#003 – Nutrient deep dive: Vitamin D
I have always been interested in food and nutrition and consider myself pretty health literate. But studying a semester of nutrition (and I am most definitely not an expert now!) has piqued my interest in the linkages between what we eat and our health span and wellbeing – and it also made me realise that it is a subject area that is complex, not well understood, and super fascinating!
Nutrition is one of those emotive topics and I am definitely not here to tell you what to eat or not to eat, but just to present some interesting factoids from what I have learned from formal and informal study. I will include references below if you want to dive in – and I am more than happy to email you any papers that spark your interest.
In the coming weeks and months we will take a deep dive into vitamins, macronutrients, micronutrients, macrominerals, microminerals, and nutritional bioactives (phew, I definitely didn’t know there were that many categories before I started studying!). And think a bit more about how increasing our awareness and knowledge of food and nutrition can improve our wellbeing.
Learning all of this (of course) makes me want to learn more, especially the public health implications of nutrition literacy and ensuring access (cost and availability) to nutritious food right across Australia.
One of the greatest discoveries in nutrition research in the past 30 years has been the multisystemic role of vitamin D – or its effects on cancer, diabetes, and muscle function (Katan et. al.).
Most of us know vitamin D as the sun vitamin. Vitamin D is different from all of the other nutrients in that the body can synthesise it (or make it itself), with the help of sunlight. Therefore it is not an essential nutrient per se, but given enough time in the sun, people need no vitamin D from foods. An essential nutrient cannot be made in the body (or can’t be made in adequate amounts for good health) and therefore must be provided by your diet.
Though called a vitamin, vitamin D is actually a hormone! We use it to make the minerals needed for bone growth and maintenance. It is also essential for brain function, cell replication and differentiation, anticancer activity, immunity, antioxidant and anti-inflammatory activity, insulin release, and blood pressure regulation. Phew, vitamin D is a powerhouse!
How do we get it?
Most of the world’s population relies on natural exposure to sunlight to maintain adequate vitamin D. Though the real story is a little more complicated! As we know (especially in Australia), prolonged exposure to sunlight increases the risk of skin cancer, and can also pre-maturely wrinkle the skin. Wearing sunscreen reduces these risks, but it also prevents vitamin D synthesis…
Did you know… Bathing or showering straight after sunlight exposure can wash away sebum that produces cholecalciferol before it can be absorbed back into the skin!
What can we do to increase our vitamin D?
For most people, exposing hands, face and arms on a clear, sunny day for 5-10 minutes during peak UV period (10am-2pm) in summer is sufficient to maintain vitamin D levels.
In Australia, a number of foods are fortified with vitamin D. It is mandatory in margarine and voluntary in low-fat milk, powdered milk, yoghurt, and soy milk.
There are very few natural food sources of vitamin D. Fatty fish contain small amounts of vitamin D. One of the more interesting ways I have read to get vitamin D in foods is by putting your mushrooms out for a sunbathe for 20-25 minutes before you eat them! You might have noticed in the supermarket that some mushrooms are marketed as a ‘sun-fortified’ or ‘enriched with vitamin D’. While this is part true, and part clever marketing, vitamin D levels decline through storage (especially when you put them in a dark place like the fridge). So maybe just DIY mushroom sunbathing!
But getting adequate vitamin D is not that simple…
There are a number of factors that can reduce our ability to synthesise vitamin D:
· Location
· Season
· Time of day
· Air pollution
· Clothing
· Sunscreen
· Poor mobility
· Indoor living.
For instance, latitude and season have enormous impacts on vitamin D synthesis. Below 40° south latitude in the Southern Hemisphere (I’m looking at you Tasmania and the entire South Island of NZ), vitamin D synthesis essentially ceases for the 3 months of winter. People living in extreme southern or northern locations may miss as much as six months of vitamin D production!
Vitamin D check
Do you:
· Have low bone density, osteomalacia (bone weakening), or osteoporosis?
· Have weak muscles?
· Have aches and pains in your muscles?
· Avoid exposure to the sun or wear sunscreen at all times when outdoors?
If you answered ‘Yes’ to any of the above, it might indicate inadequate vitamin D. But note that a number of nutritional deficiencies or health disorders can cause similar effects and further investigation is recommended.
Fascinating facts
· A lack of vitamin D causes serum calcium levels to drop and triggers a release of parathyroid hormone (PTH), which elevates serum calcium by mobilising it out of bones – in other words, low vitamin D can result in soft, weak bones – making them more prone to fracture (Paxton, 2020).
· Elevated PTH is also associated with fatigue, lethargy, depression, constipation, heartburn, peptic ulcers, nausea, vomiting, appetite loss, and vague abdominal pains, and it may increase the risk of kidney stones, pancreatitis, cancers of the colon , and the development of brown tumours (benign growths in bones) (Paxton, 2020).
· Vitamin D has been shown to prevent and relieve symptoms of inflammatory bowel disorders and arthritis (Paxton, 2020).
· Multiple Sclerosis (MS) prevalence around the world is highest in regions furthest away from the equator, believed to be due to differences in sun exposure. In Australia, there is a five-fold increased risk of MS in Tasmania compared with Queensland. Studies have shown that childhood sun exposure may be especially protective. One study found that Tasmanian children with the highest amount of summer sun exposure (averaging two to three hours a day, more on weekends and holidays) have a 70 per cent less risk of developing MS later in life compared with those experiencing less than one hour of summer sun exposure daily (Hayes, 2000).
· Vitamin D supplementation in infants and children has shown to be protective against the development of type 1 diabetes later in life. Overall, children on any dose of vitamin D supplementation were found to have a 29 per cent reduction in risk of developing type 1 diabetes compared with children not supplemented (Hypponen et al 2001).
I hope this has provided some food for thought. Let me know in the comments what surprised you the most! If nothing else, I am going to sit outside in the Autumn sun and read or eat my lunch for at least 10 minutes, most days.
Until next week, be well!
Alicia
PS. You might have noted in my bio that I am a Dr – but I am not a medical doctor, so please take the above information as a guide, and seek further information from your health professional, if needed.
For more information:
Foundations of Naturopathic Nutrition by Fay Paxton – this is the BEST book I have read on nutrition. It was a text book for my course, but it has so much valuable, well-researched information. I am still reading it now, despite finishing formal nutrition study!
Understanding Nutrition – Eleanor Whitney et al. – another text book, but heaps of great information not only on all of the nutrition elements, but also on the importance of nutrition through the life cycle.
Boost your vitamin D levels by bathing mushrooms in sunlight before eating https://www.sbs.com.au/food/article/2018/05/10/boost-your-vitamin-d-levels-bathing-mushrooms-sunlight-eating
Katan et al. “Which are the Greatest Recent Discoveries and the Greatest Future Challenges in Nutrition?” European Journal of Clinical Nutrition.
Hypponen et al “Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study”, Lancet.
Hayes et al “Vitamin D: a natural inhibitor of multiple sclerosis” Proceedings of the Nutrition Society.