scientific research in nutrition

April 12, 2017

The answer to this question does not lie in the medicine itself, but how the practitioner or naturopathe (Naturopathic Doctor in provinces other than Quebec) decides to apply the scientific literature to their clinical practice, and how they communicate with their patients what is known and not known. This is not just for naturopathes, but for ALL health care providers, and it is of my opinion that naturopathes do and should fall into this type of practice. However, it is a paradigm shift of our age, and given that naturopathic medicine is deemed to be 'traditional,' it questions the progressiveness of the profession. However, I do not think they are mutually exclusive. They are simply different levels of evidence. In fact, I find it very intriguing as a practitioner in that the more I understand the truth of the matter, what are the facts, how they are interpreted, and what I observe, to be the tenants of good practice of medicine.

 

Furthermore, health, medicine, and nutrition are redefining what it means to practice 'evidence-based,' and not all practitioners will even adopt this practice. This means, making recommendations on treatment efficacy, interactions, and prognosis based on the highest levels of evidence when it is available. And if the evidence is unclear, to say so to your client and then to make clinical judgments whether or not it is safe or efficacious to make a treatment recommendation, taking into account the different levels of evidence.

 

To practice evidence-based medicine does require an understanding of medical scientific literature, study methodology, and statistical power. Furthermore, it requires scrutiny and critical appraisal of research in order to apply the evidence in clinical practice. This takes an enormous amount of time. Up to date research tells us that RCT's (randomized controlled trials) are the most reliable research to use in medicine, and even more powerful are systematic reviews or meta-analyses that group together several similar RCT's to address an outcome measure. This means the study question requires that the intervention has been reproduced. The reproduction of clinical interventions gives the treatment greater power, especially if the confidence is high and the study sample is large. If the trial is double-blinded and compared to placebo, as opposed to an open-label study, the weight of evidence is even greater. Observational studies are another form of reliable evidence, although not as powerful as the RCT. These studies demonstrate correlation and not causation, and usually follow populations over time (cohort studies), in one specific moment in time (cross-sectional), or as a comparison (case-control). Case series, case studies, expert opinion, and clinical evidence also fall under observational studies but are considered the lowest form of evidence. It is, however, still a form of evidence, and the manner by which it is communicated (for example, giving details of the case or the clinical evidence, the number of times it was observed, the follow-up) can significantly improve compliance, trust, and patient understanding. In observational studies, looking at the number of cases lost to follow-up (and whether this was even stated in the research) is an important clinical appraisal since this can greatly skew results.

 

Many studies in nutrition are observational and therefore follow trends. For example, many small scale studies may show trends towards meat consumption and colon cancer risk, or other similar associations (1-4), however large-scale prospective cohort systematic reviews failed demonstrate such association (5). In evidence based practice, we would not recommend to stop eating meat because of this, since the more reliable prospective study did not find a link. However, it would reasonable, perhaps, to recommend limiting red meat to 500g per week. An updated analysis in 2014, however, did find a protective effect of vegetarian and vegan diet on certain cancers (6). The evidence is conclusive that adopting a vegetarian diet does reduce risk of ischemic heart disease, by around 23% (5), however if we analyse the study, the 'meat-eaters' in the study were on average 50% healthier than the general population, therefore the risk reduction may be underestimated. Sampling, therefore, may largely affect the results. We have seen this also in studying the correlation between depression and genetic susceptibility. Individual studies found an association, but meta-analysis failed to demonstrate a link (7). And we are also finding this with the acid-ash diet and the risk of osteoporosis. Large meta-analyses looking at calcium homeostasis and acidic diets, versus alkaline diets, shows no correlation between diet and risk of osteoporosis (8), despite many studies that demonstrate a link between acidic diet high in saturated sulfur-containing animal protein (and conversely low potassium-rich fruits and vegetables) with urinary calcium loss (9). The Framingham Osteoporosis study also demonstrates no link (10). However, these studies are just PART of the evidence, and does not necessarily apply to you, at your age, in your climate, with your cultural background, and your genetic susceptibility.

 

These factors, or risk factors, determine if, how, and when, you MAY develop a disease. And this is where naturopathic medicine, with the informed knowledge of science and taking into consideration the numerous risk factors, helps you choose and modify your lifestyle in the best way possible.

 

A lot of 'natural health products' are still in the debuts of research. Namely, in vitro or in vivo studies, in order to determine the mechanism of action (a reductionnist way of thinking). This can be helpful, but we also know that reductionnism has led to many errors in nutritional sciences, but significant advances in pharmacological research. The nutraceutical industry has taken advantage of these non human trials to put their products on the market. This can lead to confusion and mis-representation. Because good quality human trials are lacking on efficacy and safety, we simply do not know. I think it is important to highlight when there is information that we do not know, but on the flip side, not to discredit the entire profession when there is good science on the application of 'natural' therapeutics. It does not mean its bad, but it does not mean its good either. It is of my opinion that we stick the facts, keep our observational skills honed and working hard, and communicate effectively. We are skilled practitioners at minimizing the use of drugs and surgery when it is safe to do so. And sometimes, as David Suzuki demonstrates in his short documentary Brain Magic: the Power of Placebo, placebo does in fact has a great impact on our physical health. What does that tell us about science and medicine?

 

For more information about evidence-based practice and self-tutorial, check out 

http://guides.mclibrary.duke.edu/c.php?g=158201&p=1036021

 

1) Key TJ, Fraser GE, Thorogood M, et al: Mortality in vegetarians and non-vegetarians: a collaborative analysis of 8,300 deaths among 76,000 men and women in five prospective studies. Public Health Nutr 1998;1:33–41.

2) Fraser GE: Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists. Am J Clin Nutr 1999;70(suppl 3):532S–538S.

3) Sanjoaquin MA, Appleby PN, Thorogood M, et al: Nutrition, lifestyle and colorectal cancer incidence: a prospective investigation of 10,998 vegetarians and non-vegetarians in the United Kingdom. Br J Cancer 2004;90: 118–121.

4) Roddam AW, Pirie K, Pike MC, et al: Active and passive smoking and the risk of breast cancer in women aged 36–45 years: a population based case-control study in the UK. Br J Cancer 2007;97:434–439

5) Huang et al. 2012.Cardiovascular disease mortality and cancer incidence in vegetarians: a meta-analysis and systematic review. Ann Nutr Metab. 60:233-240.

6) Key et al. 2014. Am J Clin Nutr. 2014 Jul; 100(1): 378S–385S. Cancer in British vegetarians: updated analyses of 4998 incident cancers in a cohort of 32,491 meat eaters, 8612 fish eaters, vegetarians, and 2246 vegans

7) Culverhouse et al. 2017. Collaborative meta-analysis finds no evidence of a strong evidence of a strong association between stress and 5-HTTPLPR genotype contributing to the development of depression. Molecular Psychiatry, April 4 2017.

8) Fenton et al. 2011. Causal assessment of dietary acid load and bone disease: a systematic review and meta-analysis applying Hill's epidemiologic criteria for causality. Nutrition Journal. 10:41.

9) Sebastian A, et al. 1994 Improved mineral balance and skeletal metabolism in postmenopausal women treated with potassium bicarbonate. N Engl J Med 330:1776–1781

10) Hannan et al. 2000. Effect of dietary protein on bone loss in elderly men and women: The Framingham Osteoporosis study. J of Bone and MIn Res. 15(12):2504-12.

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