Nutrition Myths and Facts for Primary Care Physicians

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1. The recommendation that calcium consumption promotes optimal bone health and prevents osteoporosis is _____.

A. A dietary myth

B. Something health care providers should include as part of routine clinical care

C. Firmly supported by the evidence base

D. B and C only

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Answer: A. Dietary myth

Routine clinical care often includes the recommendation that calcium consumption promotes optimal bone health and prevents osteoporosis, especially in women. However, research fails to back this up. A 2014 Cochrane Review of men and postmenopausal women found that calcium supplementation, even when given with vitamin D, had only minor effects on the prevention of bone fractures. The review found that the number needed to treat to prevent one hip fracture was 1000 for community-dwelling adults and 111 for nursing home residents.¹ The US Preventative Services Task Force has said that there is not enough evidence to recommend vitamin D supplementation, with or without calcium, for the prevention of fractures in community-living women and men.² Moreover, calcium supplements have been linked to increased risk of kidney stones and cardiovascular events. Naturally occurring calcium in dairy has unclear benefits on bone health, but at least dairy has not been linked to increased risk of kidney stones or cardiovascular events. 

2. Some high-fat foods can increase satiety and help patients lose weight.

A. True

B. False

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Answer: A. True

Although dietary guidelines, including those from the American Diabetes Association, have recommended decreasing dietary fat, not all fats are the same. Some high-fat foods, such as dairy and nuts, can contribute to increased feelings of satiety. Some studies have suggested that eating higher-calorie, higher-fat foods can contribute to equivalent, or even more, weight loss than low-fat diets.³

3. Which one of the following statements is true?

A. Patients should replace saturated fats with unsaturated fats to improve cardiovascular health.

B. Saturated fats are the main culprit causing cardiovascular disease and mortality.

C. Reducing consumption of saturated fats often contributes to lower cardiovascular risk.

D. Patients should be advised to avoid ultraprocessed foods high in saturated fat.

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Answer: D. Patients should be advised to avoid ultraprocessed foods high in saturated fat.

Although dietary guidelines recommend replacing saturated fats with unsaturated fats to decrease cardiovascular risk, research does not always back this up. A 2012 Cochrane Review found that decreasing saturated fat or substituting other fats for saturated fat had no effect on cardiovascular or all-cause mortality.⁴ Saturated fats in ultraprocessed foods (such as lunch meats) have been linked to increased cardiovascular mortality.⁵ On the other hand, whole foods high in saturated fats (such as dairy) have been linked to lower incidence of cardiovascular disease.⁶

4. Functional fibers are:

A. Created in laboratories and added to ultraprocessed foods to increase their fiber content

B. Naturally occurring components of whole foods

C. An important part of the diet that can improve constipation and the risk of cardiovascular disease, diabetes, and GI and breast cancers.

D. B and C

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Answer: A. Created in laboratories and added to ultraprocessed foods to increase their fiber content

The FDA definition of a “good” fiber source is any food that contains 2.5 g of fiber, regardless of whether that fiber comes from natural sources or is added artificially (eg, functional fibers). Functional fibers are produced in laboratories and are often added to processed foods to boost their “health” rating. However, evidence is lacking to support this claim. Moreover, eating functional fibers has been linked to GI distress and nutrient malabsorption. Conversely, consumption of naturally occurring fibers (fruits, vegetables, nuts, grains, seeds) has been linked to decreased risk of cardiovascular disease, diabetes, constipation, and GI and breast cancers.

5. Cutting 3500 calories per week will result in a 1-pound weight loss per week.

A. True

B. False

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Answer: B. False

The “3500 calorie” rule is the common assumption that cutting 3500 calories per week will result in a net weight loss of 1 pound per week, but this rule does not take into account the body’s dynamic response to weight loss. During weight loss, the body activates compensatory mechanisms to prevent even more weight loss. Using the 3500 calorie rule could create false expectations. More appropriate guidance for patients might be that maintaining an energy deficit of 100 calories per day may eventually lead to a 5-pound weight loss over 1 year, and a 10-pound weight loss over 3 years.⁷

6. Diet plans that have been shown to improve weight management recommend which of the following strategies:

A. Limit processed foods

B. Eat whole foods

C. Eat foods in a form that is as close to nature as possible

D. All of the above

Please click here for answer and discussion.

Answer: D. All of the above

No long-term head-to-head trials exist, however, that can help clinicians decide which whole foods to recommend. Diets that have been linked to improved weight management have all stressed the importance of avoiding ultraprocessed foods and eating whole or minimally processed foods, in the a form that is as close to nature as possible.⁷ Studies have suggested that eating whole foods can be even more cost-effective than eating ultraprocessed foods.⁸

References:

• Avenall A, Mak JC, O’Connell D. Vitamin D and vitamin D analogues for preventing fractures in postmenopausal women and older men. Cochrane Database Syst Rev. 2014;(4):CD000227.
• Moyer VA. Vitamin D and calcium supplementation to prevent fractures in adults: US Preventive Services Task Force recommendation statement. Ann Intern Med. 2013;158:691-696.
• Hession M, Rolland C, Kulkarni U, et al. Systematic review of randomized controlled trials of low-carbohydrate vs. low-fat/low-calorie diets in the management of obesity and its comorbidities. Obes Rev. 2009;10:36-50.
• Hooper L, Summerbell CD, Thompson R, et al. Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database Syst Rev. 2012;(5):CD002137.
• O’Sullivan TA, Hafekost K, Mitrou F, et al. Food sources of saturated fat and the association with mortality: a meta-analysis. Am J Public Health. 2013;103:e31-e42.
• De Oliveira MC, Mozaffarian D, Kromhout D, et al. Dietary intake of saturated fat by food source and incident cardiovascular disease: the Multi-Ethnic Study of Atherosclerosis. Am J Clin Nutr. 2012;96:397-404.
• Lesser LI, Mazza MC, Lucan SC. Nutrition myths and healthy dietary advice in clinical practice. Am Fam Physician. 2015;91:634-638.
• McDermott AJ, Stephens MB. Cost of eating: whole foods versus convenience foods in a low-income mode. Fam Med. 2010;42:280-284.