Processed Meats Top List of Foods Linked to CHD and Diabetes

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A new study has identified 10 foods and 7 nutrients associated with the development of coronary heart disease (CHD), diabetes, and stroke. Of these, processed meats posed the highest risk of CHD and diabetes.¹

The study is the first to quantify causal effects of dietary factors on CHD, stroke, and diabetes. It is also the first to evaluate the optimal intake of various foods to promote cardiometabolic health.

“Generally, minimally processed, bioactive-rich foods like fruits, vegetables, nuts/seeds, beans/legumes, and whole grains had protective effects, whereas certain more highly processed foods such as processed meats and sugar-sweetened beverages had harmful effects,” wrote first author Renata Micah, PhD, of Tufts University (Boston), and colleagues. “Other identified protective dietary factors were characterized by relatively unique attributes, such as fish/seafood and long-chain omega-3s (linked to lower risk of fatal CHD) or yogurt (containing active probiotics; linked to lower risk of diabetes).”

Polyunsaturated fats and potassium were also linked to protective effects.

Suboptimal diet has often been recognized as a key player in chronic diseases such as diabetes and CHD. However, researchers have been hard-pressed to prove causality between dietary factors and cardiometabolic disease. Determining the magnitude of the impact represents an even greater challenge.

A systematic review and meta-analysis

To address the issue, researchers searched PubMed for studies about the impact of dietary factors on CHD, stroke, or diabetes. The search identified 23 meta-analyses and review articles published through May 1, 2015.

Because identified randomized, controlled trials provided insufficient evidence on causality, researchers evaluated qualitative studies using Bradford-Hill criteria (a set of guidelines used to evaluate causality). The analysis used a conservative approach and included only dietary factors with probable or convincing evidence of causality. It excluded dietary factors with borderline evidence for causality, including coffee, extra-virgin olive oil, monounsaturated fats, cocoa, and tea. Alcohol was also excluded.

"The analysis...excluded dietary factors with borderline evidence for causality including coffee, extra-virgin olive oil, monounsaturated fats, cocoa, and tea. Alcohol was also excluded."

Researchers also calculated quantitative relative risk estimates, using units standardized for serving size to enable comparisons across studies. Further analyses evaluated optimal consumption levels associated with lowest disease risk, as well as potential bias related to underlying patient characteristics such as age and sex. Validity analyses also evaluated potential bias related to different dietary patterns (such as overall unhealthy diets high in processed meats and sugary beverages vs overall healthy diets high in whole grains, fruits, and vegetables).

Key results

Identified 10 foods and 7 nutrients associated with CHD, diabetes, and stroke:
► Low-risk foods: fruits, vegetables, beans/legumes, nuts/seeds, whole grains, yogurt
► High-risk foods: red meat, processed meats, sugar-sweetened beverages

► Low-risk nutrients: polyunsaturated fats (replacing either carbs or saturated fats), seafood omega-3s, dietary fiber, potassium

► High-risk nutrients: trans fats, starches/sugars, salt

16/17 factors were causally linked to CHD
►  Highest risk for processed meats (relative risk [RR], 1.37 per 50-g serving/day)

8/17 factors were causally linked to diabetes
► Highest risk for processed meats (RR, 1.51 per 50-g serving/day)

Optimal intake:

► Fruits: 2 (100 g) servings/day

► Vegetables (including beans/legumes): 4 (100 g) servings/day

► Beans/legumes: 1 (100 g) serving/day

► Nuts/seeds: 5 (1 oz) servings/week

► Whole grains: 2.5 (50 g) servings/day

► Red meat, unprocessed: 1 (100 g) serving/week

► Processed meats: 0

► Fish/seafood: 3.5 (100 g) servings/week

► Yogurt: 2.5 (8 oz) servings/week

► Sugar-sweetened beverages: 0

► Nutrients: polyunsaturated fats replacing carbs or saturated fats (11% of energy); seafood omega-3s (250 mg/d); trans fats (0.5% of energy); dietary fiber (30 g/day), sodium (2000 mg/day); potassium (4500 mg/day)

Sub-analyses, Study Limitations, The Take-home>>

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Heterogeneity analyses: Generally similar effects by age and sex, sugar-sweetened beverages had larger effects for overweight vs normal-weight individuals

Validity analyses: Individual dietary factors and dietary patterns had similar effects on CV risk factors, incident CHD, and changes in blood pressure and low-density lipoprotein cholesterol

The authors noted that the optimal-intake calculations were “generally consistent” with major dietary guidelines. In particular, the optimal intake of sodium of (2000 mg/d) is consistent with World Health Organization guidelines.

They also emphasized that sodium and trans fats-identified as nutrients with causal effects on cardiometabolic conditions-are industrial additives. Levels of these factors can be decreased by home cooking or eating minimally processed foods.

Study limitations

The study had several limitations. Quantitative estimates relied mostly on prospective observational studies, which could have led to bias related to overall dietary patterns. However, validity analyses suggested low likelihood of such a bias. Also, analyses were limited to factors with the strongest evidence for causality, which may have excluded factors that could influence cardiometabolic health.

While the analysis did not identify etiological links between promising factors such as omega-3s, coffee, tea, and cocoa, the authors emphasized that the analysis was based on available evidence only. Such associations may emerge as more research accumulates.

“These new findings add to a growing evidence base that emphasizes the importance of food-based diet quality in general, and minimally processed, bioactive-rich foods in particular, as key priorities for reducing burdens of cardiometabolic diseases,” they concluded.

Take-home points

► First study to quantify causal effects of dietary factors on cardiometabolic conditions identified 10 foods and 7 nutrients associated with the development of CHD, diabetes, and stroke

►  In general, minimally processed, bioactive-rich foods such as fruits, vegetables, nuts/seeds, beans/legumes, and whole grains were associated with protective effects; more highly processed foods such as processed meats and sugar-sweetened beverages were linked to harmful effects

► Processed meats were linked to highest risk for both CHD and diabetes

► The study was also the first to evaluate optimal intake of various foods for promoting cardiometabolic health; optimal intake calculations were generally consistent with major dietary guidelines

► No causal links were found for promising dietary factors such as omega-3s, coffee, tea, and cocoa; such associations may emerge as further research accumulates

Source

1. Micha R, Shulkin ML, Peñalvo JL, et al. Etiologic effects and optimal intakes of foods and nutrients for risk of cardiovascular diseases and diabetes: systematic reviews and meta-analyses from the Nutrition and Chronic Diseases Expert Group (NutriCoDE). PLoS One. 2017;12:e0175149. doi: 10.1371/journal.pone.0175149. eCollection 2017.

Images in composite at top: Sugar ©Zsido/Shutterstock.com; Fruits/vegetables ©Monticello/Shutterstock.com; Walnuts, ©Valentin Volkov; Salmon, ©Axelpro9500/Shutterstock.com; Fish Oil, ©Morganka/Shutterstock.com; Salt crystals, ©schankz/Shutterstock.com