Nutritionist Catherine Saxelby is passionate about helping people to eat delicious, healthy, seasonal food. In her book, Complete Food And Nutrition Companion: The Ultimate A-Z Guide, she presents clear guidelines on whether or not nutritional supplements are beneficial. This is an edited extract of her advice.
Ideally, it’s best to obtain your nutrients from food, not pills. Food provides vitamins and minerals in the most biologically available form, in the right amounts and combined with other complementary nutrients that work together as a team. For example, vitamin C increases the absorption of iron, vitamin E works with selenium and vitamin C as an antioxidant defence team, folate’s biochemistry is intertwined with that of vitamins B6 and B12 vitamins, and zinc is synergistic with vitamin A.
And of course, with food, there’s little risk of overdose except under special circumstances.
But there are times when you can’t eat a balanced diet or you have a health problem that may respond to higher intakes of one or more vitamins.
Tips for taking supplements
In recent years attitudes have changed, as numerous studies have emerged suggesting antioxidant supplements in particular are associated with better health profiles. If you choose to take a supplement, there are some general rules you should follow:
- Take supplements with food or soon afterwards to help absorb them better.
- Think of them only as a top-up to your daily diet.
- Don’t take more than the suggested dosage.
- Buy a reliable brand. Cheaper brands may not have the most biologically active form (for example, natural compared with synthetic vitamin E, calcium gluconate compared with carbonate) or they may have only tiny amounts.
- Check the amount of the pure vitamin or mineral you’re getting – 1500 milligrams of calcium carbonate means 600 milligrams of pure calcium.
- Be wary of exaggerated claims made on packs and in advertising. Often the scientific evidence is scanty, preliminary or consists of anecdotes from ‘satisfied’ patients.
- A single study does not always prove the cause.
- Chewable vitamin C tablets are so acidic they can dissolve tooth enamel; if you take them, rinse your mouth well afterwards.
- Take an iron tablet with orange juice or a fruit rich in vitamin C to improve its absorption.
- Check the label if you have an allergy – most supplements are free of yeast, dairy, gluten and seafood.
- Distribute the dose over the day – two smaller tablets are usually better absorbed than one single one.
Getting the dose right
When taking any supplement, more is not better. Large single doses of certain vitamins and minerals can have undesirable side effects and even potential dangers. At high doses, vitamins act as drugs. They may interact with each other or with medications such as diuretics, anti-inflammatories, antibiotics or the contraceptive pill.
Vitamin or mineral: side effects of high doses
Vitamin A: Excess causes nausea, liver damage, dry itchy skin, hair loss, headaches and skin problems.
Beta-carotene: Turns the skin and whites of the eyes an orange-yellow colour (which slowly disappears once you cease consuming excess amounts). May also produce hair loss, nausea or blurred vision.
Vitamin D: More than 80 micrograms a day can lead to nausea, bone pain, liver damage, muscle weakness and lethargy. It also causes calcium to be deposited in soft tissues like the liver and kidneys.
Vitamin C: Not toxic, but doses greater than 2000 milligrams a day can cause upset stomach and diarrhoea. Increases the risk of iron overload.
Vitamin B6: More than 50 milligrams a day can lead to neuritis, a painful numbness or tingling in the hands and feet due to damage to the nerves.
Niacin: Mild flushing reaction at over 1000 milligrams a day.
Iron: May cause gastrointestinal upset or constipation. Can produce iron overload in someone with haemochromatosis (iron-storage disease). May interfere with absorption of zinc.
Selenium: Hair and nail loss, irritability, nerve damage.
Calcium: Can interfere with iron absorption.
What supplements can’t do
Supplements are not a magic cure-all, nor a short cut to better health. They can’t:
- Guarantee you will get all 27 or so essential vitamins and minerals that you need.
- Replace the huge number of natural phytochemicals in vegetables and fruit – over 600 carotenoids exist in plants, but you only get two or three of these in any pill (beta-carotene, lutein and zeaxanthin).
- Make up for a poor diet that’s too high in fat, salt and sugar and too low in fibre.
- Allow you to ‘eat anything’ knowing you’ve taken your vitamins and minerals.
- Give you more energy when you’re not getting enough sleep or are stressed or anxious.
- Cure a cold or Alzheimer’s.
This is an edited extract from Catherine Saxelby’s Complete Food And Nutrition Companion: The Ultimate A-Z Guide published by Hardie Grant Books RRP $39.99.
Catherine Saxelby is a nutritionist and food blogger. In 2014, she received the Bruce Chandler Book Prize from the Australian Institute of Food Science and Technology for best food writing. She has also received awards from the Dietitians Association of Australia, Dairy Australia and the Food Media Club.