Nerd-Out: Vitamin D Report

(For those of you who like to nerd-out on the science behind nutrition, I will be sharing portions of my writings for my Master's of Science in Holistic Nutrition.)

Here's the first one: Vitamin D

Photo by pepifoto/iStock / Getty Images

Photo by pepifoto/iStock / Getty Images

          Vitamin D is something I’d taken for granted until my breast cancer diagnosis four years ago. Growing up in San Diego, California, I mistakenly believed that my long days at the beach, poolside, and soccer fields would provide me enough of that essential vitamin. Moving to Colorado as an adult didn’t change my mindset about it. Living closer to the sun and hiking, camping, skiing, snowboarding, and simply sitting outside on my beautiful backyard deck supplied ample exposure to the sun’s vitamin D-rich rays, or so I thought. It wasn’t until my breast cancer diagnosis four years ago and the subsequent battery of labs, blood tests, and scans, that I discovered I was vitamin D deficient. Thus began this heightened interest in this “sunny” vitamin and a subsequent “dance” of treatments with my traditional oncologist and my naturopathic physician.  

            Known chemically as (cholecalciferol), vitamin D3 can be synthesized on human skin when exposed to ultraviolet B (UVB) radiation from the sun (Higdon & Drake, 2012, p.83). It can also be ingested in food or supplement form in the diet (Higdon & Drake, 2012, p.83). Although not prevalent in many foods, it can be found in liver, salmon, mackerel, sardines, cod-liver oil, and egg yolks, and vitamin D fortified cereals and milk (Smolin & Grosvenor, 2013, p382).  Vitamin D acts like a hormone in that several organs are affected in its metabolism, including the skin, intestine, bone, and kidneys (Smolin & Grosvenor, 2013, p.382).

            Activated in the liver and then dumped into the blood stream, vitamin D circulates and travels to the intestines, bones, and kidneys where it helps increase calcium levels in the blood (Smolin & Grosvenor, 2013, p.383). The maintenance of normal blood calcium levels is crucial to maintain the growth, density, and strength of bones and prevent their breakdown (Higdon & Drake, 2012, p.83). Vitamin D also helps regulate cell differentiation, immunity, insulin secretion, and blood pressure regulation (Higdon & Drake, 2012, p.84).  Proposed but yet unproven actions of this vitamin include cancer prevention, protection from certain autoimmune diseases such as type 1 diabetes and multiple sclerosis, and protection from cardiovascular disease and type 2 diabetes (Smolin & Grosvenor, 2013, p.384).

            Without proper levels of vitamin D consumption or absorption, only about 10-15% of calcium in the diet can be utilized, affecting bone mineralization, strength, and growth (Smolin & Grosvenor, 2013, p.384). And without access to dietary calcium, the body resorts to leaching existing calcium from the bones, leaving them at risk for bone pain, muscle aches, and fractures (Smolin & Grosvenor, 2013, p.385). In a child’s growing frame, this deficiency causes rickets, characterized by bowed legs, weak bones, and short stature (Smolin & Grosvenor, 2013, p.384). In adults, vitamin D deficiency results in osteomalacia, or soft bones (Higdon & Drake, 2012, p.85).

            Too much vitamin D (toxicity) raises blood calcium levels too high, which can result in deposits of calcium in blood vessels, kidneys, and the heart, hardening them, resulting in damage (Smolin & Grosvenor, 2013, p.386). Most vitamin D toxicity results from over-supplementation or consuming too much of fortified foods. Sunlight and unfortified foods do not pose a risk for overconsumption (Smolin & Grosvenor, 2013, p.386).

            Lack of sun exposure is the primary way people become vitamin D deficient. Living in big cities with tall buildings blocking the sun, wearing sunscreen, spending all daylight hours indoors, and living at latitudes greater than 40 degrees north or south, increase decrease the skin’s exposure to the sun (Smolin & Grosvenor, 2013, p.384-385). Dark skin, which prevents much of vitamin D synthesis in the skin, and concealing clothing worn by certain cultural and religious groups, are also risk factors for deficiency, even in sunny climates (Smolin & Grosvenor, 2013, p.385). Elderly people, those with fat malabsorption syndromes, kidney disease, and inflammatory bowel disease are also at risk for deficiency, as these conditions prevent optimal absorption of vitamin D (Higdon & Drake, 2012, p.86). Finally, exclusively breastfed infants may be at risk, particularly if they have dark skin and/or receive little sun exposure (Higdon & Drake, 2012, p. 85).

            Foods rich in vitamin D, as mentioned above, are fatty fish such as salmon, mackerel, and sardines. Organ meats, particularly liver, are high in this vitamin. Egg yolks are dense sources of vitamin D as well. Sunlight, although not a food source, is by far the best provider of vitamin D.

            Using the iProfile Food, Liquid, and Activity Form, I tracked my food intake for a day to take a peek at my nutritional habits and get a feel for how much vitamin D I eat on an average day (Smolin & Grosvenor, 2010, iProfile). According to the dietary analysis, the eggs I consumed for dinner provided 82% of my Dietary Reference Intake (DRI), while the cheddar cheese provided 11%, the goat cheese 4%, and the Shiitake mushrooms 4%. I nearly reached 100% of my DRI with these food items. With 8ug the goal, I reached 7.8ug.

            The Suggested Optimal Nutritional Allowances (SONA) for vitamin D are slightly different. 24ug is the goal in this case, and here, with my 7.8ug, I fall desperately short. Since it is difficult to meet the requirements for vitamin D through diet alone without consuming fortified milk, which I don’t drink, I need to get mine from other sources. It’s winter in Colorado, and so the days when I can expose my arms, hands, and face to the sun are limited. Even with spending long hours in the sun all summer, my vitamin D levels have faltered, for whatever reason. However, I can supplement with vitamin D capsules to make up for the lack in my diet and sun exposure. I currently take 10,000iu of vitamin D3 daily, which translates to 250ug, which exceeds both the RDA (300iu/7.5ug) and the SONA (960iu/24ug). I do this under the care of a qualified naturopathic physician to avoid toxicity. Because I’m a breast cancer survivor, we’re taking special care of my vitamin D levels to prevent recurrence.

            If it weren’t for my breast cancer diagnosis, I may still be in the dark to the important role vitamin D plays in the prevention and treatment of disease. Though sun exposure is the optimal route to satisfy requirements, some foods, including fortified foods, and supplementation, provide necessary levels to keep the body systems operating optimally.

**UPDATE: I have since started taking fermented cod liver oil daily to provide more whole food supplementation of vitamin D. I plan on discontinuing my vitamin D capsules and consume only the fermented cod liver oil. Blood tests will determine if this is sufficient-- I'll keep you posted. xoxo, SF


Higdon, J., & Drake, V. J. (2012). An evidence-based approach to vitamins and minerals: health benefits and intake recommendations. Stuttgart: Thieme.

Smolin, L. A., & Grosvenor, M. B. (2013). Nutrition: science and applications(3rd ed.). Hoboken, NJ: Wiley.

Smolin, L. A., & Grosvenor, M. B. (2010). IProfile: assessing your diet and energy balance. Hoboken, NJ: Wiley. Retrieved January 25, 2018.

The Suggested Optimal Daily Nutritional Allowances (SONA)[Online reading material for
MSHN 515, Hawthorn University]. (2017).