A large barrier in the world of performance is application to certain athletes. While many view the ability to fuel on fat through endurance races as an advantage, there is one lingering disadvantage. Our body’s anaerobic systems, the energy systems that function when there is not enough oxygen, are exclusively reliant on carbohydrate. In simpler terms this means that when you are exerting yourself at maximum intensity, you rely exclusively on carbohydrate for fuel. In ketogenic dieting, there is no carb, so there is no true max performance. Endurance athletes are rarely concerned with this, as their push to the finish is often not going to be at max performance, but many athletes rely on anaerobic systems to compete. Sprinters and those athletes who rely on short bursts of high intensity will not see a performance benefit from this diet. Most of the studies investigating performance in ketosis note an increase in perceived rate of exertion, and an inability to reach max effort (White 2007), meaning they felt like they were working harder compared to when they were eating carbs for the same intensity, and they were unable to achieve max intensity. This is why the diet is most popular in endurance sports and why Lebron James only went “low-carb” in his offseason.

Aside from the daily life and performance concerns that many will find discouraging, we also have a lack of vision for the long-term impact of the diet on health. There are quite a few personal testimonials of individuals feeling great at a healthy body weight with encouraging clinical indicators of health for 5 and even 10 years in ketosis. This is quite encouraging, but we need much longer and better controlled trials. While it is true that diets with too much carbohydrate, particularly refined and processed carbs, can cause a host of problems in very little time, we have abundant data proving a eucaloric diet containing carbohydrate is able to propel humans well into their 80’s and 90’s with similar values. The inflammation and metabolic disturbances linked to carbohydrate largely stem from excessive intake and a large calorie surplus. It is much more difficult to over consume calories on the ketogenic diet, but there are still potential issues only time will tell us. As a practitioner, I am most concerned with the long-term impact of a high fat diet on the digestive tract and accessory organs. We know too much sugar wears on our pancreas and causes insulin resistance. Is it possible that a diet with high levels of fat will wear in our production of pancreatic lipase and lead to pancreatitis? I am also concerned with the effects on the gallbladder, liver and our lymphatic system. Finally, while short-term observations suggest no adverse effects on lipid profile, we simply do not know the long-term impact on lipid levels or the cardiovascular system.

Overall, it becomes clear that while this diet has great promise in certain populations, there are severe barriers to sustainability, as well as large gaps in our understanding of the long-term impact on the body. Until more research is presented, the scope of this diet is fairly limited. Personally, I am most excited about the potential application in non-insulin dependent diabetics, as well as in ultra-endurance athletes during their training and competitive seasons. For the general population I still promote the idea of carbohydrate management as opposed to elimination, but there is always a need for Case Specific Nutrition™!

Below are some links to the most comprehensive materials I know of. Much of the research on ketogenic dieting and performance was done by Dr. Jeff Volek & Dr. Stephen D. Phinney, and can be accessed at.

http://www.artandscienceoflowcarb.com/

Dr. Peter Attia is a fascinating man with a great understanding of the physiology and potential in ketogenic dieting. For a great explanation of how our body runs on fat, I recommend his post “Keto 101”

http://eatingacademy.com/

For any other questions or concerns, fell free to contact me at casespecificnutrition.com or Pittsburgh-dietitian.com

IIFYM, acronym for ‘If It Fits Your Macro’s’, is a trending simplified diet format that has increased in popularity recently. Any why wouldn’t it? A concept that says as long as you meet your daily calorie, fat, protein, carbohydrate and fiber goals, it doesn’t matter what you eat. This core foundation allows consumers to fit their favorite ‘unhealthy’ foods into a weight loss plan. Bodybuilders and fitness enthusiasts have been the group most attracted to this ideal, and understandably so. After years of broccoli, brown rice and chicken breast every meal, this group of fitness enthusiasts were more than happy to replace their broccoli and brown rice for Cinnamon Toast Crunch and an Eggo.

I will start by saying there are some very real benefits of the IIFYM concept. Most importantly it helps teach people that weight loss doesn’t have to mean eating bland foods or following a strict regimented diet. It simplifies it to the realization that weight loss is nothing more than consuming fewer calories than your body needs. This is a fundamental stepping-stone I work with my clients to understand. Many people have predetermined notions of what starting a diet means, most of which are incorrect.

The other lesson IIFYM diet teaches is moderation. Instead of the traditional ‘restrict yourself until you finally cave then binge plan’, IIFYM teaches you things like pizza or ice cream in moderation don’t have to ruin a diet. As long as you account for what you are consuming and you meet your daily goals, weight loss will happen.

Vitamin D has been a major topic of discussion recently. Over the past 5 years this vitamin has been the focus of many scientific communities. While some of the areas of impact need more research, there is quite a bit of promise from repeated data, which makes the case for increasing daily Vitamin D intake.

A General Background

Vitamin D is a fat-soluble vitamin that is produced in the body when the skin is exposed to UV rays. It is also available in low levels from some foods. Vitamin D in foods has two common forms, D2 and D3. D2, or ergocalciferol, is a fungus or yeast derived product that is created when certain fungi or plants are exposed to UV light. D3, or cholecalciferol, is what our skin, as well as the skin of other animals produce when exposed to UVB light. It can be produced synthetically and added to foods or produced as a supplement. Once in the blood stream, Vitamin D is transported to the kidneys, where it becomes Calcitriol, the biologically active form of vitamin D.

Why should I care?

Vitamin D has many functions in the body, many of which are well established and understood. Calcitriol (active Vitamin D) circulates as a hormone in the blood and regulates the concentrations of calcium and phosphate. This helps promote important processes, such as bone growth and remodeling. Calcitriol also has an effect on immune function and neuromuscular function.

The most well-known link to vitamin D is its role in the prevention of rickets, a bone disease in children. This was discovered in 1922, and the addition of vitamin D to dairy in the 1930’s virtually eliminated rickets from the United States. For years, the levels of adequate consumption for Vitamin D (%DV, RDA, DRI), easily attained by three servings of dairy daily, have been based on the prevention of rickets. Recently however, studies have emerged suggesting that an increased serum vitamin D level beyond the levels currently recommended, can translate to reduced incidence of many diseases and disorders, which are noted in the chart below:

There are many notable areas of research. The most established is still bone health. Rickets in children, and reduction of fall risk, fractures and low bone mineral density in late adults and elderly, especially women, are the most significant. In addition to bone health, deficiency of vitamin D has been linked to higher risk of viral infections. Low levels are also associated with gestational diabetes, pre-eclampsia and low birth weight in pregnant women.

Multiple Sclerosis (MS)

Vitamin D has shown great potential in Multiple Sclerosis. Prevention and management of Multiple Sclerosis, as well as some other autoimmune disorders, are the main areas of the newest research. The study of nutritional genomics is working to better establish this link. Initially, it was observed that the farther away from the equator you get, there is an increase in both vitamin D deficient persons (less sunlight), and incidence of Multiple Sclerosis.

The most popular theory is vitamin D deficiency is an environmental trigger that turns a gene coding for MS ‘on’. With this theory, increasing vitamin D consumption and raising serum levels would succeed in turning the gene ‘off’. More studies are needed, but multiple have been done and some show very promising results.

The map is from an article titled ‘Time for more vitamin D’, which appeared in the September 2008 issue of Havrad Women’s Health Watch. The article and this image discuss the difficulty obtaining enough vitamin D from sunlight and diet. The grey area on the map shows latitudes above 37 degrees north, where very little vitamin D is synthesized, except in the summer months. People who live in these areas are at relatively greater risk for vitamin D deficiency. The article can also be found on the Harvard Harvard Health Publications website, or by clicking the picture! Some other good articles on Multiple Sclerosis and Vitamin can be found in the following links:

Vitamin D Council: Multiple Sclerosis

Overcoming Multiple Sclerosis: Sunlight and Vitamin D

Neurology: Lower serum vitamin D levels are associated with higher relapse rates in MS

Seasonal Affective Disorder (SAD)

Ever notice that the months of January-March often leave people feeling depressed. My Dad always says that February is the worst month and he would be happy to see it missing from the calendar. Are you someone who just goes through the motions when it’s snowing and overcast? Seasonal Affective Disorder (SAD) is another area of promising research for vitamin D intervention. Though the link between vitamin D and depression is not fully understood, it is established that low serum levels of vitamin D are linked with depression. It is also understood that a lack of vitamin d in the blood makes you more likely to develop depression, and taking a vitamin D supplement can improve symptoms of depression. There is direct evidence that the prevalence of SAD, the most appropriate acronym ever, is most concentrated in areas with the most extreme weather changes.

Journal of Nutrition and Healthy Aging: Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder.

Vitamin D Council: Depression

Where do I get my Vitamin D from?

As suggested earlier, our primary source of vitamin D is what we make ourselves. Vitamin D3 is synthesized from cholesterol in the body, when an adequate UVB exposure exists. Ideal scenarios include 15 minutes of daily sun exposure to approximately 40% of the total body during the middle of the day to synthesize 10,000-25,000IU. That’s easy enough right? (Not.) In reality, this is a very real problem. First, most people work indoors during peak hours of sunlight. This instantly reduces chances of exposure to evenings, weekends and vacations. To make matters worse sunscreen, the vacationers best friend, reduces vitamin D synthesis (SPF 15 reduces vitamin D synthesis up to 98%). Then you consider location and seasonality. If you live in the Northeast United States like me, chances are there are 4-6 months each year that are cloudy and cold. Not only are you inside mostly, when you do go out, your entire body is covered with clothing. We live in a world that greatly reduces our ability to synthesize vitamin D. All of these factors become quite the D-ilemma (pun intended).

There are very few foods that are a great source of vitamin D. Currently, our best sources are dairy products that have added D3, fish that have some naturally occurring D3, or in mushrooms that have been UVB irradiated for enhanced vitamin D2 content.

How much am I getting from my diet?

o Dairy is fortified with D3 (30% DV = 120IU)
o Cod Liver Oil (1390IU/15mL)
o Catfish: 425IU/3-4oz
o Salmon: 360IU/3-4oz
o Tuna canned in oil: 235IU/can
o Whole egg: 20IU/60g egg
o Mushrooms
 Shiitake: 154IU/100g
 Portabella: 10IU/100g
 Portabella exposed to UV light: 420-525IU/100g

National Institute of Health Office of Dietary Supplements: Vitamin D Fact Sheet

Current studies suggest vitamin D3 is better utilized in the body, which makes sense since it is what we can synthesize. D3 binds better to receptors, which ultimately leads to a more effective raise and maintenance of serum levels. In addition to being better utilized, it is more shelf-stable and has a longer half-life. Since there is no real price difference between D2 and D3 on the shelf, I would recommend Vitamin D3 to those looking to increase consumption. Attention Vegetarians! Vitamin D3 is from animal sources. If representatives at supplement companies tell you it is synthetic, it is still likely a product with ingredients of animal origin that were processed synthetically.

How much do I need?

The amount of vitamin D a person needs is another ‘Case Specific’ value. It varies based on sun exposure, diet, genetics, gender, age, activity level, along with many other factors. The best way to know is to get your serum 25(OH)D level checked.

The current ‘normal range’ for serum 25(OH)D is 30-100ng/mL. As the chart above notes, levels above 20ng/mL are what virtually eliminated rickets. That is what a typical person will have if they consume 3 servings of dairy daily. An additional reference to the chart suggests there are benefits from serum concentrations as high as 55ng/mL. A lot of those values are either extrapolated or very preliminary research, but show great promise. Since this test has a standard deviation (potential error) of 10ng/mL, I would recommend at least getting your levels above 40ng/mL. Levels above 50ng/mL are what I strive for, and what I would recommend to my clients. To do this, there is a generic formula for quick reference.

Generally, 100IU of D3 will raise serum 25(OH)D approximately 1ng/mL.

So for someone with a vitamin D level of 25ng/mL, to get to 45ng/mL, you would need approximately 2,000IU in addition to your current lifestyle’s consumption and sun exposure. I would like to repeat that this is formula is not fact or scientifically proven. It is more of a general reference tool to help gauge a starting point.

For those concerned with over consumption, serum levels above 150ng/mL have been associated with negative effects. The Vitamin D Council often notes that there are no issues associated with a serum level around 70ng/mL, so if there is potential benefit why not? I personally supplement 2,000IU in the summer, when I am outdoors running frequently, and 3,500IU in the winter when I am bundled up and bogged down by the Pittsburgh winters. These amounts are in addition to what I consume from dairy, eggs, and other dietary staples.

Talk to your doctor about getting your serum 25(OH)D levels checked. Ask to know the value, not just the generic ‘you are fine’. If you are below 40ng/mL, I would still recommend getting at least an addition 1,000IU of daily D3. If you are deficient (below 30ng/mL), many doctors will write a prescription for a weekly 50,000IU D2 supplement. This is an unnecessary prescription. Not only do I advise clients to buy D3 instead of D2, Vitamin D can be purchased in a much cheaper, daily dose at any supplement store, website, or chain store that carries supplements. Let your doctor know you will instead buy a D3 supplement (2,000IU-5,000IU are very easy to find), and would like to retest in 3 months.

Support of Recommendations

Compared to the DRI of 600 IU for adults set by the IOM and Food and Nutrition Board, the levels I am referencing seem high. The Vitamin D Council, an organization solely focused on Vitamin D research would suggest otherwise:

As you can see, the Vitamin D Council actually recommends 5,000IU per day. They also work to convince the FNB and IOM to increase the Tolerable Upper Limit (TUL) from 4,000IU to 10,000IU. This request is heavily based on the evidence that our bodies synthesize around 10,000IU daily from proper sun exposure without issue of toxicity. I am a great supporter of this council and their devotion to research and health. I also have a great deal of respect for the Endocrine Society. According to their documentation, the average adult will need around 1,500-2,000IU per day to receive the full benefit of vitamin D. Supplementing more than that should be based on individualized serum results, or done by those who wish to supplement with the hopes of receiving benefits hypothesized in very new research.

Final Comments:

1. My recommendations are based on the areas I feel are well established. Those are the areas I discussed in greater length. Many of the links and charts I provided may discuss information or topics I feel need more data are not ready for application to populations yet. Remember moderation, balance, and variety rule the day.

2. If I had to pick one vitamin for the general population to supplement, it would be vitamin D. It is the only vitamin I supplement daily.

3. Get your Serum 25(OH)D levels checked immediately, 3 months later to track progress.

4. Levels are typically at their lowest in March, due to the lack of sunlight experienced since approximately November. If you wish to know you low and high throughout the year, March and September (respectively) are the best times.

5. Increase your dose in the winter months, or in periods when you have further reduced sun exposure. Decrease supplemented dose in time periods when you are getting more sun exposure.

6. Stay updated on the latest research using myself or the Vitamin D council website for reference. Vitamin D is being studied intensely. Current areas in need of more research will be updated frequently. This topic is one that will be updated constantly.

Personally, I take a Vitamin D3 liquid by Metagenics. Just 2 mint flavored drops in the morning for my 2,000IU. The best part is one bottle contains over 2,200 drops, so it is by far the most cost effective Vitamin D3 supplement I have ever found. If you would like a high quality Vitamin D3 product 20% OFF with FREE shipping Click Here! 

References

1. ‘How to Make Sure That You are Getting Enough Vitamin D’. Dr. Ben Kim, Natural Health Care. http://drbenkim.com/vitamin-d-facts.htm. 2013.

2. ‘Vitamin D and Sunlight Exposure: Review’. Compiled by Walter Sorochan. http://www.freegrab.net/vitad.htm. 2011.

3. Garland C.F., Baggerly C.A. Clinical Education. ‘Disease Incidence Prevention by Serum 25(OH)D Level’. http://www.nleducation.co.uk/wp-content/uploads/Disease_Prevention_chart_uk1.pdf.

4. Gloth III F.M., Alam W., Hollis B. J Nutr Healthy Aging. 1999;3(1):5-7. ‘Vitamin D vs Broad Spectrum Phototherapy in the Treatment of Seasonal Affective Disorder. http://www.ncbi.nlm.nih.gov/pubmed/10888476.

5. Harvard Health Publications: Harvard Medical School. ‘Time for more Vitamin D’. http://www.health.harvard.edu/newsweek/time-for-more-vitamin-d.htm. September 2008.

6. Mark A. Moyard, MD, MPH. Medscape Multispecialty. Dermatology Nursing. 2009;21(1). ‘Vitamin D: A Rapid Review’. http://www.medscape.com/viewarticle/589256.

7. National Institutes of Health: Office of Dietary Supplements. ‘Dietary Supplement Fact Sheet: Vitamin D’. http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. 2011.

8. Overcoming Multiple Sclerosis. ‘Sunlight & Vitamin D’. 2010. http://www.overcomingmultiplesclerosis.org/Recovery-Program/Sunlight-and-Vitamin-D/.

9. Runia T.F., Hop W.C., de Rijke Y.B., et al. Neurology. 2012 Jul 17;79(3):261-266. ‘Lower serum vitamin D levels are associated with a higher relapse risk in multiple sclerosis. http://www.ncbi.nlm.nih.gov/pubmed/22700811.

10. Vitamin D Council. ‘Depression’. http://www.vitamindcouncil.org/health-conditions/depression/. June 2013.

11. Vitamin D Council. ‘Multiple Sclerosis’. http://www.vitamindcouncil.org/health-conditions/multiple-sclerosis/. March 2013.

12. Vitamin D Council. http://www.vitamindcouncil.org/. 2013.

13. The Endocrine Society. https://www.endocrine.org/. 2013.