Fruit-and-Vegetable Consumption May Not be Inadequate

Whitehead et al. begin their intriguing article with the following two authoritative statements (leading off their abstract and introduction, respectively): “Fruit and vegetable consumption is inadequate among adults in the United States” and “Inadequate fruit and vegetable consumption is an enduring problem that presents a significant challenge to human well-being.” ^1(p207) Although these statements are definitive, the evidence for them is less so, deriving mostly from observational studies and various problematic research designs.²

It is entirely possible that worldwide fruit-and-vegetable consumption is already at an appropriate level (or maybe even too high), and what the world's people may want to do to improve their health is consume fewer processed products like those containing refined grains and sugar. Exclusively carnivorous peoples like the Masai did just fine without eating fruits or vegetables^3,4—as did the Inuit who considered fruits and vegetables “not proper human food.”^4,5 Only after the introduction of white flour and sugar to traditional plant-avoiding diets did such peoples begin to exhibit diseases like obesity, diabetes, cardiovascular disease, and cancer.⁴ It is not clear that eating more fruits and vegetable would help. Indeed, it has not helped protect exclusively vegetarian Hindus from escaping similar chronic-disease fates; in fact, they may be disproportionately affected.⁶

Whitehead et al. suggest fruits and vegetables are beneficial because of healthy substances (like the appearance-benefitting antioxidant carotenoids) they contain.¹ When such substances are tested in randomized controlled trials, however, they mostly fail to improve health and may even cause death⁷ (famously the case for yellow-pigmented carotenoids carotenoids⁸).

An alternative hypothesis to a fruit-and-vegetable benefit through healthy substances is a benefit through substitution: perhaps fruits and vegetables promote health by displacing unhealthy foods that people might otherwise eat. Such a possibility would certainly give the appearance of a uniquely healthy effect, but would make fruits and vegetables no more “inadequate” in a person's diet than other unprocessed foods (e.g., nuts, whole grains, fish, wild game) that might replace processed foods; and no more inadequate than other foods that might supply appearance-benefiting yellow pigments (e.g., liver, eggs, cheese).⁹ In fact, if preferentially eating certain other whole foods would produce more-desirable health effects, then consuming fruits and vegetables instead could be relatively unhealthy.

Don't get me wrong, the article by Whitehead et al.¹ is incredibly interesting, is very well referenced, and makes several compelling points. Also, I am certainly not against promoting fruits and vegetables¹⁰ (particularly to displace processed foods). I just do not think we can use words like “inadequate” to describe fruit or vegetable intake. Until better evidence is available, we, in public health might proceed with more cautious statements such as: Levels of fruit-and-vegetable consumption may be less than ideal.