Multiple sclerosis and autoimmunity

Multiple sclerosis and autoimmunity

Multiple sclerosis (MS) is the most common disease of the central nervous system (the brain and spinal cord) affecting young adults in the UK. MS currently affects around 85,000 people in the UK and twice as many women as men have MS. Although it usually occurs in young adults in their twenties and thirties, MS can occur in older people. It is rarely diagnosed in children and teenagers.

Sclerosis means scarring and multiple refers to the different sites at which the scarring can occur throughout the brain and spinal cord. In MS the protective sheath (myelin) that surrounds the nerve fibres of the central nervous system becomes damaged. When myelin is damaged (demyelination) the messages between the brain and other parts of the body become disrupted. Myelin protects the nerve fibres in much the same way that household electrical wires are protected by an insulating cover. If this cover becomes damaged the normal signalling route becomes disrupted and may result in a short-circuit. The severity of the symptoms depends on how much damage has occurred to the central nervous system. For some people there may be periods of relapse where there are few symptoms, then times when the symptoms become more severe including blurred vision, paralysis, slurred speech, lack of coordination and incontinence. 

The cause of MS is not yet fully understood but is thought to be an autoimmune disease whereby the body’s immune system attacks its own tissues. As with other autoimmune diseases, it is thought that a combination of genetic factors and environmental triggers cause the disease. Environmental triggers may include viruses, components of the diet or stress. Interestingly, the incidence of MS increases the further you get from the equator, whether going north or south. For example, MS is five times more common in temperate zones than in the tropics (NHS Direct, 2005). Campbell suggests that MS is over 100 times more prevalent in the far north than at the equator (Campbell and Campbell, 2005). In Australia the incidence of MS decreases seven-fold as you move towards the equator from the south to the north (Campbell and Campbell, 2005). This geographical distribution pattern applies to other autoimmune diseases including type 1 diabetes and rheumatoid arthritis (Campbell and Campbell, 2005).

Indeed, this phenomenon has been noted since 1922 (Davenport, 1922). Campbell suggests in his book The China Study that autoimmune diseases should be considered as a group rather than as individual diseases as they share similar clinical backgrounds and sometimes occur in the same person or among the same populations (Campbell and Campbell, 2005).

The research investigating the links between diet and MS date back over 50 years to Dr Roy Swank’s work first at the Montreal Neurological Institute in Norway, then at the Division of Neurology at the University of Oregon Medical School in the US. Swank was intrigued by the geographical distribution of MS and thought it may be due to dietary practices. Swank suspected animal foods high in saturated fats may be responsible as MS seemed to occur most among inland dairy-consuming populations and less among coastal fish-eating populations. Perhaps his best known trial was that published in the Lancet in 1990. In this study Swank followed 144 MS patients for a total of 34 years. Swank prescribed a low-saturated fat diet to all the participants but the degree of adherence to the diet varied widely. He observed how their conditions progressed. Results showed that for the group of patients who began the low-saturated fat diet during the earlier stages of MS, 95 per cent survived and remained physically active for approximately 30 years. In contrast, 80 per cent of the patients with early-stage MS who did not adhere to the diet died of MS (Swank and Dugan, 1990). It was concluded that saturated animal fats increase the risk of MS.

More recent studies have extended Swank’s findings and revealed a positive correlation between the consumption of cow’s milk and the incidence of MS. This later research suggests that there could be a combination of predisposing or precipitating factors involved in the aetiology of MS, and that environmental factors, such as the consumption of cow’s milk, play a part (Agranoff et al., 1974; Butcher, 1976). These and more recent studies suggest that cow’s milk may contain some component other than saturated fat that influences the incidence of MS. For example, it has been suggested that this factor or environmental trigger may be a virus (Malosse et al., 1992).

You are more likely to get MS if other people in your family have it (especially a brother or sister). This shows that there is an element of genetic predisposition in this disease. However, twin studies have shown that only about a quarter of identical twins with MS have a twin with the disease (Willer et al., 2003). In other words for every four genetically identical sets of twins (one of whom has MS) one other twin will have the disease and three will not. If genes were solely responsible for MS, the genes that cause MS in one twin would also cause it in the other. When considering the role of genetics in a disease, it is useful to look at what happens to the risk of that disease in migrating populations. As for cancer, heart disease and type 2 diabetes, people tend to acquire the MS risk of the population to which they move, especially if they move early in life. This shows that MS is more strongly related to environmental factors and diet than genes.

While the benefits of excluding milk from the diet may not have been directly proven for MS sufferers, there is evidence that a high intake of saturated fat increases the incidence of this disease. Others studies suggest that increasing the intake of unsaturated fatty acids (such as linoleic acid), vitamin D and antioxidants may be helpful (Schwartz et al., 2005). The overall message is clear: a plant-based diet low in fat, salt and sugar (and processed foods) and high in fresh fruits, vegetables, whole grains, pulses, nuts and seeds can provide all the nutrients required for good health and reduce some of the risk factors for MS or prevent making an already existing condition worse.

As the incidence of most autoimmune diseases correlates directly to the consumption of animal foods, this approach could help prevent other autoimmune conditions that occur increasingly among populations that consume high levels of dairy and meat products.