Iron deficiency results in anaemia and fatigue. This provides a great marketing opportunity for iron supplements as no one wants to feel weak and exhausted all the time. While it is true that correcting proven iron deficiency with iron supplements will make you feel better, taking even more iron will not give you more energy. Your body maintains a store of iron and this can be measured with a blood test. Bigger iron stores are not better – how much iron you have in reserve makes no difference to blood haemoglobin (and other iron containing proteins) until you actually run out of iron. It’s a bit like a car fuel tank – the amount of fuel in the tank makes no difference to the engine as long as it does not run dry.
Too much iron in the body is harmful. And we are not just referring to severe iron overload diseases such as hereditary haemochromatosis in which iron deposition results in damage to organs such as the heart and liver. Even within the “normal” range of iron stores there is an increase in cancer, heart disease and dementia as blood levels increase. Iron becomes a pro-oxidant at higher levels – causing oxidative damage within the body. Iron supplements also inhibit the absorption of other minerals such as zinc.
Iron supplements are useful for the rapid reversal of proven iron deficiency. Increasing the intake of iron rich whole plant foods (and avoiding refined foods) will then maintain iron levels in all but the most severe bleeding disorders (which should be treated!). See Risk Associated With Iron Supplements
Most Australian health professionals equate dietary iron with red meat. Regular advertising from the meat industry reinforces this view. Chicken and fish have smaller amounts of haeme iron. Meat provides iron in the form of “haeme iron” which is a large organic molecule with four atoms of elemental iron at its core. The good thing about haeme iron is that it is very well absorbed from the gut and the bad thing about haeme iron is that the gut is unable to down regulate its absorption, even when there is too much in the body. This can result in iron overload. Red meat is not the only source of iron: the majority of dietary iron comes from the plants that we eat, even on the usual meat-rich Australian diet. A whole foods plant based diet actually provides a lot more iron than the usual Australian diet. This iron is present as elemental iron salts rather than haeme iron.
There is a persistent myth that plant sources of iron are very poorly absorbed and that vegetarians are likely to become iron deficient. However, iron deficiency does not seem to be more common in vegetarians, despite the fact that most are lacto-ovo vegetarians (dairy foods are a very poor source of iron). The good thing about the non-haeme form of iron found in plants is that the intestine can regulate how much of the iron is absorbed to ensure adequate stores but avoid iron overload. If the body is depleted of iron then the absorption can be nearly as good as for haeme iron but when the body is “fully charged” with iron absorption is very low. This is the only way that our bodies can maintain the right amount of iron as once absorbed, there is no mechanism to excrete it.
The big issue with plant sources of iron is around factors that inhibit iron absorption. Plant foods contain some substances that are promoters of iron absorption and other substances that are inhibitors of iron absorption. The inhibitors include tannins in tea (including green tea), dairy foods and the phytates in whole grains (phytates are good for you in other ways which illustrates the complexity of nutrition). The promoters of iron absorption include vitamin C and other substances in vegetables including those in onion and garlic. A study in International Journal of Food Sciences and Nutrition compared the competing effects of inhibitors and promoters and concluded that the when both were present together the effects of the promoters completely overcame the effects of the inhibitors. Our practical advice is simply to include vegetables, salad or fruit with every meal and avoid drinking tea/coffee with meals if you are trying to increase iron absorption.
Resources
Peer-reviewed articles:
- Cook, J. D., Dassenko, S. A., & Lynch, S. R. (1991). Assessment of the role of nonheme-iron availability in iron balance. American Journal of Clinical Nutrition, 54(4), 717-722.
- Gautam, S., Platel, K., & Srinivasan, K. (2011). Influence of combinations of promoter and inhibitor on the bioaccessibility of iron and zinc from food grains. International Journal of Food Sciences and Nutrition, 62(8), 826-834.
- Saunders, A.V., Craig, W.J., Baines, S.K., & Posen, J.S. (2013). Iron and vegetarian diets, Medical Journal of Australia, 199 (4 Suppl), S11-S16.
Return to Vitamins and Minerals page
Page created 11 April 2015
Page last updated 27 September 2018
Specific vitamins, minerals and other nutrients:
Most vitamin and mineral supplements are of no benefit and some may be harmful. With few exceptions we recommend that you get your vitamins, minerals, fibre and other phytonutrients from minimally processed plant foods. The supplements that may be required are related to modern living conditions rather than any inherent deficiency of a plant based diet. Clean food and water and safe food handling, whilst preventing disease, may remove most of the bacteria-derived vitamin B12 from our food supply. Indoor living can deprive us of the UV rays that are required for vitamin D synthesis. Many people take supplements as an insurance policy against dietary inadequacy or to detoxify the effects of too many rich foods. Unfortunately, supplements neither emulate the benefits of nutrients from plants, nor detoxify the harmful effects of excess animal protein, fats and processed foods.
Whole food is complex (see ‘Whole’ by T Colin Campbell in resources below). Our understanding of it is very basic. We know which nutrients are absolutely essential for life and the approximate amounts required. We have identified only a small number of the thousands of other biologically active substances in plants (known as phytochemicals or phytonutrients). We know little of the interactions between these various nutrients and phytonutrients. Often a high intake of a particular nutrient from food is associated with a health benefit, such as less cancer, but when we give them as supplements rather than as whole foods the benefit may be absent or reversed, increasing cancer risk.
There are some medical conditions in which vitamin supplements can be used as a pharmaceutical. Several of the B group vitamins can assist in reducing high homocysteine levels and this has been shown to reduce the progression of the early stages of dementia (see VITACOG study). The dietary approach would be to remove the cause of the elevated homocysteine levels by reducing animal protein consumption. While on the topic of dementia, Dr Neal Barnard recommends a vitamin B12 supplement and advises against taking supplements that contain minerals such as iron, copper and zinc as high levels of these may damage the brain.
No particular food has exclusive ownership of any particular nutrient. You do not need dairy foods for calcium, red meat for iron or fish for omega 3 oils. You do not even need to know which foods are the “best” sources of any particular nutrient. You just need to eat enough calories of whole grains, legumes, vegetables and fruits to maintain a healthy weight. And if you wish to tweak your plant-based diet to include more omega-3s, iodine, resistant starch or any other nutrient or phytochemical then we suggest that you bypass the supplements and just find some whole plant foods rich in the particular phytonutrient and make them a regular part of your diet.
See video: Dr. John McDougall Medical Message: Vitamin Supplements
Resources
- To Supplement or Not to Supplement? – Center For Nutrition Studies, 2012, updated April 2024
- Do You Need Vitamin Supplements? and Evaluating the Need for Supplementation – T Colin Campbell, PhD.
- Whole by T. Colin Campbell, PhD (2013) – Campbell argues that the nutritional value of a whole plant food item cannot be defined by the sum of its vitamins and minerals. The interaction of nutrients within the food and their assimilation within our bodies is too complex to be adequately described by a reductionist paradigm of nutrition.
- See this excerpt from ‘Whole’ by T Colin Campbell – How Accurate Are Measures of Nutrient Density? A Selection From T. Colin Campbell’s Whole: Rethinking the Science of Nutrition
- Dr. John McDougall Medical Message: Vitamin Supplements
- Some Dietary Supplements May Be More Than a Waste of Money – Dr Michael Greger (video). People taking dietary supplements may, in some cases, be paying to make themselves sick. This video covers folic acid, beta carotene, and green tea supplements
- Is a vegetarian diet adequate? Concepts and controversies in plant-based nutrition – This 2012 MJA publication discusses the adequacy of plant–based diets in the following areas: protein, iron and zinc, essential fats and vitamin B12.
- Power Foods for the Brain: an effective 3-step plan to protect your mind and strengthen your memory – Neal D. Barnard, MD (2013) – This book is a holistic guide to optimizing brain health and minimizing dementia risks. It covers both the positive and negative effects of supplements.
- See also Resources for Specific vitamins and minerals
Peer-reviewed articles
- Lin, J., Cook, N. R., Albert, C., Zaharris, E., Gaziano, J. M., Van Denburgh, M., . . . Manson, J. E. (2009). Vitamins C and E and beta carotene supplementation and cancer risk: a randomized controlled trial. Journal of the National Cancer Institute, 101(1), 14-23.
- Martinez, M. E., Jacobs, E. T., Baron, J. A., Marshall, J. R., & Byers, T. (2012). Dietary supplements and cancer prevention: balancing potential benefits against proven harms. Journal of the National Cancer Institute, 104(10), 732-739.
Last updated 11 April 2015
