Do I Need to Supplement My Diet?

Hazel Wallace Posted by Hazel Wallace on 22 May 2018 / Comments

We know vitamins and minerals are good for us, actually they are essential for us and essential for life, but does more necessarily mean better health?

In the UK, use of supplementation increased in 2015-2016, with 65% of all adults having taken some form of vitamin or supplement either daily or on an occasional basis in the 12 months ending June 2016, vs 63% in the previous year. This is also reflected in the growth of the vitamin and supplement market as they experienced a 2.2% increase in sales to £414 million (1).

Out of my own interest, I conducted a quick poll on Instagram stories, asking how many people that follow my page, take a daily multivitamin. Out of the 9862 people who took part in the poll, 35% of people said yes - and that is just a multivitamin alone. If we expand the question to other vitamins and supplements, including food supplements, I suspect that percentage would be much greater.

With such a boom in supplement use, we are now seeing even more weird and wonderful products hitting the shelves and as a result, it has become a total minefield for many of us.

So, how do we know if we need to take vitamins or supplements, and if so, which ones should we take, do they actual work, and more importantly, are they even safe?

I’m going to start with the spoiler:

If you are a healthy individual, without any specific nutritional deficiencies, you should be able to get all of the essential nutrients that your body needs through a well-balanced diet.


There are a number of caveats and exceptions to this, the main one being Vitamin D, which is made in our skin following exposure to the sun and is difficult to obtain solely through the diet. Therefore here in the UK, advice from Public Health England (PHE) is that all adults and children over the age of 1 should be taking a 10 microgram supplement of vitamin D each day throughout the autumn and winter months (2).

Furthermore, there are certain groups of people at risk of deficiencies who are recommended to take specific supplements such as;

Pregnant and breastfeeding women who are advised to take a vitamin D supplement, and at the start of the pregnancy (including the time trying to conceive) should also take a folic acid supplement until the 12th week of pregnancy.

Children aged 6 months to 5 years who should take a supplement containing Vitamin A, C and D.

At risk groups for vitamin D deficiency who should take a vitamin D supplement throughout the year.

This includes; people with darker skin, people who are not exposed to that much sun (i.e. those who are housebound or in an institution like a care home) and people who wear clothes that cover up most of their skin when outdoors. (5)

Another point to make is if you exclude certain foods from your diet, such as animal products, there is a high risk of deficiencies in certain nutrients, such as; iron and zinc, calcium, vitamin B12, Vitamin D, and omega 3 fatty acids. For this reason I recommend that vegans, i.e. those who consume no animal products, supplement with vitamin B12 at the very least as it cannot be obtained solely from plants. For more information on plant based diets and sources of the aforementioned nutrients, make sure to check out my book The Food Medic for Life.

So, there are a number of exceptions to the rule and some people do need to supplement, but no doctor, dietician, nutritionist or any other allied health professional, should prescribe a supplement without checking what the person is deficient in, or at risk of being deficient in, and also without ensuring that it safe to do so (e.g. the supplement will not interact with any other medications the person is taking).

What's the harm in supplementing if I don’t necessarily need to?

To be frank, it is unlikely these supplements are doing much benefit in healthy individuals, and most studies looking at the use of vitamin and mineral supplementation have found limited evidence to support they improve risk of disease and all cause mortality  (3,4). An extensive Cochrane review found no reduction in mortality in people who took antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium), either in healthy people or in those with diseases, and furthermore found that vitamin A, E and  beta-carotene may even increase the risk of death (5).

The thing is, the nutrients you find in food are packaged up in a very different way to those you find in a pill. Vitamins are either water soluble or fat soluble. The water soluble ones (i.e. B complex vitamins & vitamin C) if consumed in excess are likely to be passed in your urine as they cannot be stored by the body - and therefore become a very expensive toilet habit. The fat soluble ones (i.e. A, D, E & K) however, can be stored in the body and can therefore build up in our tissues, which puts us at a greater risk of toxicity if we take in more than we need.

In my own practice, I haven’t come across many cases overdosing on vitamins or supplements, the biggest cause for concern is when they interact with other medications the person may be taking, and either block their action or enhance their action. The classic example is St. Johns Wort which can interact with certain medications, most importantly, but not exclusively, oral contraceptives and warfarin (which is a blood thinning medication). Obviously a failed contraceptive method is not always ideal if it leads to an unplanned pregnancy, but a failed blood thinning medication can be lethal. Although there is some evidence that the herbal remedy is effective in the treatment of depression, if patients are self-administering this over the counter, whilst taking other medications, they could be putting their health at severe risk.

I also come across many people supplementing with iron because they feel tired and they believe it will give them energy. While it is true that a deficiency in iron (manifesting as anaemia) can leave you feeling very tired, not all tiredness is due to lack of iron and therefore supplementing with iron will not help improve your level of tiredness. Over supplementation of iron can lead to unwanted side effects, such as constipation and gastric upset, and in acute overdose it can even be lethal. This is because there is only so much iron our body can handle at one time and this is tightly regulated by important proteins in the body which bind to and regulate it.

So, iron supplements are beneficial for those who are deficient, but may cause unwanted side effects and harm in those who are not iron-deficient. If you do decide to, or are advised to, supplement with iron make sure you avoid taking it within 2 hours of other medication, as iron can interact with other medications and impair their absorption.

How to avoid taking too much of a vitamin or supplement.

To avoid taking too much of a vitamin make sure you stick to the recommended dose on the label, and if you take more than one vitamin, make sure you are not doubling up on any nutrients - for example if you take a multivitamin tablet which includes vitamin D, you don’t need an additional vitamin D supplement (unless advised by your doctor). The consequences of over supplementing depends on the vitamin and the dose. For example, if you take too much vitamin D over a long period of time, it can lead to dangerously high levels of calcium called hypercalcemia. Symptoms can range from asymptomatic (no symptoms) to vague symptoms such as abdominal pain and confusion, to kidney stones and even heart problems.

Another example I came across this week was when a woman approached me to tell me about her daughter who developed vitamin A toxicity after she had been taking a multivitamin whilst on Roaccutane for her acne. Roaccutane is the brand name for isotretinoin, which is a medication that has a similar structure to vitamin A, and so the two should not be taken together due to the risk of toxicity through cumulative overdosing. The mother said that she had not been told by her daughters doctor to not take vitamin A and that it wasn’t until she read the small print, following her daughter becoming ill, that she found the caution. This is just one example of how seemingly safe vitamins and supplements can lead to unwanted outcomes if not carefully prescribed with appropriate advice.

How do I know if it is safe to take? Who regulates supplements?

Always buy vitamins and supplements from a reputable source, such as your local chemist or high street pharmacy. Internet products may not meet UK standards and may not have gone through the same checks as products from a more reliable source. There may also be less or more of the active ingredient than claimed, and it could also contain other ingredients in addition that could cause harm or side effects.

Depending on how a supplement is classified, i.e. food or medicinal, it will be subject to different regulation. There are numerous regulations and considerations behind classifying each supplement, but generally in the UK, supplements that are considered to be foods will be regulated under general food laws by the Food Standards Agency and Department of Health, and those considered to be a medicine, will be regulated as a medicine by the Medicines and Healthcare Regulatory Agency (MHRA) (6).

How about IV vitamin drips?

Commercially marketed IV supplements are on trend at the moment (particularly in L.A. and private clinics in London) and claim to boost immunity, detox, and cure hangovers — and while they may hydrate you, it’s a pretty expensive — not to mention risky — hangover cure.

IV stands for intravenous, i.e. into your vein. Oral multivitamins are generally safe to use, when used appropriately, however administering something IV is completely different to popping a pill. We, as doctors, carefully weigh up the risks and benefits before prescribing anything IV and always review patients who are on IV medication or drips to see when we can step them down to the oral equivalent. The risks of anything administered intravenously include; increased risk of toxicity, risk of infection, risk of bleeding, phlebitis (inflammation of the vein) and electrolyte abnormalities. For context, the only real instance we give IV vitamins to people is if a) they have an individual nutrient deficiency e.g. Magnesium or b) They are severely malnourished (e.g. Alcohol dependent patient).

Take away

Just because we know vitamins and minerals are good for us, doesn’t necessarily mean that the more we have, the better our health will be, and just because the label claims it will improve your health in some shape or form does not mean it will, and just because it is sold in health food stores without a prescription, does not mean it is safe.

In theory, we should be able to get all the nutrients our body needs though a balanced diet.

You can do this by eating a diet rich in fruit and vegetables, wholegrains and legumes (beans, peas and lentils), dairy or fortified dairy alternatives, good quality meat and fish or plant foods rich in protein, such as tofu, and healthy fats from oils, nuts and seeds.

It is important for us not to forget that we eat food, not nutrients, and a wholefood compared to a supplement provides us not only with vitamins and minerals, but also other elements which cannot be obtained from nutritional supplement such as phytonutrients (special plant chemicals) and fibre.

Before buying a supplement ask yourself:

  • Why do I need this supplement and what do I hope to get from this supplement?
  • Are there any reliable sources backing it up and confirming its safety?
  • Could it affect any other medications I’m taking?


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