The National Health and Nutrition Examination Survey (NHANES) is one of those major ongoing surveys from which data related to all things health and nutrition are derived. The short entry on Wikipedia summarises the aims of NHANES very well;
Findings from the survey are used to determine the prevalence of major diseases and risk factors for diseases. Information is used to assess nutritional status and its association with health promotion and disease prevention. NHANES findings are also the basis for national standards for such measurements as height, weight, and blood pressure. Data from this survey are used in epidemiological studies and health sciences research, which help develop sound public health policy, direct and design health programs and services, and expand the health knowledge.
Whilst being a survey conducted on an American population, the results from this are interpreted and referred to globally, with NZ and Australia being no exception. It is only now, after 40 years, however, that the robustness of the survey itself and the data obtained from it, has been seriously looked at. Keep in mind the bolded statement from Wikipedia, above, as you read this summary of this NHANES review;
The study examined data from 28,993 men and 34,369 women, 20 to 74 years old, from NHANES I (1971 – 1974) through NHANES (2009 – 2010), and looked at the caloric intake of the participants and their energy expenditure, predicted by height, weight, age and sex. The results show that — based on the self-reported recall of food and beverages — the vast majority of the NHANES data “are physiologically implausible, and therefore invalid,” Archer said.
In other words, the “calories in” reported by participants and the “calories out,” don’t add up and it would be impossible to survive on most of the reported energy intakes. This misreporting of energy intake varied among participants, and was greatest in obese men and women who under-reported their intake by an average 25 percent and 41 percent (i.e., 716 and 856 Calories per-day respectively).
Under-reporting by somewhere between 25 and 40% of total energy intake is a substantial error, especially when translated into real foods and/or the macronutrient ratios. Under-reporting of food intake is nothing new and is part of the reason why almost any dietary survey should be interpreted with a significant degree of caution and scepticism. Even at an individual level, people are generally not very good at accurately recalling, assessing, and recording how much they eat.
Just yesterday, as the news broke on the above story, I was reviewing somewhere in the order of 20 diet logs filled out by one of our corporate clients who had just completed a healthy eating challenge. The following is a representative composite of most of the diet logs I reviewed;
- Breakfast: Cereal + fruit or a fruit smoothie
- Lunch: Soup or a chicken salad
- Dinner: vegetables and a small amount of lean meat
- Snacks: wholegrain crackers, low-fat cheeses, low-fat yoghurts, fruits, muesli bars
Two things really stood out when you went through the quantities reported;
- If this is all these people (mostly women) are eating (probably in the range of 1200-1500cals per day), they must be seriously starving
- Just how much sugar and refined carbohydrates are being consumed by people who believe themselves to be health-conscious and making good choices
Experience tells me many of them won’t be starving, based on the items that were left out of their food logs. I am sure that every 2-3 days, when that hunger really kicks in, that there will be some ‘naughty little one-off treat’ which made it passed the lips, but which didn’t make it on to the diet log sheet. A common trait across nearly every single log was that it was very idealistic, with the person who has filled it out going to great lengths to ensure that the person they knew would be doing the review (me – the nutritionist) knew that they had selected something that was “whole grain”, “low-fat”, or “lite”, or they stated the brand in such a way as to play on the health-halo which went with that brand. In diet surveys, you get the answers that those being surveyed think you want to hear.
If we accept that this review of the NHANES data is accurate in its assessment and that such data is seriously flawed, then much of the health knowledge and food policy, which we have accepted as gospel over the last 40 years, also needs revisiting. It needs to be tested against a new paradigm – a new yardstick. It might well be that we need a new starting point from which to begin to base sound nutritional advice from. Call me both predictable and biased, but I think that starting point should be one from our evolutionary history.