The Sunshine Vitamin: Vitamin D

With summer underway in the northern hemisphere, the increased daylight and warmer temperatures encourage us to get outside more and turn our faces to the sun. Buried in our genetic makeup is the innate understanding that we need sunlight for survival and health, and an increasing amount of information is being published about just how important it is.

Vitamin D was originally best known for its role in helping the body maintain calcium and phosphate levels, two important nutrients for building and maintaining strong bones and protecting against osteoporosis, rickets and bone fracture. But vitamin D is not just important for bone health, it is critical for overall health. This is demonstrated by the fact that virtually every cell in the body has a vitamin D receptor, and when vitamin D binds to these receptors, the expression of more than 200 genes is impacted.

Vitamin D and the Immune System

Immunity is currently a big area for vitamin D research. A study published in the American Journal of Clinical Nutrition compared vitamin D3 supplementation with a placebo in school children. The study found that the children taking supplementation had a 42% lower risk of catching the flu than the children taking the placebo. Additionally, asthma attacks almost disappeared during the same time with vitamin D supplementation in the children that had been previously diagnosed with the inflammatory condition.

Read more about boosting your immune system

Researchers at Copenhagen University explain how some of the immune benefits of vitamin D are possible. Our immune systems have many components but one of the front-line soldiers of the system are called the T-cells and they protect us from pathogens such as viruses and bacteria. The researchers discovered that the first stage of the crucial activation of the T-cells involves vitamin D. They found that when a T-cell is exposed to a virus or bacteria, it immediately extends a signalling device or ‘antenna’ which is a vitamin D receptor, that will search for vitamin D in the blood. The T-cell must have vitamin D or its activation will stop. “If the T-cells cannot find enough vitamin D in the blood, they won’t even begin to mobilize”, says Dr. Geisler, the lead researcher. This understanding of how important vitamin D is for activating the immune system has important implications for both autoimmune and infectious diseases.

Supplements, Food or Sun?

Natural food sources of vitamin D are limited to fatty fish (about 450 IU per 3 ounces of salmon), beef liver, cheese (about 14 IU for 2 ounces of cheddar) and egg yolks (about 40 IU per yolk), with a tiny amount found in some mushrooms. Other foods like milk, some cereals and orange juice are commercially fortified with added vitamin D.

Getting your vitamin D from exposing your skin to the sun is a natural (and free) option – if you live above 35 degrees latitude. For those of us above this geographic coordinate, the sun is only at the right altitude for making vitamin D in the body from about May until early October. A standard recommendation is to get about 10-30 minutes of sun at the peak of the day (11 a.m. – 2 p.m.) on as much of the skin as possible, at least twice a week. Keep in mind, this exposure must be without the use of sunscreen. Older people, obese people and those with darker-coloured skin will make less vitamin D from the same amount of exposure. As well, the UVB rays from the sun that launch the production of vitamin D in the body can also cause sunburns and other related negative effects, so make sure you keep an eye on how long you are in the sun.

If you can’t get out in the sun or eat enough vitamin D containing food, supplementation with vitamin D3 may be the answer.

How much do I need?

The daily recommended intake (RDA) for vitamin D as set out by the Nutrition Board in the US is 400 international units (IU) for infants, 600 IU for ages one to 70, and 800 IU for those over 70 years of age. There has been much discussion over the last few years about this amount and some experts believe a higher amount in needed for health in certain people.

Too much of a good thing?

As important as adequate levels of vitamin D in the body are, there is the potential to think that if some is good, more is better, especially in the pursuit of health. Like many nutrients, vitamin D follows a U-shaped curve, meaning that both very low levels and very high levels are associated with negative health outcomes. While vitamin D toxicity is unlikely at daily intakes below 10,000 IU, there is evidence to suggest that excess doses can build up to harmful levels causing high blood calcium leading to damage to the heart, stroke, kidney stones, diarrhea, vomiting and low bone density. 

Test so you don’t have to guess

Knowing what your vitamin D status is can help you make sound supplement decisions that are specific to you. To do so, ask for a blood test called 25-hydroxy vitamin D which will reflect your body’s total vitamin D from food, supplements and the sun. Then work with a functional medicine practitioner to determine the right levels for you in the context of your entire health status. Re-test a couple of times a year to understand your won specific needs.


By Jill Hillhouse BA, BPHE, CNP, RNT| August 01, 2017
Categories:  Eat

About the Author

Jill Hillhouse BA, BPHE, CNP, RNT

Jill Hillhouse BA, BPHE, CNP, RNT

Jill is a passionate advocate of whole foods eating and nutritional education. She believes that health starts on your dinner plate and she uses diet and lifestyle shifts to mitigate and reverse health conditions. Jill focuses on addressing her clients’ metabolic individuality as a key factor in her functional nutrition protocols and coaching. A strong voice for self-advocacy, Jill encourages and empowers her clients to be active participants in their own health care. Working as a nutritional practitioner since 2001, Jill is part of the integrative health team at P3 Health Clinic in Toronto, Canada, and she also maintains a private nutrition consultation practice. Jill is the co-author of The Paleo Diabetes Diet Solution: Manage Your Blood Sugar with 125 Recipes and a 30-Day Meal Plan and the best-selling book The Best Baby Food: 125 Healthy & Delicious Recipes for Babies & Toddlers. She also writes articles for a number of national online and print publications.

Jill Hillhouse is a Certified Nutritional Practitioner from The Institute of Holistic Nutrition and has earned her Bachelor of Physical and Health Education and her BA in Psychology from Queen’s University. She is certified as a First Line Therapist in Lifestyle Medicine by Metagenics and as a Stress and Wellness Consultant by the Hans Selye Foundation and The Canadian Institute of Stress. Jill has been a faculty member of The Institute of Holistic Nutrition since 2005. She is a member of The Canadian Association of Natural Nutrition Practitioners and the Institute of Functional Medicine.

Follow Jill on her website (, facebook ( and on twitter and instagram (@jillhillhouse) for commentary about new scientific studies, topical health issues and practical tools for better health.

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