The truth about detox diets – according to nutrition science

Perhaps you are searching for an alternative and ‘fail-safe’ way to shift a little excess weight and kick-start a healthier new you. For many, the promised fast results and amazing outcomes of a detox diet might seem like a very tempting solution but are they really all they are cracked up to be and can they really solve all your health and weight issues in a few short days? Unfortunately, thanks to the nature of human physiology, it is physically impossible to ‘detox’ in a few short days and the majority of products on sale claiming to do just that are a complete waste of money, and could even cause you harm. A deep dive into the scientific literature provides a bleak outlook for evidenced-based ‘detoxing’, with no detox regime, to date, proving effective as a quick fix (1,2).

What is detoxification?

Detoxification is the metabolism and removal of harmful or toxic substances from a living organism, including the human body (3, 4) and whilst we have come to associate detoxing with a short, often gruelling, nutritional regime, the processes by which we detoxify are actually working 24/7, 365 days a year. Each day, human beings come into contact with a wide variety of synthetic, environmental and internally produced chemicals and potential toxins (4,6,7) ; as a result, our bodies must be continually processing and eliminating these to prevent accumulation and any potential harm being caused. On a day to day basis this process is, for most of us, highly efficient, however there are an increasing number of chemicals that even the healthiest of systems can struggle to eliminate, in particular persistent organic pollutants (POPs) and certain heavy metals (8).

Although no specific regime is yet proven to work, the concept of using nutrition to boost detoxification is not completely rooted in myth and madness. To understand this further we need to take a look at the biological processes and systems involved in our natural detoxification mechanisms.

The main organ involved in detoxification is the liver. Here, potentially harmful substances, or toxins, are processed via phase I reactions (oxidation, reduction, hydrolysis, hydration or dehalogenation), often called biotransformation, to convert them from their original form to a more water-soluble (hydrophilic) reactive intermediate. These reactions are carried out by cytochrome P450 enzymes. The reactive intermediates produced (also potentially harmful to the body as they contribute to oxidative stress) require further processing by the liver, which occurs via phase II reactions (including conjugation, glucuronidation, sulphation, acetylation and methylation). Phase II, carried out by a range of different enzymes depending on the type of reaction required, produces an end product that can be safely excreted via the digestive tract and kidneys, in faeces and the urine.

The role of nutrition in detoxification

So where does nutrition come in? Well, each of these enzymes and reaction steps requires a number of specific nutrients in order to function. There is also evidence to suggest that certain nutritional factors can up- or down-regulate specific reactions and therefore enhance or impede Phase I or II (9).  The concept of balancing the two phases is a common feature of naturopathic and functional medicine detox practices as, in their view, if Phase I is over-stimulated without adequate Phase II support, this can lead to increasing oxidative stress and poor clearance of the reactive intermediates. Many detox diets are therefore based on the concept that supplying the body with a higher level of the cofactor nutrients (at times in the absence of anything else) and specific inducers of Phase I and/or II, will super charge your detox capacity and help revive a sluggish, overworked liver. If Phase I to II imbalance is suspected, then increased antioxidant intake may also be recommended to help address the potential elevated levels of oxidative stress (10,11).

Phase I reactions, carried out by the cytochrome P450 enzymes, appear to require several B vitamins and vitamins A & C as well as specific amino acids and phospholipids for optimal function and biotransformation, whilst a range of polyphenols and flavonoids, particularly those found in cruciferous vegetables and certain herbs, spices and teas, have been shown to induce cytochrome P450 reactions. Studies also suggest that a deficiency in certain minerals including zinc, copper, iron and selenium may also affect the efficiency of Phase I, suggesting these are also necessary for enzyme function. The hydrophilic group added to the reactive intermediate in Phase II reactions is usually supplied by a compound containing sulphur, glutamic acid, glutathione, amino acids or a methyl and acetyl group, which is either originally supplied by or facilitated by the foods that we eat. A number of studies suggest that either foods containing these groups, or that support group donation (e.g. methyl donors) can lead to induction, or at least modulation, of Phase II. For example, glutathione is necessary for glutathione conjugation reactions, the amino acids methionine and cysteine are important substrates for glutathione production, suggesting this branch of Phase II would be affected by poor protein intake. Vitamin B6, magnesium and selenium have also been found to be necessary for glutathione synthesis whilst cruciferous vegetables and those containing allium (garlic and onions), among other foods, can increase glutathione S-transferase activity (the Phase II reaction enzyme needed to add glutathione to a reactive intermediate). (9, 12, 13)

In addition to the relatively well established role of the above nutrients in the detoxification process, research has shown that a few specific nutrients and foods may aid detoxification of specific environmental toxins. For example, studies have shown that algae, coriander and natural acids found in grapes, citrus, apples and berries support heavy metal elimination, with, specifically, chlorella and nori also supporting POP and polychlorinated dibenzoate clearance in rodents. (2) Most interesting is selenium, being one of the only nutrients to be studied in humans for a specific toxin, and which has been found to increase the rate of urinary mercury excretion in humans threefold. (14)

Interestingly, whilst credible research is still extremely lacking when it comes to proving that excessive consumption of these nutrients speeds up overall detoxification in humans, advances in nutrigenetics and nutrigenomics have identified a number of genetic alternations that could impact on an individual’s Phase I and Phase II efficiency, suggesting that at least in these people targeted nutrient interventions could support optimal detox capacity if potentially compromised or they are at risk from toxin accumulation (9).

Are detoxes really a waste of time?

One of the key downfalls of research into detox diets is that, on the whole, studies conducted do not identify which toxins they are designed to eliminate, or include any measure of toxicity before and after the regime is followed. As such, much of the anecdotal evidence for the benefit of detox diets may be as a result of the more well established benefits of the associated mild caloric restriction, increased fruit and veg consumption, reduced processed and refined food intake and greater levels of movement, exercise and wellbeing-related activity, often co-prescribed. In addition, although the liver is usually the focus of a detox regime, the full process of detoxification involves a great many more biological systems, organs and cells including the digestive tract, skin and lymphatic system. As such, regimes may also focus on optimising the health or function of these systems in order to support the full ‘detox’ process and effective elimination of toxins. Which can only be a good thing, right?!

A wealth of research exists to support the health benefits of increased fruit, vegetable and specific phytonutrient consumption, (15,16,17) both for disease prevention and general wellbeing, whilst caloric restriction or intermittent fasting regimes have been shown to not only encourage fat loss but also improve a range of biomarkers of health (18,19,20,21,22) , and of course increasing exercise is a major health and wellbeing enhancer, regardless of your health goals (23,24,25,26). As such, any regime that promotes these modifications, alongside avoidance of unhealthy foods or high environmental chemical exposure, is likely to result in noticeable benefits to your overall sense of wellbeing, even in the relative short term.

So if you are still intent on doing a ‘detox’ diet you can rest assured that as long as you follow these basic principles, and do not opt for a very specific and highly restrictive (and most likely paid for) regime, you will more than likely feel much better for it. Stick with as many of these practices as possible, long term, and the benefits should continue to grow. Below is an idea of what you could consider if you wish to help kick-start a new healthier lifestyle.

What a vaguely scientific new year, new you, health-promoting (but not strictly a detox) regime might look like (8):

Below are some of the more common concepts that detox diets are often based on, together with some references supporting their potential benefits to health. Whilst these may not directly have any enhanced detox activity there is certainly a scientific basis for them helping to improving overall health and wellbeing. The below is by no means a recommendation for what you should do and advice should always be sought by a qualified nutrition professional, before embarking on a restrictive dietary regime, especially if doing so for specific health reasons.

To help address potential toxic load:

  • avoid foods that are heavily processed or contain chemical additives (27)
  • reduce exposure to environmental chemicals (switching to natural personal care products and avoiding damp or polluted environments for example) (28)
  • avoid produce known to contain high levels of pesticides (29)

To support Phase I, II and oxidative stress (and general health and wellbeing): (9,10,11,12,13)

  • increase consumption of leafy green and brightly coloured fruits and vegetables
  • increase consumption of berries and citrus fruits
  • increase intake of herbs, spices, garlic and onions
  • ensure an adequate intake of calcium, iron, zinc, selenium and magnesium through a varied diet and supplementation where required
  • consume moderate amounts of protein daily from a range of sources

To encourage toxin elimination:

  • enjoy a sauna (30,31)
  • drink adequate water-based fluids to stay hydrated (but not over hydrated)

To help support digestive health (to further support toxin elimination and reduce exposure):

  • increase consumption of fibre rich foods
  • increase consumption of natural probiotic-rich foods


If wishing to lose body fat and improve a range of markers of health and well-being:

  • moderately reduce calorie intake (35,36,37,38)
  • exercise regularly (23,24, 39,40,41)

Are detoxes dangerous?

Whilst the above is a safe and science backed way to encourage a healthier overall lifestyle and support your biochemistry, it is important to ensure you are still getting adequate nutrition and energy. A range of studies and anecdotal reports have shown that just a few days on a highly restrictive low calorie regime can lead to some serious health complications, and even long-term organ damage or death, (42,43,44) not to mention being a huge added stress on the body, which also comes with a range of negative health effects (45,46).

Poor regulation of the ‘detox’ industry means that almost anyone can create a product and sell it to the masses meaning, in many cases, you don’t know what you are getting, the products haven’t be tested for their safety and they are most certainly not going to be scientifically proven to work.


Regardless of whether your primary aim is to increase detoxification, the above, on the whole, represents a basic blueprint for better health via diet and lifestyle modifications. If for any reason you do feel you are at risk from excess toxin exposure it is important to seek help so that the proper, scientifically proven processes can be put in place. In this instance and even for a kick-start to a new healthier you, there really are no short cuts and a gruelling or intense detox diet is not the answer!


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About Sophie Tully

Sophie first trained in biomedical science, specialising in Pharmacology, before working as a drug discovery research scientist developing highly specialised cancer therapies. Leaving research to study a master's degree in Clinical and Public Health Nutrition . Sophie runs a thriving private nutrition and health consultancy business working with elite athletes and the general public to help them achieve optimal health through lifestyle and dietary interventions. Sophie also lectures for both the biomedicine and nutrition courses and is a clinic supervisor at the internationally renowned College of Naturopathic Medicine. Guest speaker and author for a number of health events and magazines, Sophie maintains her broad but scientific knowledge base by constantly burying her head in books and publications. Sophie’s main clinical and research interests lie in the role of nutrition, lifestyle, neuroscience and genetics in chronic illness, psychology and sports performance.

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