I thank Drs. Bradshaw and Loffelmann1 for their contribution to the discussion of plant versus animal product–based nutrition and response to the commentary in CMAJ.2
They suggested that the National Academies of Sciences, Engineering and Medicine in the United States have criticized the Dietary Guidelines Advisory committee (DGAC) and Dietary Guidelines for Americans (DGA) for a lack of sound science in recommending a low-saturated–fat and more plant-based diet for Americans.3 I note that the academies stressed that the findings of their report “should not be considered as judgments about the quality of prior DGA or DGAC reports.”3 It is also worth noting that the submissions to the DGA were both for and against a shift to a more plant-based diet; however, on the issue of sustainability, most submissions supported its inclusion in the guidelines.3
These comments by the academies do not sound like criticism of the US guidelines as inferred.
Bradshaw and Loffelmann1 quoted the Prospective Urban Rural Epidemiology (PURE) study4 as supporting low-carbohydrate, high-meat diets. Certainly, the socioeconomic status of those on high-carbohydrate diets was low, and we know that socioeconomic status is a powerful driver of health outcomes that may be difficult to control for.4 However, perhaps more telling is a second article by the PURE investigators in the Lancet showing that consumption of legumes, fruit and vegetables (good sources of carbohydrates) are associated with overall longevity (reduced all-cause mortality).5 Perhaps these findings may be interpreted as indicating that fat may be better than bad carbohydrates, but that carbohydrates with a low glycemic index (eaten in increased amounts by vegetarians and vegans) have benefit.
Bradshaw and Loffelmann1 also cited a meta-analysis by Astrup and colleagues that milk consumption is not associated with cardiovascular disease and all-cause mortality.6 However, no benefits were shown for milk, and the authors of the meta-analysis stated that the background diet was not reported in half the studies they assessed and that elimination of bad foods (e.g., soft drinks or meat) by milk may have falsely inflated the apparent benefits for milk and masked some of its adverse effects.6 Overall, I do not see the lack of effect of milk on all-cause mortality as a strong reason for the continued promotion of milk.6
Children and adverse effects are always a cause for concern; in this instance, Bradshaw and Loffelmann1 cited a review (that is not systematic and certainly not a meta-analysis) by Cofnas.7 This review put together the possible adverse effects of soy intake and vegan and vegetarian diets on outcomes in pregnancy and childhood intellectual development in those not consuming meat. This review is of interest, but important studies, such as one by Andres, Badger and colleagues that used magnetic resonance imaging and followed children who had consumed soy formula in early life, were not cited.8 They found no persistent effects (including anatomic changes) after feeding with soy infant formula, despite the substantial phytoestrogen content in the soy formula.8 Most importantly, Cofnas’ stance against plant-based diets runs counter to the positions of the US Academy of Nutrition and Dietetics9 and the US Department of Agriculture,10 both of which state that wisely selected plant-based diets have no negative effects on children9 and are recommended for the general population,10 as Cofnas noted in his review
I continue to conclude that well-balanced, plant-based diets can be good for human health and, perhaps more importantly, may be essential for the survival of all life on this planet.
Footnotes
Competing interests: David Jenkins is a vegan. He has received research grants from Saskatchewan Pulse Growers; Agricultural Bioproducts Innovation Program through the Pulse Research Network; Advanced Foods and Materials Network; Loblaw Companies; Unilever; Barilla; Almond Board of California; Agriculture and Agri-Food Canada; Pulse Canada; Kellogg’s Canada; Quaker Oats Canada; Procter & Gamble Technical Centre; Bayer Consumer Care; Pepsi/Quaker; International Nut and Dried Fruit Council; Soy Foods Association of North America; The Coca-Cola Company (investigator initiated, unrestricted grant); Solae; Haine Celestial; Sanitarium Company; Orafti; International Tree Nut Council Nutrition Research and Education Foundation; The Peanut Institute; Canola Council of Canada; Flax Council of Canada; Calorie Control Council; Canadian Institutes of Health Research (CIHR); Canada Foundation for Innovation; and Ontario Research Fund. He has received in-kind supplies for trials as a research support from the Almond Board of California, Walnut Council of California, American Peanut Council, Barilla, Unilever, Unico, Primo, Loblaw Companies, Quaker (Pepsico), Pristine Gourmet, Bunge Limited, Kellogg Canada and WhiteWave Foods. He has been on the speaker’s panel, served on the scientific advisory board and/or received travel support and/or honoraria from the Almond Board of California; Canadian Agriculture Policy Institute; Loblaw Companies; Griffin Hospital (for the development of the NuVal scoring system); The Coca-Cola Company; EPICURE; Danone; Diet Quality Photo Navigation; Better Therapeutics (FareWell); Verywell; True Health Initiative; Institute of Food Technologists; Saskatchewan Pulse Growers; Sanitarium Company; Orafti; American Peanut Council; International Tree Nut Council Nutrition Research and Education Foundation; The Peanut Institute; Herbalife International; Pacific Health Laboratories; Nutritional Fundamentals for Health; Barilla; Metagenics; Bayer Consumer Care; Unilever Canada and Netherlands; Solae; Kellogg; Quaker Oats; Procter & Gamble; Abbott Laboratories; Canola Council of Canada; Flax Council of Canada; Dean Foods; California Strawberry Commission; Haine Celestial; PepsiCo; Alpro Foundation; Pioneer Hi-Bred International; DuPont Nutrition & Health; Spherix Consulting; WhiteWave Foods; Advanced Foods and Material Network; Agriculture and Agri-Food Canada; Canadian Agri-Food Policy Institute; Pulse Canada; Soy Foods Association of North America; Nutrition Foundation of Italy; Nutrasource Diagnostics; McDougall Program; Toronto Knowledge Translation Group, St. Michael’s Hospital; Canadian College of Naturopathic Medicine; The Hospital for Sick Children; Canadian Nutrition Society; American Society of Nutrition; Arizona State University; Paolo Sorbini Foundation; and Institute of Nutrition, Metabolism and Diabetes, CIHR. He received an honorarium from the US Department of Agriculture to present the 2013 W.O. Atwater Memorial Lecture. He received the 2013 Award for Excellence in Research from the International Nut and Dried Fruit Council. He received funding and travel support from the Canadian Society of Endocrinology and Metabolism to produce mini cases for the Canadian Diabetes Association. He is a member of the International Carbohydrate Quality Consortium. His wife (Alexandra Jenkins) is a director and partner of Glycemic Index Laboratories, and his sister (Caroline Brydson) received funding through a grant from the St. Michael’s Hospital Foundation to develop a cookbook for one of his studies.