Taken https://www.westonaprice.org/health-topics/the-pursuit-of-happiness/?fbclid=IwAR0mSbOL_jQj9RB_7tIL7Edl-3HCK5IqRa4XQEakEe_STL9efjrTMuWmv3o#gsc.tab=0 

Weston Price observed healthy and cheerful dispositions accompanying the broad facial development and robust immunity to degenerative disease that characterized members of isolated groups eating traditional diets. He emphasized above all the importance of the fat-soluble vitamins for prevention and reversal of tooth decay and full skeletal development. Modern science has now elucidated the role of nutrient-dense animal fats in preventing mental illness and supporting the focused, goal-oriented behavior needed to confront challenges and pursue a happy, satisfying, and successful life.

Clinically defined psychiatric disorders afflict just under half of Americans for at least one period of time during their lives.1 Depression and anxiety often occur together and also often occur in conjunction with physical ailments such as inflammatory bowel disease2 and asthma.3 The lifetime prevalence of depression, anxiety, impulse control and substance abuse disorders is twice as high for people born after 1945 than for those born earlier, and the proportion of Americans suffering from three or more disorders—nearly a fifth—has more than tripled for the post-World War II generations.

As will be shown in this article, nutrient-rich animal fats are so important to a healthy psychological and emotional disposition that the orchestrated campaign to replace meat and eggs with soy and refined grains and to replace traditional animal fats with corn, soy, and canola oils has most certainly been a major factor contributing to the ongoing decimation of the American Dream.

The Fat-Soluble Vitamins

Vitamins A, D, E, and K are the four traditionally recognized fat-soluble vitamins. The essential fatty acids arachidonic acid and DHA, however, are needed in similarly small amounts and fulfill similar functions. While all of these nutrients are important to the nervous system, in this article I will discuss how arachidonic acid cooperates with vitamins A and D to promote mental health by regulating the adrenal hormone cortisol and the neurotransmitter dopamine through the potent central nervous system regulators known as endocannabinoids.

Arachidonic acid is a 20-carbon omega-6 fatty acid found primarily in eggs and liver and in smaller amounts in all other animal fats including butterfat. It is generally considered a “bad fat” because certain highly regulated enzymes can convert it into inflammatory compounds, but it is nevertheless necessary for healthy hair and skin, ovulation, and thus fertility.12 Researchers from Harvard School of Public Health followed almost 20,000 women for over eight years and found that the more high-fat dairy the women ate the less likely they were to have problems with ovulation, while the more low-fat dairy the women ate the more likely they were to fail to ovulate and thus be infertile.13 These data suggest that many people in the general population may not obtain adequate amounts of arachidonic acid.

While we obtain preformed arachidonic acid from animal fats, healthy adults can also synthesize small amounts from omega-6 linoleic acid, found in both plant oils and animal fats. Vitamin A, however, is necessary for this conversion (see Figure 2) and, as we shall see, also helps carry out dopamine signaling more directly. Vitamin A is present in large amounts in liver and cod liver oil and in small amounts in eggs and butterfat. Healthy adults can convert beta-carotene and other carotenoids present in fruits and vegetables to vitamin A, but this conversion is generally inefficient. Half of Americans consume less than the RDA for vitamin A14 and over a quarter of Americans consume less than half this amount.15

Vitamin D directly interacts with vitamin A in many contexts and is critical to maintaining blood and tissue levels of calcium. Calcium is a central regulator of arachidonic acid metabolism in virtually every type of cell, making vitamin D essential for proper handling of this nutrient. Vitamin D is present in large amounts in fatty fish and cod liver oil and in small amounts in the fats of land animals. We also obtain vitamin D when we are exposed to sunshine in the ultraviolet-B range, which at most latitudes is available only during the summer months. About half of all Americans and over 80 percent of African Americans have blood levels of vitamin D below the level needed to maximize calcium absorption.