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Do vitamin supplements work?

Take care: interactions between dietary supplements and prescription drugs commonly occur and can be significant

Joe Yammine

If you are overwhelmed by the towering shelves of vitamin and mineral supplements in the grocery store, you are not alone. Which ones really work? If so, how much? And are they worth the money?

These are good questions for anybody who wants to avoid heart disease and stroke. The very short answers to these three questions are: very few of them work, with modest capacity at best and, in general, no, they are not worth the money. Read on…

Food first

The American Heart Association position on supplements recommends that healthy people get adequate nutrients by eating a variety of foods in moderation, rather than by taking supplements. An exception, for omega-3 fatty acids, is explained later.

“Food first” is the motto because foods provide a variety of vitamins and minerals but also bioactive ingredients and fibres not found in a supplement.

Also, some supplements do not allow for full absorption of these beneficial components present in healthy food.

On the other hand, if taken on an empty stomach, some of the fat-soluble preparations may not be well absorbed.

Interactions between dietary supplements and prescription drugs commonly occur, and in some instances could be significant — as with vitamin K-containing vits and warfarin.

There isn’t sufficient data to suggest that healthy people benefit by taking certain vitamins or minerals in excess of the dietary recommended intake set by the American Institute of Medicine.

While some observational studies have suggested that lower rates of cardiovascular disease result in populations who use vitamins and minerals, it isn’t clear if this is due to the supplements themselves.

For example, supplement users may in general be more motivated by their health and diet, and hence are less overweight and more physically active.

Moreover, almost any nutrient can be potentially toxic if consumed in large quantities over a long time.

As an example, excess iron can increase the risk of chronic diseases, and too much vitamin A can cause birth defects.

What about antioxidant vitamins?

Many people are interested in antioxidant vitamins (A, C and E). This is due to suggestions from observational studies comparing healthy adults consuming these vitamins with those who did not.

However, these observations are subject to bias and do not prove a cause-and-effect relationship. More rigorous evidence does not suggest that consuming antioxidant vitamins can decrease blood pressure, lower cholesterol or improve cardiovascular health.

For instance, a recent large, placebo-controlled, randomised study failed to show any benefit from vitamin E on heart disease.

Although antioxidant supplements are not recommended, antioxidant food sources, especially plant-derived nutrients such as fruits, vegetables, whole grains and vegetable oils, are recommended for their wholesome and varied benefits.

What about omega-3 fatty acid supplements?

Fish intake has been associated with decreased risk of heart disease. In fact, some but not all research has shown that omega-3 fatty acids present in fish moderately decrease the risk of abnormal heartbeats which can lead to sudden death.

They also decrease triglyceride levels, slow down the growth rate of blockages (or plaques) inside the vessels, and may slightly lower blood pressure. Fish is also a good source of protein.

The AHA recommends that:

• People without documented heart disease eat a variety of fish — preferably omega-3-containing fish — at least twice a week.

Each serving is 3.5oz cooked, or about ¾ cup of flaked fish. Examples of these fish include salmon, herring, trout, mackerel, sardines and albacore tuna.

• Patients with documented heart disease are advised to consume about a gram of EPA + DHA (types of omega-3 fatty acids), preferably from fish, although EPA+DHA supplements could be considered.

• For people with high triglycerides (blood fats), three to six grams of EPA + DHA per day, in the form of capsules, are recommended. Patients taking three grams or more of omega-3 fatty acids should do so only under a physician’s care, as high intakes may cause excessive bleeding in some people.

When you go fishing, is there a catch? Some types of fish may contain high levels of mercury, PCBs (polychlorinated biphenyls), dioxins and other environmental contaminants.

Levels of these substances are generally highest in older, larger, predatory fish and marine mammals.

The benefits and risks of eating fish vary depending on a person’s stage of life:

• Children and pregnant women are advised by the US Food and Drug Administration to avoid eating those fish with the potential for high mercury contamination (eg, shark, swordfish, king mackerel or tilefish); to still eat up to 12oz (two average meals) per week of a variety of fish and shellfish that are low in mercury (eg, canned, light tuna, salmon, pollock, catfish, and shrimp); and to check local advisories about the safety of fish caught in local water.

• For middle-aged and older men and postmenopausal women, the benefits of fish consumption far outweigh the potential risks when the amount of fish eaten is within the FDA and Environmental Protection Agency guidelines.

•Joe Yammine is a cardiologist at Bermuda Hospitals Board. He trained at the State University of New York, Brown University and Brigham and Women’s Hospital. He holds five American Board certifications. He was in academic practice between 2007 and 2014, when he joined BHB. During his career in the US, he was awarded multiple teaching and patients’ care recognition awards. The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician. You should never delay seeking medical advice, disregard medical advice or discontinue treatment because of any information in this article.