Chew on This: Review Tackles Controversies in Nutrition for CV Health

With rapidly changing information about what constitutes an optimal diet, it can be difficult for physicians to provide patients with informed nutritional advice. A new review aims to serve as a guide by analyzing the potential CV effects of 11 different foods, beverages, and vitamins that have been subject of nutrition fads or controversies.

“As cardiologists, we are plagued with lots and lots of questions about diet and lifestyle and unfortunately the vast majority of us have very little—if any—training in this regard,” Andrew Freeman, MD (National Jewish Health, Denver, CO), lead author of the paper, told TCTMD. According to a survey conducted by Devries et al, for which Freeman was senior author, 90% of cardiologists received minimal or no nutrition training during their fellowship.

Pulling all the evidence together in one place is a way “to help get people more or less up to speed on the basics of some of the things that they may be being asked every day,” said Freeman, who has published two reviews on the topic. Last year’s document focused on everything from cooking oils and eggs to plant-based proteins and antioxidants.

The latest review, published online today ahead of print in the Journal of the American College of Cardiology, offers evidence-based advice on added sugars, dairy products, energy drinks, fermented foods, legumes, coffee, tea, mushrooms, alcohol, plant or marine omega-3 fatty acids, and vitamin B12.

Individuals should avoid added sugars and energy drinks, Freeman and colleagues say, while both dairy and fermented foods were lacking sufficient evidence to be either harmful or beneficial. All of the other foods and beverage can be consumed in moderation.

Not Many Surprises

There’s plenty of reasons to limit or avoid added sugars, as the review notes.

Several meta-analyses have found higher intakes of sugar correlated with significantly increased triglyceride levels, for example. Additionally, a National Health and Nutrition Examination Survey found that, compared to individuals who get less than 10% of their daily calories from sugar-sweetened beverages, risk of death due to CVD increased by 30% for people getting 10 to 24.9% of their calories from these drinks. The risk was nearly tripled for those who drank over 25% of their daily calories from sugar-sweetened beverages.

“Good-quality evidence has now linked added sugars to cardiometabolic and atherosclerotic CVD risk. Until food labeling changes are phased in, individuals should limit added sugar to < 10% of calories and preferably < 100 calories daily for women and < 150 calories daily for men,” the co-authors say. “Clinicians should recommend consumption of a whole foods diet with a low intake of processed foods, careful selection of foods with no or low amounts of added sugars in any form, and elimination of sugar-sweetened beverages.”

Since these sugars are everywhere and can often be hidden, patients should also learn how to read nutrition labels of processed foods, they write.

Energy drinks are also ill-advised, according to authors. While caffeine is not necessarily harmful—both coffee and tea have previously been found to have cardiovascular benefits—energy drinks can contain two to four times the caffeine concentration approved by the US Food and Drug Administration for soft drinks. While most evidence regarding energy drinks is “low quality,” the authors acknowledge, it appears that these highly caffeinated beverages increased blood pressure, platelet aggregation, and risk of arrhythmia.

The review also recommends consumption of omega-3 fatty acids, either from marine or plant sources, for cardiovascular health. And while prospective studies have not found that vitamin B12 decreases the risk for CVD, it is still “an essential nutrient in the diet and should be supplemented in those who are deficient,” Freeman et al advise.

Drink Up?

While energy drinks have negative health effects, coffee, tea and alcohol all seem to have a positive influence on CV health. Four to five cups of coffee a day appears to reduce the risks of all-cause mortality, CV mortality, and CVD by 15-20%, several meta-analyses have found. Tea drinkers also see benefits, from a decreased risk of ischemic heart disease to less all-cause mortality. In one study on tea, participants drank at least five cups of tea a day, an amount that may not be achievable by the general population, the authors note.

People need to remember that stents, bypass [surgery], and all of those good things we have come up with have done wonderful things for patients, but by and large they are temporary. Andrew Freeman

For fermented foods and beverages, such as kimchi and yogurt, there isn’t enough evidence to firmly recommend them, but Freeman et al acknowledged observational studies have found some benefit.

Alcohol, too, may in moderate amounts be helpful, they say. The relationship between alcohol consumption and CVD outcomes, however, is complex and affected by factors like gender, ethnicity, age, genetics, drinking patterns, and beverage type. Given the lack of strong evidence showing benefit and the potential harms of overconsumption, “it is not recommended that individuals initiate alcohol consumption for CV benefit,” the authors write. “For those already drinking, consumption should be limited to recommended amounts, preferably consumed with meals. Mixing of alcoholic beverages with sodas, creams, and sweeteners adversely affects their health benefits.”

Jury Still Out on Dairy

Dairy products are some of the more controversial foods included in this review, Freeman told TCTMD. While they contain important vitamins and minerals, as a category, dairy also is the number one source of saturated fat as well as sodium in the American diet. It could be that people are unaware of how much dairy they eat, especially when going out for food, he added. “They come out and put cheese on your salad. The bread has cheese baked into it, they serve it with butter. If you get pasta they put cheese on it,” he said. “We want people to be aware of that and realize that there may be some harm with dairy. We are just not 100% sure where the data will ultimately end up.”

The health effects of dairy are also dependent on what type people are consuming, said David Katz, MD Yale-Griffin Prevention Research Center, New Haven, CT), who commented on the review for TCTMD by email. Additionally, it matters what foods get skipped when people fill up on dairy products. “In general, the message about dairy is ‘We are not sure.’ But compare that to ‘we are sure’ that vegetables, fruits, beans, lentils, nuts and seeds are good for you,” he said. “So if less dairy means more beans, or more nuts, less dairy is almost certainly better. But we also are sure that ‘added sugar’ is bad, so giving up milk to drink soda is trading down.”

Changing Lifestyle

While these recommendations may be a good starting point, Katz said, future research should focus on how these various foods contribute to different diets as a whole.

“All questions about the effects of specific foods or nutrients require consideration of the 'instead of what?' question on which they are contingent,” he said. “Do coffee, tea, and wine add benefit to an otherwise optimal diet without them, or do they add benefit only when the baseline diet has liabilities?”

Freeman agreed that additional studies could clarify some of these gray areas. Ultimately, though, these recommendations are meant to guide patients toward a diet rich in whole, unprocessed foods, he said.

“People need to remember that stents, bypass [surgery], and all of those good things we have come up with have done wonderful things for patients, but by and large they are temporary,” Freeman said. “We need to change lifestyle to prevent repeat events.”