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VITAMIN D: AN ESSENTIAL VITAMIN

Vitamin D has many important roles in your body. It exists in two forms: ergocalciferol (vitamin D2) or colecaciferol (vitamin D3). As well as the absorption of calcium, vitamin D is responsible for the absorption of the essential mineral phosphate from your intestines. Other important roles include:

  • helping to fight infection
  • muscle function
  • cardiovascular function, for a healthy heart and circulation
  • respiratory system, for healthy lungs and airways
  • brain development.

This article was included in issue 69 (summer 2016) of The Menopause Exchange newsletter.

As vitamin D is important for the growth of strong bones, a lack of it causes rickets in children and weak and deformed bones called osteomalacia in adults.

Vitamin D and overall health

Vitamin D has been shown to play a role in the function of the immune system, including the prevention of cancer, especially breast cancer, and possibly heart disease and type-2 diabetes. Several other conditions have also been linked with low vitamin D status, including ME, fibromyalgia, depression and cognitive decline. Specifically in women, a lack of vitamin D has been linked to PMS, dysmenorrhea (painful periods) and uterine fibroids.

A famous study in the US which has been following up a large sample of nurses for many years (the Nurses’ Health Studies) found that nurses who had the highest blood levels of 25-hydroxyvitamin D, averaging about 50 ng/ml, reduced their risk of developing breast cancer by as much as 50 percent. The risk of breast cancer increases at the menopause and tends to be higher in those that take HRT.

Recent studies have shown that in post-menopausal women (between 45 and 65) who were prone to falls, taking vitamin D supplements results in a lower incidence of falls and improved balance.

Sources of vitamin D

  • eggs (the yolk)
  • oily fish
  • liver
  • fortified margarine and fat spreads
  • butter
  • some breakfast cereals (fortified)
  • supplements including cod liver oil

Symptoms of deficiency

A mild lack of vitamin D may not cause any symptoms, but it can leave you feeling vaguely tired with maybe some general aches and pains. Sometimes you may notice more severe symptoms including:

  • muscle/joint pain and weakness
  • bone pain
  • tiredness or fatigue
  • depression.

The only way to know for sure if you’re vitamin D deficient is by asking your GP for a blood test to measure how much 25-hydroxyvitamin D is in your blood.

Are you at risk?

Vitamin D is mostly made in your skin on exposure to sunlight. It’s not as abundant in the diet as some vitamins and, as it’s fat soluble, it’s only found in certain foods containing oils or fats. See the box for some common sources of vitamin D.

Certain circumstances can make you more likely to be vitamin D deficient and need supplements. These are:

  • dark skin
  • being over 65
  • obesity
  • certain gut, liver or kidney diseases.

There is emerging evidence that after the menopause, women with type 2 diabetes have an increased incidence of deficiency.

In the above situations, or if you don’t get any sun exposure (or very little sun is around even in the summer, such as in more northern parts of the UK), you may need to take a vitamin D supplement all year round.

Should you supplement?

In 2014, the National Institute for Health and Care Excellence (NICE) declared that around one in five adults, and around one in six children, may have low vitamin D status. This is an estimated 10 million people across England.

Recently, the Government’s Scientific Advisory Committee on Nutrition (SACN) has recommended that all adults and children from four years take a daily 10 µg vitamin D supplement from October to March, as many may be going short of this vitamin during the winter. Vitamin D may be labelled as IU (international units) or micrograms (mcg or µg). 400 IU is equivalent to 10 µg.

Previous advice has recommended that everyone over 65 should take a daily supplement of vitamin D through the year and this still holds. This is due to the less efficient absorption of vitamin D at this age. A higher dose than 10 µg may be required to correct a vitamin D deficiency but speak to a healthcare professional first.

Vitamin D blood test results

Interpretation of vitamin D blood results (25 hydroxy D):

Deficient       =     under 50 ng/ml*

Optimal        =      50-70 ng/ml

Excess         =     greater than 100 ng/ml

Multiply these levels by 2.5 to get levels as nmol/l

*The Department of Health defines a deficient vitamin D status as a plasma concentration of 25 hydroxyvitamin D of below 10 ng/ml (equal to 25 nmol/litre).

Excessive intake

As with most vitamins, healthcare professionals don’t recommend that you take high doses of vitamin D (above 25 µg daily). This is because taking too much vitamin D, if your body stores are adequate, is believed to cause problems such as increasing the risk of kidney stones. Also, vitamin D toxicity can cause a build-up of calcium in the blood, known as hypercalcaemia, which can cause poor appetite, nausea and vomiting. Weakness, frequent urination and kidney problems may also occur.

Calcium and vitamin D

If you’re taking a calcium supplement for any reason (most commonly because you have osteoporosis or are at risk of this disease), you should also take a vitamin D supplement. This is to help your calcium absorption. Most calcium supplements are combined with vitamin D for this reason.

About the author

Gaynor Bussell is a dietitian and public health nutritionist with over 20 years experience in the women’s health field.

Created summer 2016

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