Primary Research · 2005
Zinc-induced copper deficiency: a report of three cases initially recognized on bone marrow examination
Willis et al. · American Journal of Clinical Nutrition, 2005
Key finding
Documented cases of copper deficiency from chronic high-dose zinc supplementation — supports the 1–2 mg copper pairing guideline.
Abstract
PubMed · PMID 16155279 →BACKGROUND: The frequency and short-term natural history of weight loss in community-dwelling older adults have not been described. Unintentional weight loss may be more likely to continue than intentional weight loss. OBJECTIVES: The present substudy described the frequency of a > or = 5% loss or gain in body weight in community-dwelling older adults at an annual examination of the Health, Aging, and Body Composition (Health ABC) Study and 6 mo later. The weight-management practices used by the participants were also described. DESIGN: A total of 522 older adults with either a > or = 5% weight gain (n = 116) or a > or = 5% weight loss (n = 171) in the previous year were compared with a random sample of weight-stable older adults (< 5% weight loss or gain, n = 235) at the fourth annual visit of the ongoing Health ABC Study. The participants' weight-loss intention and weight-management practices were assessed by an interview. The participants' weight was reassessed 6 mo later. RESULTS: Compared with the weight-stable participants, the participants who had lost or gained weight at the substudy baseline were more likely to have subsequent weight changes. The direction of the subsequent weight change, however, was more likely toward either maintenance of or recovery from the previous weight change. Only 4% of the participants who gained weight and 11% of those who lost weight continued to gain or lose weight, respectively. Continued weight loss was more common in the participants with unintentional weight loss than in those with intentional weight loss, but the difference was not significant. CONCLUSIONS: Weight changes were common, but most participants, including those who unintentionally lost weight, maintained their weight change or resolved their weight change in 6 mo. Unintentional weight loss appears less likely to resolve than other weight changes.
Abstract sourced from PubMed, a database of the U.S. National Library of Medicine. Displayed in the authors’ own words for context; our critique is in the sections below.
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Cited in 1 guide
How to read a study like this
The same questions worth asking about any research paper, not just this one. Worth a minute even if you trust the grade.
Who was studied, and do you resemble them?
Supplement effects often depend on baseline status. Vitamin D helps people who are deficient; iron helps people who are anemic. A result in people unlike you may not apply to you.
What was measured, and does it matter in daily life?
A study that shows a blood marker moved isn't the same as a study that shows people felt or functioned better. Ask what the outcome means in practice.
How large was the effect — not just whether it was significant.
'Statistically significant' only means the effect is unlikely to be zero. It doesn't tell you the effect is large enough to notice. Look for effect sizes, not just p-values.
Who paid for the trial, and what did they stand to gain?
Industry-funded trials are several times more likely to report positive results than independent ones. It's not usually fraud — it's subtle design and reporting choices. Weight accordingly.
Has anyone else replicated this?
Single positive trials are hypotheses. Replication by independent groups is what turns a hypothesis into reliable evidence. If the only positive trial is the one you're reading, wait.
Does the dose in the trial match what's being sold?
Supplement marketing routinely cites trials that used 5–10× the dose in the product. If the effective dose was 2 g/day and the capsule has 200 mg, expect roughly no effect.
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