The following short excerpt comes from Dr. Campbell’s Whole: Rethinking the Science of Nutrition (with Howard Jacobson, PhD). It answers a frequently asked question: Is it necessary to be 100 percent adherent to a whole food, plant-based (WFPB) diet 100 percent of the time? For more information, read our webpage on Whole. To learn about the neuroadaptive benefits of fully committing to a WFPB diet, read our article on Dietary Addictions.

When I lecture publicly, I’m often asked about the numbers. Many people want precise formulas and rules. How many ounces of leafy greens should I eat daily? What proportion of my diet should be fat, protein, or carbohydrate? How much vitamin C and magnesium do I need? Should certain foods be matched with other foods and, if so, in what proportion? And the number one question I’m asked is, “Do I need to eat 100 percent plant-based to obtain the health benefits you talk about?”

If you’re asking those questions right now, here’s my answer: relax. When it comes to numbers, I am reluctant to be too precise, mostly because (1) we don’t yet have scientific evidence that fully answers these questions; (2) virtually nothing in biology is as precise as we try to make it seem; and (3) as far as the evidence suggests at this point, eating the WFPB way eliminates the need to worry about the details. Just eat lots of different plant foods; your body will do all the math for you!

As far as whether one should strive to eat 100 percent plant-based instead of something less—say, 95–98 percent—my answer is that I am not aware of reliable scientific evidence showing that such purity is absolutely necessary, at least in most situations. (Exceptions would include patients with cancer, heart disease, and other potentially fatal ailments, for whom any deviation can lead to worsening or relapse.) I do believe, however, that the closer we get to a WFPB diet, the healthier we will be. I say this not because we have foolproof scientific evidence of this, but because of the effect on our taste buds. When we go the whole way, our taste buds change and remain changed, as we begin to acquire new tastes that are much more compatible with our health. You wouldn’t advise a heavy smoker who wants to quit to continue smoking one cigarette per day. It’s much easier to go 100 percent than 99 percent, and you’re much more likely to succeed in the long run.

Excerpt From
Whole: Rethinking the Science of Nutrition by T. Colin Campbell, PhD, with Howard Jacobson, PhD
© 2013 T. Colin Campbell