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Vitamin D – “The Sunshine Vitamin”

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Vitamin D is both a fat-soluble vitamin we eat and a hormone our bodies make. Because it is a prohormone it influences your entire body. Receptors that respond to Vitamin D have been found in almost every type of human cell, from your brain to your bones. 

Functions vitamin d immune system

  • helps the body absorb and retain calcium and phosphorus which are critical for bone strength, healthy growth and building of bones and teeth
  • supports normal immune system function and improved resistance to certain diseases  
  • can reduce cancer cell growth especially in breast and colorectal cancers
  • reduces inflammation. 
  • regulates mood and helps reduce the risk of depression
  • helps support healthy weight

Research suggests that vitamin D may also play a role in:

  • Reducing the risk of multiple sclerosis (MS), rheumatoid arthritis (RA), type 1 diabetes, fibromyalgia and inflammatory bowel disease
  • Decreasing the chance of heart disease. 
  • Reducing the likelihood of severe illnesses. Although studies are mixed, vitamin D may make severe flu and COVID-19 infections less likely. 

How do we get it? 

  • Vitamin D2 (ergocalciferol or pre vitamin D) and D3 (cholecalciferol) are naturally occurring forms that are synthesised in the skin once your unprotected skin is exposed to ultraviolet-B (UVB) from the sunshinevitamin d from the sun strong bones

How much?

RDA – Recommended daily allowance 

  • infants (0–12 months): 10 mcg (400 IU)
  • children and teens: 15 mcg (600 IU)
  • adults age 18–70: 15 mcg (600 IU)
  • adults over age 70: 20 mcg (800 IU)
  • pregnant or breastfeeding women: 15 mcg (600 IU)

Too Little?

The symptoms of a vitamin D deficiency in adults may include

  • tiredness, aches, and pains
  • severe bone or muscle pain or weakness
  • stress fractures, especially in your legs, pelvis, and hips 
  • may contribute to acute respiratory distress syndrome

Why a deficiency? 

  • a lack in the diet, poor absorption, or having a metabolic need for higher amounts. 
  • not receiving enough ultraviolet sun exposure over an extended period 
  • people who cannot tolerate or do not eat milk, eggs, and fish, eg those with a lactose intolerance or who follow a vegan diet
  • People with inflammatory bowel disease (ulcerative colitis, Crohn’s disease) or other conditions that disrupt the normal digestion of fat. Vitamin D is a fat-soluble vitamin that depends on the gut’s ability to absorb dietary fat.
  • People who are obese tend to have lower blood vitamin D levels. As Vitamin D accumulates in excess fat tissues but is not easily available for use by the body when needed. 
  • People who have undergone gastric bypass surgery, which typically removes the upper part of the small intestine where vitamin D is absorbed. 

Conditions resulting from prolonged deficiency:

  • Rickets: A condition in infants and children of soft bones and skeletal deformities caused by failure of bone tissue to harden.
  • Osteomalacia: A condition in adults of weak and softened bones that can be reversed with supplementation. This is different than osteoporosis, in which the bones are porous and brittle and the condition is irreversible.

Too much?

UL – The Tolerable Upper Intake Level (the maximum daily intake unlikely to cause harmful effects on health)

  •  The UL for vitamin D for adults and children ages 9+ is 4,000 IU (unless monitored under the supervision of your doctor)

Vitamin D toxicity 

  • most often occurs from taking supplements, not from food or excess sunshine
  • Vitamin D toxicity can lead to an increase in your blood calcium levels and can result in a variety of health issues, such as – nausea, apathy, vomiting, abdominal pain, dehydration, confusion, increased thirst
  • Other symptoms of toxicity – anorexia, weight loss, Irregular heartbeat, hardening of blood vessels and tissues due to increased blood levels of calcium, potentially leading to damage of the heart and kidneys

Food Sourcesoily fish

Few foods naturally contain vitamin D, though some foods are fortified with the vitamin.

  • D2 is produced in plants and fungi  
  • D3 in animals, including flesh of fatty fish like salmon, swordfish, tuna, sardines, herring and fish liver oils like cod liver oil.
  • Smaller amounts are found in egg yolks, cheese, and beef liver.
  • Certain mushrooms contain some vitamin D2
  • Many foods and supplements are fortified with vitamin D like dairy and plant milk products, orange juice, cereal 

Sunshine

  • The amount of vitamin D absorbed can vary widely.
  • Research suggests that you need an average of 10-15 minutes of unprotected sunshine on a regular basis, over large areas of your body to prevent cancer
  • It is safest to get unprotected sun exposure between 10am to midday, but your body will manufacture vitamin D most efficiently around midday as the sun is at its highest point and it’s UVB rays are most intense. Of course, you will only need 10 – 15 minutes
  • Too much unprotected sun exposure from midday onwards can lead to skin cancer, premature aging of the skin and cataracts

Conditions that decrease exposure to UVB light and therefore lessen vitamin D absorption:

  • Use of sunscreen; correctly applied sunscreen can reduce vitamin D absorption by more than 90%. 
  • Wearing full clothing that covers the skin.
  • Spending limited time outdoors.
  • Darker skin tones due to having higher amounts of the pigment melanin, which acts as a type of natural sunscreen. 
  • Older ages when there is a decrease in 7-dehydrocholesterol levels and changes in skin, and a population that is likely to spend more time indoors.
  • Certain seasons and living in northern latitudes above the equator where UVB light is weaker 
  • The body stores vitamin D from summer sun exposure

Supplementation

  • Higher doses of vitamin D supplementation may be needed to achieve a desirable blood level as it can be hard to get enough vitamin D each day through sun exposure and food alone
  • Vitamin D supplements are available in two forms: vitamin D2 (“ergocalciferol” or pre-vitamin D) which is made from plants and vitamin D3 (“cholecalciferol”) made from animal sources
  • A meta-analysis of randomised controlled trials that compared the effects of vitamin D2 and D3 supplements on blood levels found that D3 supplements tended to raise blood concentrations of the vitamin more and sustained those levels longer than D2. 

Did You Know?

  • Catching the sun’s rays in a sunny office or driving in a car unfortunately won’t help your immune system by obtaining vitamin D as window glass completely blocks UVB ultraviolet light
  • A healthcare professional can diagnose a vitamin D deficiency by performing a simple blood test. If you have a deficiency, your doctor may order X-rays to check your bone strength.

References:

https://www.hsph.harvard.edu/nutritionsource/vitamin-d/

https://www.healthline.com/health/food-nutrition/benefits-vitamin-d

Louise Ross-Campbell
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