July, 2005 Revised March, 2007
Choosing among the foods highest in cholesterol is important for two reasons. Not only are many of these foods true super-foods -- rich in a wide array of nutrients, many of which are difficult to find elsewhere -- but cholesterol itself may be an important dietary nutrient for at least one to three percent of the population and may be essential to their health.
Smith-Lemli-Opitz syndrome (SLOS) is a genetic condition arising from the inability to convert 7-dehydrocholesterol (a common precursor of both cholesterol and vitamin D) into cholesterol. Most often, it results in spontaneous abortion within the first sixteen weeks of gestation.2 Children who are born with the defect may suffer from mental retardation, autism, facial and skeletal malformations, visual dysfunctions and failure to thrive. The current treatment is dietary cholesterol.3
SLOS is an autosomal recessive disorder, which means that both parents must contribute a defective gene in order for their child to develop the disease. Thus only one in 60,000 infants are born with the disease.
The proportion of people who carry the SLOS gene, however, is much higher. Approximately one in a hundred North American Caucasians possess a copy of the defective gene, and as many as one in fifty or even one in thirty Central Europeans possess a copy of the defective gene.2 These people, called SLOS "carriers," have reduced cholesterol synthesis, but still synthesize enough cholesterol to escape the severe risks and abnormalities that characterize clinical SLOS. SLOS carriers, then, comprise from one percent to over three percent of many populations.
An important study published in the American Journal of Psychiatry in 20044 showed that people who carry the SLOS gene are more than three times as likely to have attempted suicide as those who do not carry the gene. Moreover, the methods of committing suicide among carriers of the SLOS gene were more violent: while the one suicide attempt among controls involved an overdose of over-the-counter diet pills, attempts among SLOS carriers involved not only diet pills and deliberate inhalation of exhaust fumes but also firearms and an attempt to crash a car.
This is consistent with studies showing that low blood cholesterol levels are associated with suicide and that cholesterol levels in certain areas of the brain are lower in those who commit suicide by violent means than in those who commit suicide by non-violent means.5
Unfortunately, this study of 105 subjects was not statistically powerful enough to conclusively determine that this association was not due to chance. It was powerful enough, however, to conclusively show that SLOS carriers were more than four times as likely to have at least one biological relative who attempted or committed suicide and almost six times as likely to have a first-degree relative who attempted or committed suicide.4
Dietary cholesterol decreases aggressive and self-injurious behaviors in patients with clinical SLOS. It also improves hyperactivity, irritability, attention span, muscle tone, endocrine function, resistance to infection, and gastrointestinal problems in these patients.3
Taken together, these data suggest that dietary cholesterol may be an essential nutrient for one to three percent of the population. Moreover, there may be other differences in genetics besides the SLOS gene that may contribute to reduced cholesterol synthesis and a requirement for dietary cholesterol in other people. Clearly, then, some people not only require the rich array of nutrients in cholesterol-rich foods but may even require the cholesterol itself.
References
1. Fernandez ML. Dietary cholesterol provided by eggs and plasma lipoproteins in healthy populations. Curr Opin Clin Nutr Metab Care. 2006; 9(1): 8-12.
2. Nowaczyk MJM, Waye JS, Douketis JD. DHCR7 Mutation Carrier Rates and Prevalence of the RSH/Smith-Lemli-Opitz Syndrome: Where Are the Patients? Am J Med Genet. 2006; Part A 140A: 2057-2062.
3. Elias ER, Irons MB, Hurley AD, Tint S, Salen G. Clinical Effects of Cholesterol Supplementation in Siz Patients With the Smith-Lemli-Opitz Syndrome (SLOS). Am J Med Genet. 1997; 68: 305-310.
4. Lalovic A, Merkens L, Russell L, Arsenault-Lapierre G, Nowaczyk MJM, Porter FD, Steiner RD, Turecki G. Cholesterol Metabolism and Suicidality in Smith-Lemli-Opitz Syndrome Carriers. Am J Psychiatry. 2004; 161: 2123-2126.
5. Lalovic A, Levy E, Luheshi G, Canetti L, Grenier E, Sequeira A, Turecki G. Cholesterol content in brains of suicide completers. Int J Neuropsychopharmacol. 2007; 10(2): 159-66.