Supplements are a huge industry and many products promise more energy or balanced hormones. For most healthy women eating a varied diet, food provides almost everything they need. There are, however, some situations where a supplement makes a real difference.
Why Food Comes First
Food contains a mix of nutrients and fibre that work together, along with many other natural compounds. When researchers have tested single nutrients as supplements, they have often failed to show the same benefits as the foods they come from. In some cases, high doses have caused harm. Supplements can fill a specific gap, but they cannot make up for an unbalanced diet.
When a Supplement Makes Sense
Planning a pregnancy or pregnant. A daily folic acid supplement is recommended from before conception until the end of week 12 of pregnancy, as our pregnancy nutrition article explains. A pregnancy multivitamin can also cover iodine and vitamin D.
Low sun exposure. Many women need vitamin D in autumn and winter, or all year if they rarely spend time outdoors or have darker skin.
Vegan diets. Vitamin B12 is essential if you eat no animal foods. Iodine, and possibly omega-3 from algae, may also be needed.
A confirmed deficiency. If a blood test shows you are low in a nutrient such as iron or vitamin D, a supplement at the right dose will usually be recommended. Iron in particular should only be taken when a test shows you need it, because too much can cause side effects and, over time, build up in the body.
Getting older or taking certain medicines. Absorption of vitamin B12 falls with age and with medicines such as metformin and stomach acid tablets, so some women need a supplement.
Medical conditions. Conditions such as coeliac disease can reduce how well you absorb nutrients, and so can weight-loss surgery.
Test Before You Take
Many symptoms that supplements claim to fix, such as tiredness, could have several causes. A simple blood test can show whether you are actually low in a nutrient such as iron or B12. It also avoids taking something you do not need while the real cause goes unchecked.
More Is Not Always Better
High doses of some vitamins and minerals can cause harm. Large amounts of vitamin B6, often found in energy or stress supplements, have been linked to nerve damage. Too much vitamin D over a long time can raise calcium levels in the blood. High doses of vitamin A in pregnancy can harm the baby. If you take several products, check that you are not doubling up on the same nutrient.
Some supplements also interact with medicines. St John's wort, for example, can make the contraceptive pill less effective. Tell your doctor or pharmacist about any supplements you take.
How to Choose a Good-Quality Supplement
In most countries, supplements are regulated as foods. This means they do not have to prove they work before they go on sale, and quality varies widely. To choose well:
Look for independent testing, such as the NSF or Informed Sport logos, which check that the product contains what the label says and nothing harmful
Choose single nutrients at sensible doses rather than complex blends
Be wary of proprietary blends, which list ingredients without showing how much of each the product contains
Be cautious of products claiming to detox your body or balance your hormones, as these claims are not backed by good evidence
Avoid products that promise fast or dramatic results
A dietitian or doctor can help you decide whether a supplement is worth it for you. In most cases, building a balanced plate is the better place to spend your energy and your money.