When do you take your supplements? With breakfast or
your evening meal? Do you wash them down with water, juice or
coffee? Does it matter? Dr Sarah Brewer explains how to take
supplements for optimum health.
Although it may sound obvious, to get the most benefit from your
supplements, they must first be absorbed from your intestines and
presented to your cells in a form they can use or store. This is
known as a substance’s ‘bioavailability’. Some
substances (eg chromium) are poorly absorbed, using passive
processes such as diffusion, while others are rapidly absorbed
using active transport that quickly grab the nutrient from your
intestines when intakes are low - selenium take-up can be as high
as 98%. The amount of each absorbed nutrient that remains
bioavailable varies from person to person and also changes over
time - especially for nutrients such as iron and zinc, whose uptake
is regulated so you do not absorb too much. Absorption often
depends on the level of acidity in your stomach. As the quality of
your its lining reduces with age (a process known as atrophic
gastritis), lack of acid (known as achlorhydria) is relatively
common in older people and can lead to nutritional deficiencies.
Studies show, for example, that between 30 and 60% of people aged
over 75 are deficient in vitamin B12 and 30% are deficient in
folate - mostly due to atrophic gastritis which reduces B vitamin
absorption.
Health conditions that reduce or speed up the flow of intestinal
contents through your gut also affect absorption, as can the types
of food you eat. Bran and phytate (a substance found mainly in
unleavened wheat bread and beans) can bind minerals so they remain
unabsorbed, reducing uptake of iron, zinc, calcium and manganese.
One study found that a three-fold difference in phytate content of
food could reduce calcium absorption by as much as 25%. This
problem does not occur with leavened (yeast-raised) bread, as yeast
produces enzymes that break down phytate so mineral-binding does
not occur.
Minerals can interfere with absorption of each other, too. Iron
interferes with zinc absorption, while copper uptake is reduced by
the presence of zinc, iron and molybdenum.
Calcium
Absorption of calcium usually depends on both the presence of
vitamin D and the correct level of acidity to allow calcium salts
to break up into their soluble free ions. Low molecular weight
calcium salts such as calcium oxalate can be absorbed intact,
however, possibly by passing between, rather than through, cells in
the intestinal lining. Interestingly, scientists have found that
the bioavailability of calcium in brassica vegetables is higher
than for dairy products - 61% of calcium found in broccoli is
absorbable, compared with only 32% of that in milk. The reason
remains unknown.
Iron
this is most readily absorbed as ‘haem’ iron - the
pigment found in red meat. This is because it is taken up by a
specific haem receptor that is 2-3 times more active than the
mechanisms used to absorb non-haem (inorganic) iron. Most dietary
iron, including the salts found in supplements, is inorganic,
however. To make things more complicated, inorganic iron exists in
two forms: as ferrous (Fe2+) and ferric (Fe3+) which also have
separate uptake mechanisms. Ferric - the form in which most
plant-derived iron is obtained - is less well absorbed as it is not
very soluble in stomach acid. This can be overcome by vitamin C,
which keeps iron in the ferrous form and boosts its absorption,
which is why you may be advised to wash down iron tablets with a
glass of orange juice. Absorption is also enhanced by the presence
of alcohol and fructose.
Tea and coffee
Polyphenols such as tannic acid
(found in tea and some vegetables) bind iron and other minerals to
reduce their absorption and another unidentified component of
coffee inhibits the process. Coffee can reduce iron absorption by
up to 80% if drunk within an hour of a meal. It also lowers uptake
of zinc and, as it has a diuretic action, is associated with
increased losses of magnesium, calcium and other minerals from the
body. However, caffeine is an excellent stimulator of gastric acid
which can help the absorption of other nutrients.
Grapefruit juice
This interacts with a number of prescribed and over-the-counter
drugs. This interaction was discovered by accident when researchers
were looking at the effects of drinking alcohol with a particular
blood pressure medicine. Grapefruit juice was used as a mixer and,
while the alcohol did not affect the amount of drug circulating in
the body, the juice greatly increased blood levels of the
medication. The interaction between grapefruit and food supplements
has not been investigated and little information is known, but you
may wish to avoid drinking juice with your supplements (especially
herbs) just in case.
How to take supplements
1. Despite the problems mentioned above, vitamin and mineral
supplements are usually best taken immediately after food (just
four bites of food or a glass of juice will do). If you have not
eaten for more than 20 minutes, don’t take your supplements.
Wait until you have a snack/juice and take them then. If taken on
an empty stomach, some can make you feel sick or cause
indigestion.
2. Wash supplements down with water or orange juice. Don’t
take them with coffee or tea, as these may interfere with
absorption.
3. Fat-soluble substances (eg co-enzyme Q10, evening primrose oil,
fish oils and vitamins A, D, E, K) should ideally be taken with
food containing some fat (eg milk). If taking a fish oil supplement
that produces fishy ‘burps’, try emulsifying the oil by
shaking your dose with a little milk to increase absorption and
reduce aftertaste.
4. If taking two or more capsules of the same preparation a day,
spread these out over the day, if possible, to maximise absorption
and obtain more-even blood levels.
5. If you take a one-a-day vitamin and mineral supplement, it is
usually best after your evening meal rather than with breakfast.
This is because repair processes and mineral movements in your body
are greatest at night when growth hormone is secreted.
6. A day’s dose is better taken at the time you are most
likely to remember, however. Don’t feel you have to follow
any strict regime if you find difficulty remembering to take
supplements at a certain time, or if they do not fit in with your
particular lifestyle.
7. It’s easier to remember to take supplements if you get
into a routine and take them at the same time each day. Keep them
by your toothbrush, for example, or by your keyboard if this helps
you remember (as long as they are out of the reach of young
children).
8. It taking the lighter, gelatin capsules, look down at the floor
as you swallow to help them go down more easily. For heavier
tablets, put your head back as you swallow to help the action of
gravity.
9. Don’t swallow supplements in a hurry - if you take your
time, your throat muscle will be more relaxed and tablets are less
likely to lodge in your gullet.
10. If taking vitamin and mineral supplements make you feel
nauseated, here’s a possible solution: Whiz up all the
supplements you would normally take during the day in a food
blender, or pulverize them in a pestle and mortar. Divide the
powder into two to four equal portions. Take each portion (mixed
with milk, soup or juice) at regular intervals during the day, part
way through each meal, when your stomach juices are in full
flow.
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