Cliff Harvey PhD
Originally posted at www.cliffharvey.com
The novel coronavirus (COVID-19) poses a significant threat to public health and the global economy. In this article, Cliff looks into how we can best reduce our risks of transmission while also staying healthy
Immunity is a BIG topic right now due to the emergence of COVID-19 (the novel coronavirus). The emergence of this new form of coronavirus also resulted in greater awareness of the public health implications of other seasonal illnesses like influenza, flu-like viruses, and the common cold (itself often caused by a form of coronavirus or rhinovirus) which result in significant numbers of hospitalisations and deaths every year.
Because there is a lot of concern (and quite rightly so) about the potential implications of COVID for public health, society, and the economy, there has been a lot of discussion online about how we might avoid the virus. This advice runs the gamut from sensible, through to ridiculous (ummm 5G causes COVID… yeah… OK…)
In a nutshell, when we’re talking about immunity, we’re referring to the actions of the immune system. This system is the body’s defence system (along with physical barriers like skin) and it protects us against pathogens (viruses, bacteria, protozoa, and fungi) that can cause disease.
Note: If you’re currently feeling unwell or have any unexplained symptoms, please contact your medical doctor!
Symptoms of COVID-19 include:
What is COVID?
Coronavirus disease 2019 (COVID-19) is disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
While the majority of cases result in mild symptoms, the disease can result in pneumonia and multi-organ failure. The case fatality rate is estimated to be between 1% and 5% with the greatest impact in those older or immune-compromised. The infection is spread from one person to others via respiratory droplets, often produced during coughing or sneezing.
Reducing the spread of COVID-19
Despite what many alt-health gurus are claiming, there are NO supplements, diet interventions, or lifestyle interventions that can cure COVID-19 or prevent someone being infected and claims of such are unwarranted at best and dangerous at worst.
The best ways to reduce the spread of COVID and your likelihood of catching it are also the best practices for avoiding other cold- and flu-like viruses, namely (from the New Zealand Ministry of Health):
Can nutrition support a healthy immune system?
While there is a lot of misinformation circulating about ‘natural’ or ‘alternative’ remedies for COVID-19 and other flu-like viruses which isn’t helpful, the backlash against people talking about ways they can support the immune system through sound, sensible actions like eating a healthy diet, sleeping well, and reducing lifestyle stressors is equally unwarranted…
Yes, many of the claims being made for Supplement X or Herb Y are spurious, BUT being healthy is known to be protective against the effects of many viruses, and this is likely yo be the case with COVID-19 too. Please be clear, I’m not suggesting that being healthy will stop you catching it or prevent serious effects, but the healthier one is, the more likely it will be that they will have better resistance to infection and a stronger chance of recovery without serious effects.
In other words, the healthier you are, the more likely you will be overall to have milder effects from colds and flu-like viruses and this may mean you are less prone to serious effects from viruses like COVID-19.
A healthy diet that that provides sufficient energy, essential fats, protein, and micronutrients will help us to be healthier and more resilient in the face of pathogens. On the other hand, diets that are high in processed and refined foods, and especially those high in trans-fats and sugar are likely to worsen responses to infections.
In addition, some nutrients (many of which are commonly lacking) have been shown to help support immunity. For example, many people in New Zealand fail to get enough vitamin A from diet alone, (1) and this vitamin is intricately involved in immunity, (2) and having sufficient Vitamin A is associated with immunity to illness and infections. (3, 4) Similarly, vitamin E also has anti-inflammatory and immunomodulatory effects, (5) and vitamin D is a key immune regulator and has also shown promise for aiding several auto-immune conditions like systemic lupus and rheumatoid arthritis. (6)
Vitamin C is another vitamin getting a lot of attention in the wake of the COVID pandemic, both positive and negative. And, while contrary to popular belief, vitamin C probably won’t cure the common cold, research suggests that it might help to reduce symptoms of colds and shorten their duration, (7) and might even help to prevent the occurrence of colds in athletes and others prone to higher levels of stress (when taken regularly). (8, 9)
Research also shows that bioflavonoids from plants reduce upper-respiratory-tract infections. (10) Other antioxidant-rich foods like grapeseed, rosehips, and cacao improve antioxidant status and immunity and reduce inflammation. (11-16)
There is also the suggestion that some herbs, (17-26) spices (like turmeric), (27) and mushrooms (Lion’s Mane, Shiitake, Reishi, Chaga) may offer either anti-viral effects or provide other benefits to immune function. (28-32) Probiotic supplementation is also likely to reduce the incidence and severity of respiratory infections. (33-38)
Take home message:
None of this is to say that these foods will be effective against COVID!
But it is always prudent to improve your baseline health by eating a nutrient-dense diet based on unrefined foods.
Lifestyle and immunity
Exercise is known to improve health overall, and specifically the functions of the immune system. However, excessive amounts of exercise, leading to over-stress and overtraining can result in impaired immune function and greater risk of infections, especially colds and flu-like viruses. (39)
Stress, in particular work-related stress is known to impact the immune system and reduce resistance to infections. (40) Interestingly, the effort-to-reward ratio (how much we value the benefits from our job versus the effort it requires) has a greater effect on immunity than overwork. (41)
Other factors that can negatively affect immunity:
Take home message:
Exercising, but not overtraining, getting quality sleep, and reducing undue stress (especially work-related stress) are likely to help to increase your resilience in the face or pathogens.
I do all these things...should I even be worried about COVID?
Even if you are healthy, eat well, exercise, and get enough sleep, along with minimal stress, you can still contract COVID!
While we don’t want to promote a culture of excessive fear, it is very important to do all we can to reduce the spread of this illness as we simply do not know the ramifications of it at this time, and by all accounts it appears to be more aggressive and with a higher mortality rate than influenza.
If you’re young and healthy, you may not experience the severest effects, which typically occur in the aged and immune-compromised, or those without access to quality public health facilities, but you can still contact the illness and you can still be a carrier. In fact, someone who contracts the illness and has milder symptoms (i.e. those ‘healthier’) may be a greater ‘spreader’ of the illness because they will exhibit less symptoms and will be more likely to leave home, and may not be so prudent with actions like handwashing, sneezing, and avoiding close contact with others.
So, live a healthy lifestyle and do all you can to live your best life…BUT don’t be a dick and risk becoming a carrier who infects people who may have a lesser chance of fighting off the illness.
1. University of Otago and Ministry of Health. A Focus on Nutrition: Key findings of the 2008/09 New Zealand Adult Nutrition Survey. Wellington; 2011.
2. Wiseman EM, Bar-El Dadon S, Reifen R. The vicious cycle of vitamin a deficiency: A review. Critical Reviews in Food Science and Nutrition. 2017;57(17):3703-14.
3. Mayo-Wilson E, Imdad A, Herzer K, Yakoob MY, Bhutta ZA. Vitamin A supplements for preventing mortality, illness, and blindness in children aged under 5: systematic review and meta-analysis. BMJ. 2011;343:d5094.
4. Cruz S, da Cruz SP, Ramalho A. Impact of Vitamin A Supplementation on Pregnant Women and on Women Who Have Just Given Birth: A Systematic Review. Journal of the American College of Nutrition. 2018;37(3):243-50.
5. Nazrun Shuid A, Das S, Mohamed IN. Therapeutic effect of Vitamin E in preventing bone loss: An evidence-based review. International Journal for Vitamin and Nutrition Research. 2019:1-14.
6. Franco AS, Freitas TQ, Bernardo WM, Pereira RMR. Vitamin D supplementation and disease activity in patients with immune-mediated rheumatic diseases: A systematic review and meta-analysis. Medicine. 2017;96(23):e7024-e.
7. Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. The Cochrane database of systematic reviews. 2013;1:CD000980.
8. Van Straten M, Josling P. Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled survey. Advances in therapy. 2002;19(3):151-9.
9. Sasazuki S, Sasaki S, Tsubono Y, Okubo S, Hayashi M, Tsugane S. Effect of vitamin C on common cold: randomized controlled trial. Eur J Clin Nutr. 2006;60(1):9-17.
10. Braakhuis AJ, Somerville VS, Hopkins WG. Effect of Flavonoids on Upper Respiratory Tract Infections and Immune Function: A Systematic Review and Meta-Analysis. Advances in Nutrition. 2016;7(3):488-97.
11. Nuttall SL, Kendall MJ, Bombardelli E, Morazzoni P. An evaluation of the antioxidant activity of a standardized grape seed extract, Leucoselect. Journal of clinical pharmacy and therapeutics. 1998;23(5):385-9.
12. Kar P, Laight D, Rooprai HK, Shaw KM, Cummings M. Effects of grape seed extract in Type 2 diabetic subjects at high cardiovascular risk: a double blind randomized placebo controlled trial examining metabolic markers, vascular tone, inflammation, oxidative stress and insulin sensitivity. Diabet Med. 2009;26(5):526-31.
13. Patel S. Rose hip as an underutilized functional food: Evidence-based review. Trends in Food Science & Technology. 2017;63:29-38.
14. Espinoza T, Valencia E, Quevedo R, Díaz O. Physical and chemical properties importance of Rose hip (R. canina, R. rubiginosa): a review. Scientia Agropecuaria. 2016;7(1):67-78.
15. Araujo QRD, Gattward JN, Almoosawi S, Parada Costa Silva MdGC, Dantas PADS, Araujo Júnior QRD. Cocoa and Human Health: From Head to Foot—A Review. Critical Reviews in Food Science and Nutrition. 2016;56(1):1-12.
16. Martín MÁ, Ramos S. Health beneficial effects of cocoa phenolic compounds: a mini-review. Current Opinion in Food Science. 2017;14:20-5.
17. Almatroudi A, Alsahli MA, Alrumaihi F, Allemailem KS, Rahmani AH. Ginger: A novel strategy to battle cancer through modulating cell signalling pathways. Current pharmaceutical biotechnology. 2019.
18. de Lima RMT, dos Reis AC, de Menezes A-APM, Santos JVdO, Filho JWGdO, Ferreira JRdO, et al. Protective and therapeutic potential of ginger (Zingiber officinale) extract and -gingerol in cancer: A comprehensive review. Phytotherapy Research. 2018;32(10):1885-907.
19. Jafarzadeh A, Nemati M. Therapeutic potentials of ginger for treatment of Multiple sclerosis: A review with emphasis on its immunomodulatory, anti-inflammatory and anti-oxidative properties. Journal of Neuroimmunology. 2018;324:54-75.
20. Shergis JL, Zhang AL, Zhou W, Xue CC. Panax ginseng in Randomised Controlled Trials: A Systematic Review. Phytotherapy Research. 2013;27(7):949-65.
21. Lee DC, Lau AS. Effects of Panax ginseng on tumor necrosis factor-α-mediated inflammation: a mini-review. Molecules (Basel, Switzerland). 2011;16(4):2802-16.
22. Jamil SS, Nizami Q, Salam M. Centella asiatica (Linn.) Urban—a review. 2007.
23. Arora D, Kumar M, Dubey S. Centella asiatica-A Review of it's Medicinal Uses and Pharmacological Effects. Journal of Natural remedies. 2002;2(2):143-9.
24. Tiwari R, Chakraborty S, Saminathan M, Dhama K, Singh SV. Ashwagandha (Withania somnifera): Role in safeguarding health, immunomodulatory effects, combating infections and therapeutic applications: A review. J Biol Sci. 2014;14(2):77-94.
25. Block KI, Mead MN. Immune System Effects of Echinacea, Ginseng, and Astragalus: A Review. Integrative Cancer Therapies. 2003;2(3):247-67.
26. Nieto G, Ros G, Castillo J. Antioxidant and Antimicrobial Properties of Rosemary (Rosmarinus officinalis, L.): A Review. Medicines. 2018;5(3):98.
27. Fallah Huseini H, Zahmatkash M, Haghighi M. A review on pharmacological effects of Curcuma longa L.(turmeric). Journal of Medicinal Plants. 2010;1(33):1-15.
28. Lee HH, Lee JS, Cho JY, Kim YE, Hong EK. Study on immunostimulating activity of macrophage treated with purified polysaccharides from liquid culture and fruiting body of Lentinus edodes. Journal of microbiology and biotechnology. 2009;19(6):566-72.
29. Gaullier J-M, Sleboda J, Ofjord ES, Ulvestad E, Nurminiemi M, Moe C, et al. Supplementation with a Soluble Beta-Glucan Exported from Shiitake Medicinal Mushroom, <i>Lentinus edodes</i> (Berk.) Singer Mycelium: a Crossover, Placebo-Controlled Study in Healthy Elderly. 2011;13(4):319-26.
30. Sheu S-C, Lyu Y, Lee M-S, Cheng J-H. Immunomodulatory effects of polysaccharides isolated from Hericium erinaceus on dendritic cells. Process Biochemistry. 2013;48(9):1402-8.
31. Soccol CR, Bissoqui LY, Rodrigues C, Rubel R, Sella SRBR, Leifa F, et al. Pharmacological Properties of Biocompounds from Spores of the Lingzhi or Reishi Medicinal Mushroom <i>Ganoderma lucidum</i> (Agaricomycetes): A Review. 2016;18(9):757-67.
32. Song H-S, Lee Y-J, Kim S-K, Moon K, Moon W, Kim D, et al. Downregulatory Effect of AGI-1120 (Ñß-Glucosidase Inhibitor) and Chaga Mushroom (Inonotus obliquus) on Cellular NF-kB Activation and Their Antioxidant Activity. Korean Journal of Phamacognosy. 2004.
33. de Araujo GV, de Oliveira Junior MH, Peixoto DM, Sarinho ESC. Probiotics for the treatment of upper and lower respiratory-tract infections in children: systematic review based on randomized clinical trials. Jornal de Pediatria. 2015;91(5):413-27.
34. Ahanchian H, Kianifar H, Ganji T, Kiani M, Khakshour A, Jafari S. Probiotics in childhood upper respiratory tract infections: a systematic review. Journal of North Khorasan University of Medical Sciences. 2015;7(2):445-52.
35. Ozen M, Kocabas Sandal G, Dinleyici EC. Probiotics for the prevention of pediatric upper respiratory tract infections: a systematic review. Expert Opinion on Biological Therapy. 2015;15(1):9-20.
36. Peng Y, Li A, Yu L, Qin G. The Role of Probiotics in Prevention and Treatment for Patients with Allergic Rhinitis: A Systematic Review. American Journal of Rhinology & Allergy. 2015;29(4):292-8.
37. Güvenç IA, Muluk NB, Mutlu FŞ, Eşki E, Altıntoprak N, Oktemer T, et al. Do Probiotics have a role in the Treatment of Allergic Rhinitis? A Comprehensive Systematic Review and Metaanalysis. American Journal of Rhinology & Allergy. 2016;30(5):e157-e75.
38. Zajac AE, Adams AS, Turner JH. A systematic review and meta-analysis of probiotics for the treatment of allergic rhinitis. International Forum of Allergy & Rhinology. 2015;5(6):524-32.
39. Jones AW, Davison G. Chapter 15 - Exercise, Immunity, and Illness. In: Zoladz JA, editor. Muscle and Exercise Physiology: Academic Press; 2019. p. 317-44.
40. Nakata A. Psychosocial Job Stress and Immunity: A Systematic Review. In: Yan Q, editor. Psychoneuroimmunology: Methods and Protocols. Totowa, NJ: Humana Press; 2012. p. 39-75.
41. Eddy P, Heckenberg R, Wertheim EH, Kent S, Wright BJ. A systematic review and meta-analysis of the effort-reward imbalance model of workplace stress with indicators of immune function. Journal of Psychosomatic Research. 2016;91:1-8.
Article by HPN graduate Tammy Hume
Giving a bubba the best start to life is one of the best gifts that we can give our children.
Every parent wants their child to be as healthy as possible. But despite that, most of us simply just give little thought towards improving our health before conceiving a child. We often simply expect that regardless of how we have treated our bodies in the past that they will conceive a child with ease, grow and birth a healthy baby, which will in turn lead to a healthy child.
Post by Taryn van Meygaarden
Post by Emily White
For as long as I can remember the words ‘slip, slop, slap’ have been gospel. Whenever you step out into the sun it is hard not to think about skin cancer and thereby the importance of covering up. However scientists are now suggesting that we have taken this a bit too far with a lot of people suffering from a Vitamin D deficiency- without even knowing!
Post by Emily White
The consumption of ‘heart healthy’ vegetable and seed oil has increased drastically over the past few decades. People have shunned natural fat sources such as butter and lard in favour of these oils that are produced in something that looks more like a meth lab than your grandmas kitchen. So why is everyone telling us that these oils are good for us if they aren’t? The main reason- they are cheap as dirt to produce.
Post by Emily White
Whilst the term 'reactive oxygen species' might seem confusing and daunting it is actually quite easy to understand. Humans are aerobic organisms; this means that we use little organelles called mitochondria in order to provide energy to all of our cells. Within the mitochondria a process takes place called respiration (1).
Post by Emily White
When I first heard the words ‘intermittent fasting’, I panicked. ‘Hangry’ is a real life condition that I suffer from terribly as most of my family and friends could confirm. So why on earth would anyone voluntarily fast?
Fasting is not actually just the latest ‘fad’ and has in fact been around for thousands of years. Whether conducted on purpose or not (our ancestors didn’t exactly have a supermarket down the road), for many people the body appears to thrive in this environment. The simplest and most sustainable form of fasting is the 16/8 method. This is where you only eat for an eight-hour window (say 12pm to 8pm) and fast for the remaining 16. This means that around half of your fasting is conducted while you are sleeping and it literally just means that you may be skipping breakfast.
By Cliff Harvey ND
The ‘Blood Type Diet’ by Peter D’Adamo ND has been a popular diet choice in the natural health community for several decades. It continues to be a popular method in the complementary health field, but its use lacks robust evidence.
While there are correlations between ABO blood-type and some disorders such as carcinomas (1), and between blood type and personality traits (2) these and other findings would be considered quite preliminary and speak little to the veracity of claims for a link between diet, blood type and health outcomes.
Post by Emily White
The age-old quote, 'let food be thy medicine and medicine be thy food' by Hippocrates is certainly of relevance in todays world. Gut health is something that can be related to this and is an extremely important determinant in someone’s health. The nutrition that we provide for our body plays a huge role in this and probiotics in particular, are a very important aspect of any nutritional plan in order to optimise gut health and overall wellbeing.
Post by Emily White
Nowadays walk down any isle in the supermarket and you will almost definitely come across a soy-containing product. It seems it is in everything! Soy has dramatically increased in popularity in the last decade due to the idea that eating too much meat or dairy was bad for you and therefore soy being a great protein alternative. Soy crops are also very cheaply made into soybean oil and soy protein and so now it can be found in many processed foods. Many people are eating so much more soy then they realise and some even supplying their infants with large quantities through the use of soy based infant formula. With such an increased consumption, it really begs the question of what effect soy is actually having on your body.
By Emily White
I was scrolling through Facebook the other day (as I do all to often) and came across an article which annoyed me more than it probably should have. It was suggesting that eating red meat is literally killing you and that avoiding red meat will see you live longer, happier, smarter, slimmer …you get the idea. Basically bottom line, if you eat red meat.. you will get cancer… and you will die.
So first lets look at why everyone thinks this is the case. Numerous organisations around the world have said that eating red and processed meats can increase risk of some cancers. For starters, putting fresh red meat and processed meats into the same cancer causing category is ridiculous.. But more on that later.
Post by Emily White
Whether you are interested in nutrition or not you would have most likely heard about having a glass of lemon in warm water to start your day.
This lemon drink is often taken first thing in the morning in place of tea or coffee and has fast become a fashionably healthy lifestyle choice, right up there with raw cheesecakes and green smoothies. So is this a healthy way to start your day backed by scienced or just a silly celebrity fad?
By Cliff Harvey ND
An idea that has generated much interest within the complementary medicine and holistic nutrition fields is that of the acid-base (or acid-alkaline) balance of the foods that we eat and the potential harm that a diet that is too 'acidic' can cause.
The various compounds that result from the digestion of food and end up circulating through our bodies for eventual utilisation and/or excretion will be either acidic or alkaline.
By Cliff Harvey
As we near the end of the summer break in NZ and Australia and the Christmas and holiday season around the world, inevitably ‘detox’ diets and ‘cleanses’ jostle for space in our news feed. It’s tough to not be sucked into these ads and testimonials, especially if you’ve over-indulged in food and booze, and burnt the candle at both ends over the festive season. Let’s face it, you’re going to feel less than optimal if you’ve been eating too much, eating processed and refined foods, and drinking too much alcohol…but are detoxes and cleanses really the answer?
It’s fair to say that there is little evidence that detox diets and cleanses offer any clear benefit. There are few studies on the many ‘detox’ diets and ‘cleanses’ on the market and most of the claims are not backed by any amount of credible evidence or even plausible science.
Post by Matt Foreman
It seems every time someone opens up a sugar-free drink there is always that person that says, “you’re going to get cancer” or “do you know how bad that stuff is for you?”
Endometriosis is an inflammatory, estrogen-dependent condition associated with pelvic pain and infertility. It is not often discussed or fully understood but with an estimated 1 in 10 woman suffering from this condition it is probably worth discussing (sorry guys this post isn’t for you). As of yet there is no cure for endo however through diet and lifestyle adjustments the condition can be improved.
By Cliff Harvey
Much of the latest research is suggesting positive effects of consuming a ketogenic diet for individuals with disease. These include epilepsy, neurodegenerative disorders and obesity just to name a few.
Post by Emma Cull
Whether you are aware or not, your gut is home to a complex ecosystem of about 100 trillion microbes. These bacteria which are collectively know as the microbiome, out number your own body cells by 10 times and they are so integral to the functioning of your body that it is often referred to as the ‘forgotten organ’ (1).
Post by Emily White
Recently there has been huge interest in the possibility that there is a powerful link between the human brain and gut bacteria. Whilst majority of the current research has been conducted on animals, there are a few studies that show a compelling link between behaviour and gut bacteria in humans.
Post by Emily White
Who here is scared of kale? For anyone who has Facebook you no doubt would have recently seen numerous articles announcing the ‘dark side’ of kale- I’m not even joking here- one was literally titled ‘the dark side of kale’ as if to say it sneaks out of your fridge at night while you sleep and murders your family….
If nutrition wasn’t confusing enough, kale has literally gone from a ‘super-food’ to a ‘health warning’ overnight. So is there any truth to these claims or is it just another media storm in a teacup?
Post by Emily White
Anyone who suffers from eczema will know all too well the unbearable discomfort that it brings. Eczema, a rather broad term, is used to describe a variety of skin conditions that result in red, itchy skin. It can vary in severity, from slightly red and inflamed to full on weeping blisters.
by George Henderson
Research Assistant at AUT Human Potential Centre
When you promote a diet that allows people to eat red meat if they want to, while others
recommend that red meat be strictly limited, and people eat what they want anyway, it puts you in
the position of having to answer the familiar question, is meat a cause of disease?
The idea that eating meat causes diseases like cancer was initially driven into the public consciousness by the American temperance crusader, quack doctor and breakfast cereal salesman John Harvey Kellogg, who also popularised the idea of colonic cleanses as a cure for dietary ills. Thus the major ideas about meat and disease that we have to deal with today had a wide currency before any sort of scientific evidence existed that could be used to support them. They grew out of a vegetarian bias, the association between meat eating and alcohol consumption in the Temperance era, and the characteristic American desire to succeed by selling novel products and services.
The phrase “nutritional terrorism”, used by food historian Harvey A. Levenstein, describes a process that has been going on, with regard to meat in the diet, for over a hundred years; a war against eating habits in which the weapons are statements like “eating X causes cancer” and “eating Y prevents cancer” (so, by implication, not eating Y causes cancer too). Implicit in the phrase “nutritional terrorism” is the idea that these statements are themselves harmful, and can be used to manipulate and exploit people.
Limitations of scientific inquiry
How strong, and how plausible is the link between meat eating and cancer?
Most of the data about meat and cancer is gleaned from large cohort studies in which large numbers of more-or-less healthy participants are asked to fill out a food questionnaire. Their medical records and death certificates are then examined at some much later date. An obvious flaw with this method is that people change their diets, more so in recent times perhaps. The British diet researcher Zoe Harcombe took part in one such study (EPIC); she filled in the food questionnaire when she was a vegetarian, but by the time the study was completed she was a meat eater, and had become an eloquent advocate for the low carbohydrate diet. Zoe Harcombe’s experience also illustrates another potential flaw; because vegetarianism and veganism are still rather rare, participants can be sought for studies on meat avoidance through vegetarian clubs, as she was. This introduces an element of volunteerism into some studies which favours the vegetarians, who tend to be be more motivated and interested in diet and health issues than the meat eaters, who are likely to have become involved in a more random fashion that does not depend on their food choices.
Another question is whether other factors that might also explain cancer incidence – what are called confounding variables – have been accounted for and correctly measured.
Red meat eaters or processed meat eaters might be more likely than vegetarians to work in industries where carcinogenic chemicals are used, to do shift work, or to drink or smoke more heavily.
Do heavy drinkers or binge drinkers report alcohol intake honestly in food questionnaires?
How accurately do binge drinkers remember how much they drink?
How far does the consumption of meat, and especially cheap and “unhealthy” processed meats, reflect one’s class, educational level, occupation, and income status, and how well can these variables be measured and accounted for?
There are no trials that feed people meat to see if they develop cancer, for obvious reasons. There
are animal experiments, from which one thing becomes clear; you cannot give an animal cancer by feeding it meat. You can give an animal cancer by feeding it a carcinogenic chemical, then see if
feeding it meat makes the cancer grow or shrink, but the results are instructive. In one series of tests in rats, beef and chicken had no effect, but ordinary commercial bacon reduced the rate of
cancer. These experiments were repeated with the refinement of a nutrient deficiency (calcium),
and this time the rate of cancer increased when haeminin and haemoglobin, sources of iron found in meat, were fed. Though the conditions might not have reflected what goes on in the gut of the average person, these experiments do suggest that whether meat is harmful or indeed beneficial with regard to cancer might depend on factors such as exposure to carcinogens and nutritional status, that is, factors other than meat.
One can observe that the people who live to be older than most of us – supercentenarians, those
110 or older – are rarely vegetarians, and are often, in the news stories that celebrate their
birthdays, fond of bacon. This may merely reflect the fact that older people are at risk of losing their appetites, to the detriment of their chances of longevity, and bacon is a tasty food. But it also shows that meat eating is not inconsistent with extreme longevity.
Associations between meat eating and colorectal cancer
There is a weak but consistent correlation between meat consumption and colorectal cancer in
most, but not all, large epidemiological studies. New Zealand has one of the world’s highest death
rates from colorectal cancer, yet red meat, a protein-rich food, supplied only about 14% of the total protein in the NZ diet in 2006.
To what extent is meat consumption a factor in colorectal cancer, and what is the contribution of
other dietary and non-dietary factors?
A 2015 systematic review and meta-analysis summarised the evidence for meat in colorectal cancer studies where the subtype of meat was recorded as follows: “Comparing highest versus lowest intake, beef consumption was associated with an increased risk of CRC (RR = 1.11, 95% CI = 1.01 to 1.22) and colon cancer (RR = 1.24, 95% CI = 1.07 to 1.44), but no association was found with rectal cancer (RR = 0.95, 95% CI = 0.78 to 1.16). Higher consumption of lamb was also associated with increased risk of CRC (RR = 1.24, 95% CI = 1.08 to 1.44). No association was observed for pork (RR = 1.07, 95% CI = 0.90 to 1.27), but some between study heterogeneity was observed. No association was observed for poultry consumption and risk of colorectal adenomas or cancer.
Overall, given the modest effects observed for highest versus lowest intakes, beef consumption
alone seems unlikely to explain the large international variation of CRC incidence.”
Mechanisms that link meat and colorectal cancer
No one mechanism is favoured in the literature, but strong evidence points to heterocyclic amines
(HCA) and polycyclic aromatic hydrocarbons (PAH), which are formed when meat is “well done” and especially when it is scorched or blackened, as on a barbecue, as carcinogens.
In animal studies HCA and PAH are only carcinogenic at very high intakes. They are only carcinogenic after being activated by enzymes produced by certain bacteria in the gut, whereas probiotic species (including acidophilus and bifidus sp.) reduce the amount of these enzymes and inhibit the carcinogenic effects of HCA and PAH. Other mechanisms that are supported by some evidence are haeme iron, and the nitrates and nitrites used as preservatives in some processed meats. Red meat does not promote cancer in rodents but haeme iron has promoted cancer in rats fed a diet deficient in calcium. Interestingly, adding back calcium, adding antioxidants, or replacing the high-PUFA safflower oil in the experiment (5%E) with olive oil all reversed the cancer-promoting effect of haeme.
Insulin resistance and metabolic syndrome
A further theory is that insulin resistance caused by the high fat content of meat promotes colon
cancer. The evidence for hyperinsulinaemia and hyperglycaemia as factors in colorectal cancer is strong. Dairy fat, which is more saturated than the fat in meat, is not associated with colorectal cancer in epidemiology, and is associated with a reduced risk of type 2 diabetes, unlike fat from meat.
Trans fats have a strong correlation with colon cancer; in early epidemiology trans fats were not separated from saturated fats. Fish has an inverse association with colorectal cancer, and omega 3 fatty acids from fish increase insulin sensitivity. It is not at all obvious why meat itself should cause hyperinsulinaemia, as diets based on meat and fat have long been used to lower the requirement for insulin in type 1 diabetes and reverse hyperinsulinaemia in type 2 diabetes, but it is likely that high meat consumption in epidemiology is often associated with other factors that promote insulin resistance. If one thinks of the ways in which meat can be consumed – on pizza, in ready-to-eat meat pies, sausage rolls, hamburgers, frozen lasagne and so on – it is easier to see its association with insulin resistance and metabolic syndrome.
In the general population, high meat consumption and low fish and vegetable consumption is associated with people in blue-collar occupations whose dietary patterns may differ from those of professionals and academics. Possible confounders arise from the presence or absence of carcinogens in the workplace, and the effects of night shift work on cancer risk. Night shift workers have significantly increased colorectal cancer rates[10,11], while many different workplace
exposures are also associated with increased risk.[12,13]
In terms of a general overview of the epidemiology, the risk ratios associated with occupational and metabolic factors are greater and more consistent than those associated with red or processed meat per se. Peters et al. (ref. 12, a case-control study of colorectal cancer in young men) is interesting in presenting both occupational and dietary evidence together. Beef was not associated with colorectal cancer, deep fried food but not processed meat was significantly associated with CRC overall (OR 2.1), but significant site-specific correlation was seen with deep fried food and fried and smoked processed meat. The choice of wholemeal bread over white bread had a protective association (OR 0.6) overall. Inactivity in the workplace is a further risk factor.[14,15] Such evidence supports the view that the modern incidence of colorectal cancer is a “disease of civilization”, that is, a disease that is promoted by industrial chemical exposures, industrial food processing, fast food cooking, and the circadian disruptions produced by artificial light and the work demands of life in an industrialised society, which include both night shift work and enforced inactivity. Burkitt’s hypothesis that cereal fibre accounts for the different incidence of CRC between industrialised and non-industrialised peoples lacks strong experimental confirmation, but it is likely that a multifactorial approach to the same question will prove more rewarding.[16,17]
Benefits of meat
Meat is an easily digested food with a high bioavailability of most essential nutrients, as well as many non-essential chemicals which are required in human metabolism and not found in plants, such as carnitine and creatine. Zinc and iron are common nutritional inadequacies in populations that do not eat red meat. Low and suboptimal intake of the micronutrient selenium (Se) as noted in New Zealand has been implicated as a risk factor in CRC. Kidneys from sheep and cattle are among the best dietary sources of selenium, meat is also a source of selenium.
Iron deficiency is common in New Zealand, especially among young people, and meat is an excellent source of this mineral.
Red meat is a good source of vitamin B6, which is required for the metabolism of amino acids. Processed meats are a poor source of this vitamin. Intake of vitamin B6 is inversely associated with, and serum levels of the active co-factor form pyridoxal-5-phosphate (PLP) are strongly inversely associated with, colorectal cancer (RR 0.52). PLP is required for the conversion of dietary selenium (selenomethionine) to the active form (selenocysteine) and may also play a role in the metabolism of nitrite.
Fatty cuts of meat, in the context of a low carbohydrate diet, have a high satiating power and meat, by making the low carbohydrate diet more appetising, helps in maintaining a diet that, like any diet, needs to be maintained to be effective. The main therapeutic mechanism of a low carbohydrate diet is to reverse hyperinsulinaemia, hyperglycaemia, and other markers of the metabolic syndrome and type 2 diabetes that are risk factors for colon cancer. In part risk reduction is achieved by lowering energy intake and the resulting weight loss. However weight loss is not necessarily required for improvements in metabolic risk factors.
Serum lipoproteins, dietary biomarkers, and cancer risk
The EPIC study found that ApoA-1, HDL cholesterol, total cholesterol, and LDL cholesterol were inversely associated with CRC risk, but only the protective association with HDL was strong (RR 0.54, highest quintile compared to lowest). This latter finding has been replicated in other studies, and is consistent with hyperinsulinaemia, which suppresses HDL, being an important factor in the aetiology of CRC.
Serum biomarkers of dietary intake, chemicals that owe their presence in the blood to the consumption of specific foods, may be more reliable than subjects’ recall of the foods they ate. In a case-control study nested within the French EPIC cohort a high serum phospholipid level of the odd-chain saturated fatty acids pentadecanoic acid (15:0) and heptadecanoic acid (17:0), which are considered biomarkers of dairy fat consumption, was inversely associated with advanced colorectal adenomas (OR O.40). A similar correlation was seen for a high level of DHA and EPA, biomarkers of fatty fish consumption (OR 0.50). The ratio between long chain omega 3 PUFA and long chain omega6 PUFA was also inversely associated with advanced colorectal adenomas (OR 0.40). Similar but non-significant trends were seen in regard to non-advanced adenomas. Serum phospholipid pentadecanoate and heptadecanoate levels were inversely associated with serum levels of insulin in a prospective study..
Safety of meat in the LCHF diet
The requirement for protein in the LCHF diet is around 15% of energy, or 1g per Kg of body weight.
The consumption of protein from nuts, seeds, fish, seafood, eggs and poultry is encouraged, as well as dairy and some legumes if these are tolerated. In the context of this, and other, diets, the amount of meat consumed is a matter of taste, of cultural preference, and perhaps regard for one’s family history of disease, or one’s iron status. The use of processed meat is discouraged, with nitrate-free bacon and traditional fermented meats being preferred choices. Bacon is a convenient and popular breakfast food, but the evidence we have reviewed suggests that it should be cooked under a grill so that charring can be prevented, and similarly that red meat should not be overcooked. Boiling, in a stew, casserole, or boil-up, minimises the action of heat, as well as the loss of micronutrients, as does cooking steak to medium rare. Cooking meat slowly in liquid with the bone attached, for example in soups, stews, curries, and casseroles, supplies additional calcium in the meal.
Wholegrains are the only foods considered to be protective against CRC that are not included in the LCHF diet; however the foods eaten by people who do not eat wholegrains in epidemiological
studies include refined grains, which are not eaten on the LCHF diet. There is no study which directly compares intake of wholegrains with that of fibre from non-starchy vegetables, nuts, etc. on a grain-free diet.
The protective effect of fruit and vegetables in the diet may not be restricted to those with low meat intakes, and there may also be a protective effect of full-fat dairy products (perhaps due in part to the competition between calcium and iron).
Fermented foods which are sources of probiotic bacteria, such as yoghurt, sauerkraut, kimchi, and
sour cream, are commonly consumed with red meat in many of the world’s cuisines. A nutritious, varied diet, a healthy microbiome, and good habits of work, sleep and exercise are important determinants of metabolic health, including cancer risk, and should be considered as essential adjuncts to the carbohydrate restriction aspects of the LCHF diet.
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Post by Emily White
Essential fatty acids (as the name suggests) are vital for optimal health. The two essential fatty acids, linolenic and linoleic acid are unable to be synthesized in the body and therefore must be obtained from the diet. These fats are termed Omega-3 and Omega-6 fatty acids based on their structure. Both Omega-6s and Omega-3s need to be consumed as together they have an important role in modulating inflammation (1).
Post by Cliff Harvey ND
We've all been told time and time again that sodium (salt) is bad for us; that it's a cause of heart disease and stroke and that we should reduce our intake. The Dietitians NZ sodium fact sheet states: "Too much salt, and therefore sodium, can lead to more fluid being retained in the body. This means the heart is working harder, pumping more blood around the body, increasing pressure. High blood pressure increases the chance of having a heart attack or stroke, still two of the biggest killers in the Western world." and go on to say that "Reducing our salt intake by just a third, from around 9g (3460mg sodium) to the recommended maximum of 6g (2300mg sodium), could, in time, save over 900 Kiwi lives a year."
While this goal is admirable, the evidence seems to suggest that this isn't the case, and in fact not only is our current sodium intake safe and healthy, but reducing sodium too drastically could be related to several negative health outcomes.
It’s fair to say that most of you reading this article won’t be starving...
Well you may be starving right now if you are reading this during the dreaded 3pm slump, but my guess is that it’s only a few short steps to the fridge or the local store where calories abound!
In a sense though many people nowadays are starving, but they are starving on a full stomach.
While we have plenty of food, and plenty of ‘calories’ (fuel) we are often deficient in all the little players of nutrition—the vitamins, minerals and other secondary nutrients that provide the keys to our body’s proper function.