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. It is estimated that there are currently around 100,000 people with MS in the UK. Symptoms usually first develop between the ages of 15 and 45, with the average age of diagnosis being about 30. For reasons that are unclear, MS is twice as common in women than men and more common in white people than black and Asian people (NHS Choices, 2012r).
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. More severe symptoms include blurred vision, paralysis, slurred speech, lack of coordination and incontinence.
Around eight out of 10 people with MS will have a type of MS called ‘relapsing-remitting’. This means they will have periods of remission (that can last for days, weeks or even months) where symptoms are mild or disappear altogether. Remission is followed by a flare-up of symptoms, known as a relapse, which can last from a few weeks to few months. Usually after around 10 years, around half of people with relapsing-remitting MS go on to develop secondary progressive MS whereby symptoms gradually worsen and there are fewer or no periods of remission. The least common form of MS is primary progressive MS in which symptoms gradually get worse over time and there are no periods of remission (NHS Choices, 2012r). A subgroup of patients with relapsing-remitting MS exhibits a benign course with no disease progression and minimal disability decades after the first manifestations. Eventually, these patients may switch to a progressive state (Ramsaransing et al., 2009).
MS is 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. Recent research shows that an important environmental factor is diet (Ramsaransing et al., 2009). Other environmental triggers may include viruses or emotional factors such as stress. Interestingly, the incidence of MS increases the further you get from the equator, whether going north or south. For example, MS is relatively common in the UK, North America and Scandinavia, but rare in Malaysia or Ecuador. 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). Interestingly, in the 1970s a correlation between the world distribution of dairy production and consumption and the incidence of multiple sclerosis was noted (Butcher, 1976). It was suggested then that dairy may be a contributing factor.
The research investigating the links between diet and MS dates 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 (less than 20g per day saturated fat) during the earlier stages of MS, 95 per cent survived and remained physically active for approximately 30 years. Even those with significant disability were shown to markedly slow the progression of the disease if they could stick to the low-saturated fat diet. 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.
Other 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 other 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 also 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 and severity 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). Recent studies concur that limiting the consumption of saturated fatty acid intake and supplementing with unsaturated fatty acids in combination with more vegetables can favour prognosis in relapsing-remitting MS (Ramsaransing et al., 2009). This may be related to the anti-inflammatory properties of omega-3-fatty acids. This study also found that, compared to the daily recommended allowance, the MS patients studied had a lower than recommended intake of folic acid, magnesium, zinc and selenium. 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 vitamins, minerals and other 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.