Each year Britons spend around £442 million on vitamin and mineral supplements, with nearly half of the population buying them regularly.
While the consensus is that a healthy balanced diet should provide all your nutrient needs, the fact is many people regard supplements as a dietary safety net.
Yet did you know that how and when you take them can undo their potential benefits?
For example, there is little point in taking vitamin D on an empty stomach because it needs fat in the gut in order for it to be properly absorbed. And taking too much of one B vitamin can leave you low in another.
While the consensus is that a healthy balanced diet should provide all your nutrient needs, the fact is many people regard supplements as a dietary safety net
‘The vitamins and minerals we need to stay healthy work together in a complex and delicate balance,’ says Lindsy Kass, a sports and nutrition scientist at the University of Hertfordshire.
‘While some need each other to perform best, others can compete in the body for absorption.’
Here, our expert guide explains how you should take your supplements to ensure you get the most out of them and don’t waste your money…
Iron
At a glance: Take on an empty stomach before bed, and combine with vitamin C or A; avoid taking with dairy, tea or zinc pills.
Low iron is one of the most common nutrition deficiencies, with figures from the UK Health Security Agency showing that three-quarters of women are at risk of iron-deficient anaemia, which causes fatigue, lack of energy and heart palpitations.
This is mainly owing to women losing up to 250mg of iron during their monthly period.
‘Iron should be taken on an empty stomach, because certain foods, especially dairy, can block its absorption,’ says Aidan Goggins, a London-based pharmacist and an independent adviser to the supplement industry.
‘But vitamin C can help your body absorb iron, so it’s a good idea to combine it with this, either in the supplement, or by having a glass of orange juice,’ he says.
That’s because vitamin C bonds to iron particles, which helps them to dissolve more completely in the gut.
Vitamin A can also improve iron absorption, so taking an iron supplement that contains it — or its precursor beta-carotene — can be very useful.
But don’t wash your pills down with milk-based drinks, as the calcium in these blocks the iron receptors in the gut, impairing the absorption, says Aidan.
You should also avoid drinking tea. ‘When tea is sipped with a meal, it can inhibit the absorption of iron from your food by up to 90 per cent, and so the same negative effect is likely to happen if you take an iron pill with tea,’ he adds.
This is not just because of the dairy, but because the tannins (naturally occurring plant compounds) in tea bind to iron and block its absorption.
‘A 2017 study of UK women found that when drinking tea one hour after a meal, the amount of iron absorbed was reduced by 50 per cent — so leave at least two hours,’ advises Aidan.
Zinc is another nutrient that can compete with iron because both minerals need to attach to the same ‘transporter molecules’ in the gut.
These help nutrients get through the gut wall and into the bloodstream. Products containing zinc are, therefore, best avoided.
‘Because so many factors can interfere with your absorption of iron, I find it’s best taken as a combined supplement with vitamin C, an hour before bed — but two hours after supper,’ says Aidan.
Taking it right before bed means it may linger in the gut and irritate its delicate lining, which can trigger feelings of nausea and discomfort, he adds.
‘Leaving an hour before bed means it should have passed through into the stomach before you lie down,’ he says.
Some research suggests iron is best taken every other day.
A 2017 study by the Laboratory of Human Nutrition in Zurich, Switzerland, published in The Lancet Haematology, found that more iron was absorbed when supplements were taken on alternate, not consecutive, days.
The researchers think alternate-day dosing lowers levels of hepcidin, a protein that regulates intestinal iron absorption. High levels of it have also been linked to anaemia.
Many menopausal women take calcium to help prevent the bone-thinning disease osteoporosis. Often, the calcium is combined in a pill with magnesium, which is also good for bones
Calcium
At a glance: Take a supplement (ideally also containing magnesium, vitamin D and vitamin K) with food; look for products containing calcium citrate; avoid taking with zinc or iron pills.
Many menopausal women take calcium to help prevent the bone-thinning disease osteoporosis.
Often, the calcium is combined in a pill with magnesium, which is also good for bones. In fact, calcium and magnesium work together in some ways but also compete for absorption in the gut.
Despite this, Aidan recommends the combined pill, ‘because the extra convenience of taking them in a combined supplement probably outweighs the relatively small percentage of each that may not get absorbed,’ he says.
Vitamin D and vitamin K are also often found in calcium supplements, and both have been shown to boost overall calcium absorption. ‘You need sufficient vitamin D in your blood [equal to a supplement dose of at least 400 international units, or IUs] to be able to absorb calcium well,’ says Aidan.
‘This is because vitamin D is converted into the hormone calcitriol, which acts on cells in the gut to increase production of calcium-absorbing proteins called calbindins.’
Magnesium is also needed for the vitamin D to balance calcium levels. ‘It’s a delicate relationship,’ says Aidan. ‘So a supplement containing all four nutrients [i.e., plus vitamin K] is ideal.’
‘Taking calcium with food will also enhance absorption,’ he says. And look for supplements with calcium citrate, ‘which studies have shown is better absorbed by the gut than other cheaper forms of calcium such as calcium carbonate’, he adds.
Researchers at Florida State University in 2014 found that taking a collagen supplement with calcium helps it work even better when it comes to preventing bone loss in early menopausal women.
‘Collagen fibres form the scaffolding of our skeleton,’ says Aidan. A good supply, he adds, helps build the ideal structure for ‘calcium to be drawn and deposited into the bones where it provides their stiffness and rigidity’.
If you also use zinc or iron, take these separately from calcium as it inhibits their absorption.
Vitamin D
At a glance: Take in the evening with food (or largest meal of the day) containing fat; avoid taking with vitamin E pills.
In the winter months, around half the population is low in vitamin D, a nutrient vital for healthy bones and strong immunity.
And because we make vitamin D largely via sun exposure on our skin, the advice is to take 10 mcg daily over winter.
Like the other fat-soluble vitamins (A, E, and K), vitamin D is better absorbed if taken with a meal that contains some fat, such as avocado, egg yolks or olive oil.
One study published in the Journal of Bone and Mineral Research in 2010 found that taking it with the evening meal — usually the heaviest meal of the day — increased blood levels of the vitamin by up to 50 per cent compared with taking it either on an empty stomach or with a smaller meal.
‘Taking vitamin D with food ensures the optimal release of bile and pancreatic enzymes in the stomach that are required for the absorption of fat-soluble vitamins,’ says Aidan.
But don’t take a vitamin D supplement with a vitamin E pill as both are absorbed through the same mechanism and so compete for absorption, reducing the amount absorbed of both.
Vitamin C
At a glance: Take in the morning on an empty stomach; split larger doses throughout the day; consider taking pills that are ‘fat wrapped’.
Important for the immune system and vital for healthy skin and bones, vitamin C is a water-soluble nutrient and so, unlike some other vitamins, doesn’t need to be taken with fat.
Most water-soluble vitamins are best absorbed on a completely empty stomach, such as before breakfast, as their absorption can be hindered by proteins and fibre in food, says Aidan.
Studies suggest we can absorb doses of up to 400mg — ten times the recommended daily level of 40mg — but vitamin C isn’t stored in the body, so any excess is simply passed out in urine. That means people taking short-term, larger doses of 1,000mg — for example, during a cold — may be better splitting up the dose throughout the day to help maintain constant high levels in the blood.
Aidan says a split dose can also prevent the upset stomach some people experience with these larger doses.
A new generation of liposome-encapsulated vitamin C products — which wrap vitamin C particles in protective fat bubbles — have been found to offer higher absorption than standard oral vitamin C supplements.
According to research — funded by the liposomal technology industry — published in 2016 in Nutrition and Metabolic Insights, the fat means ‘it’s not broken down in the stomach as vitamin C would normally be but reaches the small intestine intact, where it is directly absorbed into the bloodstream,’ says Aidan.
But Lindsy Kass says that, while the liposomal delivery works, ‘a standard supplement will give you more than enough vitamin C’.
Fish oil
At a glance: Take with food (that contains fat); avoid taking before a workout or sleep.
Fish oil pills are a rich source of two omega-3 fats called EPA and DHA, which have proven benefits for a wide range of illnesses including low mood, heart disease and rheumatoid arthritis.
The key with these is timing. ‘Don’t take fish oils in the morning before you’ve eaten,’ warns Aidan. ‘They need dietary fat to help their absorption so should always be taken with a meal.’
That’s because the fat in food triggers the pancreas to release enzymes, which help break down omega-3 oils into fragments small enough to be absorbed through the gut wall.
Also, avoid taking them before a workout or sleep ‘because digesting a fish oil supplement will produce gas in your stomach’, says Aidan, ‘and strenuous activity or lying down encourage this gas to travel back up the oesophagus triggering reflux — or those unpleasant fishy burps’.
If you find it hard to digest fish oils, try also taking a supplement that contains the enzyme lipase, which boosts fat digestion.
B vitamins
At a glance: Take in the morning on an empty stomach; choose a supplement with a blend of different B vitamins.
The group of eight B vitamins — including B6, B9 (otherwise known as folic acid) and B12 — are vital for healthy blood, nerve function and energy levels.
Because of their energy-boosting abilities and the fact that they are water-soluble, they are best taken first thing in the morning on an empty stomach.
Vitamin B12, in particular, binds to the protein in the foods we eat and can then end up passing straight out of the gut as waste without being absorbed. But that’s not the only reason to take them in the morning.
A 2018 study by the University of Adelaide in Australia found that high vitamin B6 doses could interfere with sleep and induce vivid dreams.
Researchers think it stimulates the area of the brain responsible for feelings of wakefulness.
Aidan advises taking a B vitamin blend. ‘Taking one B vitamin on its own increases the body’s need for the others and can end up causing deficiencies,’ he says.
‘For example, taking folic acid alone can trigger or mask a deficiency in vitamin B12.’
Probiotics
At a glance: Take half an hour before eating; take before a meal containing some fat; avoid taking with hot drinks, juices or alcohol.
These are ‘good bacteria’ that make up part of our gut microbiome — the community of bacteria that plays a vital role in our digestive health and immune system.
A poor diet or medication such as antibiotics can kill off the good bacteria, helping bad ones thrive, which increases the risk of gut infections or digestion problems. Probiotic supplements aim to replenish levels of good bacteria.
‘The most important thing to remember with probiotics is that they are live bacteria which have to reach the gut intact to have any benefit,’ says Aidan.
So avoid taking them with anything that might destroy these delicate bugs before they reach the small intestine.
‘Hot drinks can kill them, as can the acid levels in fruit juice and alcohol, so take them with plain water,’ he says. ‘Water also helps dilute stomach acid, which further increases their survival chances.’
Consider taking them before eating. A 2011 Canadian study found that probiotics containing the bacteria Lactobacillus and Bifidobacterium had the highest survival rate when taken 30 minutes before a meal.
The study also found it helped if the subsequent meal contained some fat — probably as this reduced overall stomach acidity.
Taking probiotics half an hour after food had the opposite effect, with the lowest bacteria survival rate (probably as this is when stomach acid is at its highest).
Magnesium
At a glance: Balance carefully if combining with calcium; take at bedtime if using for a relaxing effect.
As well as being useful for bone health, if you’re taking calcium, there is evidence that magnesium may help ease anxiety, restless legs, muscle cramps, migraine and improve overall sleep.
Because calcium and magnesium can compete for absorption, if you’re taking both check the ratio — you should take roughly twice as much calcium as magnesium.
Magnesium absorption will be ‘seriously affected if the calcium dose is much higher than the magnesium dose’, says Lindsy.
Some studies also suggest that too much calcium with too little magnesium may contribute to calcification of the arteries, increasing the risk of heart disease.
If you’re taking magnesium on its own, its relaxing effect means it makes sense to take it close to bedtime and consider trying it as a lotion or cream.
‘One 2017 study found that applying a magnesium cream to the skin daily for two weeks improved blood levels of the mineral by more than 22 per cent — more than double the amount you’d receive from a magnesium tablet,’ says Lindsy.
