Are Shrimp Bad for You? A Study on Shrimp and Cholesterol
Shrimp are often given a bad rap for their high cholesterol content. Although it is true that shrimp are relatively high in cholesterol (about 200 milligrams in 3.5 ounces, or 12 large boiled shrimp), scientific research on shrimp and blood cholesterol levels suggests that shrimp may not be that bad for you, after all.
Steamed shrimp, which is naturally low in fat, can be safely included in heart-healthy diets for people without lipid problems, conclude scientists from The Rockefeller University and the Harvard School of Public Health in a report published in the American Journal of Clinical Nutrition.
The scientists evaluated the effects of including shrimp in a low-fat diet among 18 healthy individuals during a nine-week test period. Each study participant was randomly assigned to a sequence in which he or she consumed three diets in rotation for a total of three weeks each. The diets included a baseline diet excluding shrimp, a baseline diet including shrimp diet and a baseline diet including eggs. The diets were customized to meet each participant's caloric needs, but all diets had the same macronutrient composition (55% carbohydrate, 15% protein and 30% fat, including the proportion of saturated, monounsaturated and polyunsaturated fats), with the exception of their cholesterol content. The baseline diet provided only 107 milligrams of cholesterol per day, while the shrimp diet provided a daily dose of 590 milligrams of cholesterol and the egg diet delivered 580 milligrams of cholesterol.
A Diet Rich in Shrimp Increased LDL Cholesterol Levels...
When compared with the baseline diet, both the shrimp and egg diets caused similar increases in the LDL concentrations (7.1 and 10.2% respectively). LDL cholesterol is what is commonly referred to as 'bad cholesterol' as too much LDL cholesterol in the blood can contribute to the buildup of plaque in the inner walls of your arteries. Plaque is a thick, hard deposit that can cause narrowing of the arteries and increase blood pressure. In addition, plaque contributes to the hardening of artery walls, a condition known as atherosclerosis. Ultimately, plaque can result in a heart attack or stroke if a clot forms and blocks a narrowed artery.
...but the Ratio of 'Good' and 'Bad' Cholesterol Stayed Favorable
The good news: the shrimp diet also raised levels of HDL cholesterol. In fact, it raised the HDL cholesterol levels more than more than it increased levels of LDL, and the scientists concluded that the resulting HDL to LDL ratio was favorable. HDL cholesterol is known as 'good cholesterol' because high levels of HDL seem to protect against heart attack. The mechanism by which HDL protects the heart is not fully understood, but some medical experts have suggested that HDL tends to carry cholesterol away from the arteries. Low levels of HDL (less than 40 mg/dL for men, less than 50 mg/dL for women) have been associated with an increased risk of heart disease.
Shrimp Linked to Low Triglyceride Levels
The Rockefeller researchers also found that those study participants who were on the shrimp diet had significantly lower triglyceride levels than those on either the baseline or the egg diet. Triglycerides are a type of blood fat and have been associated with an increased risk of cardiovascular disease, when present in excessive amounts in the blood. One 18-year study of 460 adults found that people with triglyceride levels as low as 100 milligrams per deciliter were more than twice as likely to suffer from future heart disease than those with lower triglyceride levels.
It appears that shrimp cholesterol is much less easily absorbed than cholesterol from other high fat foods. The researchers also believe that the slightly higher n-3 fatty acid content in the shrimp diet might contribute to the findings of lower triglycerides and higher HDL with shrimp consumption. n-3 fatty acids are better known as omega-3 fatty acids and are known to offer a multitude of health benefits.