Supplements: Four vitamins to be cautious of – ‘Discuss with your doctor before taking’

This Morning's Dr Chris discusses collagen supplements

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Vitamin D supplements are commonly recommended during the winter months as it’s produced in the body when ultraviolet rays from sunlight pass through the skin and trigger vitamin D synthesis. Lack of sunlight in Winter months and not having enough sun exposure and having darker skin can affect absorption or having medical conditions that affect fat absorption can lead to vitamin D deficiency and taking a supplement daily can help.

A variety of supplements are available in high street stores, but there are some to be more wary of before taking them, according to Dr Angela Rai, GP at The London General Clinic.


Dr Rai said: “Most people will have enough calcium in their diet, however there are specific groups that may need to take calcium.

“Most people think that taking calcium will help their bones, but excess amounts can be linked to health conditions such as stomach pains, constipation, kidney stones and high calcium levels have been linked to heart disease and prostate cancer.”

Vitamin C

Dr Rai said: “Generally safe but high dose vitamin C  can cause haemolysis in people with G6PD deficiency.

“High doses can cause kidney stones in people with kidney disease.”


Dr Rai said: “Some people take multivitamins to fill nutritional gaps but there is limited evidence to support the benefits. One size does not necessarily fit all.”

St John’s wort

Dr Rai said: “A plant-based supplement, it has been used for depression, but the long-term effects are not known.

“It should not be used to replace conventional care and treatment of depression.

“St John’s Wort has many interactions with other medications and should not be taken without consulting a health care professional.”

Certain vitamins cannot be taken in pregnancy – vitamin A can be dangerous, according to Dr Rai.

He added: “Vitamins taken in pregnancy should be specific for pregnancy and from a reputable brand.”

Caution should be taken when taking any supplements, particularly when mega dosing.

But Dr Rai does recommend people consider taking the following supplements for optimum health.

Vitamin D

Also known as the ‘sunshine vitamin’, vitamin D is needed for bone growth in children and adults and can help protect older adults from osteoporosis.

Dr Rai said: “Some studies have shown that deficiency has also been related to a poor immune system, some types of cancer, type 2 diabetes, and hypertension. Vitamin D stores well in the body and therefore excess levels should not be consumed. Vitamin D toxicity can cause a build up of calcium in the blood and can lead to nausea, vomiting, frequent urination and kidney stones.”

Vitamin B12

B12 is a water-soluble vitamin and required for red cell formation, DNA synthesis and neurological function.

Dr Rai explained: “Vitamin B12 is found in animal products, such as meat, eggs, and dairy products.  Therefore, vegetarians or vegans are more likely to become deficient. Older adults may also absorb less B12, and certain medication can interfere with absorption of B12. Symptoms of deficiency include fatigue, weakness, loss of appetite, numbness or tingling of the feet, poor memory, mouth ulcers and glossitis (sore tongue).”

Folic acid

Another important type of B vitamin is folic acid and also affects red cell production. Deficiency of either B12 or folic acid can cause a type of anaemia.

Dr Rai continued: “Folate deficiency can also cause soreness and ulcers in tongue and mouth, changes in skin, hair, and nails. Women who are planning to conceive should take 400mcg of folic acid every day before they are pregnant and until at least 12 weeks of pregnancy. Folic acid can help the baby’s development and help prevent birth defects known as neural tube defects including spina bifida.”


Iron is essential for red cells and is a common deficiency leading to iron deficiency anaemia. This can be caused by heavy menstrual loss, pregnancy, lack of dietary iron, may be more common in vegetarians as iron is found in meats but there are natural plant based sources of iron such as dark green leafy vegetable, pulses, and beans.

Dr Rai advised: “Low iron can affect the immune system, aerobic capacity in physical exercise and can make the heartbeat abnormally fast.  Taking over the counter supplements should be in safe doses; stronger doses should be taken with advice from your doctor and a simple blood test can be arranged.”


Probiotics are live bacteria and yeasts and certain types of probiotics have been linked to health benefits.

Dr Rai said: “They are thought to restore the natural balance of bacteria in your gut, especially if it has been disrupted by illness or medication like antibiotics. They may help ease some symptoms of irritable bowel syndrome. For most people probiotics are safe.”

The Department of Health and Social Care recommends certain supplements for some groups of people who are at risk of deficiency.

If you’re unsure on whether or not to take a supplement, speak to your GP. 

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