Many illnesses and diseases has vitamin D as a factor! It is amazing for bone health, joint problems and osteoporosis. It is critical to help prevent breast cancer and prostate cancer, two of the most common cancers of all. It is great for blood pressure. It can help prevent or greatly improve multiple sclerosis. It helps with osteoarthritis and rheumatoid arthritis. It has great benefits for those with colitis and Chrons disease. However vitamin D deficiency is widespread in Ireland and Worldwide and is a deficiency epidemic!

Vitamin D behaves like a hormone in the body. This probably explains its powerful influence on our health. It is actually a group of ‘vitamins’ with D3 (calciferol) being the most important version for the body. It is manufactured in our skin from direct exposure to sunlight. It would take 2 x 20 minute sessions of exposure weekly to reasonably strong sunlight for you to get enough in your body. Direct exposure is the key, so being inside a window does not count; sunscreen also blocks the benefit and so does cloud cover and smog.

Most of us are not get enough exposure to sunlight. The amounts of natural vitamin D in food are not enough for the majority of us. Not a lot of foods have vitamin D. Salmon, tuna, mackerel, fish liver oils and eggs are about the best sources. There is a huge argument for supplementation of this vitamin especially in countries like Ireland. The elderly, our children, night shift workers, those who are bed ridden or chronically ill, vegetarians, low-fat dieters and dark skinned people are the most vulnerable groups and should seriously consider supplementation.

Vitamin D improves the absorption and action of calcium and phosphorus. It mobilizes minerals to bones. It is involved in the usage of many other critical body minerals like magnesium and zinc. It is vital for the maintenance and operation of body organs. Here are some details on how vitamin D influences some of our most common health conditions.

Special Note From David

Vitamin D is another great example of how basic nutrition plays a major role in our growing illness and disease. Often we over-complicate things. If we simply focussed more on just getting basic nutritional deficiencies right e.g. vitamin D, calcium and other essential minerals like zinc, magnesium and chromium we would be much healthier people! As I often say – in looking for a miracle we often over look the real miracle!

Depression & Mood

The connection between depression and mood disorders and vitamin D deficiency is well established. There is no question that having adequate levels greatly improve mood, depression, seasonal affective disorder (SAD) and other mental health conditions.


Because of its role in calcium usage, vitamin D has a huge role in bone health and especially fighting osteoporosis and osteopenia (a pre-stage to osteoporosis). As we get older our ability to synthesise vitamin D in our skin and absorb calcium decreases.  Studies have shown that the incidence of hip fractures decreased by a whopping 43% in older people who had better vitamin D levels!

High Blood Pressure

In general people with healthier levels of vitamin D tend to have healthier blood pressure readings. In one amazing study of the pregnancy related high blood pressure condition preeclampsia, the rate of preeclampsia fell by more than 40% in 666 participants when given vitamin D and calcium.


Vitamin D levels have a great influence on the severity and frequency of asthma symptoms as shown by the Harvard Medical School. The incidence of hospitalizations was also much lower in those with more vitamin D.


Vitamin D’s role in preventing or improving cancer is very interesting. The incidence of breast and ovarian cancer was less in those with better vitamin D levels. The vitamin has been shown to be effective in the treatment and prevention of prostate cancer. In lab studies vitamin D has been shown to reduce cancerous growths by as much as 50% and inhibit brain tumours and leukemia cells.


Vitamin D is of great help to those with psoriasis and can greatly reduce the ‘flakiness’ of this condition. Studies have shown that vitamin D supplements can be as good as psoriasis drugs for effectiveness and with none of the side effects and of course a lot of other added benefits!

Bowel Disorders

Interestingly one of the most frequent deficiencies seen in people with Chrons disease and Ulcerative Colitis is that of vitamin D. This suggests a possible great preventative role. What is clear is that the symptoms of these conditions greatly improve with adequate vitamin D levels.


Progressive osteoarthritis especially in the knees has been associated with vitamin D deficiency. Rheumatoid arthritis also benefits greatly from better vitamin D levels as a recent study of nearly 30,000 women over 11 years showed a 34% reduction in the risk of the disease in those who supplemented with 400IU daily.

Multiple Sclerosis

Here is yet another condition where low levels of vitamin D exist in sufferers. Oregon Health and Science University has shown that your level of vitamin D significantly influences your risk of getting this serious condition. Supplementation with vitamin D has also been shown to greatly help the effectiveness of MS therapy.

Weight Loss

Studies at the University of Minnesota and the Medical College of Georgia have shown that vitamin D levels predict your weight loss success when on a diet. Essentially this vitamin can greatly influence your results no matter how much dieting or exercise you do!

Immune System

To me your immune system is everything! I have no doubt that the cures that defy us now could come faster and better if we focussed our research on finding ways to strengthen our own immune system and let it do the job of fighting serious illness and disease. On this note Vitamin D has been shown by several research institutes to be a powerful immune system regulator. This surely is one reason why its deficiency has implications for virtually every illness and disease.


In an ideal World it would be best to get your Vitamin D naturally from exposure to sunlight. It is very difficult to get enough naturally from food. Unfortunately people living in Ireland simply do not get enough sunlight especially during the autumn/winter months. Supplementation should seriously be considered during this time unless intake of vitamin D foods together with fortified foods is of a strong and consistent level. Here are recommended supplementation levels:

  • Babies (non breastfed) – if consuming less than 1000ml/daily of vitamin D fortified formula or vitamin D fortified whole milk should supplement with 400IU daily.
  • Babies (exclusively or partially breastfed) – should receive 400IU per day shortly after birth and when weaned stop supplementation and consume a minimum of 1000ml/daily of fortified formula or fortified whole milk. If they do not get this level continue supplementation.
  • Children up to 18 years 200IU daily
  • Adults up to 70 years 400IU daily
  • Adults 71+ years 600IU daily

As always I hope you get something useful from this article and please share it with others. Someone making one simple change can lead to big improvements.

If you have any questions about anything above please email me at and I will reply.

Thanks for reading,

David McDonagh (Nutritionist, fitness trainer & creator of System 10 Weight Loss)

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My system is about real weight loss done the right way! My plan takes into account all the above reasons and more and makes sure weight loss will work for you. Don’t miss my NEW online plan starting soon where you can lose 10+ lbs in 4 weeks or 20+ Ibs in 8 weeks and get an amazing change in shape because it is real weight loss. Click here for more details on these options. Alternatively arrange a one to one consultation in your nearest clinic by clicking here.

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