In part 1 of our look at sleep and the immune system, we focused on sleep itself. In part 2, we examine the link between sleep and immune function.

We’ve all heard that getting enough sleep is important, but what about how it supports our health and our immune system? Often, when we get ill, we may feel that we want to take to our beds and 'sleep it off.' Perhaps our bodies are trying to help us fight off the infection as efficiently as it can? Sometimes, when people try and ‘push through,' it may take longer to feel better than it might have done if they'd rested up. It’s difficult to say for sure, but anecdotally, it often seems to be the case.

Let’s look at what the science suggests, and we'll end on a few key points from some research that supports the importance of sleep for our health.

Sleep and Immunity

Does getting sufficient sleep have an impact on the resilience of our immune system and our health? For most, that means typically somewhere between 7-9 hours of regular sleep, per night. Might sleep influence how we are affected by an attack on our body, such as from bacteria or viruses? Or our long-term health?

Although research into the effect of sleep on our immune system is still in its infancy, there is emerging evidence that sleep is essential for our health. It suggests sleep impacts our immune system, and our immune response affects our sleep (1). Research is providing some scientific support for the anecdotal evidence mentioned initially.

This emerging evidence highlights some important considerations for our long-term health. For example:

  • The World Health Organization (WHO) has now classed disruption to our sleep patterns and circadian rhythm as a 'probable carcinogen’ (2).
  • Other research, over the last decade, indicates that long-term chronic/habitual sleep deficiency is a risk factor for adverse health outcomes. It has observed associations with increased risk associated with the development of low-grade inflammatory disorders. Examples include metabolic disorders like hypertension (3) cardiovascular disease, obesity, diabetes, neuropsychiatric disorders, and increased chronic pain conditions (1).

These effects are understood to be through adversely affecting our innate immune system response. The system we can think of as our ‘first line responders’.

So, sleep appears important for our long-term health through our innate immune system.

Different research has looked at the effect of sleep in connection with our immune response to vaccination. This research relates to the efficiency of our adaptive immune response. Findings suggest that proper sleep supports the development of our adaptive immune system, particularly its ability to develop the immune system's memory. Several human studies have indicated that sufficient sleep after a vaccination doubles the immune defence response to that specific threat. The same principle may also be the case in response to infection.

So, sleep also appears to be important for the priming of our adaptive immune system. It suggests insufficient sleep may lead to reduced immune response and thus reduced future protection and higher future health risks.

What did research suggest?

A recent research paper (1), concluded by emphasising the need to educate people on the importance of good sleep habits. Here is what they said:

  • Adequate sleep helps to maintain our immune resilience and is a biological need.
  • Getting sufficient sleep has been associated with a reduction in infectious disease risk.
  • People receiving vaccinations require education about the need to get sufficient sleep after receiving them to enhance their immune response according to this particular research.
  • Other research has found chronic sleep deficiency associated with increased risks for developing chronic health conditions. These chronic conditions include cardiovascular disease, diabetes, obesity, some cancers; Also, neuropsychiatric and neurodegenerative conditions.

For information and tips to help sleep, see our blog on sleep (part 1 of 2). If these tips don't help, there may be other issues that could be contributing to sleep your problems. These may benefit from support through a functional medicine practitioner. 

 Nigel Fawthrop is a nutritional therapist based in Edinburgh. 



  1. Besedovsky L, Lange T, Haack M. The sleep-immune crosstalk in health and disease. Physiol Rev. 2019 Jul 1;99(3):1325–80.
  2. Adams P. The breast cancer conundrum. Vol. 91, Bulletin of the World Health Organization. 2013. p. 626–7.
  3. Gangwisch JE, Heymsfield SB, Boden-Albala B, Buijs RM, Kreier F, Pickering TG, et al. Short sleep duration as a risk factor for hypertension: Analyses of the first National Health and Nutrition Examination Survey. Hypertension. 2006 May;47(5):833–9.

In part 1 of our look at sleep and the immune system, we’ll focus on sleep itself. It is one of the most powerful things there is for supporting good health, and it’s free. In part 2, we’ll examine the link between sleep and immune function.

We may often consider diet and exercise as critical factors for maintaining good health, but much less frequently are we likely to think of our sleep as an instrumental part of maintaining good health, either for now and for future maintenance of health. Sleep is essential to support life and to function well. It is so important that we spend approximately a third of our lives asleep, and there is a good reason for that. It supports the functioning of many of our biological, physical and neurological processes. Without sleep, we wouldn’t survive very long.

Poor sleep quality can have a significant adverse effect on both our mental and physical health. Unfortunately, we often become so used to the impact on our day to day function that we don’t recognise the consequences of inadequate sleep. Sleeping less than 6 hours a night has seen associations with increased susceptibility to infectious diseases (1). Poor sleep can decrease our performance alertness (2). It has also been associated with chronic health conditions such as hypertension, obesity, diabetes, cardiovascular disease, increased cancer risk for some cancers, neuro-degeneration, mental health issues, low mood, reduced stress resilience, and a reduced life expectancy (3). Research suggests one in three of us don’t get sufficient sleep (4), often seen as around seven and a half hours of regular sleep a night.

Sleep helps our body to repair itself. Mathew Walker, a neuroscientist, states that “sleep is the single most effective thing we can do to reset our brain and body health each day”(4).

Here are a few tips to help optimise sleep:

  • Establish a regular sleeping and waking pattern - even at weekends
  • Aim to give yourself around 8 hr sleep each night
  • Avoid heavy meals within at least 3 hrs before bed
  • Enhance your sleeping environment – dark/cool/quiet.
  • Try Meditation/deep breathing exercises before bed for relaxation.

If you’ve tried these, but still having problems:

Other factors that are adversely affecting you’re the quality of your sleep, such as imbalances of blood sugar, hormones or stress responses, and maybe affecting your quality of sleep, which needs further investigation. Seeing a functional medicine practitioner about your sleep may help optimise your sleep, immune system, and your health. 

 Nigel Fawthrop is a nutritional therapist based in Edinburgh. 



  1. Prather AA. Better together: Sleep, circadian genes, and immunity. Brain, Behavior, and Immunity. Academic Press Inc.; 2020.
  2. Abrams RM. Sleep Deprivation. Vol. 42, Obstetrics and Gynecology Clinics of North America. W.B. Saunders; 2015. p. 493–506.
  3. Besedovsky L, Lange T, Haack M. The sleep-immune crosstalk in health and disease. Physiol Rev. 2019 Jul 1;99(3):1325–80.
  4. Anon. Why lack of sleep is bad for your health - NHS [Internet]. NHS - Live well. 2018 [cited 2020 May 12]. Available from:
  5. Matthew Walker. Why We Sleep. Penguin Books; 2017.

Why Broccoli?

Most people when they hear ‘eat your broccoli’ may think of it as being just one of the government’s recommended ‘5-a-day’ fruit and vegetables (1) and that they know it's important to eat your greens. Some may think of the overcooked, soft broccoli they endured with their school meals?

So…. Does it matter what vegetables we eat or how we prepare them, as long as we eat some? Are there any that stand out that may be more advantageous for protecting our health?

Research into the possible health benefits of broccoli and other cruciferous vegetables is now starting to support the long-held practice of eating broccoli or its ancestors.

How long have we been eating broccoli?

Evidence of eating broccoli or its ancestral forms have been dated back to Roman times (2) and some have suggested that evidence exists that we have been eating ancestral forms dating back to approximately 6000 BC (3). Broccoli is a member of the cruciferous family, with well known ‘cousins’ such as kale, brussels sprouts, cauliflower, cabbage, along with lesser-known ‘cousins’ including Chinese cabbage and pak-choi (4).

Wild broccoli, brassica oleracea, has over time, been cultivated into different forms of cruciferous vegetables we know today (5). Today’s, broccoli has its origins from Italy from the 19th and 20th century, with Braccium from the Latin, meaning ‘arm’ (2).

So, with a long history and current interest in research, let’s take a look:

What’s in Broccoli?

Firstly, broccoli is packed with nutrients and is also low in calories, so we can say ‘broccoli is a low calorie, nutrient-dense food’. It has lots of similar good nutrients that many healthy green vegetables may have. Nutrients such as magnesium, potassium, zinc, iron, selenium and is also packed with vitamins such as vitamin C and vitamin E, vitamin K, together with B vitamins such as Folate (aka. Folic Acid), vitamin B6, antioxidants such as lutein and other carotenoids, and is also a really good source of fibre too (2).

So, what makes broccoli stand out above some of the others?

Well, broccoli is also a sulphur-containing vegetable, with compounds called glucosinolates and other sulphur compounds. These have been found to produce many bioactive compounds with interesting and potentially health-promoting properties. Some of these bioactive compounds include things called indoles and isothiocyanates and sulforaphane. Compounds which have been researched more and more to investigate their potential heal properties.

What’s the evidence for health benefits so far?

Research has found associations between the consumption of broccoli (and other brassicas), with a reduced risk of the occurrence of some chronic diseases, such as cancer, cardiovascular disease, cataracts, and other age-related conditions.

Many of these conditions have been found to share some common risk factors such as oxidative damage from highly reactive molecules called free radicals, that can react and disrupt healthy cells and molecules, fats and potentially damage our DNA, which then can contribute to further damage and ill health over time.

Anti –Carcinogenic?

Although the development of cancer is a complex process, regular consumption of broccoli and other cruciferous vegetables has been associated in epidemiological studies with reduced risks for some cancers, including breast cancer, prostate cancer etc (6). The isothiocyanates have seen particular attention as potential anti-carcinogenic in its properties, and it was concluded in the summary
for one study concluded that there was enhanced cancer protection by consuming cruciferous vegetables including broccoli than a diet focused on more generalised fruit and vegetables (6).

Detoxification and Oestrogen Balance

Detoxification has become an ‘common term’ with detox smoothies, detox tea, detox fasts etc. There is a big movement on the internet with this trend (7). But, is there scientific evidence to support the claims of detoxification properties of broccoli? So first, what is the definition of detoxification in the context of our body. It has been described as the mobilization and elimination of toxicants, which includes our redundant hormones, through changing their structure, or ‘biotransformation’ through a 2-stage process (8).

Of the bioactive compounds investigated from broccoli include Isothiocyanates, Indol-3-carbinol, and sulforaphane, which between them can positively influence the physiological stages of detoxification, a process which principally occurs in the liver. In many cases, the ‘phase 1’ detox process produces more damaging, pro-carcinogenic, and oxidation damaging compounds, and the ‘phase 2’ transforms these to safer waste product which the body can the excrete and get rid of. These special bioactive compounds support more advantageous phase 1 processes and also supports the phase 2 processes helping to protect the body from damaging products. Selenium, in broccoli, is although thought to contribute to cancer protection, although scientists are discovering how this works exactly (6). Research has also found that the ability to affect these processes may even help enhance caffeine metabolism too (10).

Oestrogen metabolism.

When oestrogen is metabolized from the body, there are healthier ways it can do this or unhealthier, more pro-carcinogenic, DNA damaging and oxidation damaging ways. And yes, men have oestrogen too, especially if men are carrying more fat, as molecules from fat cells are able to convert testosterone to oestrogen. The good news is that research has found that these bioactive compounds, such as the Isothiocyanates and Indol-3-carbinols help to support the healthier routes in the removal of oestrogen (11) and therefore may potentially help reduce the risk of damage from the unhealthier routes of detoxification of oestrogen.

More potential health benefits?

Anti-oxidant protection? But what does that mean?

We’ve mentioned oxidative damage, that can arise during detoxification, but it can also happen as a result of many other normal processes in the body, including our energy production. As well as internal sources of ‘oxidation damage’, there are plenty from the outside ranging from toxins we may breathe, or eat including pesticides on our food, but also from damaging UV light too, perhaps things like cataracts on the eye.

Broccoli, as we saw in the nutrients contains antioxidants which act directly against these damaging molecules, such as Vitamin C, vitamin E, and lutein and other carotenoids, plus minerals zinc and selenium which help support our own ‘homegrown’ powerful ‘endogenous’ antioxidants. However, research is finding that the sulphur compounds from broccoli, such as one called sulforaphane, really helps to promote the internal production of these powerful internal antioxidants, which are being found to be crucial for our internal protection oxidation damage (12) (13).

Health benefits associated with antioxidant properties of broccoli?

Recent research in the lab concluded that sulforaphane containing foods, which includes broccoli and a good source, may possibly contribute to delaying the onset of cataracts, but it is early days to say definitively (14) (15). However, other studies have found that antioxidants such as lutein, and other carotenoid, contained in broccoli, have been found to offer cataract protection in a nurses health study (16) .

Any other research evidence

Other areas of health that research has shown promise in CVD risk reduction suspected to be through the combination of nutrients in cruciferous vegetables such as broccoli (17). A recent population study observed stronger long-term correlations of beneficial weight management with higher consumption of high fibre/low glycaemic, (low sugar-producing) foods such as broccoli, when compared to lower fibre, higher glycaemic (higher sugar-producing) foods, such as cabbage or carrots (18)

So, can we have too much of a good thing?

What do we need to watch out for and are there any people who need to be really cautious or concerned about eating lots of broccoli? Yes, for some people. People who suffer from allergies such as Grass seed, dust mites, pollen, dogs / cats, fruits / nuts/ asthma, skin conditions such as eczema, dermatitis, may have what are known as atopic allergy, and these people sometimes find higher intakes harder to tolerate (19).

Broccoli contains something called goitrogens, which in high quantities may adversely affect the function of the thyroid glands, however, those who suffer from lower thyroid function or ‘Hypothyroid conditions’ will need to seek guidance, and moderate the amount consumed. Indications from thyroid specialist practitioners are that small portions of cooked broccoli are usually ok, rather than raw (20) (21)
People taking Warfarin need to discuss their intake with their GP, as the higher levels of vitamin K content can affect the action of the medication. Research has that when significant quantities, such as 450g per day were eaten, health issues arose. A safer approach is to consult with your GP and keep them informed (19).

Finally, there is reference for symptoms of bowel discomfort, bloating and flatulence if too much broccoli is eaten. Also because of the higher sulphur content, flatulence may have that hydrogen-sulphide smell, of rotten eggs branch (22).

Does it matter how we prepare it and eat it?

Research has found that food preparation and also the body's gut bacteria, affects the availability of these important bioactive compounds from broccoli (6).

The greenness of the broccoli is important too, reflecting the chlorophyll content, the greener broccoli was found to have importance for the final nutrient quality of the vegetable (23). Of the various different cooking methods available, which included boiling, microwaving, stir-frying/boiling or steaming, research concluded that domestic preparation methods can significantly affect the final nutrient availability and that overall steam cooking was the preferred method (23) (24).

So, Let’s Recap, Is Broccoli really a superfood?

Well, research has suggested that broccoli has some different and perhaps greater beneficial health potential that some of its other green leafy vegetables like spinach and salad and also over other vegetables such as carrots. There is a growing amount of evidence to suggest that there is potentially a risk-reducing benefit to help protect against certain types of cancer, supports detoxification and oestrogen balancing, together with other potential benefits for our cardiovascular health, and overall contributory effect for healthy weight management.

With the cautions, if you are concerned, seek professional advice.

And finally, choose to eat green healthy broccoli, that has been cooked well and certainly consider steaming for best effect according to research findings.


 Nigel Fawthrop is a nutritional therapist based in Edinburgh. References available on request. 

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