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Providing perspectives on recent research into vitamins and nutritionals


Measuring Optimal Nutritional Status and Landing on the Moon

By Michael McBurney

Good health depends upon good nutrition. And by good nutrition, I mean validated, biological measures of nutritional status. Nutritional status isn’t defined by today’s food choices. Nutritional status is a reflection of long term dietary intake. Thirty-one years ago, Dr George H Beaton and colleagues published that 1-day data was a very inadequate estimation of usual intake of individuals. Researchers were cautioned about the risk of false negative conclusions when analyzing relationships between diet and health.  Because of intra-individual variability, most dietary recalls are now collected over 2 days but estimating usual intake of nutrients still has limitations.

Nevertheless, healthy diet and lifestyle patterns are associated with decreased risk of all-cause cardiovascular disease (CVD) and cancer mortality. Reedy and associates report that it doesn’t really matter which index is used [Healthy Eating Index (HEI), the Alternative Healthy Eating Index (AHEI), the alternate Mediterranean Diet (aMED), or Dietary Approaches to Stop Hypertension (DASH)], the same conclusion is reached. The healthiest people, those with the 12-28% reduced risk of all-cause, CFD, and cancer mortality, eat a more nutrient-rich diet, are more physically active, are leaner, and less likely to smoke. They are usually older and college graduates. In other words, eating a healthy diet is good for us and the 4 dietary indices are generally the same.

Unfortunately, the majority of us don’t regularly adhere to healthy lifestyles (diet and behavior). Inadequate nutrient intakes are common. According to the CDC’s Second Nutrition Report, significant percentages of people are actually deficient in vitamin B6, iron, vitamin D, vitamin C, and B12. This suggests that a greater proportion of the population will have suboptimal nutrient levels in the blood and tissues.

When nutrient levels are suboptimal, dietary supplementation can be important. For example, lutein and zeaxanthin are important to maintain vision. These carotenoids and essential vitamins and minerals are plentiful in colorful vegetables and fruit – unfortunately, food groups that are not consumed as recommended. In a new meta-analysis of 12 prospective studies and 2 randomized controlled trials (RCTs), Zhao and colleagues report a strong inverse correlation between multivitamin/mineral supplements and age-related cataracts. The longer that supplements were used, the greater their impact.  Probably typical dietary intakes of lutein and zeaxanthin are low.

People wouldn’t need to supplement if we followed dietary recommendations. That is the ideal. The reality of food choices is often different. The fact remains, nutritional tissue levels will fall below optimum when the diet isn’t nutrient-rich. Cells require nutrients for metabolic processes. Without optimal concentrations in blood and tissues, cellular functions can be compromised. Longevity and health can be affected.

Unfortunately, scientists and health professionals haven’t defined optimal levels for many nutrients. The lack of consensus has occurred partly because of a lack of data but primarily because more it takes more resources and to collect and analyze biological samples.

Nutrition research shouldn’t default to the easiest path. It wasn’t easy to set a course to put humans on the moon. It took commitment. Nutrition researchers needs to follow this example. Need to take the next step. Need to measure biomarkers of nutritional status, not usual intake, to define nutrient-health relationships.

Main Citations

Reedy J, Krebs-Smith SM, Miller PE, Liese AD, Kahle LL, Park Y, Subar AF. Higher diet quality is associated with decreased risk of all-cause, cardiovascular disease, and cancer mortality among older adults. 2014 J Nutr doi: 10.3945/jn.113.189407

Zhao L-Q, Li L-M, Zhu H, Epidemiological Evidence-Based Eye Disease Research Group. The effect of multivitamin/mineral supplements on age-related cataracts: A systematic review and meta-analysis. 2014 Nutrients doi: 10.3390/nu6030931

Other Citations

Beaton GH, Milner J, McGuire V, Feather TE, Little JA. Source of variance in 24-hour dietary recall data: implications for nutrition design and interpretation. Carbohydrate sources, vitamins, and minerals. 1983 Am J Clin Nutr 37:986-995

Dodd KW, Guenther PM, Freedman LS, Subar AF, Kipnis V, Midthune D, Tooze JA, Krebs-Smith SM. Statistical methods for estimating usual intake of nutrients and foods: A review of the theory. 2006 J Am Diet Assoc doi:10.1016/j.jada.2006.07.011

Curran-Celentano J, Hammond Jr BR, Ciulla TA, Cooper DA, Pratt LM, Danis RB. Relation between dietary intake, serum concentrations, and retinal concentrations of lutein and zeaxanthin in adults in a Midwest population. 2001 Am J Clin Nutr 74:796-802